Cell Cycle Flashcards
Name the 3 stages of cell cycle
Interphase
Mitosis
Cytokinesis
Explain the 3 steps in interphase
G1 - cell increases in size and new biomass is created
S - semi conservative replication
G2 - cell gets ready for division
ATP is synthesised and stored
New organelles synthesised
Explain cytokineses
When the cytoplasm splits into 2 (mitosis) or 4 (meiosis) new cells
Define Gene
Section of DNA which codes for a specific protein
Explain Prophase
1- nuclear membrane starts to break down
2- centrioles move to the poles and start spindle fibre production
3- chromosomes super coil and become visible
4- chromosomes are now presented as sister chromatids
Purpose of mitosis
To increase cell number and growth of of organelles
To repair damaged tissues
To replace dead/worn out cells
Purpose of Metaphase
1- centrioles complete production of spindle fibre
2- spindle fibre attach to chromosomes centromere
3- chromosomes align on the equator
Purpose of Anaphase
1- spindle fibre shorten
2- centromere split
3- identical sister chromatids pulled to opposite poles
4- v shape is created
Purpose of Telophase
1- nuclear membrane starts to form around each set of chromosomes
2- chromosomes unwind and become invisible
Unregulated mitosis
Cells go under cell division in mitosis
They differentiate into tissue and organs
If mutation occurs - uncontrolled cell division can occur
This is rapid and a tumour develops
If it goes into the tissue/body this means cancer
What is binary fission
It’s Asexual reproduction in prokaryotic cells which involves
- replication of circular DNA and plasmids
- cytoplasm dividing into 2 daughter cells, each with one copy of DNA and variable number of plasmids
How does binary fission divide into 2
Cell elongates from the middle
Separates 2 DNA molecules
New cell wall (murein) formed down the middle
Divides into 2 cells
Mitotic index equation
MI = N.O condensed chromosomes
——————————————
Total N.O cells
Haploid definition
Single set of chromosomes
Diploid definition
Two sets of chromosomes
Process of meiosis
Dna replicated in S phase
Chromosomes go through 2 nuclear divisions (Pmat)
1st division - homogulous chromosomes (2n) pair up and separate forming (2n)
2nd division - chromatids (2n) separate (1n) in one cell
Meiosis extra info
Diploid organisms produce haploid gametes
Creates 4 genetically identical daughter cells
Gametes (1n) fuse firming zygote (2n)
Ensure chromosome number stays constant from one generation to the next
Crossing over - (1st division) P M
1- homogulous chromosomes associate (bivalent forms)
2- chiasmata form (entanglement)
3- equal lengths of alleles exchanged
4- new combination of alleles produced
Independent segregation (1st division ) Metaphase
Homologous chromosomes attach to spindle fibres and they pair up side y side and can be reshuffled in any combination
Importance of meiosis
1- halves the number of chromosomes
2- restores full number at fertilisation
