Classic Mendelian Genetics II

Question 1

In veterbrates, what does the gonad have the potential to develop into?

Answer 1

either a testis or an ovary

Question 2

homomorphic?

Answer 2

female has the genotype XX

Question 3

heteromorphic?

Answer 3

male has genotype XY

Question 4

Describe the difference between the X and Y chromosome:

Answer 4

X chromosome is larger and longer than the Y chromosome

Question 5

What are the designated sex chromosomes in birds?

Answer 5

Z and W

Question 6

male genotype in birds?

Answer 6

homomorphic - ZZ

Question 7

female genotype in birds?

Answer 7

heteromorphic (ZW)

Question 8

What is the sry?

Answer 8

sex-determining region of the Y chromosome (a single gene)

Question 9

Sry expression…

Answer 9

testes –> testosterone –> masculine brain phenotype

Question 10

No sry expression…

Answer 10

Ovaries –> relatively low testosterone –> female brain phenotype

Question 11

What does the sry gene encode?

Answer 11

a protein called testis-determining factor (TDF)

Question 12

XY with a defective Sry gene becomes….

Answer 12

female

Question 13

An XX mouse inserted with the Sry gene transgenically added to another chromosome becomes…

Answer 13

male

Question 14

Males with XY have only one copy of a gene so they are?

Answer 14

hemizygous

Question 15

Females that have two X chromosomes may have?

Answer 15

Heterozygous X chromosome alleles

Question 16

The gene for Factor VIII is involved in blood clotting cascade is X/Y linked?

Answer 16

X

Question 17

What is haemophilia A?

Answer 17

a disease where an X-linked recessive trait that is non-functional so no Factor VIII is produced resulting in impaired blood clotting

Question 18

Canine Muscular Dystrophy in Golden Retrievers is?

Answer 18

an X-linked recessive trait

Question 19

Lyonisation?

Answer 19

During embryonal development, one of each X chromosomes is randomly inactivated in female cells
so that half of them have an active Xm chromosome and half have an active Xp chromosome
All cells derived from those embryonal cells will have the same X chromosome inactivated forming a mosaic like pattern

Question 20

What is a Barr body?

Answer 20

the inactive X chromosome in a female somatic cells

Question 21

What is a gonad?

Answer 21

the primary reproductive organs

Question 22

Where is the sry gene located?

Answer 22

Y chromosome