Topic 4: Sex Linkage and Pedigrees Flashcards
females are _______
homogametic
males are ______
heterogametic
_______ are in most of our chromosomes
autosomes
______ chromosomes are differently represented in sexes
sex
wildtype (most common phenotype of a population) is denoted with a _____
+
males and females have different phenotypic ratios in F1/F2
reciprocal crosses give different results
“criss-cross inheritance”
these are all indicators of…
sex-linked inheritance
Thomas Hunt Morgan studied…
drosophila flies (fruit flies!)
______: transmission of recessive allele on the X chromosome
X-linked recessive
______: transmission of dominant allele on the X chromosome
X-linked dominant
______: transmission of recessive allele on autosomes (ex: aa)
autosomal recessive
______: transmission of dominant allele on autosomes (ex: AA, Aa)
autosomal dominant
______-______ traits: alleles are carried in both sexes but the phenotype only shows up in one sex
sex-limited
______-______ traits: inheritance patterns vary between the sexes even if the genotype is the same, usually influenced by hormone levels
sex-influenced
how does sex determination work in drosophila flies?
X:A (X:autosome) ratio
if X/A = 1, _______
if X/A <0.5, _________
if X/A 0.5-1, __________
- female
- male
- intersex
sex determination in mammals depends on…
presence of Y chromosome
sex determination in birds, some reptiles, certain fish, moths, and butterflies uses the ______ system
Z/W system
in the Z/W sex determination system, how are females defined?
ZW, heterogametic and hemizygous
in the Z/W sex determination system, how are males defined?
ZZ, homogametic
in the Z/W sex determination system, does Z or does W behave like X-linked genes in mammals?
Z-linked genes behave like X-linked genes
W-linked genes are _____ (only occur in females)
matrilineal
in roundworms and nematodes, they use X:A ratio to determine sex, a roundworm with the genotype XX would be _________
hermaphrodite, usually self-fertilizes
in roundworms and nematodes, they use X:A ratio to determine sex, a roundworm with the genotype X0 would behave as _________
male, and produce “super-sperm” that can outcompete sperm from hermaphrodites, which increases genetic variation!
true/false: you can’t have multiple sets of sex chromosomes involved in sex determination
false, platypus have 5 pairs of sex chromosomes! (X1Y1X2Y2X3Y3X4Y4X5Y5 = male)
true/false: some reptiles and certain fish depend on environmental factors for sex determination
true! clownfish change sex depending on the temperature of water they’re in!
_____________ balance the expression of X-linked genes
dosage compensation mechanisms
______: one X chromosome is randomly inactivated in each female somatic cell
X-inactivation
an inactivated X-chromosome in females becomes…
a Barr body (localized to a specific region of the wall of the nuclear envelope)
Since X-inactivation is random… 1/2 somatic cells inactivate ______ and 1/2 somatic cells inactivate
- maternal chromosome/alleles
- paternal chromosome/alleles
since mom and dad’s chromosomes may not be the same in X-inactivation, the daughter is heterozygous! which consequently results in…
a mosaic of 2 kinds of cells (we get individual cell phenotypic expression!)
what’s an example of X-inactivation that results in a mosaic?
female calico cats!
