Variation and Sexual Reproduction

Question 1

Costs of sexual reproduction?

Answer 1

males unable to produce offspring
only half of each parent’s genome passed onto offspring, disrupting successful parental genomes

Question 2

Benefits of sexual reproduction?

Answer 2

increase in genetic variation in the population

Question 3

Why can asexual reproduction be a successful reproductive strategy?

Answer 3

whole genomes are passed on from parent to offspring

Question 4

When is maintaining the genome of the parent an advantage?

Answer 4

particularly in very narrow, stable niches or when re-colonising disturbed habitats

Question 5

Examples of asexual reproduction in eukaryotes

Answer 5

vegetative cloning in plants and parthenogenesis in lower plants and animals that lack fertilisation

Question 6

Advantage of asexual reproduction?

Answer 6

offspring can be produced more often and in larger numbers

Question 7

Parthenogenesis is more common in

Answer 7

cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity

Question 8

What is parthenogenesis?

Answer 8

reproduction from a female gamete without fertilisation

Question 9

What is meiosis?

Answer 9

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

Question 10

In diploid cells, chromosomes typically appear as

Answer 10

homologous pairs

Question 11

What are homologous chromosomes?

Answer 11

Same size, same centromere position, same sequence of genes at same loci

Question 12

What are linked genes

Answer 12

those on the same chromosome

Question 13

What can crossing over result in?

Answer 13

new combinations of the alleles of these genes

Question 14

How many haploid cells are produced during meiosis?

Answer 14

4

Question 15

What is the independent assortment?

Answer 15

Each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin

Question 16

What gene in most mammals determines the development of male characteristics?

Answer 16

The SRY gene on the Y chromosome

Question 17

What happens In homogametic females?

Answer 17

one of the two X chromosomes present in each cell is randomly inactivated at an early stage of development

Question 18

What does X chromosome inactivation prevent?

Answer 18

a double dose of gene products, which could be harmful to cells

Question 19

What are hermaphrodites?

Answer 19

Species that have functioning male and female reproductive organs in each individual.

Question 20

Other features of hermaphrodites?

Answer 20

They produce both male and female gametes and usually have a partner with which to exchange gametes

Question 21

Benefit of being a hermaphrodite?

Answer 21

If the chance of encountering a partner is an uncommon event, there is no requirement for that partner to be of the opposite sex

Question 22

In some species sex can change as a result of…?

Answer 22

size, competition, parasitic infection

Question 23

How is environmental sex determination controlled in reptiles?

Answer 23

temperature of egg incubation

Question 24

What is X chromosome inactivation?

Answer 24

A process by which most of one X chromosome is inactivated