Mitosis and Meiosis Flashcards
What is the purpose of Mitosis?
To duplicate an existing cell and split, important in growth, healing and a pretty universal technique.
What are the four phases of the cell cycle?
1.M phase
2.G1 phase
3.S phase
4.G2 phase
Main functions of the cell cycle phases?
G1-Required for cell growth and to double mass of proteins and organelles
S phase- DNA synthesis
G2-Between S and M phase.
Why are gap phases important?
Allow cell to grow and monitors conditions before commiting to S phase and mitosis
What happens during S phase
DNA replication and chromatin proteins
And activate proteins involved in DNA replication
What happens during M phase?
5 stages of mitosis and cytokinesis (cell div)
What are the stages of mitosis called?
Prophase
prometaphase
metaphase
Anaphase
Telophase
What can major events in external environment or other factors do in the cell cycle?
Can stop cell division at checkpoints
What do cancer cells do in cell cycle?
They ignore cell cycle control system and run the checkpoints
What happens during M phase to sister chromatids?
Sister chromatids separated into identical daughter cells
What happens during prophase?
Replicated chromosomes condense
Centrosomes replicate and move apart and mitotic spindles form
What happens during prometaphase?
Nuclear envelope breaks down and the kinetocore of the chromosomes attach to spindle microtubules
Kinetocore is bonded to centromere of the chromosome
What happens during metaphase?
Chromosomes align between spindle poles and microtubules attach sister chromatids to whatever pole they are close to
What happens during anaphase?
Sister chromatids seperate as microtubules get shorter and spindle poles move apart pulling them to each pole
What happens during telophase
Daughter chromosomes arrive at poles and decondense and nuclear envelope forms on both ends of
End of mitosis
What happens during cytokinesis?
Formation of a contractile ring that pinches cell into two
Two genetically identical daughter cells with one nuclei each
Overview of sexual reproduction
Occurs in diploid organisms -two sets of chromosomes
Required haploid cells (sperm egg) to fuse and restore diploid state however with genetically distinct offspring
What makes a chromosome?
And where is a centromere?
Two sister chromatids
Centromere is in the middle of the chromatids/chromosome
What the major difference between meiosis and mitosis?
Mitosis goes through cell division once whereas meiosis goes through cell division twice to form four haploid cells
Gametes are produced by two meiotic cell divisions, what are they call and what do they do?
Meiosis I - Homologous chromosomes are separated (unique to meiosis)
Meiosis II - sister chromatids are separated (same as mitosis)
Overview of meiosis I
Duplicated homologous paternal and maternal chromosomes pair up next to each other and exchange piece of each other then line up on equator and pulled apart
Two daughter cells are formed
What are the 5 stages of Meiosis I?
Prophase I
Prometaphase I
Metaphase I
Anaphase I
Telophase I
What happens in Prophase I?
Duplicated chromosomes from S phase condenses and homologous chromosomes recognise each other
Form a bivalent four chromatid structure
How does DNA crossover happen and where does it take place in prophase I?
Takes place at the chiasmata by double strand breaking into chromatid DNA
What happens during prometaphase I?
Nuclear envelope breaks down and kinetocore microtubules attached to chromosomes
What happens during metaphase I?
Paired homologous chromosomes align in middle of spindle equator via microtubules and are randomly orientated
What happens during anaphase I?
Homologous chromosomes seperate and sister chromatids stay attached moving to opposite poles
What happens during telophase I?
Spindle fibres disconnect from sister chromatids and 2n 2n haploid nuclei envelopes form
Overview of meiosis II
No DNA replication between Meiosis I and II
Sister chromatids pulled apart to produce 4 haploid daughter cells (inheriting either maternal or paternal copy of each chromosome).
What stages in meiosis II
Same as I but with number II on the end of em
What would you compare meiosis II ?
Meiosis II is the same as mitosis
What does meiosis produce?
Genetically different haploid cells via prophase I
