Cell Division, Chromosome Segregation & Genetic Varieation Flashcards
List the four stages of the eukaryotic cell cycle.
1) G1 phase (gap 1)
2) S phase (synthesis)
3) G2 phase (gap 2)
These are collectively known as interphase. Followed by:
4) M phase
What is mitotic cell division?
Chromosomes are replicated & then divided to form two identical daughter cells.
Describe the interphase of the eukaryotic cell cycle.
The cells grows during G1, the first gap phase. Replication of chromosomes occurs during S phase, then prepares for division during G2 (gap 2).
What two processes occur during M phase of the cell cycle?
Mitosis & cytokinesis.
Define cytokinesis.
The process of the cytoplasm dividing after mitosis, separating the cell into two daughter cells. Final stage of the cell cycle.
What are the four stages of mitosis?
1) prophase
2) metaphase
3) anaphase
4) telophase
What are chromatids?
Chromosomes replicate during the interphase of the cell cycle to form sister pairs of chromatids.
What occurs during the prophase of mitosis?
Sister pairs of chromatids become condensed enough to be visible under a light microscope. Nuclear envelope begins to break down.
What occurs during metaphase of mitosis?
Chromosomes attach to mitotic spindle fibres and line up long the equator of the cell.
What occurs during anaphase in mitosis?
Spindle Microtubules shorten, pulling chromatids a parting and resulting in equally segregated chromosomes at opposite ends of the cell.
What occurs during telophase of mitosis?
New nuclear envelopes develop around the separate chromosomes. This is the end of mitosis and cytokinesis can the occur.
What is meiosis?
The cell division which occurs to form gametes containing half the number of chromosomes.
Instead of two diploid cells the division results in four haploid cells.
What are the phases of meiosis?
Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Prophase 2 Metaphase 2 Anaphase 2 Telophase 2
What is recombination or genetic cross over?
During meiosis homologous chromosomes are physically paired together in a process known as synapsis.
Matching DNA sequences line up exactly, allowing the swapping of sections of DNA sequence. This is genetic recombination.
What occurs during prophase 1 in meiosis?
Homologous chromosomes are physically paired up a the protein complex called synaptonemal complex.
This then dissembles leaving homologues held together by their crossover genes.
What occurs during metaphase 1 of meiosis?
Homologous pairs of chromosomes still attached to each other are aligned at the metaphase plate (unlike mitosis where individual duplicates line up instead of pairs).
In meiosis, what is independent assortment?
The random segregation of chromosomes due to the different orientations of the homologous pairs during metaphase 1.
What occurs during anaphase 1 in meiosis?
Homologous pairs separate and move to opposite ends of the cell.
This is different to mitosis where individual sister chromatids segregate.
what is the difference between a cell undergoing mitosis after telophase and a cell undergoing meiosis after telophase 1?
In mitosis the diploid cells are genetically identical. In meiosis genetic recombination and independent assortment have resulted in non identical diploid cells.
What results from telophase 1 in meiosis?
Two diploid daughter cells, non identical to each other and the parent cell.
What occurs during meiosis 2?
Chromosomes again align on the metaphase plate (again in random orientations) and the individual sister chromatids finally segregate during anaphase 2.
What is the end result of meiosis?
Four haploid cells with a single copy of each chromosome.
These contain different genetic combinations from the diploid germ cell as a result of genetic recombination.
