Sex linked traits Flashcards
What determins if the baby is a boy or not
The SRY gene
What happens if the SRY gene is present
Testes form
What happens if the SRY gene is absent
Ovaries form
Why is the x chromosome bigger than the y chromosome
The x chromosome has way more genes than the y chromosome
Do both men and women have x chromosomes
Yes, women have 2 x chromosomes and men have 1 x chromosome
What are sex linked traits
Traits on sex chromosomes, usually on the x chromosome
Does a recessive trait on the x chromosome show more on men or women and why?
Men because they only need 1 copy of the recessive allele while females need 2
Do recessive x linked disorders happen more in men or women, why?
men because the Y chromosome can not help as it does not have a superscript
Can sons inherit x-linked disorders from their father? why?
No because the father only gives their son the Y chromosome
How are dominant alleles in sex linked traits represented
With capital chromosomes and capital alleles (ex: X ᴴX ᴴ or X ᴴ Y)
How are recessive alleles in sex linked traits represented
With capital chromosomes and lower case alleles (X ʰX ʰ or X ʰ Y)
What is a carrier
Someone who does not have a sex linked disorder but have it in their genotype and can pass it to their kids
(ex: Xᴴ Xʰ)
In humans, the recessive allele that causes a form of red-green colour blindness (b) is found on the X chromosome. Find the genotype and phenotype of the F1 gen from a father who had colour vision and a mother who is heterozygous for colour vision.
Genotypes: 25% X ᴮ X ᴮ
25% X ᴮ Y
25% X ᴮ X ᵇ
25% X ᵇ Y
Phenotypes: 100% girls have colour vision
50% boys have colour blindness
What are pedigrees
Family tree of phenotypes
What do the roman numerals on the left side of the pedigrees mean
The generations
What do the numbers under each shape mean
The individuals in that generation
What does the square shape represent
men
What do the circles represent
Women
What do the coloured in shapes mean
Affected individuals, have the trait/disease
What do we track using pedigrees
Autosomal dominant and autosomal recessive
How can we know if a pedigree is autosomal dominant
-There is atleast one affected parent
-genotypes of affected individuals are either homozygous or heterozygous dominent
How can we know if a pedigree is autosomal recessive
-Parents dont have to be affected -genotypes of affected individuals are homozygous recessive
How do we solve pedigrees
- Determine if it is autosomal dom or autosomal recessive
- Determine who has the disorder and fill in their genotypes
- Determine who doesnt have the disorder and fill in their genotypes
