What is genetics?


Genetic therefore attempts to explain how to inherit and characteristics of living things, which may be so, physiological and even behavioral change. Thus, the intention of this text is to present as genetics is to study how these characteristics are passed from parents to children, grandchildren and why, in turn, vary generation after generation.

genes finding them

Between 1884 (the year of the death of Mendel) and 1888 mitosis and meiosis described. The core was identified as the location of genetic material, and suggested that the “qualities” were carried by chromosomes to daughter cells during mitosis.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

mitosis and meiosis

Cells reproduce by duplicating their contents and then dividing by two. The division cycle is the fundamental means by which all living beings spread. In unicellular species such as bacteria and yeasts, each cell division produces a new organism. It multicellular species many sequences of cell divisions are required to create a new individual; cell division is also needed in the adult body to replace lost by wear, deterioration or programmed cell death. Thus, an adult human must produce many millions of new cells every second just to maintain steady state and cell division if the individual dies within a few days stop.

The cell cycle comprises the set of processes that a cell should be performed to fulfill the exact DNA replication and segregation of replicated chromosomes into two separate cells. The vast majority of the cells also double its mass and duplicate all its cytoplasmic organelles in each cell cycle: In this way during the cell cycle of a complex set nuclear and cytoplasmic processes must be coordinated with one another.


Plants and animals are composed of billions of individual cells organized into tissues and organs that perform specific functions. All cells of any plant or animal have arisen from a single initial cell-the fecundado- egg by a process of division. Mitosis is nuclear division associated with the division of somatic cells – cells of a eukaryotic organism that will not become sex cells. A mitotic cell divides and forms two identical daughter cells, each of which contains a set identical to the parent cell chromosomes. After each of the daughter cells divide again again, and so the process continues. Except in the first cell division, all cells grow to a size approximately twice the original before dividing. In this process the number of chromosomes (i.e., DNA) and each of the duplicate sets traveling over an array of microtubules to a center of the dividing cell is doubled, and constitute the chromosomes of each of the two formed daughter cells.

During mitosis there are four phases:
Prophase: A chromatic spindle begins to form outside the cell nucleus, chromosomes condense while. Cell envelope breaks spindle microtubules and chromosomes capture.

Metaphase: The chromosomes line up at a midpoint forming a metaphase plate.

Anaphase: The sister chromatids separate abruptly and are driven to opposite poles of the spindle, while elongation increases more spindle pole separation.

Telophase: The spindle continues chromosomes elongating while the poles are coming to and released spindle microtubules; The membrane was subsequently begins to thin in the middle and finally breaks. After that, around the nuclear envelope chromosomes reconstructed.

Phases of Mitosis. Here we can see   how the process is reached.                         Reference: http://publications.nigms.nih.gov/insidethecell/ch4_phases_allbig.html

In this video we can see the process of mitosis.

Reference: https://www.youtube.com/watch?v=C6hn3sA0ip0&app=desktop


Higher organisms that reproduce sexually are formed from the union of two special sex cells called gametes. The gametes originate through meiosis, process of dividing germ cells. Meiosis differs from mitosis in that only each new cell is transmitted one chromosome of each of the pairs of the original cell. Therefore, each gamete contains half the number of chromosomes to other body cells. When two gametes, the resulting cell, called a zygote unite in fertilization, contains all the double set of chromosomes. Half of these chromosomes are from one parent and the other half the other.

Since the meiosis consists of two cell divisions, these are distinguished as Meiosis I and Meiosis II. Both events significantly differ from those of mitosis. Each meiotic division is formally divided into states: prophase, metaphase, anaphase and telophase. Of these the most complex and longest running is the prophase I, which has its own divisions: Leptotene, Citogeno, Pachytene, Diplotene and Diakinesis.

