Pedigree Analysis, Sex-Linked & Sex-Associated Inheritance

Question 1

Sex-linked inheritance - Understand why male and female ratios differ.

Answer 1

X and Y chromosomes are not homologous

Most sex-linked traits are X-linked

Question 2

Sex-linked inheritance

Answer 2

• Males only need to inherit one recessive allele to show an X-linked trait, but females need to inherit 2
• X-linked or Y-linked
• Males never pass it to their sons

Question 3

X-linked dominant

Answer 3

• do not skip generations
• affect males and females
• affected males pass trait on to all daughters and none of their sons (affected male must have an affected mother)
• affected females (heterozygous) pass the trait on to about half their sons and half their daughters
• Daughters of affected fathers will always at least be a carrier

Question 4

Y-linked traits

Answer 4

• appear only in males

- all male offspring affected

Question 5

Autosomal Recessive Traits

Answer 5

• appear equally in males and females
• tend to skip generations
• more likely to appear among progeny of related parents (inbreeding)

Question 6

Autosomal Dominant Traits

Answer 6

• appear equally in males and females
• do not skip generations
• unaffected persons do not transmit the trait
• affected persons have at least one affected parent

Question 7

Sex influenced

Answer 7

phenotype is influenced by the sex of an individual, but not limited to not sex or another
- heterozygote will express one trait in one sex, and the alternative traits in the other sex

ex: pattern baldness in humans

Question 8

Sex limited

Answer 8

phenotype is limited to one sex

ex: hen feathering

Question 9

cytoplasmic inheritance

Answer 9

• Involves the chloroplast and mitochondrial genomes
• progeny receive their mitochondria and chloroplast from the female parent
• maternal source determine outcome of progeny