Meiosis and genetic variation

Question 1

Are normal body cells diploid or haploid?

Answer 1

Diploid (2n)

Question 2

Why are human cells diploid?

Answer 2

Each cell has two of each chromosome, one from mother and one from father

Question 3

What is a homologous pair?

Answer 3

Two chromosomes that have the same genes but can have different alleles

Question 4

What is the diploid number for humans?

Answer 4

46

Question 5

Are gametes diploid or haploid?

Answer 5

Haploid (n)

Question 6

What is the haploid number for gametes?

Answer 6

23

Question 7

What occurs at fertilisation?

Answer 7

Haploid sperm fuses with a haploid egg making a normal diploid number of chromosomes

Question 8

What does random fertilisation produce?

Answer 8

Zygotes with different combinations of chromosomes

Question 9

How does fertilisation produce genetic diversity?

Answer 9

The random fertilisation causes the mixing of genetic material

Question 10

Where does meiosis take place?

Answer 10

Reproductive organs

Question 11

What type of cells divides in meiosis?

Answer 11

Normal diploid cells

Question 12

What type of cells are formed in meiosis?

Answer 12

Haploid gametes

Question 13

What happens before meiosis occurs?

Answer 13

The DNA unravels and replicates so there are to copies of each chromosomes called chromatids, cell becomes 2 x 2n

Question 14

What is the second stage that takes place before meiosis?

Answer 14

The DNA condenses to form double-armed chromosomes, each made from two sister chromatids which are joined in the middle by a centromere

Question 15

What happens during Meiosis 1?

Answer 15

Chromosomes arrange themselves in homologous pairs

The homologous pairs are then separated, halving the chromosome number

Question 16

What is the chiasma?

Answer 16

The point at which recombination occurs

Question 17

What is recombination?

Answer 17

During meiosis 1, the chromatids of the homologous chromosomes cross over each other and swap bits of chromatids

Question 18

How does recombination create genetic variation?

Answer 18

Creates different combinations of alleles

Each of the 4 daughter cells contain chromatids with different alleles

Question 19

What happens during Meiosis 2?

Answer 19

The pairs of sister chromatids that make up each chromosome are separated as the centromere is divided

Question 20

What is produced from meiosis?

Answer 20

4 haploid daughter cells, each genetically different from each other

Question 21

What is independent segregation?

Answer 21

When the homologous pairs separate in meiosis 1, it is completely random which chromosome from each pair ends up in each daughter cell

Question 22

How does independent segregation produce genetic variation?

Answer 22

The daughter cells have completely different combinations of those maternal and paternal chromosomes, leads to genetic variation in potential offspring

Question 23

How can you tell if a cell has halved?

Answer 23

If the number of chromosomes in the daughter cells are half that of the parent cells

Question 24

What are the three outcomes of meiosis?

Answer 24

• Produces cells with half the number of chromosomes as the parent cell
• Daughter cells are genetically different from one another and the parent cell
• Produces 4 daughter cells