In this image processes is explained meiosis Reference: http://www.ib.bioninja.com.au/higher-level/topic-10-genetics/101-meiosis.html
In this image the process is explained.
Reference: http://www.ib.bioninja.com.au/higher-level/topic-10-genetics/101-meiosis.html

In this video we can see the meiosis process,  phase by phase:

Reference: https://www.youtube.com/watch?v=-DLGfd-Wpr4

Coming back  to the history of genes:
In 1903 Walter Sutton and Theodore Boveri formally proposed that chromosomes contain genes. The chromosome theory of inheritance is one of the foundations of genetics and explains the place where the physical support of the principles of Mendel.
The location of many genes (Mendel factors) was determined by Thomas Hunt Morgan and his colleagues in the early twentieth century. Morgan’s experimental organism was the fruit fly: Drosophila melanogaster. These organisms are ideal for genetics, have small size, they are easy to care for, are likely to mutate and have a short generation time (7-9 days). Have only four pairs of chromosomes.
The role of chromosomes in sex determination was deduced by Morgan from work with fruit flies.
During metaphase, homologous chromosomes are facing. If microphotography and then trimmed and sorted homologous chromosomes karyotype is obtained.

Genetics is the study of the variations between human beings and how these variations are transmitted in a family. Our DNA is the basis of our genetics.

Genetics is the branch of science concerned with genes, heredity, and variation in living organisms. It seeks to understand the process of trait inheritance from parents to offspring, including the molecular structure and function of genes, gene behaviour in the context of a cell or organism (e.g. dominance and epigenetics), gene distribution, and variation and change in populations.

Genetics is the science of information transfer from one generation to another. We learn the laws of inheritance in all creatures big and small, how they evolve and how they change. On the molecular level we learn about DNA and RNA, on the cellular level we discover what makes a cell cancerous, and on an organismal level we examine the reproductive habits of various organisms. Crucial principles include the structure, function, and transmission of genes. Laboratory techniques explore genetic engineering from the “inside.” Genetics is crucial to all of biology, hence a genetics major has great flexibility. This is excellent preparation for advanced study in biological sciences, law, genetic counseling, and many health-related professions.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

In this video we can find how genes are explained.

Reference: https://www.youtube.com/watch?v=5MQdXjRPHmQ&app=desktop

What is a gene?

The gene is the storage unit of living things. They are also the units that are inherited, passing from father to son. A gene is a DNA segment coding for a protein. Encode here means that each gene contains information for the production of a protein that will perform a specific function in the cell in the body. Actually it is more complex, since some genes do not code for proteins but are regulatory and some genes give rise to more than one protein.

It is estimated that humans contain about 20,000 genes.

Reference information: http://dciencia.es/adn-genes-cromosomas/

Chromosomes                                                                                      Reference: http://www.maxisciences.com/chromosome/wallpaper

In this video genetics is explained.

Reference: https://www.youtube.com/watch?v=B_PQ8qYtUL0&app=desktop

What is a chromosome?

The first thing we must remember is that our cells do not have a single “cluster” of DNA in the nucleus, but this DNA is organized, stored in a structured manner. These structures that organizes the DNA are called chromosomes.

Human cells have 23 pairs of chromosomes (46 chromosomes in total), of which half comes from the mother and half from the father

Reference information: 



Here we can see in detail a total of 23 chromosomes. Reference: http://horadefisioterapia.blogspot.mx/2013/07/un-metodo-para-desactivar-el-cromosoma.html

This video explains the structure of a chromosome and different things of its identity.

Reference: https://www.youtube.com/watch?v=xUrlreMaUrs&app=desktop

Two types of chromosomes:
The autosomes whose counterparts are similar in size and location of the centromere, for example the pair 21 has a size and torque 9 has a different size 21.
The sex chromosomes in which each member of the pair may differ in size depending on the organism from which they originate.
In humans and Drosophila, males have a smaller sex chromosome called Y (male), and a larger one called X (female).
Males are XY, and are said to be heterogametic.
Females are XX, and are therefore homogametic by.
In grasshoppers, which Sutton studied there is no Y, male chromosomes only have X and X0 is the notation.
Other organisms (birds, butterflies) have males and females heterogametic homogametic.
Males (if heterogametic) contribute to the X or Y to their offspring, while females contribute either X. Therefore in these cases the male determines the sex of the offspring. Remember that in meiosis each chromosome is replicated and one copy of each is carried by the gamete.

Normally Drosophila eyes are red but Morgan discovered a mutant with a different color of eyes (white) and tried to duplicate her Mendel’s experiments. Most mutations are usually recessive, so the appearance of a white-eyed mutant gave Morgan a chance to study in animals, Mendel observed phenomena. But instead of getting a result type 3: 1 in F2 (second crossing) the ratio was nearly 4: 1 (red eyes white eyes) and, moreover all individuals in the F2 generation of white eyes were male.

