10.2 inheritance

Question 1

what are LINKED gene loci?

Answer 1

linked genes – genes found on the SAME CHROMOSOME

Question 2

the closer the loci of two linked genes,

Answer 2

the less frequently they are separated by crossing over

Question 3

how do linked genes affect each other during allele inheritance

Answer 3

the allele inherited for one gene does NOT affect which allele will be inherited for the other gene

Question 4

how are recombinants involving linked genes drawn?

Answer 4

t b (one chromosome)

one loci

each letter codes for a different trait

Question 5

two distinct possibilities for the genotype of a heterozygous parent in a LINKAGE PROBLEM (linked genes)

Answer 5

tb

and

tB

Question 6

how to test for linkage (test cross)

Answer 6

heterozygous parent x homozygous recessive parent

• not linked: follow mendels law of indep assortment, 1:1:1:1
• non-mendelian ratios obtained, genes likely to be linked

Question 7

during a test cross to test for linkage, the lower the recombinant frequency,…

Answer 7

the closer the linked genes are on the chromosome

Question 8

what is sex-linkage

Answer 8

any gene found on the sex chromosomes

Question 9

what is autosomal linkage

Answer 9

two genes found on the same autosomal chromosome (a non-sex chromosome)

Question 10

test for recombinant phenotypes

Answer 10

test cross (homozygous recessive for both traits)

Question 11

polygenic traits

Answer 11

more than one gene may affect a single trait

Question 12

pleiotropic genes

Answer 12

a single gene may affect multiple traits

Question 13

epistatic genes

Answer 13

a gene may impact the expression of another gene

Question 14

penetrance of the allele

Answer 14

some alleles are not expressed in all individuals

Question 15

expressivity of the allele

Answer 15

some alleles are expressed with varying intensity

Question 16

law of independent assortment

Answer 16

unlinked genes segregate independently (As a result of meiosis)

Question 17

what did thomas hunt morgan discover

Answer 17

non-mendilian ratios in Drosophila (fruit flies as a model organism)

LINKED GENES
(Eg eye colour and wing development)

Question 18

why druit flies as a model organism for mendilian ratio discovery

Answer 18

• small, compact
• reproduce fast
• distinct male and female
• short life cycle
• produce hundreds of offspring

Question 19

what is a dihybrid cross?

Answer 19

the genetic crossing of two organisms that examines the inheritance of two different traits, each controlled by separate genes

Question 20

what is the law of independent assortment

Answer 20

unlinked genes segregate independently as a result of meiosis

Question 21

what did morgan observe in the flies

Answer 21

red eyes vs white eyes

• observed a male with white eyes (instead of red)

Question 22

how is the most common allele of any trait represented

Answer 22

+

eg heterozygous
Cy/+ or Cy+ Cy

Question 23

how are mutant alleles represented

Answer 23

one / a few letters

Question 24

what is autosomal linkage

Answer 24

2 genes found on the same autosomal chromosome

Question 25

2 reasobs for non-mendilian ratios

Answer 25

1. sex linkage (gene on sex chromosomes)
2. autosomal linkage (2 genes on same autosomal chromosome)

Question 26

continuous variation

Answer 26

a range of phenotypes – also affected by environment

eg height in humans

Question 27

what is the purpose of the chi-squared test

Answer 27

assess the degree of difference between expected and observed results