Meiosis

Question 0

Diploid cell

Answer 0

• (2n)
• Cells contain 2 complete sets of each type of chromosome
• One set originated from the father and one from the mother

Question 1

Haploid cell

Answer 1

• (n)
• cells containing a single set of unpaired chromosomes

Question 2

Meiosis

Answer 2

• One diploid cell (2n) divides
• To form 4 haploid cells (n)
• chromosome number reduced to half
• Production of gametes (or gametophyte generation in plants)

Question 3

Alternation of generations

Answer 3

Alternation between diploid and haploid phases

Question 4

Stages of meiosis

Answer 4

Meiosis 1:

• Prophase 1;
• Metaphase 1;
• Anaphase 1;
• Telophase 1

Meiosis 2:

• Prophase 2;
• Metaphase 2;
• Anaphase 2;
• Telophase 2

Question 5

Homologous chromosomes

Answer 5

• Chromosomes containing the same gene sets
• Similar size, shape and information
• One paternal and the other maternal

Question 6

One duplicated chromosome at metaphase can be labelled with…

Answer 6

• Two sister chromatids
• joined together at the centromere

Question 7

DNA replication takes place during

Answer 7

Interphase (S-phase)

Question 8

Meiosis Prophase 1

Answer 8

• Nuclear membrane breaks down
• Chromosomes condense
• Bivalents form
• Crossing over occurs
• Centrioles produce spindle

Question 9

Meiosis Metaphase 1

Answer 9

• Homologous chromosomes align along equator
• Independent assortment of chromosomes
• Spindle fully formed
• Diagrams show evidence chiasmata

Question 10

Meiosis Anaphase 1

Answer 10

• Homologous chromosomes move to opposite poles
• Spindle threads contract pulling chromosomes
• Diagrams show evidence chiasmata

Question 11

Meiosis Telophase 1

Answer 11

• Each pole has haploid (n) chromosomes
• Nuclear membrane reforms
• Spindle disappears
• Cytokinesis usually visible

Question 12

Meiosis Prophase 2

Answer 12

• Nuclear membrane disappears
• Chromosomes condense
• Spindle apparatus forms

Question 13

Meiosis Metaphase 2

Answer 13

• Single chromosomes line up at equator
• Spindle fully formed

Question 14

Meiosis Anaphase 2

Answer 14

• Sister chromatids split at centromere into two chromosomes
• Spindle contracts pulling single copy chromosomes to opposite poles

Question 15

Meiosis Telophase 2

Answer 15

• Nuclear membranes reform
• Spindle disappears
• Cytokinesis occurs
• Four haploid daughter cells produced

Question 16

Purpose of meiosis

Answer 16

• In animals: production of gametes (n)
• In plants: production of spores/gametophyte generation (n)

Question 17

Gametogenesis and what it is called in males and females

Answer 17

• Production of gametes
• In males: spermatogenesis
• In females: oogenesis

Question 18

Alternation of generations

Answer 18

When organisms alternate between haploid (n) and diploid (2n) forms during their life cycles

Question 19

Groups that have an alternation of generations

Answer 19

• Protists
• Fungi
• Plants:
• Bryophytes
• Pteridophytes
• Gymnosperms and
• angiosperms

Question 20

The different life forms of mosses and ferns

Answer 20

• Gametophyte (n) produces gametes (n)
• Gametes fuse to form zygote (2n)
• Zygote grows into sporophyte (2n)
• Sporophyte undergoes meiosis to produce spores (n)
• Spores grow into gametophyte

Question 21

Ploidy

Answer 21

The chromosome number in an organism

Question 22

The importance of meiosis

Answer 22

• Chromosome number halved - to maintain ploidy when gametes fuse
• Cells produced after meiosis genetically unique - introduces and mixes up variation of genes in a species

Question 23

How variation is ensured in offspring through meiosis

Answer 23

• Random independent assortment of chromosomes and segregation
• Chiasma formation during crossing over
• Random gametes involved in fertilisation

Question 24

Term used when a problem occurs during meiosis result in a new chromosome number

Answer 24

Aneuploidy (a-new-ploidy)

Question 25

Nondisjunction of chromosomes

Answer 25

• When a chromosome pair(s) fails to separate during meiosis
• resulting in aneuploidy for the gametes formed

Question 26

Polyploidy

Answer 26

• When cells have more than two complete sets of chromosomes.
• More common in plants.

Question 27

Down’s syndrome

Answer 27

• Person with a ploidy of 47
• Extra chromosome number 21
• Also called trisomy 21

Question 28

Causes of Down’s syndrome

Answer 28

• An extra chromosome 21
• Possibly greater risk from external factors e.g. Radiation
• Risk increases with maternal age

Question 29

Medical conditions associated with Down’s syndrome

Answer 29

• Developmental difficulties
• Hearing and vision defects
• Heart abnormalities
• Leukemia
• Thyroid disorders
• Dementia in later life
• Shorter lifespan

Question 30

Similarities between mitosis and meiosis

Answer 30

• DNA replicates prior during interphase
• Nuclear membrane and nucleolus break down during prophase
• Spindle forms during prophase
• Chromosomes condense during prophase
• Chromosomes line up on equator during metaphase
• Spindle contracts during anaphase
• Cytokinesis follows both meiosis and mitosis

Question 31

Different locations in mitosis vs meiosis

Answer 31

• Mitosis: all somatic cells and asexual reproduction
• Meiosis: reproductive organs (in humans: testes and ovaries)

Question 32

Process differences between mitosis and meiosis

Answer 32

• Mitosis both haploid or diploid cells divide; meiosis only diploid
• Mitosis has one division of chromosomes; meiosis separation in meiosis 1 and division in meiosis 2
• Mitosis has no pairing of homologous chromosomes; meiosis pairing occurs
• Mitosis one nuclear division; meiosis has two
• Mitosis has only one cytokinesis event; meiosis has two

Question 33

Differences in the cells produced between mitosis and meiosis

Answer 33

• Mitosis produces two cells; meiosis four
• Mitosis maintains chromosome number; meiosis halves it
• Mitosis daughter cells with same genes; meiosis with unique genes
• Mitosis daughter cells identical; meiosis unique

Question 34

Functional differences between mitosis and meiosis

Answer 34

Mitosis:

• growth,
• repair and
• asexual reproduction

Meiosis:

• for gamete formation,
• to maintain chromosome number in life cycle