Cross a homozygous for the white male with a female homozygous for red gives an entirely offspring have red eyes. Red is dominant over white. However, cross a homozygous white eyed female to male red eyes, gives an unexpected result: all males have white eyes and all females red eyes. This can be explained if the gene for red color is on the X chromosome

Characteristic X-linked Traits

The genotypic expression is more common in males
The children can not inherit from their parents, but daughters.
Sons inherit their Y chromosome from their father
Only a few genes, including the testis-determining factor (for its acronym in English TDF) that promotes the development of the male phenotype were identified on the Y chromosome.

Image of chromosome x Reference: http://www.dailymail.co.uk/sciencetech/article-2104924/Male-Y-chromosomes-NOT-die-shows-monkey-study.html

A special type of sex-linked inheritance

Cells in female mammals may be a dark spot chromatin: Barr bodies, which are interpreted as the inactivated X chromosome in the cells of female mammals. Since females have two X chromosomes, the Lyon hypothesis suggests that either X chromosome is inactivated in some somatic cells during embryonic development (totally random). Cells mitotically reproduce these embryonic cells have the same chromosome inactivated. An interesting example of this phenomenon is that color blindness (human characteristic that is linked to sex) when given to women sometimes have color blindness in one eye but not the other.

Lissencephaly smooth or brain syndrome is characterized by a brain in which the grooves are absent and folds. The reason for this rare disease is the lack of nerve cell migration toward the cortex during embryonic development. It is caused by a mutation in a gene called “double blind”, located on the X chromosome, whose presence prevents migration. Men who are suffering from lissencephaly gene mutated (the person can not feed himself, walking, sitting, communicate, suffers seizures and ….., there is no cure).

In carrier females heterozygous gene that prevents migration because one of the X chromosomes of cells to migrate is off randomly, results in a cell “lottery” which depends on the degree of disability which has the person (enrolled, among others, epileptic symptoms), prenatal diagnosis for women’s case reveals if you have the mutation but not the degree of disability.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

Genes and chromosomes, Mendelian Inheritance No

In addition to the complications of the polygenic control or pleiotropy there are other cases in which the percentages of Mendelian inheritance are not met: cytoplasmic inheritance and linked mutations.


The “bound” occurs when the genes are on the same chromosome. Remember that sex-linked genes are located on the sex chromosome X. The associated groups are invariably the same number as the pairs of homologous chromosomes an organism possesses. Recombination occurs when the cross (crossing-over) breaks the relationship between the groups, as in the case of size and color of the wings of the body studied by Morgan. Chromosome mapping was based on the study of the frequency of recombination between alleles.
Since mutations may be induced (by radiation or chemicals), Morgan and colleagues could produce new alleles subjecting the fruit fly to mutagens (agents which cause mutations). The genes are located in specific regions of certain chromosomes, called locus (plural loci). A gene is therefore a specific segment of the DNA molecule.

Alfred Sturtevant, being a student in the laboratory of Morgan, postulated that crossing-over would be less common among genes adjacent to each other on the same chromosome and that it would be possible to plot the sequence of genes along the chromosome Fly fruit using the frequency of crossing-over.

The genetic map distance is expressed in units of mapping (mapping unit 100 = 1 recombination fertilized eggs, or a chance of 1% recombination).

The map to the chromosomes of Drosophila melanogaster is well known (link to the main map). In the diagrams of maps you can see for example that

eye color and long edges are far apart (as indicated by the existence of a greater number of recombinations between them)
the color of the eyes and the size of the wings are close (as indicated by the lower frequency of recombination between them).

