2.1.6 cell division, diversity, organisation Flashcards
cell cycle 4 stages
G1 (growth 1)
Synthesis
G2 (growth 2)
Mitosis (cytokineses)
what triggers going from one phase to enouther
cyclins
3 parts of interphase
g1
s
g2
what happes in G1
- growth
- PROTEIN SYNTHESIS, cells make enzymes, proteins for growth
- CHECKPOINT: dna damage etc, approve going to the next
what happens in g2
- more growing
- DNA is error checked and repaired
does the cell grow during mitosis
no
in whcih part of cell cycle is there the most mRNA produced
- G1
- protein syntehsis and production of mRNA in transcription
product of mitosis
2 genetically identical daughter cells
4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
how many chromosomes in human nucleus
46 (23 pairs)
Prophase
- chromosomes SUPERCOIL and become visible
- nuclear envelope disintegrate
- nucleolus disappears
- centrioles move to opposite poles
metaphase
- chromosomes line up at equator of cell
- SF attach to centromeres
anaphase
- sister chromatides pulled apart at centromre
- SF shorten
- separated chromatids pulled to opposite poles by microtubule spindle fibres
telophase
- nuclear enevlope reforms
- SF breaks down
- new nucleoluses formed
cytokineses
cytoplasm and organelles divides into 2
structure of chromosome (post DNA rep)
2 identical chromatids joined together at CENTROMERE
centrosome
pair of centrioles
what in plants can you use to study mitosis
meristem tissue (root tip)
purpose of mitosis
- growth
- replace cells, repair tissues
- asexual reproduction eg ameoba
what type of cells does mitosis produce
diploid
what type of cells does meiosis produce
haploid gametes
meoisis 1
PMATC (1)
P1
- nuclear envelope breaks down into vesicles
- nucleolus disintegrates
- chromosomes condense and become visible
- CROSSING OVER occurs
crossing over is
what is a bivalent
a pair of homologous chromosomes
M1
- chromosomes line up along equator
- spindle fibres formed and attach to ccentromere
- INDEPENDENT ASSORTMENT
A1
- centrioles pull apart chromosomes to opporite ends
T1
- chromosomes at opposite poles
- SF break down
- nuclear envlopes reform and nucleoluses
cytokineses 1
- cytoplasm divides
product of meiosis 1
2x haploid cells (NOT GENETICALLY IDENTICAL)
what happens between m1 and m2
- no interphase
p2
- nuclear enevlope breaks down, nucleolus disintegrates
- chromosomes condense
m2
- chromosomes line up at equaotr
- spindle fibres form and attach to centromeres
a2
-chromatids separate and move to opposite poles
t2
- nuclear envelope reforms
- nucleoli reform
cytokineses 2
- cytoplasm divides
total product of meiosis
- 4 haploid cells
how do you count chroosomes
by number of centromeres present
p1
- chromosomes supercoil, visible
- nuclear envelop breaks down, nucleous disintigerates
- CHROMOSOMES COME TOGETHER AS HOMOLOGOUS PAIRS
- crossing over occurs
waht is crossing over
PROPHASE 1
- non sister chromatids swap sections of DNA
- CHROMATIDS HAVE NEW ALLELE COMBO
- the more they cross over depends on how close they are
M1
- pairs of homologous chromosomes line up at equator
- spindle attaches to centromere
- INTEPENDENT ASSORTMENT
independent assortment
METAPHASE 1 (snd2)
- Homologous chromosome pairs line up at equator
- maternal and paternal can end up facing either pole
- maternal and paternal have different alleles
- PRODUCES LARGE NUMBER OF ALLELE COMBOS
a1
- each chromosome (containing 2 chromatids) in the homolgous pair is pulled to an opposite pole
t1
- 2 nuclear envelpoes reform
- then cytokinesis
- HAPLOID