Mitosis & Meiosis

Question 1

What is the enzyme that unwinds supercoiled DNA?

Answer 1

Topoisomerase

Question 2

What are the arms of chromosomes called?

Answer 2

P & Q

Question 3

What is G0?

Answer 3

Where stable cells that don’t divide are- Not preparing for devision

Question 4

What dyes stain chromopsomes?

Answer 4

Giemsa: G-Banding, Quinacrine: Q-Banding

Question 5

What is G1?

Answer 5

(11-12 hours) Cells increase in size and organelles

Question 6

What is G2?

Answer 6

Shorter growth phase

Question 7

What is S-Phase?

Answer 7

Cells synthesise a complete copy of DNA and replicates micro-tubule organising structure called centrosome that seperates DNA in M phase.

Question 8

What are the 3 stages of interphase?

Answer 8

G1, S phase, G2

Question 9

What are the steps of Mitosis?

Answer 9

Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis

Question 10

What happens in prophase?

Answer 10

Chromatin condenses into chromosomes, centrosomes nucleate microtubules and move to opposite poles of nucleus

Question 11

What happens in prometaphase?

Answer 11

Nuclear membrane breaks down, microtubules invade nuclear space, chromatids attach to microtubules, no longer has a nucleus

Question 12

What happens in metaphase?

Answer 12

Chromosomes line up along equatorial plane

Question 13

What happens in anaphase

Answer 13

Sister chromatids seperate and are pushed to opposite poles of the cell

Question 14

What happens in telophase?

Answer 14

Nuclear membranes reform, chromosomes unfold into chromatin

Question 15

What happens in cytokinesis?

Answer 15

The cytoplase divides to form 2 cells

Question 16

Drugs that target mitosis?

Answer 16

Taxol & vinca alkaloids prevent mitotic spindle, Ispinesib target spindle poles, Colchicine like drugs target anaphase

Question 17

In meiosis when is there crossing over of genetic material?

Answer 17

Prophase 1

Question 18

What happens in prophase 1 of meiosis?

Answer 18

Crossing over occurs to allow for genetic diversity

Question 19

What happens in metaphase 1 of meiosis?

Answer 19

Random assortment on metaphase plate- resulting in genetic diversity

Question 20

What happens in meiosis 2?

Answer 20

Sister chromatids seperate, haploid cells produced

Question 21

Sperm production? (Gametogenesis)

Answer 21

primordial germ cells undergo lots of mitoses
to produce multiple spermatogonia. Meiotic divisions start at puberty and continue during adult life. Cytoplasm divides equally. Millions of mature sperm continuously
produced.

Question 22

Eggs? (Gametogenesis)

Answer 22

Primordial germ cells undergo 30 mitotic divisions to give rise to oogonia. They enter prophase of meiosis and start by the 8th month of embryonic life. Everything put into suspension-prophase stops. cells enter ovulation 10-50 years later. cytoplasm divided unequally. Meiosis 1 is completed at ovulation. Meiosis 2 only completed if fertilisation occurs. When dividing cytoplasm divides unequally. I egg is produced and 3 polar bodies are produced which die.

Question 23

What is Non-Disjunction? Give example

Answer 23

Failure of chromosome pairs to separate in Meiosis 1 or sister chromatids to separate properly in meiosis 2. E.g. Downs syndrome

Question 24

What is monosome? Give example

Answer 24

Loss of a chromosome. E.g. Turners syndrome

Question 25

What is gonadal mosaicism?

Answer 25

Occurs when precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines (due to errors in mitosis)

Question 26

What is Dcl-2?

Answer 26

A gene which prevents apoptosis, and keeps the cell alive

Question 27

What does helicase do in DNA replication?

Answer 27

Seperates double-stranded DNA into single strands

Question 28

What does DNA Polymerase do?

Answer 28

Binds to exposes nitrogenous bases and adds nucleotides to forma DNA molecule

Question 29

What does ligase do?

Answer 29

An enzyme which can connect two strands of DNA together by forming a bond between the phosphate group of one strand and the deoxyribose group on another

Question 30

What is telomerase?

Answer 30

the enzyme responsible for protecting chromosome ends from shortening during DNA replication to avoid potentially catastrophic DNA loss. If they get too short repressor genes will stop the cell dividing

Question 31

What are labile cells?

Answer 31

Cellx that multiply constantly throughout life. High regenerative ability, high rate of turnover, susceptible to toxic effect of ratiation/ drugs. e.g. intestinal epithelium/ haemopoetic cells/ bone marrow.

Question 32

What are stable cells?

Answer 32

Cells that multiply only when needed. They have good regenative ability and a slow rate of turnover. e.g. hepatocytes, endocrine glands.

Question 33

What are permanent cells?

Answer 33

Cells unable to replicate in postnatal life. e.g. neutrons/ cardiac ,muscle.

Question 34

What is hyperplasia?

Answer 34

Increased number of cells.

Question 35

What is hypoplasia?

Answer 35

Failure of development of an organ.

Question 36

Metaplasia

Answer 36

Adaptive reversible transformation of one terminally differentiated cell type into another.