Sex linked genetic traits

Question 1

how many sex chromosomes do female mammals have

Answer 1

they have two x chromosomes. each ovum produced by meiosis will have one x chromosome

Question 2

how many sex chromosomes do male mammals have

Answer 2

they have one x and y chromosomes each. sperm produced by meiosis will either have an x or a y chromosome

Question 3

are some genetic traits determined by genes on the sex chromosomes.

Answer 3

yes

Question 4

why does the y chromosome have fewer genes than the x chromosomes?

Answer 4

The Y chromosome is shorter than the x chromosome so it has fewer genes

Question 5

why are some genetic traits more common in males than in females

Answer 5

genes on the x chromosome do not have a corresponding gene in the y chromosome, due to this some genetic conditions are more common in males than in females

Question 6

what are some examples of sex-linked traits

Answer 6

Colour-blindness and haemophilia

Question 7

what are the conditions for a recessive trait to express itself in a female

Answer 7

• the recessive trait needs to be carried in an x chromosome
• the female must have two recessive alleles

Question 8

what is a carrier

Answer 8

a female is known as a carrier when they have a recessive allele but it is masked by a dominant allele eg X^BX^b
she is able to pass the trait off to her offspring but does not have it herself

Question 9

For recessive traits carried on the X chromosome, a male only needs to have one recessive allele to show the trait WHY?

Answer 9

because there is no second allele to mask the recessive allele

Question 10

define hemizygoues

Answer 10

the term hemizygoues is used to describe genes on the X chromosome in males, as there is only one X chromosome.