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

cytoplasmic inheritance

We know that chloroplasts and mitochondria contain DNA, and whose genes control certain aspects of photosynthesis and respiration. The legacy of these genes is independent of sexual reproduction and usually takes place through the mother, denominating cytoplasmic inheritance.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

Reference: http://lib.znate.ru/docs/index-104616.html?page=4

polytene chromosomes

They are found in the salivary glands of the fruit fly (Drosophila). They are a hundred times larger than the chromosomes of cells from the body and when stained presented light and dark bands. Geneticists used this fact to correlate changes in chromosome bands with changes in Drosophila allowing assign a physical location to the genes of the same.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

Chromosomal abnormalities

Chromosomal abnormalities include inversion, insertion, duplication, and deletion. These are types of mutation. Since DNA is information, and that it has a starting point, an investment produces an inactive or altered protein. Also alters a deletion or duplication of the gene product.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

The modern concept of the gene

While Mendel speculated about the characters, we now know that genes are DNA segments encoding a specific protein. These proteins are responsible for phenotype expression. The basic principles, such as described by Mendel, segregation and independence of the characters are applicable even in cases of sex-linked inheritance.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

Here we can see the structure of an X chromosome , it is a chromosome where genetic information is carried and genetic information  is found in DNA. Reference: http://elregalodelaherencia.blogspot.mx/2013_09_01_archive.html


The seven pairs of characters Mendel exhibited complete dominance, which is not as common as you might think. There are other possibilities:

Co-dominant and multiple alleles

Codominant alleles

are cases where, in heterozygotes, expressed both genotypes present, ie it is possible to observe the two phenotypes. An example of multiple and codominant alleles is ABO system that classifies blood. The blood compatibility is determined by a set of three alleles: Ia, Ib and I0 at a locus, combinations produce different types or phenotypes four blood: A, B, AB and O. The multiple alleles originate from different gene mutations on the same . A and B are codominant on O.

In codominancia both alleles are expressed. The heterozygous for both alleles expressing dominant characters. AB blood type has on the surface of red blood cells both antigens. Since none is dominant over the other and both are dominant relative to O are said to be codominant.

The only possible genotype for a person with type O is OO.
The type A can have an AA or AO genotype.
Type B, genotype BB or BO.
Type AB has only genotype (heterozygous).

incomplete dominance

Incomplete dominance is a condition in which neither allele is dominant over the other. The condition is recognized for expressing heterozygous an intermediate phenotype in relation to parental phenotypes. If a red camellia plant is crossed with a plant with white flowers, the progeny will be all pink. When a rose pink crosses another, the offspring is 1 red, 2 pink, and white.

Interactions between genes

While one gene makes one protein, usually the protein interacts with other, in reality most of the phenotypic characteristics result from the interaction of many different genes of an organism.
It may be that a completely different phenotype when a characteristic is affected by two or more different genes, appear. For example the crest of hens is determined by two genes Rr and Pp.

RR or Rr crest rosette
PP or PP pea ridge
But when P and R appear together in the same individual the result is a ridge in walnut (new phenotype)

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes


Epistasis is the term used when a gene the expression of other masks. If the A gene masks the effect of B is said that A is epistatic with respect to B. Bateson described a different phenotypic ratio in the color of flowers (purple or white) sweet pea scent, which could not be explained by the laws of Mendel. This ratio was 9: 7 instead of 9: 3: 3: 1 is expected on a dihybrid cross between heterozygotes. What happens is that when the two genes (C and P) in any of them homozygous recessive (cc or pp) are epistatic (or are hiding) the other. For there to purple flowers C alleles must be present and P.

Reference information:



Reference: http://www.mhhe.com/cgi-bin/netquiz_get.pl?qfooter=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195fq.htm&afooter=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195fa.htm&test=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195q.txt&answers=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195a.txt

Gene expression and environment

Phenotypic expression is the result of its interaction with the environment.
Siamese cats have their extremities dark due to temperature effects in the product of gene expression (in this case an enzyme). The enzyme involved in pigment production only works at the low temperature of the extremities.

polygenic inheritance

Polygenic inheritance is responsible for many characters that seem simple from the surface together. Many characters such as weight, shape, height, color and metabolism are governed by the cumulative effect of many genes The polygenic inheritance is not expressed at all as discrete characters, as in the case of Mendelian characters. Instead recognized polygenic traits expressed as rankings for small differences (continuous variation). The result is a curve with a mean value at the peak and extreme values in both directions.
The height in humans is a type of polygenic inheritance. The height in humans is not broken. If one plots the different heights in this course, a continuous variation is evident, with an average height and extreme, very high and very low variations. When inheritance shows continuous variation because this is controlled by the additive effect of two or more pairs of separate genes. The inheritance of EACH gene follows the rules of Mendel.

