Human Pedigrees

Question 1

What are the characteristics of a Mendelian disease?

Answer 1

Monogenic or caused by mutation of a single gene, and very rare among the population

Question 2

Autosomal Dominance characteristics

Answer 2

does not skip generations, only needs 1 copy to be sick, very rare so its usually Aa with aa thus 50% transmission

Question 3

Autosomal recessive characteristics

Answer 3

can skip generations, need 2 copies, 2 unaffected parents who are carriers can have affected child

Question 4

X-linked Dominant characteristics

Answer 4

2x more common in women, does not skip generations, affected males have all affected daughters and no affected sons

Question 5

X-linked recessive characteristics

Answer 5

all daughters are carriers, male-male transmission not seen, more common

Question 6

What is reduced penetrance?

Answer 6

individuals who have a disease-causing genotype but do not develop the disease phenotype

Question 7

What is age-dependent penetrance?

Answer 7

A delay in the age of onset of a genetic condition

Question 8

What is ascertainment>

Answer 8

a systematic distortion in measuring the true frequency of a phenomenon due to the way in which the data are collected

Question 9

p^2+2pq+q^2 = 1

Answer 9

p is the frequency of ‘a’ allele and q is frequency of ‘A’ allele. p^2 represents the frequency of homozygous genotype ‘aa’ and vice versa