MEIOSIS

Question 1

What are homologous chromosomes pairs

Answer 1

Chromosomes that have the same “address” of alleel - these chromosomes are usually similar in size shape and genetic composition

Question 2

What is diploid and haploid

Answer 2

Diploid is 2n =46
Haploid is n = 23

Question 3

What is a karyotype

Answer 3

The complete diploid set of chromosomes arranged according to their size shape and number in homologous pairs - consists of 22 pairs of autosomes + 1 pair of gonosomes (XX or XY)

Question 4

What 2 categories is the cell cycle divided into

Answer 4

• interphase
• dividing phase

Question 5

What is interphase

Answer 5

• period between 2 consecutive cell divisions. Cell growth and replication of DNA take place during interphase. Note the chromatin network is visible during this phase

Question 6

What are the 2 types of cell division

Answer 6

• mitosis
• meiosis

Question 7

What is mitosis

Answer 7

• the division of somatic (body cells) for growth, repair damage of tissue and asexual reproduction
• 2 identical daughter cells produced from mother cell - they are identical to each other

Question 8

Briefly describe the 4 phases of mitosis

Answer 8

P: -chromotain network shortens and thickens to become visible chromosomes (joined by centromere)
- nuclear membrane disappears
- centrioles move to opposite poles and spindle fibres develope
M: - chromosomes move to equator
- spindle fibres attach to centromeres
A: - chromotids separate and move to poles (now called daughter chromosomes)
- cytokinesis begins
T: - daughter chromosomes position themselves at poles
- spindle fibres disappear
- nuclear membrane is formed around daughter chromosomes + a nucleolus
- cytokinesis is now complete and 2 identical cells are complete

Question 9

What is meiosis

Answer 9

Formation of gamete’s or spores - the chromosome number is halved (2n - n) it’s also known as reduction division

Question 10

Why is there 2 stages of meiosis

Answer 10

• the first division the chromosome number is halved and genetic material is exchanged
• second division is like normal mitosis where daughter chromosomes separate from each other

Question 11

What happens in prophase 1

Answer 11

• chromatin network shortens and thickens and becomes visible chromosomes
• homologous chromosomes arrange in pairs - they lie close together and from bivalent (2 homologous chromosomes/4 chromatids)
• each chromosomes of the bivalent splits into chromatids
• crossing over takes place - the place where crossing over happens /breakage occurs is the chiasmata
• the nucleus and nuclear membrane disappear
• Centrioles move to poles and spindle fibres form

Question 12

What happens at metaphase 1

Answer 12

• bivalents position themselves on equator
• chromosomes lie in double row or either side of equator
• spindle fibres attach to centromeres

Question 13

What happens in anaphase 1

Answer 13

• spindle fibres contract and shorten pulling chromosomes to poles
• homologous pairs are separated
• cytokinesis begins

Question 14

What happens in telophase 1

Answer 14

• chromosomes group at poles
• spindle fibres disappear
• nuclear membrane and nucleolus forms
• cytokinesis is complete and there’s now 2 daughter cells - each daughter cell has haploid number (n) and the chromosomes are double stranded with exchanged genetic material

Question 15

What happens in prophase 2

Answer 15

Nucleolus and nuclear membrane disappears + spindle fibres for,

Question 16

What happens in metaphase 2

Answer 16

• chromosomes move to equator and align in a row
• spindle fibres attach to centromeres

Question 17

What happens in anaphase 2

Answer 17

• centromere of each chromosome splits
• chromatids separate and move to opposite poles
• they are now daughter chromosomes
• cytokinesis begins

Question 18

What happens in telophase 2

Answer 18

• the chromosomes in each daughter cell are single stranded with recombinant chromatids
  -the spindle fibres disappear
• nuclear membrane and nucleolus forms and cytoplasm divides
• cytokinesis is now complete and 4 daughter cells are formed each with haploid number
  (4 sperm or 1 egg with 3 polar bodies that dissolve)

Question 19

Purpose of meiosis

Answer 19

• formation of gametes(gametogenesis x oogenesis or spermatogenesis)
• takes place in ovaries or testes

Question 20

What is the importance of meiosis

Answer 20

Chromosome number is halved
Gametes with different gene combinations are produced leads to genetic variation - this is because of crossing over

Question 21

How is there genetic variation in meiosis

Answer 21

• crossing over - recombinant genes occur
• random assortment of chromosomes on the equator during metaphase 1
• random fertilisation - which sperm fuses with which egg - consequently the new individual is unique

Question 22

What is aneuploidy

Answer 22

• a chromosome mutation where there is an extra chromosome or missing chromosome
  An eg would be Down syndrome where there are 47 instead of 46 - the pair 21 doesn’t separate during anaphase 1

Question 23

How are mitosis and meiosis similar list 3

Answer 23

• both a cell division process
• both require DNA replication during interphase before division begins
• both have the4 phases PMAT

Question 24

What are the differences of mitosis and meiosis table form

Answer 24

Mitosis. | meiosis
- takes place in body cells - takes place in reproductive organs
- takes place in damaged. - takes place in sporangia of the sporophyte generation
tissue