6.7 Production of haploid gametes

Question 1

How many chromosomes are in a somatic cell?

Answer 1

46

Question 2

What is reduction division?

Answer 2

Production of gametes through dicision in meiosis that reduces the chromosome umber from diploid to haploid

Question 3

What is crossing over?

Answer 3

When non-sister chromatids of homologous chromosomes exchange corresponding segments

Question 4

What is independent assortment?

Answer 4

The formation of random chromosomes combinations during meiosis that contributed to variation

Question 5

When does crossing over occur?

Answer 5

Prophase I

Question 6

What is bivalent?

Answer 6

A pair of homologous chromosomes that are held together by at least one crossover

Question 7

Name the stages of meiosis

Answer 7

Interphase, prophase 1, metaphase 1, anaphase 1, telophase 1, prophase 2, metaphase 2, anaphase 2, telophase 2

Question 8

What happens before meiosis?

Answer 8

A diploid cell has 4 chromosomes (2n=4)

Question 9

What happens during interphase?

Answer 9

DNA is replicated, results in sister chromatids

Question 10

What happens during prophase 1?

Answer 10

Chromosomes condense and nucleur envelope degrades, crossing over occurs

Question 11

What happens during metaphase 1?

Answer 11

Homologous chromosomes line up alongside each other down the equator of cell

Question 12

What happens during anaphase 1?

Answer 12

Seperated from each other, centromeres are pulled to opposite poles by spindle fibres

Question 13

What happens during telophase 1?

Answer 13

Nuclear envelope reforms around each set of chromosomes, fibres disappear, cytokenisis occurs, forms two new cells

Question 14

What happens during prophase 2?

Answer 14

Re-condense if necessary and nuclear envelope breaks down

Question 15

What happens during metaphase 2?

Answer 15

Chromosomes line up along the equator

Question 16

What happens during anaphase 2?

Answer 16

Replicated chromosomes are seperated into single strands by spindle fibres, pulling sister chromatids apart

Question 17

What happens during telophase 2?

Answer 17

Nuclear envelope reforms around each set of chromosomes, cytokinesis occurs, forms 4 haploid daughter cells (n=2)

Question 18

What does meiosis produce?

Answer 18

Sex cells with infinite variation due to crossing over and independent assortment

Question 19

What is meiosis?

Answer 19

The process that produces haploid gametes from a diploid cell

Question 20

What cells are diploid?

Answer 20

Somatic cells

Question 21

What cells need to be haploid and why?

Answer 21

Egg and sperm cells because they combine so the offspring has the right amount of chromosomes

Question 22

How many divisions are there in meiosis?

Answer 22

2

Question 23

How many daughter cells result from one round of meiosis?

Answer 23

4 daughter cells

Question 24

Describe the process of crossing over

Answer 24

One arm of each homologous chromosome joins (synapses) with the same arm of the pair; mum and dad’s chromosomes are now mixed

Question 25

Describe independent assortment

Answer 25

Each sex cell with recieve one copy of each chromosome; the copy of each chromosome that ends up in each sex cell is random-they assort independently

Question 26

Why is variation important?

Answer 26

Increased genetic diversity from sexual reproduction aids with the species survival. They are better equipped to survive in changing, unstable environments. Species cannot evolve