Chromosomes, The Cell Cycle And An Introduction To Its Regulation

Question 1

In eukaryotic cells, chromatids are composed of?

Answer 1

DNA + RNA + Proteins

Question 2

2 types of protein in chromatin

Answer 2

Acidic

Basic (histones)

Question 3

Chromatin associated with?

Answer 3

Molecules (phospholipids, enzymes)

Question 4

How is chromatin packed?

Answer 4

Into Nucleosomes

Question 5

Genes

Answer 5

Specialised functional sites along chromosomes

Question 6

Histones

Answer 6

Rich in basic amino acids
Core: H2A, H2B, H3, H4
Linker: H1, H5
Important in compacting DNA and chromatin regulation

Question 7

Interphase

Chromatin forms in interphase nuclei?

Answer 7

Non-mitosis phases of the cell cycle

Heterochromatin and euchromatin

Question 8

Tissues divided into 3 groups by their rates of turnover

Answer 8

Continuous renewal - epidermis, intestinal epithelium; seen at microscopic level; cell population depends on…
Conditionally renewing: liver, kidney, endocrine glands; only divide in disease to replace lost cells
Static/non-proliferative -cardiac, nerve cells

Question 9

Cell cycle

Answer 9

A fundamental unit of time at the cellular level which defines a cell’s life cycle;
Period time between formation of cell and when it divides to form 2 Daughter cells;
Significance - development, growth, differentiation, disease

Question 10

Nucleus of a resting, non-growing cell is in?

Answer 10

Interphase

Question 11

G0 phase

Answer 11

Cells divide infrequently or not at all;

Cells express differentiated function;

Question 12

S phase

Answer 12

DNA + RNA + Proteins are replicated

Question 13

Duplicated chromosomes are called?

Answer 13

Sister chromatids

Question 14

Mitosis

Answer 14

Nuclear division (karyokinesis)
Separation of 2 Sister chromatids of each chromosome and accurate distribution of one of each pair of Sister chromatids to each Daughter cell;

Question 15

Prophase

Answer 15

Chromatin condenses to form visible chromosomes;
Chromosome - 2 Sister chromatids + centromere;
Centrioles duplicate;
Centrioles move to form 2 poles and acts as MTOCs;
Microtubules form spindle apparatus between centrioles;

Question 16

Prometaphase

Answer 16

Nucleoli regress;
NM breaks down;
Chr move towards equator;
Each pair of Sister chromatids has an attachment site called kinetochore which attaches to spindle;

Question 17

Metaphase

Answer 17

Metaphase plate;
Spindle consists of microtubules running pole to pole or pole to chromosome;
Latter microtubules run to the centromere of SC and attach at kinetochores;

Question 18

Telophase

Answer 18

Cleavage;
NM reforms;
Nucleoli reappears;
Chromosomes become less condensed;

Question 19

Cytokinesis

Answer 19

Nuclei of daughter cells are now in G1 ; some growth and production of cytoplasmic constituents;

Question 20

5 stages of Prophase I

Answer 20

Leptotene;
Zygotene;
Pachytene;
Diplotene;
Diakinesis

Question 21

Leptotene

Answer 21

Chromatin condense to form chromosomes;
Not yet split into Sister chromatids;
Chromosomes are not visible;

Question 22

Zygotene

Answer 22

Homologous pairs form bivalents -maternal, paternal
Synapsis;
Split into Sister chromatids;

Question 23

Pachyetene

Answer 23

Crossing over; chiasma; Long vs short

Question 24

Diplotene

Answer 24

Joined at centromere and chiasma;
Long stage;
Oocytes remain in this stage

Question 25

Diakinesis

Answer 25

Chiasma moves towards end of chromatids (terminalisation)

Question 26

Metaphase I

Answer 26

Each bivalent has two centromeres that arrange themselves by chance on opposite sides of the metaphase plate;

Question 27

Genetic variation

Answer 27

Metaphase I - Independent assortment of chromosomes
Pachytene -crossing over
Anaphase I (Each pole has a mixture of maternal and paternal chromosomes)
Fertilisation

Question 28

Which processes are asymmetric?

Answer 28

Anaphase and telophase I/II

Question 29

Oogenesis

Answer 29

Forms a small PB and large ovum;
First PB also undergoes meiosis II- 2 PB
Therefore - 3pb and 1 ovum