Inheritance / Genetic disorders

Question 1

earwax inheritance pattern

Answer 1

Autosomal dominant (G - wet > A - dry)
ABCC11 gene on Chromosome 16 - codes for protein that transports lipids across membrane

Question 2

bitter taste inheritance pattern

Answer 2

Autosomal dominant (tasing > non-tasting)
TAS2R8 gene of Chromosome 7 - codes for taste receptor

Question 3

Huntington’s disease inheritance pattern (neurodegenerative disorder)

Answer 3

Autosomal dominant (mutant > dominant)
HTT gene/protein - 7-35 CAG repeats normally, >35 for disease

Question 4

Autosomal dominant examples

Answer 4

earwax
bitter taste
Huntington’s

Question 5

Autosomal codominant examples

Answer 5

blood type, where antigens present correspond with genotype (IA, IB, i)

Question 6

Autosomal incomplete dominance examples

Answer 6

sickle cell anemia

Question 7

sickle cell anemia inheritance pattern

Answer 7

incomplete dominance (A - normal and S - sickle)
HBB gene on Chromosome 11 - codes for haemoglobin

Question 8

X-linked recessive disease examples

Answer 8

R/G colour-blindness
Haemophilia
G6PD deficiency

Question 9

X-linked dominant disease example

Answer 9

OTC deficiency
OTC enzyme processes excess nitrogen from protein metabolism
deficiency of OTC enzyme leads to buildup of ammonia

Question 10

R/G colour-blindness inheritance pattern

Answer 10

X-linked recessive
OPN1LW/OPN1MW gene on X chromosome - mutation causes abnormal opsin pigments in cone cells of retina, leading to insensitivity to green light

Question 11

haemophilia inheritance pattern

Answer 11

X-linked recessive
Abnormal alleles code for proteins that cannot participate effectively in blood clotting process

Question 12

G6PD deficiency inheritance pattern

Answer 12

X-linked recessive
G6PD enzyme prevents oxidative damage to RBC
mutation leads to premature RBC breakdown

Question 13

definition of chimeric inheritance

Answer 13

only genetic info from one parent due to 2 gametes fusing following meiosis

Question 14

lyonization purpose

Answer 14

One epigenetic mechanism that influences the diversity in phenotypes for female carriers is X chromosome inactivation (lyonization)

Prevents females from having twice as many X chromosome gene products as males

Question 15

what happens in lyonization

Answer 15

One of the two X chromosomes in each diploid cell becomes inactivated during early development

Selection is random

On average, 50% of maternal X chromosome and 50% of paternal X chromosome is inactivated

Skewed inactivation of normal X chromosomes can lead to manifestation of haemophilia in female carriers