sex-linked traits

Question 1

In the early 1900’s, a researcher named Thomas Morgan discovered that sex chromosomes are either

Answer 1

X or Y

Question 2

For the 23rd pair of chromosomes,

Answer 2

females have XX and males have XY.

Question 3

During oogenesis, females will only produce eggs with an

Answer 3

X chromosome

Question 4

During spermatogenesis, male produce sperm with either an

Answer 4

X or Y chromosome Therefore, the father’s sperm determines the sex of the baby.

Question 5

The X chromosome is physically larger than the Y chromosome.

Answer 5

Therefore, the X chromosome can carry more genes than the Y chromosome.

Question 6

The presence of a gene on a sex chromosome (X or Y) is called sex linkage.

Answer 6

Sex-linked traits are physical traits whose genes are on the X or Y chromosome.

Question 7

Examples of sex-linked traits:

Answer 7

Colorblindness
Hemophilia
Muscular dystrophy

Question 8

A female (having two X chromosomes) can be

Answer 8

AA, Aa, or aa. This is a complete dominance type of inheritance.

Question 9

A female genotype is written:

Answer 9

XAXA (Homozygous dominant)
XAXa (Heterozygous or carrier)
XaXa (Homozygous recessive)

Question 10

But a male has only one X chromosome.

Answer 10

Therefore, whichever gene he gets (dominant or recessive) will determine his phenotype.

Question 11

a male genotype is writte

Answer 11

XAY (Dominant)
XaY (Recessive)
No letters are written with Y’s.
Males can never be carriers.

Question 12

Punnett squares for sex-linked traits will use

Answer 12

X’s and Y’s. All are complete dominance.