Variation and Sexual Reproduction

Question 1

Identify the two disadvantages of sexual reproduction.

Answer 1

1. Males, who generally comprise half the population are unable to reproduce.
2. Offspring only receive half of their parents genome.

Question 2

Identify the benefit of sexual reproduction.

Answer 2

Provides the raw materials for adaptation.

Question 3

In co-evolutionary interactions between parasites and hosts, why may parasites option for a sexually reproducing host? (5).

Answer 3

1. Hosts better able to resist and tolerate parasitism, have greater fitness.
2. If hosts reproduce sexually, the genetic variation in their offspring reduces the chances that all will be susceptible to infection.
3. Parasites with increased virulence, better able to feed, reproduce and find new hosts also have greater fitness
4. If parasites reproduce sexually, the genetic variation in their offspring increases the chances of some offspring having improved ability to exploit host.
5. The selection pressure created by evolved resistance of the hosts drives the evolution of parasites to increase their virulence.

Question 4

Describe asexual reproduction.

Answer 4

Involves the production of genetically identical offspring by a single parent.
No genetic variation.

Question 5

Identify the 3 benefits of asexual reproduction.

Answer 5

1. It can be a rapid reproductive strategy in narrow stable niches.
2. Conserves advantagous genomes.
3. Offspring develop rapidly, thus allowing early establishment in new habitats.

Question 6

identify the 2 costs of asexual reproduction.

Answer 6

1. Not able to adapt easily to chances in their habitat.
2. Doesn’t provide variation necessary for natural selection.

Question 7

Between horizontal and vertical gene transfer, which has faster evolutionary changes?

Answer 7

Horizontal gene transfer.

Question 8

What are the two processes of asexual reproduction in eukaryotes.

Answer 8

1. Vegetative cloning
2. Parthenogenesis.

Question 9

Discuss the process of parthenogenesis.

Answer 9

1. Development of unfertilised eggs.
2. Resulting offspring are haploid.
3. More common in cooler climates with low parasite diversity.

Question 10

Define meiosis.

Answer 10

The division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte.

Question 11

What is the name of the point of contact between two non-sister chromatids.

Answer 11

Chiasmata.

Question 12

What is the product of the exchange of genetic material at the chiasmata?

Answer 12

Genetically different recombinant chromosomes.

Question 13

Is the orientation of chromosomes at the equator random or organised?

Answer 13

Random.

Question 14

Where to the spindle fibres attach.

Answer 14

The centromere.

Question 15

What are the similarities in a homologous pair?

Answer 15

1. Same genes at the same loci
2. The same size.
3. Same position of centromere.

Question 16

What does cytokinesis produce?

Answer 16

Two sister daughter cells.

Question 17

What are the features of meiosis. (2).

Answer 17

1. Four haploid daughter cells are produced.
2. Sister chromatids are seperated.

Question 18

What is the term given to an individual who produces both male and female gametes.

Answer 18

Hermaphrodite.

Question 19

What are two examples of environmental sexual determination.

Answer 19

1. In reptiles, the temperature of eggs determines sex.
2. In some species, the ratio of sex is adjusted to resource availability.

Question 20

Some animals can change sex as a result of;

Answer 20

1. Size
2. Competition
3. Parasitic infection

Question 21

What is the term given to an individual who has two the same gene and two different genes.

Answer 21

Heterogematic and homogematic.

Question 22

Describe the process resulting in male characteristics.

Answer 22

A gene called SRY carried on the Y chromosome, determines the development of male characteristics by encoding and expressing a protein called testes-determining factor (TDF).

Question 23

Discuss random X chromosome inactivation.

Answer 23

1. One X chromosome in each cell is randomly inactivated.
2. Which X chromosome is inactivated is random.
3. Prevents a double dosage of a potentially harmful gene.