Mitosis, meiosis, chromosomes and genetics

Question 1

where is the telomere on a chromosome and what does it do

Answer 1

found at one end of the chromosome and stops them unraveling

Question 2

what does telomerase do

Answer 2

rebuilds the telomere as they become smaller with each cell division

Question 3

what does Bp mean

Answer 3

base pairs

Question 4

which arm is shorter and which is longer on a chromosome, p or q

Answer 4

p is the shorter arm, p stands for petit

Question 5

what dye stains G banding on chromosomes

Answer 5

Giemsa

Question 6

what dye stains Q banding on chromosomes

Answer 6

Quinacrine

Question 7

what happens in G0 of the cell cycle

Answer 7

the cell is mitotically inactive

Question 8

what happens in S phase of the cell cycle

Answer 8

DNA and centrosome replication

Question 9

what happens in G1 of the cell cycle

Answer 9

the cell grows and many intracellular components are replicated. the cell also undertakes cell monitoring to make sure that it can undergo the process of mitosis

Question 10

what happens in G2 of the cell cycle

Answer 10

the cell grows more and also replicates it organelles, makes proteins and organises itself to undergo mitosis

Question 11

what does a high number of mitoses indicate

Answer 11

a possible malignant tumour, only malignant tumors are graded, benign are not

Question 12

how do many anti-cancer drugs work ?

Answer 12

they are more like anti-mitosis drugs e.g. Colchicine which prevents anaphase or taxol/vinca alkaloids which target the mitotic spindle

Question 13

what does crossing over do and when does it occur

Answer 13

it makes the daughter cells genetically different from its parents and it only happens in prophase 1

Question 14

what is spermatogonia

Answer 14

they are primordial/undifferentiated sperm cells

Question 15

what are Oogonia

Answer 15

they are immature/primordial egg cells

Question 16

what is gonadal mosaicism

Answer 16

In the gametes there is meant to be one population of identical spermatogonia/oogonia but in this case there are 2 or more due to a genetic mutation. This mutation is not present in the somatic cells and so the parent is healthy but the child can be affected. Most common on autosomal (non-sex) genes and X linked. e.g. Osteoporosis imperfecta

Question 17

Prophase

Answer 17

• Chromatin condenses in chromosomes
• Centrosomes nucleate microtubules and move to opposite poles of the nucleus

Question 18

Prometaphase

Answer 18

• Nuclear membrane breaks down
• Microtubules from centrosomes invade the nuclear space
• Chromatids attach to microtubules

Question 19

Metaphase

Answer 19

chromosomes line up along the equatorial plane (metaphase plate)

Question 20

Anaphase

Answer 20

• sister chromatids separate
• they are then pulled to opposite poles of the cell

Question 21

Telophase

Answer 21

• Nuclear membranes reform
• Chromosomes unfold into chromatin
• Cytokinesis begins

Question 22

Sperm production

Answer 22

• Primordial germ cells -> lots of mitoses -> spermatogonia
• mitotic divisions begin at puberty,
• the cytoplasm divides evenly and after meiosis II there are 4 equal gametes,
• they are continuously produced and the process takes 60-65 days

Question 23

egg production

Answer 23

• primordial germ cell -> 30 mitoses -> oogonia
• Oogonia enter prophase 1 by the 8th month of intra-uterine life
• cells then enter ovulation 10-50 years later
• the cytoplasm is divided unequally so there is one huge egg cell and 3 smaller polar bodies that apoptose
• Meiosis 1 is completed at ovulation
• Meiosis 2 is only completed if fertilisation occurs

Question 24

what is non-disjunction

Answer 24

failure of chromosome pairs to separate in meiosis 1 or if sister chromatids fail to separate in meiosis 2

Question 25

what is a disease allele

Answer 25

the allele that carries the pathogenic variant

Question 26

what is polymorphism

Answer 26

frequent hereditary variations at a locus

Question 27

what does congenital

Answer 27

present from birth

Question 28

Karyotype

Answer 28

an individuals complete set of chromosomes

Question 29

what does the body tolerate better, duplications or deletions

Answer 29

duplications