Mitosis and Meiosis

Question 1

what are the base pairings in DNA?

Answer 1

A–T (2 bonds) and C–G (3 bonds)

Question 2

3 types of genetic stages (3 C’s) what are they and what stage is each in?

Answer 2

Chromatin - cells not in replication
Chromosomes - during replication
Chromatids - after replication

Question 3

what is the Q and P arm?

Answer 3

Q = long arm
P = short arm

Question 4

describe the 3 stages of interphase…

Answer 4

G1 - no visible activity, rapid growth, normal metabolic function, new organelles form, protein synthesis of spindle fibre formation
S - DNA doubles through replication, histone proteins double, centrosome replication, finish with double the chromosomes
G2 - chromosomes condense, energy stores accumulate, mitochondria and centrioles double

Question 5

describe prophase…

Answer 5

the chromatin condenses into chromosomes.
centrosomes nucleate microtubules (several tubulin moleules interact to form a microtubule seed) and move to opposite sides of the nucleus

Question 6

describe prometaphase…

Answer 6

the nuclear membrane breaks down
microtubules invade nuclear space
chromasomes attach to microtubules that come from the centrosome
cell nucleus no longer there

Question 7

describe metaphase…

Answer 7

chromosomes line up along equatorial plane

Question 8

describe anaphase…

Answer 8

sister chromosomes (same as chromatid) separate 
pulled to opposite ends as spindle fibres contract

Question 9

describe telophase…

Answer 9

nuclear membrane forms
chromosomes unfold into chromatin
cytokinesis begins

Question 10

what are the start and stop codons?

Answer 10

start = ATG
stop = TAG

Question 11

describe meiosis 1…

Answer 11

chromosome number is halved
in prophase 1 - crossing over occurs between non-sister chromosomes
in metaphase 1 - random assortment occurs on the metaphase plane

Question 12

describe meiosis 2…

Answer 12

sister chromosomes separate, 4 haploid cells produced

Question 13

Sperm production process…

Answer 13

primordial germ cells –> lots of mitoses –> spermatogonia (cell produced at early production stage)

Question 14

when do spermatogonia undergo meiotic divisions?

Answer 14

during puberty

Question 15

how long do the spermatogonia take to mature?

Answer 15

60 - 65 days

Question 16

Ovum production process…

Answer 16

primordial germ cells –> 30 mitoses –> oogonia (immature egg cell, diploid)

Question 17

when does an oogonia enter prophase 1?

Answer 17

by the 8th month intrauterine life - the process is then suspended until puberty

Question 18

well does a ovum enter ovulation?

Answer 18

10 - 50 years later

Question 19

how does the oogonia divide and when do meiosis 1/2 occur?

Answer 19

the oogonia cytoplasm divides evenly into 1 egg and 3 polar bodies that apoptose
Meiosis 1 - completed at ovulation
Meiosis 2 - completed if fertilisation occurs

Question 20

what is Gonadal mosaicism?

Answer 20

when precursor germline cells to ova or sperm are a mix of 2 or more genetically different cell lines

Question 21

give examples of conditions caused by gonadal mosaicism?

Answer 21

osteogenesis imperfecta, brittle bones, blue whites of the eyes, duchenne muscular dystrophy

Question 22

what is somatic mosaicism?

Answer 22

genetic fault present in only some body tissues