3.1. Mitosis and Meiosis Flashcards
Define ‘Cell Cycle’
Series of growth and development steps a cell undergoes between its formation and duplication/division.
Define ‘Interphase’
Phase where cell grows and makes a copy of its DNA.
Define ‘Mitosis’
Phase where cell separates its DNA into 2 sets and divides, forming 2 new cells.
(MITOSIS)
What happens in… EARLY PROPHASE
- Chromosomes condense
- Mitotic spindle begins to form
- Nucleolus disappears
(MITOSIS)
What happens in… LATE PROPHASE/ PRO-METAPHASE
- Chromosomes become even more condensed, so they are very compact
- Nuclear envelope breaks down, releasing chromosomes
- Mitotic spindle grows more and some microtubules start to capture chromosomes
(MITOSIS)
What happens in… METAPHASE
- Chromosomes line up at the metaphase plate under tension from the mitotic spindle
(MITOSIS)
What happens in… ANAPHASE
- Sister chromatids separate
- The chromosomes of each pair are pulled towards opposite ends of the cell
- Microtubules not attached to chromosomes elongate and push apart, separating the poles and making the cell longer
(MITOSIS)
What happens in… TELOPHASE
- Mitotic spindle is broken down into its building blocks
- 2 new nuclei form, one for each set of chromosomes
- Nuclear membranes and nucleoli reappear
- The chromosomes begin to decondense and return to their ‘stringy’ form
(MITOSIS)
What happens in… CYTOKINESIS
- The division of the cytoplasm to form 2 new cells, each with a complete set of chromosomes identical to those of the mother cell
What is the purpose of meiosis?
To produce gametes (sex cells)
What is a GAMETE?
Spermatozoon, oocyte
What is MEIOSIS?
A 2 step process of cell division that is used to make gametes
What is CROSSING OVER?
Process in which homologous chromosomes trade parts
What are HOMOLOGOUS CHROMOSOMES
Set of chromosomes (one from each parent) that are very similar to one another and have the same size/shape
How many gametes will a single parent cell produce?
4
What happens in… PROPHASE I?
- Homologous chromosomes pair up and exchange fragments (crossing over)
- The starting cell is DIPLOID
What are CHIASMATA?
The points at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over occurs.
What happens in… METAPHASE I?
Homologue pairs line up at the metaphase plate for separation
What happens in… ANAPHASE I?
- Homologues pulled apart and move to opposite ends of the cell
- Sister chromatids of each chromosome remain attached to one another and don’t come apart
What happens in… TELOPHASE I?
- The chromosomes arrive at opposite poles of the cell
- Cytokinesis usually occurs at the same time as telophase I, forming 2 haploid daughter cells
The second round of cell division is meiosis II, what is the goal of this?
To separate sister chromatids
What happens in… PROPHASE II?
- Starting cells are the haploid cells made in meiosis I
- Chromosomes condense and the nuclear envelope breaks down, if needed
- The centrosomes move apart, the spindle forms between them, and the spindle microtubules begin to capture chromosomes
What happens in… METAPHASE II?
Chromosomes line up individually along the metaphase plate
What happens in… ANAPHASE II?
Sister chromatids separate and are pulled towards opposite poles of the cell
What happens in… TELOPHASE II?
- Newly forming gametes are haploid
- Nuclear membranes form around each set of chromosomes and the chromosomes decondense
- Cytokinesis splits the chromosome sets into new cells forming 4 haploid cells
