9.2 Sexual reproduction

Question 1

What is sexual reproduction?

Answer 1

Involves the combination of genetic information from male and female sex cells to form a new unique individual.

Question 2

What are multicellular organisms composed of?

Answer 2

• Somatic cells

- Germ cells (sex cells)

Question 3

What are somatic cells?

Answer 3

• Are all the cells other than gametes (sex cells)

- Are diploid, which means they make two copies of each chromosome.

Question 4

What is meiosis?

Answer 4

The process of cell division that produces gametes.

Question 5

What happens during Prophase I?

Answer 5

• Nuclear membrane disappears
• Chromosomes become visible
• Chromosomes pair up with their homologous partner
• They cross over each other
• Centrioles move to poles of the cell

Question 6

How many chromosomes are there in diploid human cells?

Answer 6

46

Question 7

How many chromosomes are there in haploid human cells?

Answer 7

23

Question 8

What are gametes?

Answer 8

Sex cells:

• Sperm (male)
• Eggs (female)

Question 9

What is the importance of the chromosomes crossing over during Prophase I?

Answer 9

It adds variation since the DNA of both the male and female are being randomly exchanged.

Question 10

What are the stages of meiosis?

Answer 10

1. Interphase I
2. Prophase I
3. Metaphase I
4. Anaphase I
5. Telophase I and Cytokinesis
6. Prophase II
7. Metaphase II
8. Anaphase II
9. Telophase II and cytokinesis

Question 11

What is Spermatogenesis?

Answer 11

The process of meiosis in males that produces sperm

Question 12

What is Oogenesis?

Answer 12

The process of meiosis in females that produces eggs

Question 13

Where in the body does meiosis occur?

Answer 13

In the testes and ovaries

Question 14

How many divisions are there in meiosis?

Answer 14

2

Question 15

How many daughter cells are produced in meiosis?

Answer 15

4

Question 16

What types of cells are the daughter cells produced by meiosis?

Answer 16

Gametes

Question 17

During what phase of meiosis are the chromatids separated?

Answer 17

During Anaphase II

Question 18

Name 4 advantages of sexual reproduction:

Answer 18

• Long-term evolutionary potential
• Unfavourable genetic variation is eliminated from the population more efficiently
• Generates genetic variation and selects for beneficial genetic variation more efficiently
• Populations are better able to adapt to and survive changing environmental conditions

Question 19

Name 3 disadvantages of sexual reproduction:

Answer 19

• Slower reproductive rate
• Recombination can break apart beneficial genomic combinations and introduce deleterious variation to the population
• Energetically costly

Question 20

What can happen if meiosis goes wrong?

Answer 20

• The sperm or egg produced (gamete) could have the wrong number of chromosomes.
• If the gamete is used in fertilisation the resulting offspring (zygote) will have an abnormal number of chromosomes in each cell.

Question 21

What is meiosis referred to when it has gone wrong?

Answer 21

Anenploidy

Question 22

What is non-disjunction?

Answer 22

When gametes are missing a chromosome or have an extra chromosome, which is caused by a chromosome failing to separate during meiosis.
eg. Down syndrome

Question 23

What is the effect of having 2 Y chromosomes?

Answer 23

It can lead to higher levels of testosterone

Question 24

What are the 4 types of damage to chromosomes structures?

Answer 24

• Deletions
• Translocation
• Duplication
• Inverson

Question 25

What is polyploidy?

Answer 25

Damage meiosis which can cause there to be an extra complete set of chromosomes.