Reference: highered.mheducation.com

Polygenic inheritance is distinguished by

1.-Quantified by measuring more than counting
2.-Two or more pairs of genes contribute to the phenotype
3.-The phenotypic expression covers a wide range
Human shown in
2.-Systemic Lupus Eritromatoso (Lupus) (link to an article regarding lupus and genetics)
3.-Weight (link to an article on the weight and genetics)
4.-Eye Color (link to an article about eye color)
6.-Skin color
7.-Many forms of behavior

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

In this picture we can see how the physical characteristics are part of the inheritance. Reference: http://cdn.media.discovermagazine.com/~/media/Images/Issues/2013/May/trait-1b.jpg?mw=900


Pleiotropy known by the effect of a single gene in more than one characteristic. Sickle cell anemia is a human disease in tropical areas where malaria is common. Individuals who suffer have countless problems due to pleiotropic effect of the allele for sickle cell anemia.

Reference information: http://www.biologia.edu.ar/genetica/genet2.htm#genes

Reference: http://mumtazticloft.com/PigeonGenetics1.asp

What is DNA?

DNA is the genetic code that acts as the book of recipes to tell our bodies how to grow and develop. Our genetic code is very similar, even among people who are not related.All share 99.9% of our DNA!

Only 0.1% of our DNA is different from others. However, this small difference is what makes us unique. That means we all share most of the written cookbooks our information, but there are some variations in recipes. Every cell in the human body (we have trillions of cells) contains our entire genetic code of DNA. While DNA is very small, contains a lot of information.

It is the Deoxyribonucleic Acid. Is a molecule present in almost all of our cells containing genetic information. This molecule has the code to determine all the features and operation of an individual. It is also responsible for transmitting the information of who we are our children, the molecule of heredity. As we see, the key word is “information”.

Each DNA molecule is a kind of very long word, a double helix formed by a specific combination of four letters, A (adenine), T (thymine), C (cytosine) and G (guanine). As we see, something extremely simple, as is the combination of only four letters, leads to something as complex as a living being.

Reference information: 



Each DNA molecule is a kind of very long word, a double helix formed by a specific combination of four letters, A (adenine), T (thymine), C (cytosine) and G (guanine). As we see, something extremely simple, as is the combination of only four letters, leads to something as complex as a living being.
Each DNA molecule is a kind of very long word, a double helix formed by a specific combination of four letters, A (adenine), T (thymine), C (cytosine) and G (guanine). As we see, something extremely simple, as is the combination of only four letters, leads to something as complex as a living being. Reference image: http://www.astrochem.org/sci/Nucleobases.php

This video explains some things we do not know about genetics.

Reference: https://www.youtube.com/watch?v=bVk0twJYL6Y&app=desktop

What is RNA?

It is the ribonucleic acid. It is a very similar molecule to DNA but performs other functions. Basically it is the molecule that “media” between DNA and proteins. DNA, as we have seen, carries information from him and proteins are made. But by itself is not capable of interacting with cell structures that act as protein factories. Here comes the RNA to “help”.

RNA is also able to perform other actions within the cell. Some are regulatory RNA, participating in cellular activities as a driver, saying when a gene is to be converted into protein and when not.

Reference information: http://dciencia.es/adn-genes-cromosomas/

ibonucleic acid (RNA) functions as genetic messengers and builders of the cellular world. Reference image: http://www.scienceprofonline.com/genetics/ribonucleic-acid-rna-structure-and-function.html

This video explains what RNA is

Reference: https://www.youtube.com/watch?v=PFP0WDfoaR0&app=desktop

What is a protein?

Proteins are molecules that “do the work”. Bricks are formed by very different from those that form DNA or RNA. In this case they are called essential amino acids and there are 22 combination which gives rise to different proteins.

To give you an idea of the functions of proteins: the muscles are composed essentially of protein, the hair too; hormones are proteins, saliva proteins is full, blood coagulated by the action of them also …
DNA, which contains the information, passes this information to RNA, from which yes and proteins, which are molecules that carry out functions that we see in our body are manufactured.

