Cell DIvision Flashcards
A cell has what three possible destinys
- live and function without dividing
- grow and divid
- die
What is the cell theory
States that all organisms are made of cells and all cells come from pre-existing cells
In somatic cell division, how do cells divide
Mitosis: diploid (2n) to diploid (2n)
In reproductive cell division, how do cells divide
Through meiosis - diploid (2n) to haploid (1n)
Why do somatic cells divide
- growth and development
- tissue renewal
in regards to cells
What do somatic cells result in
2 daughter cells that are genetically and functionally identical to the parent cell
Do all somatic cells divide
Many, but not all, some more than others
What are somatic cells doing most of the time?
Going about their functions, within interphase
What is happening in the G1: Growth or Gap phase 1 (interphase)
Most cellular activities are occuring here.
What is happening in the S: Synthesis of DNA phase (interphase)
DNA replication occurs where strands are separated at the H bonds holding the nucleotides together.
New strand of DNA is synthesied opposite each of the old strands.
What is happening in the G2: Growth or Gap Phase 2 (interphase)
Checks for correct DNA synthesis as it preapres for the mitotic phase (synthesis of the proteins and enzymes are required, gathering of reactants).
Replication of centrosomes is completed.
What are the three phases involved in Interphase of the eukaryotic cell cycle
G1 (growth or gap phase 1), S (syntheis of DNA), G2 (growth or gap phase 2)
How long does the G1 phase take
8-10 hours
How long does the G2 phase take
4-6 hours
How long does the S phase take
8 hours
What are the 4 parts of the mitotic phase
- prophase
- metaphase
- anaphase
- telophase and cytokinesis
in terms of chromosomes
What does a human diploid have
46 chromosomes, 23 from each parent
During interphase, DNA ___
Replicates
During prophase, DNA __
Condenses
and there are two identical chromatids per chromosome called sister chromatids
What are sister chromatid
Two identical chromatids per chromosome
During metaphase, chromosomes __
“line up”
What happens during anaphase
Sister chromatids separate before the nuclear envelope reforms in the telophase
Daughter cells are __ to the parent cell
Identical
What does the cell cycle result as an end product
Two daughter cells that are genetically identically to the parent cell
What do the G1 checkpoints in the cell cycle check fore
- Is the DNA undamaged
- is cell size and nutrition okay
- are appropriate cell signals present
What happens if the G1 checkpoint is not satisfied
Exit to G0
What do the M checkpoints check for
- Are all chromosomes attatched to spindles
What happens when there is without full chromosome attatchment during the M signal
Stop signal received
Where does meiosis occur
Occurs in the gonads (ovaries and testes
What is the purpose of meiosis
- produces gametes which are haploid (single set of 23 chromosomes)
- fertilisation then restores the diploid number of chromosomes (2n)
- produces cells that are genetically different from the parent cell
How many stages of meiosis are there
2
What is Meiosis 1
Separates homologous chromosomes
What happens in Prophase 1
Synapsis: when two sister chromatids of each pair of homologous chromosomes pair up. The four chromatids are called a tetrad
What happens in Metaphase 1
What happens in Anaphase 1
Sister chromatids remain attatched and homologous chromosomes separate
What happens in Telophase 1 and Cytokinesis
Cleavage furrow
How is Meiosis ll different to Meiosis l
Very similar but meiosis ll is not preceded by DNA replication
For mitosis, DNA replication occurs in ____ but in meiosis it occurs in ___.
- both diploid and haploid cells
- diploid cells only
For DNA replication in mitosis, it occurs during ____ but for meiosis, it occurs during ______.
- interphase before mitosis begins
- interphase before meiosis l but not meiosis ll
What is the number of divisions for mitosis compared to meiosis
For meiosis, there is 1 (including prophase, prometaphase, metaphase, anaphase and telophase)
For mitosis, there is 2 (including prophase, metaphase, anaphase and telophase
For the synapsis of homologous chromosomes, does it occur in meiosis and mitosis (and if so when)
Does not occur for mitosis
For meiosis: occurs during prophase 1 along with crossing over between non-sister chromatids; resulting chiasmata holds pairs together due to sister chromatid cohesion
What is the number of daughter cells and genetic composition in mitosis and meiosis
Mitosis: two
Meiosis: Four
For mitosis, what is the number of daughter cells and genetic composition
Two, each genetically identical to the parent cell, with the same number of chromosomes
For meiosis, what is the number of daughter cells and genetic composition
Four, each haploid (n); genetically different from the parent cell and from each other
Three sources
What are the sources of variation as a result of meiosis
- Independent assortment at metaphase 1
- crossing over at prophase 1
- Fusion between two gametes
