cell cycle

Question 1

def: allele

Answer 1

different versions of the same gene

Question 2

def: gene

Answer 2

section of DNA that codes for one specific polypeptide

Question 3

def: chromosome

Answer 3

independent DNA molecules which has supercoiled into a condensed form

Question 4

def: homologous chromosomes

Answer 4

have the same genes in the same gene loci but different alleles of the genes

Question 5

def: sister chromatid

Answer 5

one of the two strands of a chromosome that are joined together by a single centromere prior to cell division

Question 6

def: haploid

Answer 6

cell that contains only a single copy of each chromosome (i.e. the gametes)

Question 7

def: diploid

Answer 7

cell in which the nucleus contains two sets of chromosomes

Question 8

def: somatic cell

Answer 8

a normal body cell, 2n

Question 9

what is interphase and what are the 3 stages of interphase?

Answer 9

Interphase - cell carrying out normal functions and getting ready to divide
G1 phase - cell increases in size and new biomass (proteins) is made
S phase - DNA replicates by semi-conservative replication
G2 phase - ATP content is increased, new organelles are synthesised, and cell is now ready for mitosis/meiosis

Question 10

after interphase, what are the next 2 stages?

Answer 10

nuclear division - nucleus divides into 2 or 4
cell division (cytokinesis) - division of cytoplasm producing 2 or 4 new cells

Question 11

how are chromosomes drawn?

Answer 11

2 identical sister chromatids joined together in the centre by a centromere

Question 12

what is mitosis used for?

Answer 12

increasing cell numbers and growth of an organism;
repair of damaged tissues;
replacement of worn out / dead cells

Question 13

what are the products of mitosis?
where else can mitosis be used?

Answer 13

2 genetically identical daughter cells (same number of chromosomes as parent cell, same alleles of same genes in same gene loci);
asexual reproduction which occurs in stable favourable environments

Question 14

prophase:

Answer 14

nuclear membrane starts to break down,
centrioles start to move to the poles of the cells and make spindle fibres,
chromosomes supercoil and condense, thicken and becomes visible,
each chromosome appears as 2 identical sister chromatids joined at the centromere

Question 15

metaphase:

Answer 15

centrioles complete production of spindle fibres,
chromosomes are attached to the spindle fibres at the spindle fibres by centromere,
chromosomes align down the equator of the cell

Question 16

anaphase:

Answer 16

spindle fibres contract/ shorten, centromere splits,
identical sister chromatids are pulled apart to opposite poles,
making a V shape

Question 17

telophase:

Answer 17

a nuclear membrane starts to reform around each sets of chromosomes,
chromosomes unwind/ uncoil become shorter and thinner and become visible

Question 18

cytokinesis:

Answer 18

cytoplasm divides forming 2 identical daughter cells

Question 19

what are the products of meiosis?

Answer 19

4 genetically identical daughter cells,
increases variation within the population

Question 20

process of meiosis:

Answer 20

DNA replicated in S phase of cell cycle,
chromosome then goes through 2 nuclear divisions:
in first meiotic division, homologous chromosomes pair up and are separated,
in second division, chromatids are separated

Question 21

how does crossing over lead to genetic variation between daughter cells during meiosis 1?

Answer 21

homologous chromosomes associate (bivalent form);
chiasmata form (chromosomes twist);
equal lengths of non sister chromatids/ alleles are exchanged;
producing new combinations of alleles

Question 22

how does independant segregation lead to genetic variation between daughter cells during meiosis 1?

Answer 22

• during metaphase of the first nuclear division, the homologous chromosomes attach to spindie fibres and pair up side by side and can be reshuffled in any combination;
• maternal and paternal chromosomes are reshuffled in any combination on the equator of the cell;
• variation of gametes produce new combination of characteristics which means member of species will have advantageous allele which wil allow them to survive if environment changes

Question 23

equation of mitotic index:

Answer 23

number of cells with condensed chromosomes (PMAT) / total number of cells
x100

Question 24

what does a greater mitotic index value mean?

Answer 24

faster rate of cell division

Question 25

equation for time a cell has spent in mitosis:

Answer 25

mitotic index x time of cell cycle

Question 26

how does an embryo grow?

Answer 26

zygote develops by undergoing mitosis,
cells differentiate as they are produced,
cell division stops when these tissues have formed.

Question 27

def: cancer

Answer 27

cells undergoing uncontrolled cell division

Question 28

how is the cell cycle controlled?

Answer 28

tumour suppressor genes code for proteins that slow down the cell cycle

proto-onco genes code for proteins that speed up the cell cycle

Question 29

how can cancer appear?

Answer 29

mutations occur in one of these control genes then cell division continues uncontrollable rapidly,
cells produced are abnormal, a tumour develops,
spreads around the body = cancerous

Question 30

how can cancer be treated?

Answer 30

with drugs that inhibit cell division,
may stop DNA replication, spindle fibre formation, cytokinesis

Question 31

binary fission:

Answer 31

replication of circular DNA and plasmids,
cell elongates from middle separating 2 DNA molecules,
new murein cell wall begins to form down the middle,
division of cytoplasm to produce 2 daughter cells,
each with a single copy of circular DNA and variable number of copies of plasmids

Question 32

when is binary fission used?

Answer 32

asexual reproduction in prokaryotic cells;
fast in optimum conditions
mitochondria and chloroplasts replicate this way

Question 33

how to look at cell in mitosis:

Answer 33

add a drop of water to slide
obtain a thin section and place on slide
stain with postassiym iodide
lower converslip with mounted needle

Question 34

serial dilution:

Answer 34

C1 x V1 = C2 x V2
C1 = desired diluted conc/ mol dm-3
V1 = desired vol/ cm3
C2 = original conc
V2 = unknown vol of stock sol