INDEPENDENT WORK of the STUDENTS

Date: 2015-10-07; view: 430.

ORGANIZATIONAL STRUCTURE of the PRACTICAL STUDY

Sex-linked inheritance

The sex chromosomes (heterosomes) not only have the genes for sex but they also carry for some characters, such are said to be sex-linked, and they may be possessed by either sex. The inheritance of these characters is different from the inheritance of those characters whose genes are on autosomes. The pattern of heredity of sex-linked characters does not follow Mendel's laws.

The sex-linked characters in human beings are:

X-linked recessive. For instance, hemophilia, color blindness, and kind of night-blindness.

X-linked dominant. For instance, vitamin D resistant rickets.

Y-linked. For instance, a lot of hairs of ear (hypertrichosis).

THEORETICAL QUESTIONS NECESSARY FOR ACHIEVING of the PRACTICAL CLASSES

1. Original positions of the Chromosome theory of inheritance by Т. Morgan.

2. Linkage inheritance of the genes. The groups of linked genes. Complete and incomplete linkage of genes.

3. Genetic maps of chromosome. Method of their building.

4. Classification of the mechanism of definition of the sex.

5. Sex-linked inheritance

To acquisition of practical skills of using the genetic laws solve tasks.

1. Hyperplasia of teeth enamel is inherited as dominant, X-linked character. Parents are ill, but son was born without illness. What are the genotypes of parents? What phenotype will have the second sun?

2. Hypertrichosis of ear is X-linked character. What is possibility of birth the child with illness, if his father has this character?

3. Lack of sweat's glands is X-linked, recessive character. Albinism is recessive autosome linked character. Parents are healthy, but their son has two diseases. Indicate the possible genotypes of the parents. What is possibility of following birthing of sick and healthy children?

4.Woman has 0 group of blood and normal vision. She was married to man with color blindness (daltonism) and A group of blood. What must be the genotypes of parents, if the child has daltonism and 0 group of blood?

5. The distance between genes A and B within a chromosome is equal 10 M (Morgan), the distance between genes A and C is equal 3 M, the distance between genes B and C is equal 7 M, the distance between genes D and B is equal 2 M, and the distance between genes D and C is equal 5 M. Build the chromosome map.

6. The genes A and B are localized on distance of 20 M. Define genotypes of F1 and their probability, if parents are heterozygotes.

P AB//ab x Ab//aB

G n.c.o. AB, ab Ab, aB

40% 40% 40% 40%

c.o. Ab, aB AB, ab

10% 10% 10% 10%

F1

Answer. The probability genotypes of F1 is:

Ab//Ab 16% AB//Ab 16% AB//Ab 4% Ab//Ab 4%

Ab//aB 16% AB//aB 16% AB//aB 4% Ab//aB 4%

Ab//AB 4% AB//AB 4% AB//AB 1% Ab//AB 1%

Ab//Ab 4% AB//Ab 4% AB//Ab 1% Ab//Ab 1%

7. Genes of eliptocytosis and Rh factor are localized in the first chromosome of human being on distance of 3 M. What gametes are formed by woman, and what is probability of their forming, if genes of eliptocytosis and Rh + factor were inherited from her mother. Her father is healthy and has Rh – factor.

8. The genes of color blindness and hemophilia are X-linked. The distance between these genes is equal 9,8 M (Morgan). The mother of wife has the both of pathological traits. But the father of wife is healthy. The husband is healthy too. What is probability of birthing of healthy and sick children?

9. Genes of cataract and polydactylia are autosome and dominant. They are complete linked each other. Wife inherited gene of polydactylia from mother and gene of cataract – from father. Her husband is healthy. What is probability of birthing of healthy and sick children?