The genetic basis of variaton

Question 1

What was used to study resemblance of relatives and formulate a theory of inheritance?

Answer 1

Correlation and regression

Question 2

What two laws did Mendel’s particulate inheritance have?

Answer 2

Law of segregation and law of independent assortment

Question 3

WHat is particulate inheritance?

Answer 3

The inheritance of discrete characteristics via genes that are independently expressed w/o the blending of characters from one generation to the next

Question 4

Issue with the theory of blending inheritance?

Answer 4

Variation would slowly be eroded and everyone would end up a some similar, mean-like, phenotype

Question 5

What is an example of smthn that is non-genetic, inherited from parents and can affect a phenotype?

Answer 5

Epigenetic marks

Question 6

Phenotypic plasticity meaning?

Answer 6

Same genotype makes diff phenotypes depending on the environment it is in

Question 7

What is a locus?

Answer 7

A location in the genome where any string of nucleotides can be present

Question 8

What is an allele?

Answer 8

Different DNA sequences that provide different phenotypic outcomes

Question 9

Relationship between alleles and a locus?

Answer 9

Alleles are found at a locus

Question 10

What about a gene causes differences?

Answer 10

Differences in alleles present at that locus

Question 11

What does allelic differences cause?

Answer 11

Variation in a trait

Question 12

Can you have a gene for x (i.e. gene for obesity)?

Answer 12

Generally no–> instead there is allelic differences at that locus which can lead to obesity/not obesity

Question 13

What has a phenotypic effect, genes or alleles?

Answer 13

Allelic differences

Question 14

What effect on trait variation do genes that have no sequence variation have?

Answer 14

No effect–> if everyone has the same alleles then their trait values will be the same

Question 15

What effect on trait variation do genes that have sequence variation have?

Answer 15

They do have an effect as allelic differences leads to trait variation

Question 16

Does every gene in the genome affect at least one trait?

Answer 16

No–> Some genes where everyone has the same sequence and so there is no effect on trait variation as all of the traits are the same

Question 17

What is the effect of a locus on a phenotypic trait dependent on?

Answer 17

The contrast of the different alleles that can be present at that locus

Question 18

How could a gene for a trait (i.e. when knocked out x trait occurs) actuallr occur in real life?

Answer 18

If a mutation caused the allele to be deleted from the genome–> effect is the same as a knockout

Question 19

Why are the genes which have the most variation for their trait not necessarily the most important for survival?

Answer 19

The most important for survival may be so important and so precise that any mutation would lead to improper development of the individual–> die and so dont pass on mutation

Question 20

What is polygenic inheritance?

Answer 20

The trait value for an individual is the sum of the effects of the alleles (from their homologous chromosomes) at the L loci affecting that trait

Question 21

What does measuring the resemblance of offspring to their parents tell you?

Answer 21

The proportion of variation that is caused by heritable genetic effects

Question 22

What is narrow sense heritability?

Answer 22

The proportion of variation among parents that will appear as variation among their offspring

Question 23

Narrow sense variability to do with prediction?

Answer 23

The degree to which you can predict offspring phenotype given parental phenotype

Question 24

How are discrete identifiable categories lost in traits?

Answer 24

There are many mendelian factors underlying a single trait

Question 25

What is additive/codominance?

Answer 25

Each A2 allele increases trait value yby the same amount (equivalent to each A1 decreasing the trait value by that amount)

Question 26

Does the same genotype produce the same phenotype every time?

Answer 26

No

Question 27

What is roughly the max amount of loci that we can distinguish are involved in a trait?

Answer 27

5 ish

Question 28

What is broad sense heritability?

Answer 28

The amount of trait variation that can be attributed to genetic differences

Question 29

How can variation have a genetic basis (broad sense heritability) but not have the offspring resembling their parents?

Answer 29

Diseases caused by recessive mutations--> parent has disease but offspring is heterozygote and so wont have it Traits that arise only due to a v specific combination of alleles from several loci--> recombination stops this

Question 30

How can you have non-heritable genetic variation?

Answer 30

Variation relying on one combination of alleles may not be heritable if the combos are not predictable

Question 31

What is overdominance?

Answer 31

The heterozygote has a more extreme phenotype than either of the homozygotes

Question 32

How is overdominance an example of non-heritable genetic variation?

Answer 32

The alleles are passed down but the phenotype will only be shown if it is a heterozygote

Question 33

Which individuals is narrow sense heritability measuring resemblance between?

Answer 33

Individuals that share alleles

Question 34

Why is sibling resemblance often greater than parent-offspring?

Answer 34

Offspring have one allele in each pair identical to their parents whereas siblings can either have none, one or both--> dominance can lead to siblings resemble each other bc they share a diploid genotype, not just alleles

Question 35

Example of sibling being more similar than parent-sibling?

Answer 35

parents are both heterozygous for a trait which the homozygous recessive is an extreme phenotype. 1/4 kids have homo recessive but neither parent does

Question 36

What is additive genetic effect?

Answer 36

Each A1 allele adds x amount to the trait value--> the A1A2 genotype is halfway between the A1A1 and the A2A2

Question 37

Dominance for heterozygotes?

Answer 37

The diff between the heterozygote and the average of the homozygotes

Question 38

What can the genetic component of variance be split into?

Answer 38

The heritable part and the dominance part

Question 39

What can phenotypic variance be due to?

Answer 39

Genetic factors and environmental factors