cell cycle Flashcards
def: allele
different versions of the same gene
def: gene
section of DNA that codes for one specific polypeptide
def: chromosome
independent DNA molecules which has supercoiled into a condensed form
def: homologous chromosomes
have the same genes in the same gene loci but different alleles of the genes
def: sister chromatid
one of the two strands of a chromosome that are joined together by a single centromere prior to cell division
def: haploid
cell that contains only a single copy of each chromosome (i.e. the gametes)
def: diploid
cell in which the nucleus contains two sets of chromosomes
def: somatic cell
a normal body cell, 2n
what is interphase and what are the 3 stages of interphase?
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
after interphase, what are the next 2 stages?
nuclear division - nucleus divides into 2 or 4
cell division (cytokinesis) - division of cytoplasm producing 2 or 4 new cells
how are chromosomes drawn?
2 identical sister chromatids joined together in the centre by a centromere
what is mitosis used for?
increasing cell numbers and growth of an organism;
repair of damaged tissues;
replacement of worn out / dead cells
what are the products of mitosis?
where else can mitosis be used?
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
prophase:
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
metaphase:
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
anaphase:
spindle fibres contract/ shorten, centromere splits,
identical sister chromatids are pulled apart to opposite poles,
making a V shape
telophase:
a nuclear membrane starts to reform around each sets of chromosomes,
chromosomes unwind/ uncoil become shorter and thinner and become visible
cytokinesis:
cytoplasm divides forming 2 identical daughter cells
what are the products of meiosis?
4 genetically identical daughter cells,
increases variation within the population
process of meiosis:
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
how does crossing over lead to genetic variation between daughter cells during meiosis 1?
homologous chromosomes associate (bivalent form);
chiasmata form (chromosomes twist);
equal lengths of non sister chromatids/ alleles are exchanged;
producing new combinations of alleles
how does independant segregation lead to genetic variation between daughter cells during meiosis 1?
- 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
equation of mitotic index:
number of cells with condensed chromosomes (PMAT) / total number of cells
x100
what does a greater mitotic index value mean?
faster rate of cell division
equation for time a cell has spent in mitosis:
mitotic index x time of cell cycle
how does an embryo grow?
zygote develops by undergoing mitosis,
cells differentiate as they are produced,
cell division stops when these tissues have formed.
def: cancer
cells undergoing uncontrolled cell division
how is the cell cycle controlled?
tumour suppressor genes code for proteins that slow down the cell cycle
proto-onco genes code for proteins that speed up the cell cycle
how can cancer appear?
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
how can cancer be treated?
with drugs that inhibit cell division,
may stop DNA replication, spindle fibre formation, cytokinesis
binary fission:
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
when is binary fission used?
asexual reproduction in prokaryotic cells;
fast in optimum conditions
mitochondria and chloroplasts replicate this way
how to look at cell in mitosis:
add a drop of water to slide
obtain a thin section and place on slide
stain with postassiym iodide
lower converslip with mounted needle
serial dilution:
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
