cell division W5 Flashcards
what are three broad reasons that cell division occurs
repair tissues
reproduction
replace themselves
what cells undergo MITOSIS
somatic cells
what cells undergo meiosis
Germ cells
what does ploidy refer to
number of sets of chromosomes in a cell
products of mitosis are ….
diploid and genetically identical
products of meiosis are …
haploid and genetically different
are gametes (sperm and egg cells) haploid or diploid
haploid
what is the symbol for haploid
n
what is the symbol for diploid
2n
phases of the cell cycle
G1
S
G2
M
how many chromosomes does a human cell have
22+sex chromosome
G1 phase (gap 1) describe (3)
cell is functioning normally
major period of cell growth
requires protein synthesis
S phase (synthesis) describe (4)
Dna is replicated
chromosomes are duplicated
minor period of cell growth
also required protein synthesis
G2 phase (gap 2) describe (2)
rapid cell growth and protein synthesis
preparing for M phase
M phase (mitosis) describe (4)
cell is dividing
no DNA synthesis (chromosomes already duplicated
no protein synthesis
no gene expression
what disease is caused by uncontrolable cell division
cancer
how is the cell cycle regulated
through specific proteins called CYCLINS
what are cyclins
specific proteins that control the cell cycle
what is the consequence of inactivation of cyclins
leads to loss of normal control of cell division which can lead to problems such as cancer
how are sister chromatids separated during mitosis
spindle fibres attacht to kinetochore
chromosonal changes are divided into four phases what are they
prophase
metaphase
anaphase
telophase
describe prophase
individual chromosomes become visible as chromatin condenses
describe metaphase
chromosomes line up in the middle of the cell
describe anaphase
chromosomes separate
describe telophase
chromosomes decondense and become chromatin angain
what happens when centrioles duplicate
the promote assembly of the mitotic spindle microtubules
what is cytokinesis
the division of the sytoplasm to produce two daughtercells
what is the ring between the two halves of the cell during cytokinesis called
contractile ring which is in the cleavage furrow
where does meiosis occur (2)
to form …
germ cells, in testes and ovaries
to form sperm and eggs
what are the main phases of meiosis
meiosis 1
meiosis 2
how many cells are produced from mitosis and are they identical to parent cell
2 daughter cells that are identical to parent cell
how many cells are produced from meiosis and are they identical to the parent cell, are they identical to each other
four daugher cells
all different
and different to parent cell
each daughter cell of meiosis is a …..and contains …copy of each chromasome
hapolid
one
do both emiosis and mitosis have phrophase
metaphase
anaphase
telophase
yes
what are the phases in meiosis 2
similar to mitosis but no ‘S’ phase
G1
G2
M
what happens during meiosis 1
replicated chromosomes exchange DNA and divide
what is homologous recombination
exchange of nucleotide sequences between two similar (homologous) DNA molecules
meiosis- what is synapsis
formation of tetrad
pairing/fusion of homologous chromasomes
meiosis - what is chasma
point where two homologous non sister chromatids exchange genetic material
during which phase does rocombination occur
prophase 1
what contributes to genetic variation (2)
independent assortment
homologous recombination
mitosis and cell cycle role in disease(1)
errors contribute to cancer progression
meiosis roles in disease (3)
- problems with chromosome segregation can contribute to genetic disorders such as down syndrome
- infertility
- recombination events associated with genetic disorders
