chapter 4

Question 1

What are the types of gene interactions?

Answer 1

More than 2 alleles per gene, dominance can be incomplete, multiple genes can affect one trait, interaction with nongenetic factors

Question 2

What is the molecular basis of dominance?

Answer 2

When there are recessive and dominant genes and the dominant one mask the recessive

Question 3

The dominant/recessive relationship depends on what?

Answer 3

The protein being produced

Question 4

What is haplosufficency?

Answer 4

one copy of it is enough for normal function in heterozygotes

Question 5

What is haploinsuffiency?

Answer 5

one copy of it is not enough for normal function

Question 6

What is an example of a recessive mutant allele?

Answer 6

Wild-type allele (R+) produces enzyme; mutant allele (r) doesn’t. (haplosufficent)

Question 7

What is an example of a dominant mutant allele?

Answer 7

Mutant allele (T2) produces insufficient enzyme; heterozygous individuals are mutant (haploinsufficient).

Question 8

What are the loss of function mutations?

Answer 8

Null (amorphic) and leaky (hypomorphic)

Question 9

What is a null mutation?

Answer 9

the complete loss of function

Question 10

What is a leaky mutation?

Answer 10

the partial loss of gene function

Question 11

What are double negative mutations?

Answer 11

Mutant protein spoils multimeric complex

Question 12

What are the gain of function mutations?

Answer 12

hypermorphic and neomorphic (usually dominant)

Question 13

What is hypermorphic?

Answer 13

increased activity in genes compared to normal

Question 14

What is neomorphic?

Answer 14

mutations acquire novel gene activities not
found in the wild type

Question 15

What are the types of dominance?

Answer 15

Incomplete, codominance, and multiple alleles

Question 16

What is incomplete (partial) dominance?

Answer 16

Heterozygote shows intermediate phenotype (e.g., flower color)

Question 17

What is codominance?

Answer 17

Both alleles fully expressed (e.g., ABO blood group)

Question 18

What are multiple alleles?

Answer 18

Allelic series(order of dominance among alleles), like the C-gene for mammalian coat color (C > c^ch > c^h > c).

Question 19

What are the alleles for ABo blood type?

Answer 19

I^A, I^B and i
(I^A and I^B are completely dominant over i but are codominant with each other)

Question 20

The c^h allele is what?

Answer 20

temperature sensitive

Question 21

How is blood type determined?

Answer 21

by an antigen-antibody reaction on a microscope slide

Question 22

Blood group antigens are based on what?

Answer 22

sugar modifications on the H antigen

Question 23

What is a recessive lethal allele?

Answer 23

Homozygous individuals die (e.g., yellow coat color in mice)

Question 24

What are lethal alleles?

Answer 24

They are recessively inherited and they can cause single gene mutations to kill an organism

Question 25

What are embryonic lethal allele?

Answer 25

They are detected by missing progeny classes.

Question 26

What is delayed onset lethal alleles?

Answer 26

Some lethal alleles act after reproduction (e.g., Huntington’s disease)

Question 27

What is complete penatrance?

Answer 27

If a given genotype always produces the same phenotype

Question 28

What is incomplete penetrance?

Answer 28

when some people with a disease-causing mutation (change) in a gene develop the disease while others don’t

Question 29

What is variable expressivity?

Answer 29

The degree to which a trait is expressed varies.

Question 30

What are sex limited traits?

Answer 30

Only expressed in one sex (e.g., milk production in mammals).

Question 31

What are sex influenced traits?

Answer 31

Expression varies between sexes (e.g., beards in goats).

Question 32

What is nonpenetrance?

Answer 32

An organism that does not produce the phenotype generally associated with the genotype

Question 33

What is fully penetrant?

Answer 33

When the genotype is always expressed in the phenotype

Question 34

What is an example of incomplete penetrance?

Answer 34

Polydactyly - an autosomal dominant condition in which affected individuals have more than five fingers and toes

Question 35

What is gene environment interaction?

Answer 35

the influence of the environment on the expression of genes and on the phenotypes of organisms

Question 36

What is pleiotrophy?

Answer 36

the alteration of multiple distinct traits by a mutation in a single gene. ex: drosophila and sickle cell

Question 37

What is gene interaction?

Answer 37

It refers to the collaboration of multiple genes in producing a single phenotypic trait or group of related traits.

Question 38

What are anabolic pathways?

Answer 38

Biosynthesis of complex compounds.

Question 39

What are catabolic pathways?

Answer 39

Degradation of complex compounds.

Question 40

true or false. Signal Transduction and Developmental Pathways also involve gene interactions.

Answer 40

true

Question 41

Who proposed the one-gene-one enzyme hypothesis?

Answer 41

Beadle and Tatum after studying Neurospora crassa.

Question 42

Each gene controls the production of what?

Answer 42

a single enzyme, affecting a specific step in a metabolic pathway

Question 43

What was Horowitz's experiment about?

Answer 43

The genetic dissection of met− mutants in Neurospora.

Question 44

What is the purpose of Horowitz experiment?

Answer 44

To determine steps in the methionine biosynthesis pathway and identify steps affected by mutations.

Question 45

What was the results of Horowitz experiment?

Answer 45

To identify the specific steps blocked by mutations based on growth patterns.

Question 46

Do all genes code for enzymes?

Answer 46

no, some produce structural, regulatory, or transport proteins.

Question 47

Som genes produce what instead of proteins?

Answer 47

RNA

Question 48

What protein needs to combine with others to function

Answer 48

B-globin

Question 49

What is epistasis?

Answer 49

A type of gene interaction where one gene's mutation can prevent the production of a phenotypic outcome, altering expected ratios in offspring.

Question 50

Why can phenotypic rations deviate from mendel's classic 9:3:3:1 ratio? (6 ways)

Answer 50

Because of gene interaction

Question 51

What is the ratio for no interaction?

Answer 51

9:3:3:1 Cross between blue budgies (BByy) and yellow budgies (bbYY) leads to F1 with wild-type green feathers (BbYy).

Question 52

What is the ratio for Complementary Gene Interaction?

Answer 52

(9:7) when genes work in tandem to produce a single product. crossed two pure-breeding strains of white-flowered sweet peas

Question 53

What is the ratio for Duplicate Gene Action?

Answer 53

(15:1) they encode the same product. A dominant allele at either locus gives rise to a wild-type phenotype

Question 54

What is the ratio for Dominant Gene Interaction?

Answer 54

9:6:1 Plants that have one or two dominant alleles for just one of either of the genes will have round fruit and those with only recessive alleles of both genes will have long fruit

Question 55

What is the ratio for Recessive Epistasis?

Answer 55

9:3:4 homozygosity for the recessive allele at one locus will mask the phenotypic expression of the alleles at a second locus

Question 56

What is the ratio for Dominant Epistasis?

Answer 56

12:3:1 a dominant allele at one locus will mask the phenotypic expression of the alleles at a second locus

Question 57

What is the ratio for dominant suppression?

Answer 57

13:3 a dominant allele at one locus completely suppresses the phenotypic expression of the alleles at a second locus