4.4 (Test 1) Flashcards
What are Y-linked traits?
Traits caused by mutations in the MSY region of the Y chromosome.
How are Y-linked traits inherited?
They pass only from father to son and never through females.
Why are there so few Y-linked traits?
The Y chromosome has very few genes and has a limited effect on phenotype.
What are the main functions of the Y chromosome?
Male determination, Sperm formation, Male viability
Why do XX females function without a Y chromosome?
The Y chromosome has a limited effect on phenotype beyond male traits.
Do all sex-related traits come from X and Y chromosomes?
No, some autosomal genes cause differences between males and females.
What are sex-limited traits?
Traits that affect a structure/process found only in one sex.
Can a gene be autosomal but still sex-limited?
Yes, because the trait only appears in the sex that has the relevant structure.
What is the ‘stuck’ mutation in fruit flies?
A recessive autosomal mutation that prevents males from retracting their penis after mating.
Why does the ‘stuck’ mutation only affect males?
Females don’t have penises or claspers, so they aren’t affected.
Can an autosomal gene be sex-limited?
Yes, if it controls a trait that only appears in one sex.
What are sex-influenced traits?
Traits that appear in both sexes, but their expression differs due to hormones.
What causes male pattern baldness?
An autosomal gene influenced by sex hormones.
How does inheritance of male pattern baldness differ between sexes?
Heterozygous Males → Bald in their 20s; Heterozygous Females → No major hair loss; Homozygous Males & Females → Both bald (but later in females).
Is pattern baldness dominant or recessive?
Dominant in males, recessive in females.
What does baldness in John Adams & John Quincy Adams suggest?
Male pattern baldness likely involves an autosomal gene.
What are sex-linked traits?
Traits caused by genes on the X chromosome.
How do X-linked traits inherit differently in males and females?
Males inherit their father’s Y chromosome and mother’s X chromosome; Daughters inherit their father’s X chromosome; Males are hemizygous (only have one X chromosome).
How does X-inactivation affect female gene expression?
It ensures that males and females produce equal amounts of X-linked proteins.
Do all alleles work the same in males and females?
No, their effects depend on chromosomes and hormones.
