M7 Inheritance and Populations

Question 1

What is Mendel’s first law of Inheritance - linked to monohybrid Inheritance

Answer 1

The characteristics of an organism are determined by alleles which occur in PAIRS. Only one of a pair of alleles can be present in a single gamete.

Question 2

What is meant by pure breeding?

Answer 2

Homozygous

Question 3

How do you test the genotype of an organism?

Answer 3

Test Cross- by crossing with homozygous recessive.

Question 4

What is codominance? How do you write this?

Answer 4

When both alleles in a heterozygous organism are dominant.

Both alleles are independently and fully expressed so the phenotype is a mixture of the two conditions.

Written as capital letters but as superscripts of letters that refer to the gene.
e.g. C^R C^W = Pink colour

Question 5

What is the name of the place that genes occupy on a chromosome?

Answer 5

Locus

Question 6

What test can be used to measure the extent of the deviation between observed and expected results?
What are the degrees of freedom?

What is the usual P value?

When is the difference significant?

Answer 6

Chi squared test

The greater the calculated value of Chi squared, the greater the extent of deviation.

Degrees of freedom = number of categories - 1.
P = 0.05

Difference is significant if the Chi squared value is greater than or equal to the critical value.

Question 7

All gametes females produce will carry the X chromosome, so females are described as ___________. However males are described as ____________ since half the gametes will carry the X chromosome, and half will carry the Y chromosome.

Answer 7

Homogametic

Heterogametic

Question 8

What is Sex linkage?

Answer 8

When a phenotypic characteristic is inherited as a result of a gene carried on the X chromosome that is absent from the Y chromosome.

Question 9

What is Mendel’s Second Law of Inheritance? (The Law of Independent Assortment) - linked to dihybrid inheritance.

Answer 9

Each member of an allelic pair may combine randomly with either of another pair.

Question 10

What is the typical phenotypic ratio for a dihybrid F2 generation?

Answer 10

9:3:3:1

(only for non-linked genes)

Question 11

What is Autosomal linkage?

Answer 11

When genes occur on the same chromosome (are linked).

Question 12

What happens when recombination of alleles takes place? What type of genotypes are produced?

Answer 12

CROSSING OVER occurs between linked alleles. The further apart the genes are on the chromosome, the more chance there is of crossing over taking place and RECOMBINANT genotypes being produced.

Question 13

What is progeny another word for?

Answer 13

Offspring

Question 14

The _________ the recombinant frequency, the further apart the alleles are on the chromosome.

Answer 14

Higher

Question 15

What is Epistasis? How does this affect the ratio?

Answer 15

Where one gene influences another.

F2 ratios are not 9:3:3:1, but are stilll multiples of 1/16

Question 16

What is the Hardy Weinberg Principle?

Answer 16

After one generation, the allele frequency of any population will reach equilibrium (remain constant) in the absence of any disturbing factors. (e.g. selection advantage)

Question 17

What are the 5 Hardy Weinberg Assumptions?

Answer 17

• No mutations occur
• The popultion is isolated
• There is no selection (alleles equally likely to be passed on to next generation).
• Population is large
• Mating within population is random

Question 18

What is Allele frequency always out of?

Answer 18

1

Question 19

What are the Hardy Weinberg Equations?

Answer 19

p + q = 1
p^2 + q^2 + 2pq = 1