Chromosomes, Cell Division, Meiosis and Chromosome Abnormalities

Question 1

what is the structure of a eukaryotic chromosome?

Answer 1

Linear
telomeres at the edges
centromere in the middle

Question 2

where are the regions of euchromatin and heterochromatin in a eukaryotic chromosome?

Answer 2

heterochromatin in the middle

euchromatin at the edges (however telomeres are composed of euchromatin)

Question 3

what are the different phases in mitosis?

Answer 3

G1
S
G2
M

Question 4

what happens in the G1 phase?

Answer 4

cell grows

Question 5

what happens in the S phase?

Answer 5

DNA is replicated

Question 6

what happens in the G2 phase?

Answer 6

cell prepares to divide

Question 7

what happens in the M phase?

Answer 7

cell division (mitosis)

Question 8

what are the 5 different phases of mitosis?

Answer 8

prophase
metaphase
anaphase
telophase
cytokinesis

Question 9

what happens in prophase?

Answer 9

chromosomes condense
nuclear membrane disappears
spindle fibres form from the centriole

Question 10

what happens in metaphase?

Answer 10

chromosomes aligned at the equator of the cell
attached by fibre to each centriole
maximum condensation of chromosomes

Question 11

what happens in anaphase?

Answer 11

sister chromatids separate at centromere
separate longitudinally
move to opposite ends of the cell

Question 12

what happens in telophase?

Answer 12

new nuclear membranes form

each new cell contains 46 chromosomes (diploid)

Question 13

what happens in cytokinesis?

Answer 13

cytoplasm separates

Question 14

what is a centromere?

Answer 14

constricted region which joins sister chromatids

Question 15

what is the centromere composed of?

Answer 15

repetitive DNA sequences (satellite DNA)

also the site of the kinetochore

Question 16

what is the kinetochore?

Answer 16

protein complex that binds to microtubules (involved in chromosome separation during cell division)

Question 17

is the structure of heterochromatin condensed or open?

Answer 17

condensed (silenced)

Question 18

is the structure of euchromatin condensed or open?

Answer 18

open (active)

Question 19

what are the two tandemly repeated extragenic DNA sequences

Answer 19

satellite DNA

minisatellite DNA

Question 20

what are the two types of extragenic sequences that make up approx. 45% of the genome?

Answer 20

SINEs (short interspersed nuclear elements)

LINEs (long interspersed nuclear elements)

Question 21

what is the structure of chromatin?

Answer 21

DNA packaged with histone proteins

Question 22

are histones positively or negatively charged?

Answer 22

positively charged

Question 23

what are histones packaged into?

Answer 23

units called nucleosomes

Question 24

what is the structure of a nucleosome?

Answer 24

146 base pairs of DNA (1.8 turns) wrapped around a core of 8 histone proteins

Question 25

what does further "wrapping" of nucleosomes lead to?

Answer 25

formation of a solenoid structure, where the DNA is compacted by a factor of approx. 40

Question 26

what are the 4 levels of condensed chromatin structure?

Answer 26

1: nucleosome 2: chromatin fibre 3: fibre-scaffold complex 4: chromosome

Question 27

what are the purposes of packaging DNA?

Answer 27

negatively charged DNA neutralised by positively charged histone proteins DNA takes up less space Inactive DNA can be folded into inaccessible locations until required

Question 28

what is the karyotype?

Answer 28

the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.

Question 29

what types of FISH probes are there?

Answer 29

unique sequence probes centromeric probes telomeric probes whole chromosome probes

Question 30

what does FISH stand for?

Answer 30

fluorescent in situ hybridisation

Question 31

what is hybridisation?

Answer 31

he process of combining two complementary single-stranded DNA or RNA molecules and allowing them to form a single double-stranded molecule through base pairing.

Question 32

what is meiosis?

Answer 32

cell division in germ cells

Question 33

what creates genetic diversity in meiosis?

Answer 33

recombination of chromosomes

Question 34

what do diploid cells divide into during meiosis?

Answer 34

haploid cells

Question 35

what is oogenesis?

Answer 35

egg formation

Question 36

what is spermatogenesis?

Answer 36

process of sperm formation

Question 37

what goes through more divisions; eggs or sperm?

Answer 37

sperm - leads to a higher chance of mutation

Question 38

what is produced along with the egg in oogenesis?

Answer 38

polar bodies

Question 39

what happens in fertilisation?

Answer 39

two haploid cells form 1 diploid cell (zygote)

Question 40

what determines the gender of the child in fertilisation?

Answer 40

if the sperm contains an X or a Y chromosome

Question 41

where is mitochondrial DNA inherited from?

Answer 41

solely the mother

Question 42

what is X inactivation?

Answer 42

when an X chromosome is randomly inactivated in a female zygote