Genes in populations 4

Question 1

what are discontinuous traits and and an example?

Answer 1

discrete classes of phenotype e.g. blood group

Question 2

what are continuous traits and an example?

Answer 2

phenotypes don’t fall into classes e.g. height

Question 3

what are threshold traits and an example?

Answer 3

appears like a discontinuous trait but is caused by a continuous distribution e.g. type 2 diabetes

Question 4

`for any locus with 2 alleles how many genotypes are there?

Answer 4

3

Question 5

what is a quantitative trait locus?

Answer 5

lots of genes contributing to one trait that are close together

Question 6

what are quantitative traits influenced by and are they heritible?

Answer 6

genetics and the environment and yes they are heritable

Question 7

what is Vp?

Answer 7

phenotypic variance - total variation within a population for a phenotype

Question 8

what are the 2 components which make up phenotypic variance?

Answer 8

1) variation due to differences in the genotype

2) variation due to environmental effects

Question 9

what is H2?

Answer 9

broad sense heritability - the proportion of phenotypic variation in a population that is due to genetic differences

Question 10

what happened when genetic variance increases?

Answer 10

heritability increases

Question 11

what is directional selection?

Answer 11

shifts the overall population by favouring an extreme

Question 12

what is stabilising selection?

Answer 12

acts against extreme phenotypes

Question 13

what is divergent selection?

Answer 13

favours variants of opposite extremes

Question 14

why if selection is acting does genetic variance not decrease?

Answer 14

1) mutation
2) migration
3) hidden genetic variation in the genome not expressed in the phenotype

Question 15

genetic variation at the PRNP gene is associated with resistance / susceptibility with which disease?

Answer 15

Kuru