Chromosomal Genetics

Question 1

The Chromosomal Theory of Inheritance:

Answer 1

Genes @ specific sites (Loci)
Homologous chromosomes = Homo loci
Laws of IA & Segregation

Question 2

Morgan and his fruit flies led him to the conclusion that…

Answer 2

Eye color was linked to sex

Question 3

Why did it show in males?

Answer 3

Only one X chromosome, no wild-type allele present to mask it.

Question 4

Which sex chromosome is smaller?

Answer 4

Y

Question 5

Mammals are on the __ sex system.

Answer 5

XY
XO - Insects
ZW - Birds, fish

Question 6

A gene located on either sex chromosome is called a…

Answer 6

Sex-linked gene
On y = y-linked
On x = x-linked

Question 7

Fathers pass x-linked alleles to their…

Answer 7

Daughters, not to their sons.

Question 8

Mothers pass x-linked alleles to…

Answer 8

Sons & daughters

Question 9

If an x-linked trait is due to a recessive allele, a female will only express the phenotype if she is:

Answer 9

Homozygous for the allele

Question 10

Any male receiving a recessive allele from his mother will…

Answer 10

Express the allele

Question 11

Who has more x-linked recessive disorders? M or F?

Answer 11

Males

Question 12

In females with two X chromosomes, one is __________.

Answer 12

Inactivated

Question 13

Inactivated X chromosome becomes a:

Answer 13

Barr Body

Question 14

T/F X inactivation is Random.

Answer 14

TRUE

Question 15

As a consequence of X inactivation, females consist of a __________ of two types of cells.

Answer 15

Mosaic - 2 Phenotypes

Question 16

An easy observation of X inactivation in mammals?

Answer 16

Calico Cat!

Question 17

Why the cat?

Answer 17

Color genes on X chromosome. Some shut down, some don’t.

Question 18

Can male cats be Calico?

Answer 18

Yes - If nondisjunction occurs and the male has XXY chromosomes.

Question 19

If a male has XXY chromosomes we can tell by:

Answer 19

Presence of Barr Bodies

Question 20

If an female has genes for color blindness on one X chromosome will it be observable?

Answer 20

Maybe not - if X inactivation silences color blind gene, then no.

Question 21

This phenomena is known as…

Answer 21

Incomplete Silencing