Finally, an example. All human beings have a gene called TYR. This gene is located on chromosome number 11 of the nucleus of our cells. Encodes a protein called “tyrosinase”. This protein is responsible for one of the stages of production of melanin, which is the substance that gives color to our skin, hair and eyes. Well, when DNA Tyr gene is altered, mutated, that error is transferred to RNA, which in turn to an “anomalous” tyrosinase will lead. The protein will have a letter changed in your code and it’s like instead of “tyrosinase” we write “pirosinasa” for example. That causes can not carry out its function and causes what is known as albinism.

Reference information: http://dciencia.es/adn-genes-cromosomas/

Reference: http://breakingmuscle.com/nutrition/how-much-protein-do-you-need-science-weighs-in

This video explains what proteins are

Reference: https://www.youtube.com/watch?v=PFP0WDfoaR0&app=desktop

*Albinism is a genetic condition in which there is a congenital absence of pigment (melanin) of eyes, skin and hair in humans and other animals caused by a mutation in the genes.

How is that genes cause illness?

Genes are not intended to cause disease. The vast majority of our genes help the body grow and function like a healthy person, all the time from pregnancy to adulthood. It is an abnormal change in a gene that causes a disease in a person or causes a person is at risk of getting a disease.

There are other causes Huntington’s disease; if a person has the mutation will develop the disease. Other changes in DNA cause only a person is at risk of developing a disease. We call these variations or polymorphisms. For example, people with certain polymorphisms in the APOE gene have an increased risk of developing Alzheimer’s disease. It is possible that people with this specific change never develop Alzheimer’s disease, and it is also possible that people without this change develop Alzheimer’s disease without it. This shows that although our genes can tell us if we are at risk of developing many diseases, not always predict whether or develop the disease. Our environment and lifestyle, just like our genes, are very important in predicting the risk of developing the disease factors.

How Genes are transmitted in a family?

You get half the genes from his mother and half from their father.
Since genes largely determine the physical appearance, you his father looks so much like her mother, but is a completely unique mix. You also transmits half their genes to their children. But there is no way to choose which genes can be transmitted. The genes can be transmitted within a family in different patterns of inheritance. Examples include autosomal dominant, autosomal recessive or X-linked genetic Many syndromes caused by genetic mutations follow one of these patterns of inheritance.

Autosomal recessive pattern of inheritance

Cystic fibrosis (Cystic fibrosis, CF) is a genetic disease of the lungs and digestive system caused by mutations in the CFTR gene. It has an autosomal recessive pattern of inheritance. This means that both his father and his mother must be carriers of the CFTR mutation to have a child with cystic fibrosis. Carrier parents of cystic fibrosis have a 25% chance of having a child with the disease.

Autosomal dominant inheritance

There are many diseases that follow this pattern of inheritance. For an autosomal dominant condition, a person has a mutation in only one copy of the gene associated with the disease. For example, Marfan syndrome is an autosomal dominant genetic condition that causes abnormalities in the joints, heart and eyes. People with this condition are usually very tall and thin. People with Marfan syndrome can lead a normal and healthy life, but have a higher risk of cardiac complications dangerous, so you should visit the doctor regularly. A person with Marfan syndrome have a mutation in one copy of FBN1 gene. This mutation causes the FBN1 gene does not function normally and causes the characteristics of the condition. When a person with Marfan syndrome have children, you can transmit any copies of the FBN1 gene: the one with the mutation and not have the mutation. If your child inherits the copy with the mutation, also have Marfan syndrome. If your child inherits a copy without the mutation, will not have Marfan syndrome. Therefore, each child has a 50% chance of having Marfan syndrome.

Pattern of X-linked inheritance

The last type of inheritance pattern is called X-linked is called X-linked because the gene mutation that causes the disease is located on the X chromosome Girls have two copies of the X chromosome, while males have a alone. They have a Y chromosome instead of a second chromosome X. Therefore, it is possible that a girl with a gene that does not work (due to a mutation) in one of their X chromosomes is not affected, because you have another X chromosome which compensates the gene is not working. But a man with the same non-working gene on their X chromosome is affected by the condition. This is because it does not have a second copy of the gene to compensate for the gene does not. An example of X-linked disorder is a muscular disease called Duchenne muscular dystrophy (DMD). Usually, only boys DMD. A man with DMD have a mutation in the DMD gene on its chromosome X. A girl with the same mutation in the X chromosome does not have the disease, and having a second copy of the DMD gene that functions in the other chromosome X. This case, the girls will be carriers. A woman who is a carrier is at risk of having children with DMD. Each of their children has a 50% chance of inheriting the X chromosome with the DMD gene does not. If your child is male and inherits the gene that does not work, develop DMD.

