Heritability

Question 1

Concordance

Answer 1

• a twin pair are concordance when both twins have the same disease expression
• discordant if one has disease whilst the other does not

Question 2

Heritability

Answer 2

-main measure of genetic variation in polygenic traits
-epistasis- gene-gene interaction
-basically how much is genetic and how much is environmental
schizophrenia is 80, bipolar >80, depression 40, GAD 30, panic 40, phobia 35, alcohol 60

Question 3

Hardy Weinberg equilibrium

Answer 3

in absence of mutation, non-random mating, selection and genetic drift, the genetic constitution of the population remains the same from one generation to the next

Question 4

Genetic drig

Answer 4

• refers to the gene frequency change caused by limitations in population size
• explains why some genetic diseases are common in small isolated populations
• in small population the chances of random distribution is limited as probabilities of the combination are restricted ‘founder effect’

Question 5

Genetic flow

Answer 5

gene flow refers to to the exchange of genes between populations.
due to migration or other social reasons, the populations studied are no ‘closed’ populations any more

Question 6

Consanguinity

Answer 6

• Non-random mating occurs and mutations are preserved within a closed pedigree due to consanguinity
• autosomal recessive diseases are more often seen in consanquineous families

Question 7

High frequency of mutations

Answer 7

environmental exposure can provoke mutations at a higher frequency than expected in a stable population e.g living near a nuclear reactor leak

Question 8

Epistasis

Answer 8

-gene- gene interaction between different alleles at different genes

Question 9

Locus heterogeneity

Answer 9

• exists when the same disease phenotype can be caused by mutations in different loci
• it becomes especially important when genetic testing is performed by testing for mutations at specific loci e.g early onset Alzheimers can be caused by mutations in chromosome 1, 14 and 21

Question 10

Allelic heterogeneity

Answer 10

• refers to the same disease phenotype resulting from different types of mutations at the same loci
• in cystic fibrosis nearly 600 different mutations at the same site of chromosome 7 result in the same disease

Question 11

Pleiotropy

Answer 11

• exists when a single disease-causing mutation affects multiple organ systems
• common feature of genetic diseases