Meiosis

Answer 1

prophase 1
homologous chromosomes pair up and exchange fragments(crossing over)
Metaphase 1
homologous pairs line up at the metaphase plate
Anaphase 1
Homologues separate to opposite ends of the cell. Sister chromatids stay together
Telophase 1
Newly forming cells are are haploid (n=2)

Question 2

When does crossing over occur

Answer 2

crossing over occurs at prophase 1

Question 3

What is chiasma

Answer 3

the middle of the chromosome

Question 4

The aim of meiosis

Answer 4

creating 4 gene

Question 5

Three mechanisms by which meiosis promotes genetic variation

Answer 5

• Crossing over between non-sister chromatids during prophase 1
• random assortment of homologous chromosomes during metaphase 1
• fusion of gametes from different parents

Question 6

Why do we want genetic variation

Answer 6

Allows us to improve survival rate
- increases biodiversity

Question 7

What is a chromosome called after crossing over

Answer 7

Bivalent

Question 8

How many different chromosome combinations do gametes have

Answer 8

2^23

Question 9

Which chromosome is affected when downsyndrome accurs?

Answer 9

21st chromosome

Question 10

Two phases of non-dysjunction

Answer 10

1. Homologous pairs in anaphase 1 (all four daughter cells will be affected)
2. sister chromatods chromatids in anaphase 11 (only two of the daughter cells affected)

Question 11

Factor of downsyndrome occuring more frequently?

Answer 11

Increasing age

Question 12

What is karyotiping:

Answer 12

The image of 23 pairs of chromosomes

Answer 13

1. chorionic villi sampling where cells are taken from the placenta
2. Amniocentesis cells from amniotic fluid

Question 14

Issue with chorionic villi sampling where cells are taken

Answer 14

higher risk of miscarriage

Question 15

Whats good about Amniocentesis cells from amniotic fluid

Answer 15

lower risk of miscarriage