What is genetic testing?
Genetic testing is a type of medical test that analyzes DNA of a person. Genetic tests are used to diagnose or determine the type of disease a person has.

Genetic testing can also be used to determine whether a person is a carrier of a disease or if one is present illness in his family. There are many types of genetic testing. Some tests a specific gene analyzed directly, while other analyzes the packet structure of our DNA (chromosomes). Usually, the person requesting genetic testing is a physician, often a geneticist. A geneticist is a specialized physician who diagnoses and treats genetic syndromes.

Tests to diagnose a genetic condition

One of the main ways in which genetic testing is used to diagnose a genetic condition. A person who shows signs or symptoms of a particular disease may need genetic testing performed for the diagnosis is made. That is because the disease is caused by a change, or mutation in DNA. A physician, usually a specialist in genetics (geneticist) asks these types of tests. Frequent testing for diagnosis are the chromosomal karyotype, chromosome microarray or single gene testing.

A chromosome karyotype simply analyzes the number and amount of chromosomes that a person has. Chromosomes are packets of DNA. Normally, humans have 46 chromosomes. However, some genetic disorders are caused by an increase or decrease in the number of chromosomes. Down syndrome is a genetic condition in which the person has an extra chromosome No. 21. Having that extra chromosomal material generates the characteristics of Down syndrome include some degree of mental retardation, short stature and heart problems at birth.

The multigene chromosome microarray is a genetic test that also analyzes chromosomes, but a multigene microarray analyzes chromosomes in much greater detail. Multigenic microarray can determine if additional DNA very small or missing pieces in a person. There are many genetic diseases caused by these relatively small imbalances DNA.

A single gene genetic test is a test that examines only a specific gene associated with a genetic condition known. For example, we know that a genetic condition called Huntington (Huntington disease, HD) disease is caused by the HD gene. HD gene mutations cause a person to develop abnormal movements and impaired thinking and memory and eventually leads to death. If a person has symptoms of HD, a geneticist probably ask for a genetic test to analyze specifically the HD gene to determine if there is a mutation in the gene.

Test carrier

Carrier testing is a type of genetic test used to determine whether a person is a carrier of a genetic condition. Carriers of genetic diseases not normally associated with symptoms being carriers. In fact, most people have no idea they are carriers of a genetic condition. A person who is a carrier is so called because she does not have the disease but are at risk of having children who have the disease. Sickle cell disease is an example. Sickle cell disease occurs when a person has TWO mutations, one on each copy of a specific gene (HBB gene). A person with sickle cell disease inherited one copy of the mutation from each parent. Her mother and father, who had sickle cell disease, were carriers of the condition. If both parents are carriers of a genetic condition, there is 1 in 4 (or 25%) chance that each child with the condition. There are many other diseases that a person can carry. The odds that a person is a carrier of one of these conditions often depend on their ethnicity. For example, a person of Puerto Rican origin has around 1 in 21 chance of being a carrier of a type of albinism called Hermansky-Pudlak syndrome, while a person originating from northern Europe has about 1/29 chance of being a carrier of a disease called cystic fibrosis. When a couple is thinking about having children, it is important to talk to your doctor about the possibility of being carriers of a genetic condition and ask for carrier testing.

Tests to determine the risk of future disease

There are some genetic tests to determine if a person is at risk of developing a disease in the future. There are very few conditions for which is available this type of test. These tests are usually offered to people who have very strong family history of a condition such as colon, breast cancer or Alzheimer’s disease cancer, but still do not have the condition. Usually a very important decision on a test done like that, because some people might not want to know if it is possible to develop in the future a disease that do not yet have. For some conditions such as Alzheimer’s disease, there is no prevention or cure. For other diseases, they can take steps to prevent the disease if a person knows that is at risk. For example, genetic testing for BRCA genes is available for women with a strong family history of breast cancer. Women who have a mutation in one of the BRCA genes have a high risk (up 80% over its life) of developing breast cancer. It is recommended that women with a BRCA mutation begin screening studies performed much earlier than other women.

