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BIOL 2320 - Genetics > Gene Interruption > Flashcards

Gene Interruption Flashcards

1
Q

Describe a metabolic pathway

A

Multistep process that either synthesizes (ex. amino acids, sugars) or degrades a complex molecule (ex. cellular respiration breaks down sugars)

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2
Q

What is an anabolic pathway?

A

A metabolic pathway that synthesizes complex molecules with the sequential action of genes and enzyme catalysts

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3
Q

What is a catabolic pathway?

A

A metabolic pathway that breaks down complex molecules through the sequential action of genes and enzymes as catalysts

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4
Q

Describe how metabolic pathways work

A

Genes work together in sequential order to produce a final product

if all the genes in a pathway are functional, they will produce enzymes to convert a compound to another compound in a step process

ex. Met 2 codes for enzyme homoserine transacetylase to convert homoserine to cysteine

then Met B codes for cystothionine gamma synthetase to convert cysteine to cystathionine… etc.

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5
Q

What happens if a gene in the pathway is not functional?

A

the gene will not be able to code for the enzyme that will convert the current compound to the next compound

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6
Q

What is Neurospora?

A

A haploid fungus

Model organism

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7
Q

Why is Neurospora a model organism?

A

It is a simple organism that is easy to study

mates quickly

mycelium is multinucleate (haploid)

if two different fungi have different mating types and come into contact, they can fuse to create a diploid cell that will undergo meiosis to recombine and produce new haploid offspring

they synthesize everything they need to grow

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8
Q

Describe prototroph

A

An organism that has the wild type phenotype and no mutations and can grow on minimal plating (has everything it needs)

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9
Q

Describe auxotroph

A

An organism that has a mutation in a gene required to synthesize an essential molecule

cannot grow on minimal medium

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10
Q

What does minimal medium usually contain?

A

minerals, water, a carbon source (glucose usually)

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11
Q

How are the genes involved in the synthesis of a particular amino acid studied?

A

Geneticists screen for mutants by looking for auxotrophs

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12
Q

What kind of medium will an auxotroph be able to grow on?

A

Minimal medium + the essential molecule they cannot produce

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13
Q

How do geneticists screen for mutants?

A

take prototrophic neurospora and radiate with mutagens (ex. X ray) to create mutations

plate these on complete medium to allow both prototrophs and auxotrophs to grow

transfer to minimal medium to determine which are auxotrophs (will not grow)

auxotrophs transferred to minimal media + different amino acids to identify the pathway

mutant strains that required methionine to grow are methionine auxotrophs

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14
Q

Describe a complementation test

A

a test to cross mutants to determine the number of genes involved in the mutation

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15
Q

What happens if you give a mutant a compound that is made in the metabolic pathway after the step where the pathway is blocked?

A

the mutant can make the end product

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16
Q

What happens if you give a mutant a compound that is made in the metabolic pathway before the step where the pathway is blocked?

A

The mutant will not be able to make the product

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17
Q

What are the steps of identifying genes involved in determining petal colours in peas (for example)?

A

expose plants to mutagens to create mutations

look at offspring to identify and isolate mutants in gene for petal colour = peas with non-wild type phenotype

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18
Q

T or F: many phenotypes are controlled by more than one gene

A

true

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19
Q

How do you identify if the mutation occurs in the same gene or in different genes?

A
  1. complementation test

2. analyze double mutants

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20
Q

how do you get the double mutants?

A

by crossing mutants from the complementation test

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21
Q

How do you conduct a complementation test for a diploid organism

A

Cross 2 homozygous mutant lines to produce heterozygote F1

22
Q

How do the genes interfere if the F1 of a complementation test is heterozygous wild-type? Why?

A

The parents are mutants in different genes because both mutations were required to produce the wild-type phenotype

23
Q

How do the genes interfere if the F1 of a complementation test is heterozygous mutant? Why?

A

Parents are mutant in the same gene because two copies of the mutant allele were required to show the mutant type

24
Q

How can we tell if the two genes causing a mutation are interacting or acting independently?

A

by examining the phenotype of the double mutant organism

25
Q

What is a double mutant?

A

An organism that is homozygous for the recessive/mutant gene

Created from complementation test F1

26
Q

What is the phenotypic ratio for genes that do not interact?

A

regular dihybrid

9:3:3:1

27
Q

What are 3 important phenotypic ratios for when genes do interact with each other?

A

9: 3:4
9: 7
12: 3:1

28
Q

Which ratio will you see if there is complementary gene interaction?

A

9:7

29
Q

Describe complementary gene interaction

A

the genes in a biochemical pathway act in tandem to produce a phenotype

Wild type action from both genes is required to produce the WT phenotype

mutations of one or both genes produces a mutant phenotype

30
Q

In complementary gene interaction, how is the wild type phenotype produced?

A

When both genes are functioning for the wild type

31
Q

In complementary gene interaction, how is the mutant phenotype produced?

A

When either of the genes have mutations

32
Q

What is the ratio for recessive epistasis?

A

9:3:4

33
Q

Describe recessive epistasis

A

the recessive allele of one gene masks or reduces the expression of alleles of a second gene

the mutation of one gene blocks the biochemical pathway and the mutant phenotype is produced

34
Q

What is the phenotypic ratio of dominant epistasis?

A

12:3:1

35
Q

Describe dominant epistasis?

A

when a dominant allele (functioning) of one gene masks or reduces expression of alleles of a second gene

36
Q

What are 2 reasons that organisms can have the same genotype but not the same phenotype?

A

Sex-limited inheritance

sex-influenced inheritance

37
Q

Describe sex-limited inheritance

A

These genes are located on autosomes in male and females, but the phenotype is only expressed in one sex

38
Q

Why is the phenotype of a sex-limited gene only expressed in one sex?

A

differences in concentrations of sex hormones

39
Q

Give an example of sex-limited inheritance

A

genes that affect sperm production will only show phenotype in male sex

genes that affect milk production will only show phenotype in organisms with mammary glands

40
Q

T or F: sex-limited inherited genes can be passed on to offspring even if the parent did not express the phenotype

A

true

41
Q

Describe sex-influenced inheritance

A

genes located on autosomes so both male and females receive

expression of phenotype affected by concentration of

42
Q

Define complete dominance

A

one copy of the dominant allele produces enough functional protein to carry out normal cellular function

43
Q

How does the phenotype of a homozygous dominant compare to a heterozygote when there’s complete dominance

A

the phenotypes are the same

44
Q

Define haplosufficient

A

when a gene only requires one copy to express the normal function

45
Q

T or F: wild type alleles are haplosufficient in complete dominance

A

True

46
Q

Are mutations of haplosufficient genes dominant or recessive?

A

recessive

47
Q

Explain complete dominance when the wild-type allele is recessive

A

one copy of the wild type allele does not produce enough functional protein to allow normal cellular function

48
Q

Define haploinsufficient

A

when a gene requires more than one working copy to function properly

49
Q

Mutations of haploinsufficient genes are recessive or dominant?

A

dominant

50
Q

How does the phenotype of a heterozygote compare to homozygotes when a gene has incomplete dominance?

A

the heterozygote phenotype is an intermediate of two extreme homozygotes

51
Q

What is the phenotypic ratio of the F2 generation when there’s incomplete dominance?

A

1:2:1

52
Q

Which allele is dominant and which is recessive during incomplete dominance?

A

neither allele is dominant or recessive

BIOL 2320 - Genetics (12 decks)

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