Cell & Nuclear Division Flashcards
Outline the process of Prophase I
- Chromatin condenses to form discrete chromosomes
- Synapsis —> homologous chromosomes pair up to form bivalents
- Chiasma formation —> Crossing over occurs between non-sister chromatids of homologous chromosomes, forming chiasma
- Exchange of alleles between non-sister chromatids occurs
Outline the process of Metaphase I
- Homologous chromosomes align in pairs at the metaphase plate
- Each chromosome is attached to the kinetochore microtubules from the pole it faces
Outline the process of Anaphase I
- Homologous chromosomes separate to opposite poles of the cells
- Each homologue pulled by shortening kinetochore microtubule
- Non-kinetochore microtubule elongate & slide in opposite direction, elongating the cell
Outline the process of Telophase/Telophase I/Telophase II
1.Chromosomes decondense to form chromatin
2. Spindle Fibres disintegrate
3. Nuclear envelope reforms and nucleolus reappears
Outline the process of cytokinesis (Animals)
- Formation of Cleavage Furrow —> Cell Surface Membrane invaginates towards the equator of the cell, forming a cleavage furrow.
- Cleavage Furrow deepens and pinches the cell into two, forming two daughter cells
Outline the process of cytokinesis (Plants)
- Fluid filled vesicles appear in the middle of the cell
- and coalesce to form a cell plate, separating the two daughter cells
Outline the process of Prophase II
- Chromatin condenses to form discrete chromosomes
- Centrioles duplicate and move to opposite poles
- Spindle Fibres start to form
- Nucleus membrane disintegrate & nucleolus disappears
Outline the process of Metaphase/Metaphase II
- Chromsomes align at the metaphase plate
- Each chromosome is attached to kinetochore microtubules from both poles
Outline the process of Anaphase/Anaphase II
- Centromere **divide*
- Kinetochore microtubules shorten, pulling daughter chromosomes to opposite poles of the cells
- Non-kinetochore microtubules elongate and slide in opposite directions, elongating the cell
Outline the process of Prophase
- Chromatin condenses to form discrete chromosomes
- Pair of centrioles move to opposite poles of the cell
- Spindle Fibres start to form
- Nucleus Membrane disintegrates and nucleolus disappears
Define Homologous Chromosomes
- Set of one maternal chromosome and one paternal chromosome
- similar in size, shape, centromere position and staining pattern
What is the significance of mitosis in maintenance of genetic stability?
Mitosis produces two genetically identical daughter cells with same number of chromosomes through:
1. S phase of Interphase —> Semi-conservative DNA replication maintains genetic integrity of genetic information in genetically identical daughter cells by using parental DNA as template
- Prophase —> Chromosomes are condensed to prevent entanglement of chromatin and DNA breakage during separation of sister chromatids
- Anaphase & Telophase —> Daughter chromosomes are distributed equally to each daughter cells
What’s the significance of mitosis on growth of cell?
Growth: New cells must be genetically identical to existing ones to ensure new cells have similar function.
What’s the significance of mitosis on growth, repair and regeneration of cell?
Growth: New cells must be genetically identical to existing ones to ensure similar function
Repair/replacement: Damaged cells
Outline the significance of mitosis on repair/regeneration of cell?
Damaged cells must be replaced by cells genetically identical to the original one, to ensure new cells function similarly to cells replaced.
What is the significance of mitosis on asexual reproduction?
- To ensure offspring is genetically identical to the parent
- Allow favourable traits to be passed down from generation to generation
Why is there a need to regulate cell cycle tightly?
- For normal growth and development
- Checkpoints are stop or go ahead signals to determine if cell cycle can proceed
- When there is dysregulation of checkpoints of cell division or cells escape the cell cycle control mechanism
- it will lead to uncontrolled division of cells, formation of tumour and possibly cancer
Why is there a need to regulate cell cycle tightly?
- For normal growth and development
- Checkpoints are stop or go ahead signals to determine if cell cycle can proceed
- When there is dysregulation of checkpoints of cell division or cells escape the cell cycle control mechanism
- it will lead to uncontrolled division of cells, formation of tumour and possibly cancer
Explain the significance of meiosis in sexual reproduction
- Meiosis produce 4 haploid gametes from one diploid parent cell
- Fusion of gamete produces zygote with full set of chromosomes
- hence ensuring constant chromosome number in every generation
How does meiosis ensure genetic variation?
- Crossing over between non-sister chromatids of homologous chromosomes in prophase I results in new combination of alleles on chromatids
- Independent assortment of homologous chromosomes at metaphase plate and their subsequent separation in metaphase I & anaphase I respectively results in gametes with 2^n possible different combination of paternal and maternal chromosomes
- Random orientation of non-identical sister chromatids at metaphase plate and their subsequent separation in metaphase II and anaphase II results in gametes with new combination of alleles on chromosome
- Random fusion of gametes during fertilisation result in offspring with variety of genotypes and possibly phenotypes
How does meiosis ensure genetic variation?
- Crossing over between non-sister chromatids of homologous chromosomes in prophase I results in new combination of alleles on chromatids
- Independent assortment of homologous chromosomes at metaphase plate and their subsequent separation in metaphase I & anaphase I respectively results in gametes with 2^n possible different combination of paternal and maternal chromosomes
- Random orientation of non-identical sister chromatids at metaphase plate and their subsequent separation in metaphase II and anaphase II results in gametes with new combination of alleles on chromosome
- Random fusion of gametes during fertilisation result in offspring with variety of genotypes and possibly phenotypes
Similarities between Mitosis and Meiosis?
1) Interphase and semi-conservative DNA replication precedes both processes
2) Kinetochore microtubules attach to kinetochore at centromeres of chromosomes for both processes
3) Cytokinesis occurs at the end of both processes
Accept: Comparision between mitosis and meiosis II
Difference between Meiosis I and Meiosis II?
Prophase:
No pairing of homologous chromosomes vs Homologous chromosomes pair up;
No chiasmata formation vs chiasmata formation
No crossing over vs crossing over may occur
Metaphase:
Pairs of sister chromatids align at the metaphase plate vs Pairs of homologous chromosome line up along metaphase plate
No independent assortment of homologous chromosomes vs independent assortment of homologous chromosomes
Anaphase:
Centromere divide, sister chromatids separate vs Centromere do not divide, homologous chromosome separate
Overall differences:
Form somatic cell with full set of chromosomes vs form gametes with half set of chromosomes
Daughter cells genetically identical vs daughter cells not genetically identical
Difference between Meiosis I and Meiosis II?
Prophase:
No pairing of homologous chromosomes vs Homologous chromosomes pair up;
No chiasmata formation vs chiasmata formation
No crossing over vs crossing over may occur
Metaphase:
Pairs of sister chromatids align at the metaphase plate vs Pairs of homologous chromosome line up along metaphase plate
No independent assortment of homologous chromosomes vs independent assortment of homologous chromosomes
Anaphase:
Centromere divide, sister chromatids separate vs Centromere do not divide, homologous chromosome separate
Overall differences:
Form somatic cell with full set of chromosomes vs form gametes with half set of chromosomes
Daughter cells genetically identical vs daughter cells not genetically identical
