Meiosis

Question 1

What is meiosis?

Answer 1

a form of nuclear division occuring in germ cells

Question 2

What is the product of meiosis?

Answer 2

Haploid cells that carry only one copy of each chromosome

Question 3

What happens to haploid gametes at fertilisation?

Answer 3

fuse to form a diploid zygote (embryo)

Question 4

What are the stages of mitosis and what occurs at each stage?

Answer 4

Question 5

What are the stages of meiosis?

Answer 5

Question 6

What are the 5 stages of prophase 1

Answer 6

Question 7

Describe the process of spermatogenesis

Answer 7

Question 8

Describe the process of oogenesis

Answer 8

Question 9

How does spermatogenesis differ from oogenesis?

Answer 9

The second meiotic division in oogenesis results in a single haploid ovum and a polar body (package of chromosomes that is not used any further)

Question 10

What is an allele?

Answer 10

alternative version of the same gene

Question 11

What are the sources of genetic variation?

Answer 11

Question 12

What is independent assortment of chromosomes?

Answer 12

Random orientation of homologous chromosomes at metaphase of meiosis I

Question 13

What is X chromosome inactivation?

Answer 13

During embryonic development one of the X chromosomes inherited by a female is inactivated so there is only 1 copy of X-linked genes

Question 14

What is non-disjunction?

Answer 14

Chromosomes remain linked together in meiosis I or II - leads to an abnormal number of chromosomes in germ cells

Question 15

What is aneuploidy?

Answer 15

The fertilization of gametes in which non-disjunction has occured - leading to abnormal numbers of a particular chromosome

Question 16

What is a monosomic zygote?

Answer 16

only has one copy of a particular chromosome

Question 17

What is a trisomic zygote?

Answer 17

has 3 copies of a particular chromosome

Question 18

What is polyploidy?

Answer 18

a condition in which an organism has more than 2 complete sets of chromosomes:
- triploidy (3n)
- tetraploidy (4n)

Question 19

What are the different types of chromosomal abnormality that can occur?

Answer 19

deletion
duplication
inversion
translocation (moves a segment from one chromosome to another)

Question 20

What does non-disjunction aneuploidy cause?

Answer 20

infertility

Question 21

Describe meiosis I

Answer 21

Prophase I:
- nucleolus shrinks
- centrioles migrate to poles
- spindle forms
- chromosomes condense
- chiasmata form (crossing of genetic material)
Metaphase I:
- nuclear envelope disappears
- homologous chromosomes move to equator
- centromeres of each bivalent chromosomes orientate to opposite poles
Anaphase I:
- homologous chromosomes separate to opposite poles
- one chromosome with 2 chromatids at each pole
Telophase I:
- cytoplasmic division
- spindle breaks down
- nuclear envelope and nucleoli form

Question 22

Describe meiosis II

Answer 22