Mitosis and Meiosis

Question 1

What is a telomere?

Answer 1

repeated sequence, shorten with replication, causes senescence

Question 2

What are sister chromatids?

Answer 2

X shaped chromosomes, 2 identical dna molecules, same alleles

Question 3

What is a homologous pair?

Answer 3

Not X shaped, same DNA sequence, genes may be different variants (alleles)

Question 4

What is diploid vs haploid?

Answer 4

Diploid = full 46 chromosomes, haploid = 23 chromosomes

Question 5

List the stages of mitosis

Answer 5

Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis

Question 6

List the stages of meiosis

Answer 6

Prophase I, metaphase I, anaphase I, telophase I, Interkinesis – Prophase II, metaphase II, anaphase II, telophase II, cytokinesis

Question 7

Describe interphase

Answer 7

Everything in the cell cycle apart from mitosis: G1, S, G2, mitosis, G0

Question 8

What is chiasma?

Answer 8

a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands.

Question 9

What is independent assortment vs crossing over?

Answer 9

crossing over is the process of exchange of DNA between homologous chromosomes whereas the independent assortment is the process in which the chromosome pairs align themselves at the middle of the cell

Question 10

List the function of G1, S and G2

Answer 10

Cell enters G1 - cytoplasmic components are made, S phase - copy of each chromosome is made, G2- more growth so cell is ready to divide, checking for DNA errors, repair if needed

Question 11

How does a sperm cell develop?

Answer 11

Spermatogenesis = Stem cell –> primary spermatocyte –> meiosis I –> 2 secondary spermatocyte –> meiosis II –> 4 spermatids –> maturation –> mature sperm

Question 12

Describe the development of an oogonia

Answer 12

Oogenesis = Oogonia –> mitosis –> born –> primary oocyte –> meiosis –> stops at prophase I –> monthly 1 primary oocyte finishes meiosis I –> becomes secondary oocyte, ovum, released from ovary –> fertilisation –> meiosis II

Question 13

What are the consequences of faulty meiosis?

Answer 13

Third of all identified miscarriages, Infertility, Leading cause of mental retardation

Question 14

How are chromosomes grouped?

Answer 14

Grouped according to size, groups A-G, X = C, Y = G

Question 15

What is karyotype?

Answer 15

the number and visual appearance of the chromosomes in the cell nuclei of an organism or species, Chromosome number, sex complement, structural changes –> 47,XY,+21 = male with trisomy 21

Question 16

What is trisomy?

Answer 16

extra copy of a chromosome is present

Question 17

What is monosomy?

Answer 17

presence of only one chromosome from a pair, cell line usually lost unless involves X

Question 18

Describe nondisjunction

Answer 18

failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

Question 19

What does aneuploidy mean?

Answer 19

presence of an abnormal number of chromosomes in a cell, result of mitotic nondisjunction

Question 20

What is mosaicism?

Answer 20

presence of 2 or more cell lines in an individual degree depends on when: first post-zygotic division, later mitotic divisions

Question 21

What is a post-zygotic mutation?

Answer 21

change in an organism’s genome that is acquired during its lifespan, instead of being inherited from its parent(s) through fusion of two haploid gametes.

Question 22

What stage does crossing- over occur?

Answer 22

meiosis prophase I

Question 23

What stage does random assortment occur?

Answer 23

meiosis metaphase I

Question 24

What happens during prophase?

Answer 24

chromosomes condense, spindle fibres form, nuclear envelope starts to break down

Question 25

What happens during prometaphase?

Answer 25

kinetochore microtubules penetrate nuclear region

Question 26

Explain what happens during metaphase

Answer 26

chromosomes line up in the middle, metaphase plate

Question 27

Describe anaphase

Answer 27

microtubule spindles pull chromatids to separate ends

Question 28

Explain telophase

Answer 28

chromosomes reach opposite ends, spindles disappear, nuclear membrane forms, cleavage furrows appear

Question 29

What happens during cytokinesis?

Answer 29

cleavage furrow at the equator of cell, constricting tightens by contraction of filaments, cell eventually divides into 2 daughter cells

Question 30

what happens at a cell cycle checkpoint to allow the cycle to continue?

Answer 30

the proteins controlling the checkpoints are phosphorylated

Question 31

what is the structure of a chromosome?

Answer 31

short (p) arm, long (q) arm - held together by centromere

Question 32

what are the 4 chromosome structures due to centromere placement?

Answer 32

metacentric, submetacentric, acrocentric, telocentric

Question 33

what links sister chromatids?

Answer 33

centromere (consists of repetitive sequences)