1.6 cell division Flashcards
cell division consists of…
- nuclear division (karyokinesis)
- cytoplasmic cleavage (cytokinesis)
what are the two types of nuclear division?
mitosis and meiosis
briefly, what is the process of mitosis?
- process where a cell nucleus divides to produce 2 daughter nuclei that are genetically identical to the parent cell
- accompanied by cytokinesis to produce 2 genetically identical daughter cells
what are the objectives of mitosis (2, short)
- double the no. of nuclei
- maintain genetic stability
which type of nuclear division produces genetically identical daughter cells?
mitosis
does mitosis or meiosis produce haploid daughter cells?
meiosis
briefly, what is the process of meiosis?
- a process where 4 genetically different haploid nuclei is produced from a diploid nucleus
- involves 2 consecutive divisions
- each division accompanied by cytokinesis to produce 4 genetically different haploid daughter cells
name three processes in which mitosis is significant (in the syllabus)
- asexual repro
- growth of organism
- embryonic development
- tissue repair
what are the phases involved in the cell cycle
- interphase
- G1 phase
- S phase
- G2 phase
- mitosis + cytokinesis
- resting phase
what occurs in the G1 phase?
- rapid cell growth -> increase in cell size
- new organelles, protein and cytoplasm are synthesised
- high levels of RNA and ATP synthesis
_________ is synthesised continually throughout the cell cycle
cytoplasm
at which part of the cell cycle is metabolism highest?
at interphase
which phase involves DNA replication?
S phase
plant cells [have/don’t have] centrioles
don’t have
what occurs in S phase?
- DNA replication
- centrioles (for animal cells) and centrosomes replicate
which phases involve the synthesis of organelles?
G1 and G2
what occurs in the G2 phase?
- duplication of organelles
- synthesis of proteins + spindle fibres
at the end of interphase how much DNA is there?
4n
what are the four stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
in which phase does chromatin supercoil?
prophase
what is the function of centrioles in cellular division? (short)
centrioles organise spindle fibres
what occurs during prophase?
- supercoiling of chromatin to chromosomes → chromosomes are visible
- nuclear envelope disintegrates
- spindle fibres form
two sister chromatids are held together at the…
centromere
what occurs during metaphase?
- chromosomes aligne randomly at the equatorial plate of the mitotic spindle
- spindle fibres attach to kinetochore on centromeres
in forming the mitotic spindle, what do spindle fibres attach to (specific)
kinetochore proteins located at the centromeres of the chromosomes
when in mitosis do the centromeres divide?
during anaphase
what is the amount of DNA present in the cell in anaphase?
4n
if the cell begins with x chromosomes how many chromosomes are there in the cell during anaphase?
2x
if the cell begins with x chromosomes how many chromosomes are there in the cell during metaphase?
x
what is the difference between sister chromatids and chromosomes?
- chromatids are connected by centromeres
- separate chromatids are chromosomes
how are chromosomes counted?
no. chromosomes = the no. of centromeres
what happens in anaphase
- centromeres divide
- kinetochore microtubules shorten
- causes sister chromatids to separate
- sister chromatids pulled to opposite poles as daughter chromosomes
what happens in telophase?
- daughter chromosomes uncoil to form chromatin
- nuclear envelope reforms around chromatin → nucleolus appears
- spindle fibres disintegrate
how does cytokinesis occur in plant cells? (4 short)
- vesicles produced by golgi apparatus gather at equator
- vesicles fuse tgt to form cell plate
- cell plate stretches across the cell → forms middle lamella
- cellulose builds up on each side of the middle lamella → forms cell walls of 2 new plants cells
how does cytokinesis occur in an animal cell?
- centre of the cell ‘pinches’ in along the equatorial plane
- cleavage furrow forms
- furrow deepens and plasma membrane on each side joins up → gives 2 separate cells
how do you calculate mitotic index?
(no. of cells in mitosis)/(total no. of cells)
what is the mitotic index
indication of the percentage of cells undergoing cell division
what controls the cell cycle?
cyclins
what are cyclins?
a family of proteins that activate cyclin-dependent kinases (Cdk) to control the progression of cell through controlling the cell cycle
cylins bind to…
Cdk
what does Cdk do to proteins?
it phosphorylates them
how do cyclins regulate the cell cycle?
- relative amts of diff cyclins at ea phase control the cell cycle
- they bind to and activate diff Cdk
- Cdk phosphorylates and activates diff regulatory proteins
- the quantity and type of regulatory proteins fluctuate throughout the cell cycle → drives the cell cycle
what are mutations?
mutations refer to changes to the gene sequence of a cell which result in a change in gene expression
tumours form because cells that ________ or _______ (actions) _________ _____________ , which normally limits their growth
avoid, overcome, control mechanisms
what is metastasis?
the spread of cancer cells from the primary tumour to another part of the body via the bloodstream or lymphatic system, forming a secondary tumour
exposure to ________ increases the chances of cancer
mutagens
why is cancer more common for older people?
as a person grows old they accumulate gene mutations
what are oncogenes?
genes that originally regulate the cell cycle but when mutated can cause cancer
how do oncogenes cause cancer?
- they originally regulate the cell cycle
- when mutated, this causes a malfunction in the regulation of the cell cycle
- thus leads to uncontrolled cell division -> cancer
what are the 6 hallmarks of cancer?
- self-sufficiency in growth signals
- insensitivity to anti-growth signals
- evasion of apoptosis
- limitless cell division
- angiogenesis
- tissue invasion + metastasis
what mutation enables self-sufficiency in growth signals in cancer cells?
mutation of proto-oncogenes to oncogenes
what gene mutation causes insensitivity to anti-growth signals and the evasion of apoptosis?
tumour suppressor genes
how does the expression of the gene encoding for telomerase lead to cancer?
- expression of gene encoding for telomerase maintains telomeres
- makes cells immortal
- thus enables limitless cell division
what occurs in angiogenesis?
new blood vessels are formed to transport O2 and nutrients to support the tumour
what mutation enables tissue invasion and metastasis?
- changes in genes expression for:
- cell adhesion molecules on the surface of cancer cells
- thus can dislodge
- the recruitment of proteases
- digest surrounding tissues to enter bloodstream and metastasise
- cell adhesion molecules on the surface of cancer cells
why does smoking have high correlation with cancer?
- there are carcinogens in cigarettes
- this greatly increases the chances of cell mutations in mouth, oesophagus, lungs
