Activity:
1 .- Print this information
2 .- In Book lists and lists the characteristics of the two types of chromosomes that are mentioned here.
3 .- Explains how sex is genetically determined in humans. 4 .- Equematiza
two basic types and subtypes of chromosomal abnormalities.
5 .- Name five diseases or syndromes caused by chromosomal abnormalities of type numeric.
6 .- With the support of the punnet box says the following: If the father is a hemophiliac ( x Y) and healthy non-carrier mother (XX) (is healthy and does not carry genes in addition to forward disease), why their daughters are healthy carriers and children will be healthy without being carriers. LOS
CHROMOSOMES
The number of chromosomes of somatic cells is always even, since each somatic cell has two sets of chromosomes and each chromosome of a series has its counterpart in the other. The chromosomes are homologous because they come from each parent. That is why any information for the same characters but not necessarily the same information, since one parent was unable to provide an allele for a gene and the other parent to another.
Autosomes CHROMOSOME TYPES: chromosomes not involved in sex determination. Sex or heterocromosomas
: In many organizations, one pair of chromosomes counterparts is different from the rest.
SEX DETERMINATION IN HUMANS
during gametogenesis (formation of gametes, which have a single set of chromosomes, ie they are haploid) eggs produce females carrying an X chromosome, whereas in males, half of the sperm have an X chromosome and the other half, a Y chromosome The presence of a Y chromosome makes a male embryo to differentiate and develop as testes rather than ovaries. This indicates that there are genes (holándricos) typical of males in the Y chromosome, that are not present in X.
determination system XY is proper to man and many others animals. Females being XX gametes will equal X chromosome, sex homogametic and males being XY, given two types of gametes, one X chromosome and one Y-chromosome The probability that at fertilization, the gametes join, be a combination XX (female) or XY (male) is 50%.
ZW determination system: in other species (butterflies, birds, for example) the opposite occurs, is homogametic males (ZZ) and females heterogametic (ZW).
XO Measurement System: other species (fish, many insects, amphibians) that have no Y chromosome, the sex determined by the number of X chromosomes, male XO and XX female.
genetic determination system: the sex determining genes are located in one or more chromosomes.
Measurement System Haploid / Diploid: other species (Hymenoptera: ants, bees, etc) the males are haploid (have only one set of chromosomes) and females are diploid can not speak of sex chromosomes
Measurement System by environment: species determine their sex by environmental factors, others are hermaphroditic. HEREDITARY DISEASES
Chromosomes are strands in a spiral that contains the DNA. Humans have 23 pairs of chromosomes. Some types of chromosomal alterations affecting the number of chromosomes, an entire chromosome or only a portion of it.
Errors rarely occur during replication of DNA are mutations that cause suffering chromosomes. These mutations can also be caused by high temperatures, radiation and various chemicals. Most chromosomal abnormalities that impair the body slide. These mutations are transmitted hereditarily and for this reason, the number of carriers of mutated genes tends to increase due to reproduction of species, but also tends to decrease because individuals with genetic mutations do not survive or reproduce less than their .
ANOMALIES CHROMOSOME
These can be inherited from the parent or may occur with no family history.
Although chromosomal abnormalities can be very complex, there are two basic types: numerical and structural. NUMBER
are subdivided into:
Euploidía is the alteration in the normal haploid number of an organism. Euploidía individuals have a number of "games" of homologous chromosomes different from usual. The euploidía can be of two types:
• Monoploidía: that organisms have haploid (n), means that only have one chromosome of each type.
• Polyploidy: the individuals have several complete sets of homologous chromosomes (triploid 3n, 4n tetraploidy ...). Aneuploidy
suffering in this group are the most common in humans. They occur when a single pair of chromosomes decrease or increase, these conditions are known as syndromes, and can affect both autosomes and sex chromosomes. Cells that have lost a chromosome monosomy (2n - 1) for that chromosome, while those with an extra chromosome showed trisomy (2n + 1) for the chromosome involved. The most common are: Down, Turner, Noonan, Klinefelter, Lesh-nylan. Almost all autosomal monosomy lead to death shortly after conception and only a few trisomies are viable. STRUCTURAL
involve changes in the structure of one or more chromosomes. They can be incredibly complex, but basically are:
• Deletions: they involve the loss of material from a single chromosome. The effects are serious, since there is loss of genetic material.
• Investments: takes place when two courts within the same chromosome and the intermediate segment rotates 180 ° (inverted) and re-unite, forming a chromosome that has the sequence structurally changed. Although the holder of an investment can be completely normal, you risk an embryo with a chromosomal imbalance. This is because an inverted chromosome has difficulty with its normal counterpart pair during meiosis, which can produce gametes containing chromosomes derived unbalanced if there is an unequal cross.
• Translocations: involve the exchange of material between two or more chromosomes. If translocation is reciprocal (balanced) the risk of problems for the individual is similar to that of investment. Problems arise when the translocation from a balanced parent gametes are formed that contain both products of translocation. When this gamete combines with a gamete normal of the other parent, the result is an unbalanced embryo which is partially monosomic for one chromosome and partially trisomic for the other. Structural alterations
Karyotype
numerical and structural abnormalities can be subdivided into two main categories: constitutive, those with which they are born, and learned, and changes arising secondary to other diseases such as cancer. HEMOPHILIA
is a recessive genetic disease linked to chromosome X that is the difficulty of the blood to clot properly. It is characterized by the appearance of internal and external bleeding due to partial deficiency of a clotting protein called antihemophilic globulin (clotting factor).
thus has a much higher prevalence in males, where it acts as a character holándrico:
▪ With a hemophiliac father and mother healthy non-carrier: 100% of their daughters will be healthy carriers (carrier allele inherited from the father), and 100% of the children will be healthy non-carriers (who are not receiving the X carrier).
▪ With a hemophiliac father and mother healthy carrier (heterozygous): 50% of daughters are healthy carriers and 50% of daughters will be hemophiliac (die as women can not have hemophilia). As for male children, 50% are hemophiliacs (they receive a single maternal X, which in this case is the carrier) and 50% will be healthy non-carriers (have received no default X). ▪
* With a healthy father and healthy carrier mother: 50% of daughters will be healthy non-carriers, and 50% will be healthy carriers. As for boys, as in the previous case, 50% are hemophiliacs and 50% will be healthy non-carriers.
* Note that there is no possibility of a healthy male carrier.
Hemophilia is a condition suffered by almost exclusively male, and almost all hemophiliacs are children of healthy mothers, who carry the gene, meaning that their ancestors existed a hemophiliac.
