Lesson test: Where variation comes from

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Where variation comes from

1.[3p]
Why does sequencing a mother, a father and their child give a cleaner mutation rate than counting mutant colonies?

Counting mutants measures mutations that survived selection, while trios count them before selection acts

Correct

Trios use more individuals

The answer is: Counting mutants measures mutations that survived selection, while trios count them before selection acts

Colony counts cannot detect point mutations

The answer is: Counting mutants measures mutations that survived selection, while trios count them before selection acts

Trios avoid the need to know the genome size

The answer is: Counting mutants measures mutations that survived selection, while trios count them before selection acts

2.[2p]
A child carries about 63 new mutations and coding exons are about 1.5 per cent of the genome. How many new mutations fall in coding sequence?

CorrectNot quite: 0.94

3.[2p]
Most new mutations in a human child come from the father, and the number rises with his age.

True

Correct

False

The answer is: True

4.[3p]
With a per-base rate of $2.1 \times 10^{- 10}$ and a genome of $4.6 \times 10^{6}$ bases, how many cells out of a million acquire a mutation each generation?

CorrectNot quite: 966

5.[3p]
What do the two hypotheses predict for the fluctuation test, and what decides between them?

Induction predicts variance equal to the mean, mutation predicts variance far above it, so the scatter decides

Correct

Induction predicts more resistant colonies on average, so the mean decides

The answer is: Induction predicts variance equal to the mean, mutation predicts variance far above it, so the scatter decides

Mutation predicts no resistant colonies at all, so presence decides

The answer is: Induction predicts variance equal to the mean, mutation predicts variance far above it, so the scatter decides

Both predict the same distribution, so the test cannot decide

The answer is: Induction predicts variance equal to the mean, mutation predicts variance far above it, so the scatter decides

6.[3p]
Why are the samples drawn from one bulk culture essential to Luria and Delbrück's argument?

They show that plating and counting are not themselves overdispersed, so the excess variance is biology

Correct

They provide a larger sample size

The answer is: They show that plating and counting are not themselves overdispersed, so the excess variance is biology

They show that phage kills sensitive cells

The answer is: They show that plating and counting are not themselves overdispersed, so the excess variance is biology

They measure the mutation rate directly

The answer is: They show that plating and counting are not themselves overdispersed, so the excess variance is biology

7.[3p]
Which of these are sources of new variation, as this lesson uses the term?

Select all that apply

Point mutation, which modifies an existing gene

Correct

Gene duplication, which frees a spare copy to change

Correct

Recombination, which makes new combinations of existing alleles

Correct

Natural selection, which favours some variants over others

The answer is: Point mutation, which modifies an existing gene, Gene duplication, which frees a spare copy to change, Recombination, which makes new combinations of existing alleles

8.[3p]
An infection holds $10^{11}$ bacteria and a resistance mutation arises at $10^{- 8}$ per cell. How many resistant cells are present before treatment starts?

CorrectNot quite: 1000

9.[2p]
Match each example to what it illustrates.

Primate colour vision
Antifreeze in Antarctic fish
The globin cluster
The Lederberg replica plate

resistant cells traced to a plate never exposed
an opsin gene duplicated and the copies diverged
a trypsinogen gene modified into a new function
one ancestral gene copied and recopied

Show the answer

Primate colour vision: an opsin gene duplicated and the copies diverged Antifreeze in Antarctic fish: a trypsinogen gene modified into a new function The globin cluster: one ancestral gene copied and recopied The Lederberg replica plate: resistant cells traced to a plate never exposed

1.[3p] Why does sequencing a mother, a father and their child give a cleaner mutation rate than counting mutant colonies?

2.[2p] A child carries about 63 new mutations and coding exons are about 1.5 per cent of the genome. How many new mutations fall in coding sequence?

3.[2p] Most new mutations in a human child come from the father, and the number rises with his age.

4.[3p] With a per-base rate of 2.1×10−10 and a genome of 4.6×106 bases, how many cells out of a million acquire a mutation each generation?

5.[3p] What do the two hypotheses predict for the fluctuation test, and what decides between them?

6.[3p] Why are the samples drawn from one bulk culture essential to Luria and Delbrück's argument?

7.[3p] Which of these are sources of new variation, as this lesson uses the term?

8.[3p] An infection holds 1011 bacteria and a resistance mutation arises at 10−8 per cell. How many resistant cells are present before treatment starts?

9.[2p] Match each example to what it illustrates.

1.[3p]
Why does sequencing a mother, a father and their child give a cleaner mutation rate than counting mutant colonies?

2.[2p]
A child carries about 63 new mutations and coding exons are about 1.5 per cent of the genome. How many new mutations fall in coding sequence?

3.[2p]
Most new mutations in a human child come from the father, and the number rises with his age.

4.[3p]
With a per-base rate of $2.1 \times 10^{- 10}$ and a genome of $4.6 \times 10^{6}$ bases, how many cells out of a million acquire a mutation each generation?

5.[3p]
What do the two hypotheses predict for the fluctuation test, and what decides between them?

6.[3p]
Why are the samples drawn from one bulk culture essential to Luria and Delbrück's argument?

7.[3p]
Which of these are sources of new variation, as this lesson uses the term?

8.[3p]
An infection holds $10^{11}$ bacteria and a resistance mutation arises at $10^{- 8}$ per cell. How many resistant cells are present before treatment starts?

9.[2p]
Match each example to what it illustrates.