Sex linked genetic traits
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how many sex chromosomes do female mammals have
they have two x chromosomes. each ovum produced by meiosis will have one x chromosome
how many sex chromosomes do male mammals have
they have one x and y chromosomes each. sperm produced by meiosis will either have an x or a y chromosome
are some genetic traits determined by genes on the sex chromosomes.
yes
why does the y chromosome have fewer genes than the x chromosomes?
The Y chromosome is shorter than the x chromosome so it has fewer genes
why are some genetic traits more common in males than in females
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
what are some examples of sex-linked traits
Colour-blindness and haemophilia
what are the conditions for a recessive trait to express itself in a female
• the recessive trait needs to be carried in an x chromosome • the female must have two recessive alleles
what is a carrier
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
For recessive traits carried on the X chromosome, a male only needs to have one recessive allele to show the trait WHY?
because there is no second allele to mask the recessive allele
define hemizygoues
the term hemizygoues is used to describe genes on the X chromosome in males, as there is only one X chromosome.