Chromosomes, the cell cycle, and introduction to its regulation

Question 1

What does DNA form a complex with

Answer 1

RNA and proteins

Question 2

What do DNA, RNA and proteins combine to form

Answer 2

chromatin

Question 3

2 protein types in chromatin

Answer 3

Basic (mainly histones)

acidic

Question 4

What else is chromatin associated with

Answer 4

PHospholipids
enzymes
other molecules

Question 5

What is chromatin packed into

Answer 5

Bead like structures called nucleosomes

Question 6

What does each nucleosome comprise of

Answer 6

2 loops of DNA double helix wrapped around a cluster of 8 histones

Question 7

What are chromosomes formed from

Answer 7

The supercoiing and condensation of chromatin

Question 8

What are genes

Answer 8

Specialised functional sites arranged along the chromosomes

Question 9

Why are histones important

Answer 9

Important in compacting DNA and in chromatin regulation

Question 10

What are the two forms of chromatin in interphase nuclei

Answer 10

Heterochromatin

Euchromatin

Question 11

What’s heterochromatin

Answer 11

More condensed and densely staining.

Question 12

Where is heterochromatin found

Answer 12

Near nuclear envelope

Question 13

What does heterochromatin represent

Answer 13

Genes which are switched off

Question 14

What are the two types of heterochromatin

Answer 14

Constitutive

Facultative

Question 15

What’s euchromatin

Answer 15

less condensed and lightly staining

Question 16

where is euchromatin found

Answer 16

more central location

Question 17

What does euchromatin represent

Answer 17

genes which are switched on

Question 18

What is constitutive heterochromatin

Answer 18

can’t get switched on

Question 19

what’s facultative heterochromatin

Answer 19

can get switched on

Question 20

What are the two stages of mitosis

Answer 20

karyokinesis

cytokinesis

Question 21

Stages of karyokinesis

Answer 21

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 22

What groups can the tissues of the body be divided into

Answer 22

Continuously renewing
Conditionally renewing (e.g. liver, kidney, endocrine glands)
Static or non-proliferative

Question 23

How is the cell cycle regulated

Answer 23

1) Cyclin dependent kinases (CDK’s) bind to cyclin and become active
2) CDK’S cause phosphorylation to activate or inactivate target proteins
3) Proteins coordinate cell’s entry to next phase of cell cycle

Question 24

How to inhibit cell cycle

Answer 24

the Kip family genes halt the cell cycle in G1 by binding and inactivating complex of cyclin and CDK (therefore its called a tumor suppressor)

Question 25

In meiosis, what happens in prophase 1

Answer 25

leptotene
zygotene
pachytene
diplotene
diakinesis

Question 26

what happens in leptotene

Answer 26

Chromosomes condense (not split into sister chromatids) 
-chromomeres are visible along their length

Question 27

what happens in zygotene

Answer 27

• Homologous chromosomes (maternal-paternal) pair together to form bivalents
• chromosomes now split into sister chromatids and local sites of alignment (synapsis) develop between sister chromatids of homologous pairs

Question 28

what’s a bivalent

Answer 28

pairing of homologous chromosomes

Question 29

Another word for crossing over

Answer 29

chiasma formation

Question 30

What happens in pachytene

Answer 30

synapsis is completed and crossing over occurs

• at chiasmata, genetic info exchanged between homologous pairs
• exchange more likely to happen between long stretches of chromatid arms than short ones

Question 31

what’s diplotene

Answer 31

chromatids are held together by chiasmata as well as by the centromeres

Question 32

What’s diakinesis

Answer 32

Chiasmata appear to move toward the ends of the chromatids

Question 33

What’s the difference between male and female diplotene

Answer 33

In women, chromatids are held in this phase for decades

Question 34

What’s metaphase 1

Answer 34

Each bivalent has 2 centromeres and these arrange themselves by chance on opposite sides of the metaphase plate

Question 35

What happens in anaphase 1

Answer 35

• Chromosomes move to opposite poles of the cell.

- Each pole has a mixture of maternal and paternal chromosomes

Question 36

What happens in telophase 1

Answer 36

• Each daughter cell has half the diploid number of chromosomes
• The nuclear envelope may reassemble before prophase 2 of the second meiotic division (meiosis 2)

Question 37

What happens in meiosis 2

Answer 37

Similar to what happens in mitosis 2

-Centromeres now split at kinetochores. and sister chromatids move to opposite cells

Question 38

Difference between gametogenesis in M AND F

Answer 38

sperm; four gametes produced

egg; forms one egg and 3 polar bodies

Question 39

When is genetic variation introduced

Answer 39

• Pachytene; between homologous chromosomes at chiasmata
• Anaphase 1; Independent assortment
• Fertilisation

Question 40

Different types of chromosome

Answer 40

Metacentric- when centromere is in middle of chromosome

Acrocentric- when centromere is not at middle

Question 41

What’s a karyotype

Answer 41

Sum of all chromosomes in a nucleus arranged in size, location of centromere and arranged in homologous pairs

Question 42

Main chromosomal abnormalities

Answer 42

Trisomy 21- 3x chromosome 21
Kleinfelters- HAve xxy sex
Turner’s syndrome- Xo have only one sex chromosome