sexual reproduction

Question 1

briefly summarise how sexual reproduction works?

Answer 1

• two parents (1 male, 1 female)
• each parent produces haploid gametes
• via meiosis
• a male and female gamete fuse via fertilisation
• produces diploid zygote

Question 2

what are the advantages of sexual reproduction?

Answer 2

• produces offspring with genetic variation
• members of a species have advantageous alleles to survive new threats
• so clones are more vulnerable

Question 3

XX chromosomes

Answer 3

female

Question 4

XY chromsomes

Answer 4

male

Question 5

what are autosomes?

Answer 5

pairs of chromosomes that are not sex chromosomes

Question 6

define haploid chromosome

Answer 6

• contains 1 set of chromosomes
• 23
• 1 member of each homologous pair

Question 7

define gamete

Answer 7

• sex cells
• male = sperm
• female = egg

Question 8

what is the product of sexual reproduction in a flowering plant?

Answer 8

seed

Question 9

what are some advantages of asexual reproduction over sexual reproduction?

Answer 9

• colonise a stable environment quickly
• don’t need to find a mate

Question 10

which 3 processes lead to increased genetic variation during meiosis?

Answer 10

• crossing over
• independent assortment
• random fertilisation

Question 11

when does crossing over occur?

Answer 11

prophase 1

Question 12

what happens during crossing over?

Answer 12

chromatids twist around and swap alleles

Question 13

how does crossing over increase genetic variation?

Answer 13

new combinations of alleles occur
- more phenotypes expressed
- respond to natural selection under threat

Question 14

when does independent assortment of paired chromosomes occur?

Answer 14

metaphase 1

Question 15

what happens during independent assortment of paired chromosomes?

Answer 15

• bivalents line up on cell equator
• different combinations of chromosomes in each daughter cell of first division

Question 16

how does independent assortment of paired chromosomes increase genetic variation?

Answer 16

there are new chromosome combinations in each daughter cell of the first division

Question 17

when does independent assortment of single chromosomes occur?

Answer 17

metaphase 2

Question 18

what happens during independent assortment of single chromosomes?

Answer 18

each replicated chromosome aligns in an independent position

Question 19

how does independent assortment of single chromosomes increase genetic variation?

Answer 19

creates unique chromatid combinations of each daughter cell of the second division

Question 20

what is random fertilisation?

Answer 20

any sperm fertilises with any egg

Question 21

how does random fertilisation increase genetic variation?

Answer 21

each individual is completely unique

Question 22

how do you calculate the possibilities of gametes produced by one parent?

Answer 22

2 to the power of the haploid number

Question 23

how do you calculate the possibilities of combinations produced by sexual reproduction?

Answer 23

2 to the power of the haploid number squared

Question 24

outline the events that lead to genetic variation in gametes (5)

Answer 24

• meiosis
• mutation = random
• crossing over of chromatids, swapping alleles in prophase 1 creating new allele combinations
• independent assortment in metaphase 1&2 - bivalents line up in middle of cell and new chromosome combinations form
• random fertilisation - offspring is completely unique