Transmission Genetics

Question 1

What is the principle of maximum parsimony?

Answer 1

The simplest explanation that is consistent with you data, which we would use to come up with a hypothesis

Question 2

What are the three steps in coming up with a genetic hypothesis?

Answer 2

Step 1 = specify all variables (eg one gene coloured allele etc)
Step 2 = draw out the cross
Step 3 = statistical test your observed vs expected results (chi squared)

Question 3

When P is greater than 0.05 what can we conclude from a chi squared test?

Answer 3

There is no significant deviation from expectation at the 5% confidence level

Question 4

When P is less than 0.05, what can we conclude from a chi squared test?

Answer 4

There is significant deviation from expectation at 5% confidence - reject hypothesis

Question 5

What is a null hypothesis?

Answer 5

the difference between observed and expected values are due to chance and chance alone (Ho)

Question 6

What is the difference between polygenes and oligogenes?

Answer 6

there are only several oligogenes each having a large impact on quantitative character however there are many polygenes with a smaller affect on quantitative character

Question 7

Is a meristic character quantitative or qualitative?

Answer 7

Quantitative - it is a countable discontinuous variation, but is still quant as it is numerical.

Question 8

When would genes be said to be acting additively?

Answer 8

When substitution of one allele for another alters the phenotypic value by a certain amount, irrespective of other alleles present at other loci

Question 9

In and additive character, what should the extremes of the F2 correspond to?

Answer 9

The extreme phenotypic values in F2 should correspond to P1 and P2 values

Question 10

What is the difference between heritability in the broad and narrow sense?

Answer 10

heritability in the broad sense is total genetic component over total phenotypic variance. Heritability in the narrow sense is the additive genetic component over the total phenotypic variance. Better predictor of breeding success.

Question 11

What is the realized heritability in a pilot experiment of estimating h2?

Answer 11

Realised heritability is the response to selection divided by the selection differential

Question 12

What is the selection differential?

Answer 12

The mean of the selected parents - the total mean

Question 13

What is the response to selection?

Answer 13

The mean of the offspring - the total mean

Question 14

How can you calculate the regression of offspring?

Answer 14

Plot the mid parent value on the x axis compared with the mean of offspring on the y axis and draw a line of best fit

Question 15

What is the ‘mid parent value’?

Answer 15

The average parental phenotypic score as a pair

Question 16

Can you still calculate the regression of offspring if a phenotypic score is sex linked?

Answer 16

Yes, use only the parent value from the mother - but double the steepness of the slope

Question 17

What is inbreeding depression

Answer 17

Inbreeding depression occurs when deleterious alleles become more homozygous in the population (not the ones selected for)

Question 18

What is the norm of reaction?

Answer 18

The way a particular gene will respond to a change in the environment

Question 19

What is concordance?

Answer 19

The extent to which twins share the same character (discontinuous value)

Question 20

What does regression of offspring in humans represents?

Answer 20

Regression of offspring in humans represents familiarity and NOT heritability (because you cannot say that the environment has acted independently of genotype)

Question 21

What are lod scores used to calculate?

Answer 21

Lod scores are a statistical test to analyse QTL mapping