Lesson test: How fast selection works

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How fast selection works

1.[2p]
What is fitness, in the algebra of this lesson?

The average number of offspring left by a genotype in a particular environment, taken relative to the best

Correct

The strength, health or longevity of an individual

The answer is: The average number of offspring left by a genotype in a particular environment, taken relative to the best

A property of a species that determines its survival

The answer is: The average number of offspring left by a genotype in a particular environment, taken relative to the best

The proportion of a population carrying an allele

The answer is: The average number of offspring left by a genotype in a particular environment, taken relative to the best

2.[3p]
A favoured allele with $s = 0.1$ starts at 1 per cent. How many generations until it reaches 99 per cent?

CorrectNot quite: 97

3.[2p]
Why does selection act fastest when an allele is near 50 per cent?

The rate depends on $p q$ , which is largest at one half

Correct

Heterozygotes are commonest there and are always the fittest

The answer is: The rate depends on $pq$, which is largest at one half

Mutation supply is highest at intermediate frequencies

The answer is: The rate depends on $pq$, which is largest at one half

Dominance disappears at intermediate frequencies

The answer is: The rate depends on $pq$, which is largest at one half

4.[3p]
Haldane's calculation makes the melanic moths 1.5 times as fit as the pale form. What selection coefficient is acting against the pale form?

CorrectNot quite: 0.333

5.[2p]
Selection against a rare dominant allele is more efficient than selection against a rare recessive.

True

Correct

False

The answer is: True

6.[3p]
Under a lethal recessive, $1 / q$ rises by one each generation. How many generations take $q$ from 0.02 to 0.01?

CorrectNot quite: 50

7.[3p]
With $w_{A A} = 0.89$ , $w_{A a} = 1$ and $w_{a a} = 0.20$ , what is the equilibrium frequency of the $a$ allele?

CorrectNot quite: 0.121

8.[3p]
Which are true of the sickle-cell polymorphism?

Select all that apply

Neither allele can be eliminated, because whichever is rare sits mostly in heterozygotes

Correct

The population pays a permanent reduction of about 9.7 per cent in mean fitness

Correct

Allison established the malaria link in 1954 by comparing lowlands with highlands

Correct

Selection eventually removes the sickle allele wherever malaria is present

The answer is: Neither allele can be eliminated, because whichever is rare sits mostly in heterozygotes, The population pays a permanent reduction of about 9.7 per cent in mean fitness, Allison established the malaria link in 1954 by comparing lowlands with highlands

9.[2p]
Match each symbol to what it stands for.

$w$
$s$
$\overline{w}$
$q^{*}$

relative fitness of a genotype
selection coefficient, one minus fitness
equilibrium frequency under overdominance
mean fitness of the population

Show the answer

$w$ : relative fitness of a genotype $s$ : selection coefficient, one minus fitness $\overline{w}$ : mean fitness of the population $q^{*}$ : equilibrium frequency under overdominance

1.[2p] What is fitness, in the algebra of this lesson?

2.[3p] A favoured allele with s=0.1 starts at 1 per cent. How many generations until it reaches 99 per cent?

3.[2p] Why does selection act fastest when an allele is near 50 per cent?

4.[3p] Haldane's calculation makes the melanic moths 1.5 times as fit as the pale form. What selection coefficient is acting against the pale form?

5.[2p] Selection against a rare dominant allele is more efficient than selection against a rare recessive.

6.[3p] Under a lethal recessive, 1/q rises by one each generation. How many generations take q from 0.02 to 0.01?

7.[3p] With wAA=0.89, wAa=1 and waa=0.20, what is the equilibrium frequency of the a allele?

8.[3p] Which are true of the sickle-cell polymorphism?

9.[2p] Match each symbol to what it stands for.

1.[2p]
What is fitness, in the algebra of this lesson?

2.[3p]
A favoured allele with $s = 0.1$ starts at 1 per cent. How many generations until it reaches 99 per cent?

3.[2p]
Why does selection act fastest when an allele is near 50 per cent?

4.[3p]
Haldane's calculation makes the melanic moths 1.5 times as fit as the pale form. What selection coefficient is acting against the pale form?

5.[2p]
Selection against a rare dominant allele is more efficient than selection against a rare recessive.

6.[3p]
Under a lethal recessive, $1 / q$ rises by one each generation. How many generations take $q$ from 0.02 to 0.01?

7.[3p]
With $w_{A A} = 0.89$ , $w_{A a} = 1$ and $w_{a a} = 0.20$ , what is the equilibrium frequency of the $a$ allele?

8.[3p]
Which are true of the sickle-cell polymorphism?

9.[2p]
Match each symbol to what it stands for.