Genetic Diversity and Adaptation MS.pdf

Question 1

0 6 . 4 Use your knowledge of directional selection to explain the results shown in Table 3.
[3 marks

Answer 1

1. The scientists selected/used for breeding plants
   that produced 2n gametes;
2. (So these plants) passed on their alleles (for
   production of 2n gametes to the next
   generation);
3. The frequency of alleles for production of 2n
   gametes increased (in the population)

Question 2

Scientists investigated the effect of hunting on the genetic diversity of otters. Otters
are animals that were killed in very large numbers for their fur in the past.
The scientists obtained DNA from otters alive today and otters that were alive before
hunting started.
For each sample of DNA, they recorded the number of base pairs in alleles of the
same gene. Mutations change the numbers of base pairs over time.
The figure below shows the scientists’ results.

(c) The scientists obtained DNA from otters that were alive before hunting started.
Suggest one source of this DNA. (1)

Answer 2

Bone / skin / preserved remains / museums.

Question 3

(d) What can you conclude about the effect of hunting on genetic diversity in otters?
Use data from the figure above to support your answer. (2)

Answer 3

1. Hunting reduced the population size so only a few alleles left
   (Bottleneck)
2. otters today from few surviving populations
3. Interbreeding

Question 4

(e) Some populations of animals that have never been hunted show very low levels of
genetic diversity.
Other than hunting, suggest two reasons why populations might show very low
levels of genetic diversity. (2)

Answer 4

1. Population might have been very small / genetic bottleneck;
2. Population might have started with small number of individuals / by one
   pregnant female / founder effect;
3. Inbreeding.
   Allow any two

Question 5

Q4.Malaria is a disease that is spread by insects called mosquitoes. In Africa, DDT is a
pesticide used to kill mosquitoes, to try to control the spread of malaria.
Mosquitoes have a gene called KDR. Today, some mosquitoes have an allele of this
gene, KDR minus, that gives them resistance to DDT. The other allele, KDR plus, does
not give resistance.
Scientists investigated the frequency of the KDR minus allele in a population of
mosquitoes in an African country over a period of 10 years.
The figure below shows the scientists’ results.

(b) Suggest an explanation for the results in the figure above.

(6)

Answer 5

1. Mutation produced KDR minus / resistance allele;
2. DDT use provides selection pressure;
3. Mosquitoes with KDR minus allele more likely (to survive) to reproduce;
4. Leading to increase in KDR minus allele in population.

Question 6

The KDR plus allele codes for the sodium ion channels found in neurones.
(c) When DDT binds to a sodium ion channel, the channel remains open all the time.
Use this information to suggest how DDT kills insects. (2)

Answer 6

1. Neurones remain depolarised;

2. So no action potentials / no impulse transmission.

Question 7

(d) Suggest how the KDR minus allele gives resistance to DDT.
(2)

Answer 7

1. (Mutation) changes shape of sodium ion channel (protein) / of receptor
   (protein) ;
2. DDT no longer complementary / no longer able to bind.

Question 8

(b) In this investigation, what is meant by genetic diversity? (1)

Answer 8

(b) Number of different alleles of each gene.

Question 9

(c) The scientists concluded that the bluethroat showed greater genetic diversity than
the willow flycatcher. Explain why they reached this conclusion. Use calculations to
support your answer. (2)

Answer 9

1. Has greater proportion of genes / percentage of genes showing
   diversity;
2. Percentage is 35% compared with 28% / proportion is 0.35 compared
   with 0.28.
   Allow correct figures that are not rounded up, i.e., 34.9% /
   0.349 and 27.8% / 0.278

Question 10

Define term gene pool [2 marks]

Answer 10

All the different alleles of all the genes

in a population at a given time

Question 11

Explain how this mutation may lead to a change in the MEca protein [4 marks]

Answer 11

Changes in the DNA base/nucleotide sequence

changes in the amino acid sequence/primary structure

alters the hydrogen/ionic/disulfide bonds

causing a change in tertiary structure

Question 12

Describe how a population of Staphylococcus Aureus bacteria can become resistant to antibiotics (3)

Answer 12

Genetic variation arises by random mutation

mutation is advantageous because it gives the bacteria resistance to antibiotic

resistant bacteria more likely to survive

surving bacteria reproduce by binary fission , passing on advantageous allele to next generation

the frequency of the allele increases over subsequent generations

Question 13

The scientist concluded that Bacterium B was likey to be more deadlt if it spread.

Compare the results in F1 and give explantion for statement (3)

Answer 13

Both bacteria unable to grow in presence of methicillin

Bacteria A was unable to grow in presence of penicillin whereas growth of bateria B was not inhibited by P

This means Bacteria B has a resistance to penicillin

so more difficult to treat in hospitals