Ch. 6: Gene Interaction

Question 0

What is the One-gene-one-enzyme (polypeptide) hypothesis?

Answer 0

One gene specifies one enzyme; stains would not grow on one medium unless supplemented with various vitamins, amino acids, etc.

Question 1

Studies with fungus

Answer 1

Neurospopora Studies

Question 2

What did Srb/Horowitz uncover?

Answer 2

The synthetic pathway for arginine; precursor ->

Question 3

Gene interaction

Answer 3

When genes interact in various ways to produce a given character

Question 4

Double Mutants

Answer 4

Need to form double mutants to detect gene interactions; must know what each separate meant does and must make sure

Question 5

Complementation Test (Cis/Trans Test)

Answer 5

Crossing mutants to see whether the two mutants are the same or different ; mutants must construct in the Trans position

Question 6

What does it mean when two different mutants are crosses and get Complementation?

Answer 6

Must mean that there are two different genes involved

Ex. Corn snakes have two different loci for color

Question 7

9:3:3:1 Modifications

Answer 7

Suggests that genes are interacting in some way; several modifications of 9:3:3:1 are possible but all combinations will have these four numbers

Question 8

Epistasis

Answer 8

Occurs when genes at different loci control the expression of the same character

Question 9

Dominant Epistasis

Answer 9

Two genes in the same pathway interact
Ex. Foxgloves- phenotype is PETAL color. One affects color intensity and another where pigment is deposited. Could leave the throat white and petals with color or vice versa

Question 10

Suppression

Answer 10

Some genes suppress the action of others
Ex. A mutant reverts to wild type in presence of suppressor gene at another locus (purple eyes in Drosophilia is mutant and wild type is red)

Question 11

Genetic Environment

Answer 11

Genes have effects on other genes, either directly or because of their location

Question 12

Heterochromatin Region

Answer 12

Areas of the chromosome that are not genetically active

Question 13

Biosynthetic Pathways

Answer 13

Alleles at a genetic loci act by producing molecules, typically enzymes

Question 14

Developmental Pathways

Answer 14

Alleles at genetic loci that act to lead to growth and differentiation

Question 15

Signal transduction pathways

Answer 15

Transmit instructions from an extra cellular signal that activates a protein that eventually turns genes on/off

Question 16

What is an allele that occurs most frequently in nature called?

Answer 16

Wild type allele

Question 17

What is an allele that deviates from the wild type allele?

Answer 17

Mutant

Question 18

When the wild type allele is dominant it is called?

Answer 18

Haplosufficient

Question 19

If the mutant is the dominant allele then the wild type is considered to be?

Answer 19

Haploinsufficient

Question 20

Codominance

Answer 20

Two alleles come together in heterozygote and produce a different phenotype that is not simply an intermediate.
Ex. AB blood type

Question 21

Incomplete dominance

Answer 21

Heterozygotes being intermediate and possibly a different phenotype

Question 22

Multiple alleles

Answer 22

When there are 3 or more alleles segregating at a locus in a population
Ex. ABO blood type

Question 23

Lethal alleles

Answer 23

Some mutations are lethal when in single or double doses

Question 24

Dominant Lethals

Answer 24

Alleles that when even one dose is present, kills the organism
Ex. Huntington’s disease

Question 25

Recessive Lethals

Answer 25

More common, takes two doses to kill an organism

Question 26

Pleiotropy

Answer 26

Multiple phenotypic effects from a single gene

Question 27

Temperature sensitive

Answer 27

Some conditional mutants are affected by temperature, because the enzyme the gene produces is most effective at a certain temperature

Question 28

Alkaptonuria

Answer 28

Disease in which people cannot metabolize homogentisic acid and accumulation turns urine black

Question 29

Tay-Sachs

Answer 29

Autosomal recessive causes this lethal disease that does not show for first few months, but then children usually do by age 3

Question 30

Duchenne muscular dystrophy

Answer 30

An x-linked recessive disorder not usually seen until 3 to 5 years and usually die in 20s

Question 31

Penetrance

Answer 31

Sometimes mutant gene does not always fully express phenotype

Question 32

Expressivity

Answer 32

Expresses variability of phenotypic expression

Question 33

Variable penetrance

Answer 33

Ex. 5 purple dots, 4 left blank

Question 34

Variable expressivity

Answer 34

All dots have color but all with varying shades of purple