topic 3

Question 1

what are the causes for mutant dominance

Answer 1

haploinsufficiency and dominant negative

Question 2

haploinsufficiency vs dominant negative

Answer 2

haploinsufficiency is when one copy of the wildtype allele is not enough to produce a wildtype phenotype
a dominant negative is when the mutant interferes with a protein by binding to it and interfering with its functions so wildtype phenotype isn’t expressed “spoiler proteins”

Question 3

an allele capable of causing death is called

Answer 3

lethal allele

Question 4

what genes are those that without them the organism dies

Answer 4

essential genes

Question 5

what is a pleiotropic allele

Answer 5

allele that affects several properties of an organism

Question 6

what is penetrance

Answer 6

percentage of individuals with a given allele who express that allele phenotype

Question 7

what is expressivity

Answer 7

the intensity of the phenotype being expressed by the allele (severity of phenotype)

Question 8

what is the one-gene-one-enzyme hypothesis and how was it refined

Answer 8

one gene controls one specific enzyme and it was refined to one-gene-one-polypeptide where one gene controls one polypeptide

Question 9

what is being tested in a complementation test

Answer 9

whether two mutations belong on the same gene

Question 10

what is recessive epistasis

Answer 10

the double mutant phenotype shows pheno of only one mutation and has a ratio of 9:3:4

Question 11

what do you call the single mutation that has the same phenotype as the double mutation

Answer 11

epistatic

Question 12

what do you call the single mutation that is not expressed in the double mutation

Answer 12

hypostatic

Question 13

what do you call it when a mutant allele of one gene masks the expression of a mutant allele of another gene and expresses its own phenotype instead

Answer 13

epistasis

Question 14

what has a 9:7 ratio

Answer 14

a double mutation where the both single mutations have the same phenotype as the double mutant

Question 15

what has a 9:3:4 ratio

Answer 15

a recessive epistasis where the double mutation only expresses the phenotype of one of the single mutations

Question 16

what has a 12:3:1 ratio

Answer 16

a dominant epistasis where a dominant allele displays epistasis

Question 17

what is a suppressor

Answer 17

a mutant allele that reverses the effect of a mutation of another gene

Question 18

what has a 13:3 ratio

Answer 18

a scenario where a double mutation results in wild-type because one mutation masks the other (suppressor has no phenotype)

Question 19

what has a 9:3:3 ratio

Answer 19

a synthetic lethal where the double mutant is lethal

Question 20

what has a 14:2 ratio

Answer 20

suppressor is like mutant

Question 21

what phenotypic ratio do lethal alleles lead to?

Answer 21

9:3:3 because 1 wouldn’t exist bc organism would die

Question 22

what do you call it when some organisms with a certain gene does not display the phenotype

Answer 22

incomplete penetrance

Question 23

how do you explain scenarios where someone has the trait of a dominant disorder but will never develop symptoms

Answer 23

incomplete penetrance

Question 24

what is kind if trait is needed to be able to perform a complementation test

Answer 24

recessive single gene

Question 25

what does it mean when mutant genes fail to complement (offsprings are all mutants)

Answer 25

it means they are on different loci (diff genes)

Question 26

how can you tell when complementation occurs

Answer 26

when all offspring are wild type

Question 27

state all the double mutant interactions and their phenotypes after a dihybrid cross

Answer 27

no interaction (9:3:3:1)
same pathway (9:7)
recessive epistasis (9:3:4)
dominant epistasis (12:3:1)
supressor mutations (13:3)

Question 28

what is dominant epistasis

Answer 28

when one mutant allele is also able to mask the WT trait so you end up with a 12:3:1 phenotype ratio

Question 29

what are synthetic mutations

Answer 29

mutations individually do not cause mutated phenotype, mutant phenotype only shows when both mutant genes are showing

Question 30

what are supressor mutations

Answer 30

they reverse the effect of mutation in another gene and result in 13:3 ratio