genetic diseases

Question 1

Simple vs. Complex diseases

Answer 1

Simple = one locus - one phenotype – one “disease allele” (basically non-existent)

Complex = many genes. Often strong environmental effect. (e.g. Diabetes, Asthma and allergy, Schizophrenia, alcoholism…)

Question 2

Allelic heterogeneity

Answer 2

Different mutations at the same locus leads to the same/similar .phenotype(s).

Question 3

Complex heterozygote

Answer 3

Two recessive heterogeneous mutations in in a specific locus gives rise to a disease. Ex. both parts are found in the same gene, but have different mutations.

Question 4

Metacentric

Answer 4

Centrosome placed in the middle of the chromosome.

Question 5

Imprinting

Answer 5

epigenetic, phenotype depends on the parent
(methylation of a gene can depend on the parent it originates from. One deleted gene (father) + one shut off gene (mother) can give a phenotype!)

Question 6

• μ
• s
• q
• w
• A
• h

Answer 6

• μ = probability of wildtype mutating into deleterious form (mutation rate, usually 10^-5 - 10^-6)

• s = selection (any factor that lowers reproduction).
(s=1 –> guaranteed death before reproduction)

• q = allele frequency
• w = offspring’s chance of survival
• A = allele
• h = between 1 and 0 (h=0 recessive disease, h=1/2 co-dominance, h=1 dominant disease)

Question 7

Allele frequencies at equilibrium:

• Dominant autosomal
• Incomplete dominance
• Recessive autosomal
• X-linked recessive

Answer 7

• Dominant autosomal –> 𝑞=𝜇𝑠
• Incomplete dominance –> 𝑞=𝜇ℎ𝑠
• Recessive autosomal –> 𝑞=√𝜇𝑠
• X-linked recessive –> 𝑞=3𝜇𝑠

Question 8

For random pairing

p and q = frequency of one of the alleles

Answer 8

q = P(A2), p = P(A1) = p^2 + pq + q^2