Mitosis and Meiosis

Question 1

What is mitosis

Answer 1

Part of the cell cycle that produces new cells with the same genetic content

Question 2

Important processes involved in the production of identical daughter cells

Answer 2

DNA replication, chromosome duplication, chromosome separation

Question 3

What is cell division

Answer 3

Process where a parent cell divides into 2 daughter cells

Question 4

Where does mitosis occur

Answer 4

occurs in somatic cells (body cells) producing cells with a diploid number of chromosomes

Question 5

Where does meiosis occur

Answer 5

occurs in the sex organs to produce sex cells (gametes) with a haploid number of chromosomes

Question 6

What are the 2 mains phases in the mitosis cell cycle

Answer 6

Interphase (made up of 3 stages, 90% of cell cycle), M-phase consisting of mitosis (nuclear division) and cytokinesis (division of the cytoplasm at the end of telophase)

Question 7

3 stages of interphase

Answer 7

First gap phase (G1)- cell increases in size and makes the mRNA and proteins needed for S phase, Synthesis (S)- cell duplicates its genetic material (chromosomes), Second gap phase (G2)- nucleus is well defined, rapid cell growth and protein synthesis, cell prepares for mitosis

Question 8

Steps of cytokinesis

Answer 8

Interphase- DNA replicated, centrioles replicated, defined nucleus, Prophase- DNA condenses, nuclear membrane and nucleolus disintegrates, chromosomes appear as chromatids, miotic spindle forms, centrioles move to opposite poles, Metaphase- chromosomes line up on the equator of the cell, Anaphase- spindle fibres retract pulling chromosomes to opposite poles, cell elongates, Telophase- nuclei reform, cell elongates and furrow develops, Cytokinesis- 2 independent cells

Question 9

What does meiosis produce

Answer 9

gametes for reproduction

Question 10

What does meiosis involve

Answer 10

DNA replication, chromosome pairing, two successive nuclear divisions that distribute haploid sets of chromosomes to each gamete

Question 11

What must occur before meiosis

Answer 11

mitosis occurs forming 2 identical chromatids held together at the centromere

Question 12

What steps in meiosis produce genetically different gametes

Answer 12

crossing over (prophase)- allows DNA to break and swap creating new gene combinations, random assortment (metaphase)- chromosomes independently line up resulting in variation of alleles, non-disjunction (anaphase)- homologous chromosomes fail to separate meaning extra of less chromosomes

Question 13

What is crossing over

Answer 13

When chromatids cross and some genetic material from one chromatid can swap to the other chromatid

Question 14

What is random assortment

Answer 14

Homologous chromosomes line up randomly in metaphase 1 meaning that different allele combinations are possible

Question 15

What is non-disjunction

Answer 15

Failure of homologous chromosomes to separate properly during anaphase 1, Failure of sister chromatids to separate properly during anaphase 3

Question 16

What can non-disjunction cause

Answer 16

chromosomal abnormalities- when a zygote is formed by a gamete that has undergone a non-disjunction event resulting in offspring having extra or missing chromosomes in every cell of their body, conditions such as Patau’s syndrome (trisomy 13), Edwards syndrome (trisomy 18), Down syndrome (trisomy 21), Klinefelter syndrome (XXY)

Question 17

What causes Klinefelter syndrome

Answer 17

Error (nondisjunction) results in either the mother’s egg or the father’s sperm having the extra X chromosome (equal chance of either happening), If the reproductive cell with the extra x chromosome contributes to the genetic makeup of a child, the child will have one or more extra X chromosomes in each of the body’s cells

Question 18

Who does Klinefelter syndrome effect and how

Answer 18

affects males physical, behavioural and cognitive development and functioning, causes problems such as a small penis, small testes and infertility, Affects 1 in every 500-1,000 newborn males

Question 19

Difference between main processes of mitosis and meiosis

Answer 19

Mitosis- 1 duplication, 1 nuclear division

Meiosis- 1 duplication, 2 nuclear divisions

Question 20

Difference of what mitosis and meiosis produce

Answer 20

Mitosis- produces 2 diploid cells, new cells for growth and repair
Meiosis- produces 4 haploid cells, gametes for sexual reproduction

Question 21

Difference in homologous chromosomes in mitosis and meiosis

Answer 21

Mitosis- homologous chromosomes don’t pair off

Meiosis- homologous chromosomes do pair off

Question 22

Difference in the makeup of chromosomes in mitosis and meiosis

Answer 22

Mitosis- chromosomes don’t change genetic makeup

Meiosis- genetic makeup of chromosomes can be changed through crossing over

Question 23

Difference in separation in mitosis and meiosis

Answer 23

Mitosis- chromatids separate so that each new cell gets a complete set of daughter chromosomes
Meiosis- first division- members of homologous pairs separate so the new cell gets a haploid set of chromosomes, second division- chromatids separate giving 4 haploid cells

Question 24

First steps of meiosis

Answer 24

Prophase 1: Nuclear membrane disappears, Centrioles move to poles, Spindle fibres form, Homologous chromosomes line up and overlap at the chiasmata which allows for the crossing over of genetic material
Metaphase 1: Homologous chromosomes line up randomly on the equator
Anaphase 1: Homologous chromosomes separate and move towards opposite poles (segregation)
Telophase 1: Cytoplasm divides to form 2 cells with a diploid number of chromosomes, Cells aren’t identical (unlike mitosis)

Question 25

Second steps of meiosis

Answer 25

Interphase 11: No replication of DNA, only time passes
Prophase 11: Spindle fibres forming, Each daughter cell has 1 chromosome from each pair
Metaphase 11: Chromosomes (2 sister chromatids) line up on the equator
Anaphase 11: Chromatids separate each moving to the opposite pole so non-disjunction can occur
Telophase 11: Nuclear membrane forms, 4 haploid daughter cells are produced, 4 sperm but 1 egg (3 polar bodies)- to be covered in spermatogenesis and oogenesis