ch 5 gene interaction

Question 1

haplosufficiency

Answer 1

one copy of the normal gene is able to confer a normal phenotype (dominance)

Question 2

haploinsufficiency

Answer 2

one copy of the normal gene is unable to confer the normal phenotype (recessive)

Question 3

mutations of haplosufficient genes are

Answer 3

recessive

Question 4

mutations of haploinsufficient genes are

Answer 4

dominant

Question 5

complete dominance

Answer 5

alleles which, when combined in the heterozygote show a phenotype indistinguishable from one of the homozygotes

Question 6

incomplete dominance

Answer 6

alleles which, when combined in the heterozygote show a phenotypic intermediate between the homozygotes
ex. snapdragons: red and white parents make pink progeny

Question 7

codominance

Answer 7

alleles which, when combined in the heterozygote show phenotypic characteristics of both homozygotes
ex. blood groups: A, B, and AB

Question 8

antigen/antibody

Answer 8

ex. blood type A = antigen A on blood cells, anti-B antibodies
blood type AB has antigen A and B, no antibodies
blood type O has no antigens, Anti-A and anti-B antibodies

Question 9

sickle cell anemia

Answer 9

tropical disease caused by a mutation in the gene coding for hemoglobin
HBa/HBa - no anemia
HBs/HBs - anemic, sickle cell shaped

Question 10

lethal alleles

Answer 10

an allele whose expression results in the death of the individual expressing it (may be recessive or dominant)

Question 11

pleiotropic mutation

Answer 11

a mutation that affects several different phenotypic characteristics
ex. Ay in mice affects both coat color and survival

Question 12

penetrance

Answer 12

the percentage of individuals who develop the phenotype associated with their genotype
(all have the same genotype)

Question 13

100% penetrant at birth

Answer 13

genotype represents phenotype
ex. cystic fibrosis

Question 14

expressivity

Answer 14

the extent to which a given phenotype is expressed in an individual
(all have the same genotype, degree to which they express phenotype is different)

Question 15

biosynthetic pathways

Answer 15

series of steps

Question 16

complete medium

Answer 16

has everything it needs to grow

Question 17

prototroph

Answer 17

an organism that will survive on minimal medium
- wild type

Question 18

auxotroph

Answer 18

an organism that will not survive on minimal medium, but whose growth depends on supplementation of medium with a specific substance

Question 19

biosynthetic pathways pair-wise feeding rule

Answer 19

downstream mutants feed upstream mutants

Question 20

complementation test

Answer 20

a test for determining whether two mutations are in different genes (they complement) or the same gene (they fail to complement)
- cross the two recessive mutants together, phenotype of progeny will differ if the mutants represent two alleles of one gene or mutation in two different genes

Question 21

if the mutations are alleles on the same gene:

Answer 21

the two mutation fail to complement, therefore they represent two alleles of the same gene
P: a-1/a-1 B+/B+ x a-2/a-2 B+/B+
F1: a-1/a-2 B+/B+
results in an auxotroph

Question 22

if mutations are in different genes

Answer 22

the two mutations complement one another, therefore they are in different genes
P: a-1/a-1 B+/B+ x A+/A+ b-1/b-1
F1: A+/a-1 B+/b-1
results in a prototroph

Question 23

rules for a complementation test

Answer 23

1. can only be done with recessive mutations
2. two different genes? progeny will be wild type = complementation
3. two alleles of the same gene? progeny will be mutant = no complementation

Question 24

heterokaryon

Answer 24

a cell composed of different nuclear types (multiple nuclei) in a common cytoplasm (result of fusing two haploid cells)

Question 25

4 types of gene interactions

Answer 25

1. complementary gene action
2. epistasis
3. suppression
4. redundancy

Question 26

complementary gene action ratio

Answer 26

9:7

Question 27

complementary gene action

Answer 27

harebells example
production of blue pigment is controlled by genes w1+ and w2+
last step gives blue pigment, therefore all other intermediates are white

Question 28

recessive epitasis ratio

Answer 28

9:3:4

Question 29

epistasis

Answer 29

the phenotype of a mutant allele at one gene overrides the phenotype of a mutant allele at another gene, such that the double mutant has the same phenotype as the first mutant
blue and magenta flower example
intermediates have different phenotypes

Question 30

dominant epistasis ratio

Answer 30

12:3:1

Question 31

suppression ratio

Answer 31

13:3

Question 32

suppression

Answer 32

a mutation in one gene can cancel the effect of a mutation in a second gene, resulting in a wild type phenotype

Question 33

genetic redundancy ratio

Answer 33

15:1

Question 34

genetic redundancy

Answer 34

two independent genes that produce the same phenotypic effect when present individually or when present together

Question 35

3 types of haploid gene interactions

Answer 35

epistasis
suppression
redundancy