Genetic disorders

Question 1

germline v somatic mutations

Answer 1

germline mutations are heritable; 1/2 gametes of offspring will be carriers
somatic mutations>no gametes carry the mutation

Question 2

when do polyploidies and aneuploidies normally occur

Answer 2

during cell division in the female germline
eg during egg production

Question 3

splice site mutations

Answer 3

occur at spice acceptor site
affects efficiency at which spliceosome recognises the site

Question 4

haploinsufficiency

Answer 4

half the amount of protein product is not enough for normal functioning

Question 5

dominant negative effect

Answer 5

one copy is normal but the mutated copy interferes with the normal function of the normal protein

Question 6

locus heterogeneity

Answer 6

mutations in different genes can lead to the same trait/disease
deviation from mendelian inheritance

Question 7

incomplete penetrance

Answer 7

deviation from mendelian inheritance
normally observed in dominant modes of inheritance
varying degree of penetrance of a disease in different individuals; some may not display it

Question 8

x mosaicism

Answer 8

one of the X chromosomes in females is inactivated in the female early embryo
random process
deviations from expected mendelian predictions

Question 9

heteroplasmy

Answer 9

cells have different ratios of mutated mitochondria
random
cannot be predicted

Question 10

heteroplasmy in disease

Answer 10

siblings can have differing severities of disease or none at all
symptoms can manifest if there is a threshold number of mutated mitochondria

Question 11

polygenic model

Answer 11

genetic variants each contribute additively to heritability (narrow sense)

Question 12

outcome of polygenic model v mendelian

Answer 12

proportion of offspring affected with a disease would be lower
large number of risk alleles needed to be inherited for disease to manifest

Question 13

the carter effect

Answer 13

If a disease is less common in one sex, then an affected person of that sex must have inherited a higher genetic burden — and so is more likely to pass on the condition to their children

Question 14

sex dimorphism

Answer 14

one sex is more frequently affected than the other
for some diseases, males and females will have different disease thresholds

Question 15

heritability

Answer 15

the phenotypic variation in a given population that is due to variation in genetic factors within the population

Question 16

broad sense heritability

Answer 16

genetic variance/ phenotypic variance
includes narrow sense (additive variance), dominance variance and epistatic variance

Question 17

narrow sense heritability

Answer 17

Va/Vp proportion that is additive