In the future, doctors may use most genetic tests to predict a person’s risk of developing a disease. When performing genetic tests like this, a doctor may be able to determine a person’s risk of developing many common diseases and preventive measures can be taken. Therefore it is extremely important to study the genetic causes of disease. If we understand what the genetic causes, doctors can determine who is at risk of developing the disease based on their genes.

Reference information: http://geneticsawareness.org/esgen/aprende-acerca-de-la-genetica/que-son-las-pruebas-genetica

General references:

  1. http://www.biologia.edu.ar/genetica/genet2.htm#genes
  2. http://publications.nigms.nih.gov/insidethecell/ch4_phases_allbig.html
  3. https://www.youtube.com/watch?v=C6hn3sA0ip0&app=desktop
  4. http://www.ib.bioninja.com.au/higher-level/topic-10-genetics/101-meiosis.html
  5. https://www.youtube.com/watch?v=-DLGfd-Wpr4
  6. http://www.biologia.edu.ar/genetica/genet2.htm#genes
  7. https://www.youtube.com/watch?v=5MQdXjRPHmQ&app=desktop
  8. http://dciencia.es/adn-genes-cromosomas/
  9. http://www.maxisciences.com/chromosome/wallpaper
  10. https://www.youtube.com/watch?v=B_PQ8qYtUL0&app=desktop
  11. http://ghr.nlm.nih.gov/handbook/basics/chromosome http://dciencia.es/adn-genes-cromosomas/
  12. http://horadefisioterapia.blogspot.mx/2013/07/un-metodo-para-desactivar-el-cromosoma.html
  13. https://www.youtube.com/watch?v=xUrlreMaUrs&app=desktop
  14. http://www.dailymail.co.uk/sciencetech/article-2104924/Male-Y-chromosomes-NOT-die-shows-monkey-study.html
  15. http://www.biologia.edu.ar/genetica/genet2.htm#genes
  16. http://lib.znate.ru/docs/index-104616.html?page=4
  17. http://www.biologia.edu.ar/genetica/genet2.htm#genes
  18. http://elregalodelaherencia.blogspot.mx/2013_09_01_archive.html
  19. http://www.ecured.cu/index.php/Epistasis
  20. http://www.mhhe.com/cgi-bin/netquiz_get.pl?qfooter=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195fq.htm&afooter=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195fa.htm&test=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195q.txt&answers=/usr/web/home/mhhe/biosci/genbio/maderbiology7/student/olc/art_quizzes/0195a.txt
  21. http://www.biologia.edu.ar/genetica/genet2.htm#genes
  22. http://cdn.media.discovermagazine.com/~/media/Images/Issues/2013/May/trait-1b.jpg?mw=900
  23. http://www.biologia.edu.ar/genetica/genet2.htm#genes
  24. http://mumtazticloft.com/PigeonGenetics1.asp
  25. http://geneticsawareness.org/esgen/aprende-acerca-de-la-genetica/que-es-la-genetica
  26. http://dciencia.es/adn-genes-cromosomas/
  27. http://www.astrochem.org/sci/Nucleobases.php
  28. https://www.youtube.com/watch?v=bVk0twJYL6Y&app=desktop
  29. http://dciencia.es/adn-genes-cromosomas/
  30. http://www.scienceprofonline.com/genetics/ribonucleic-acid-rna-structure-and-function.html
  31. https://www.youtube.com/watch?v=PFP0WDfoaR0&app=desktop
  32. http://breakingmuscle.com/nutrition/how-much-protein-do-you-need-science-weighs-in
  33. https://www.youtube.com/watch?v=PFP0WDfoaR0&app=desktop
  34. http://geneticsawareness.org/esgen/aprende-acerca-de-la-genetica/que-son-las-pruebas-genetica
  35. http://www.quimicaweb.net/Web-alumnos/GENETICA%20Y%20HERENCIA/Paginas/1.htm


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