L10 - Cell Division Flashcards
Why do somatic cells divide
Growth and development, tissue renewal
Do all somatic cells divide?
Not all, e.g neurons do not
What are the phases of the cell cycle
G1 phase, S phase, G2 phase, mitotic phase
What happens during G1 phase
Cell duplicates organelles and cytosolic components, centrosome replication begins
What happens during S phase
DNA replication
What happens during G2 phase
Checks for correct DNA synthesis, synthesis of proteins and enzymes required, replication of centrosomes completed
What is G0
Exit from cell cycle (nondividing cell) e.g nerve cells
What are the stages of mitotic phase (in order)
Prophase, metaphase, anaphase, telophase (PMAT)
What happens during interphase
DNA replicates, prepares for mitotic phase
What happens during prophase
Centrosome moves to opposite poles of cell, mitotic spindle forms
DNA condenses into two identical chromatids per chromosome (called sister chromatids)
What happens during metaphase
The condensed chromosomes align at the cell equator
What happens during anaphase
Spindle fibres pull sister chromatids apart, separating chromosomes
What happens during telophase
Nuclear envelope reforms
How many chromosomes in a haploid human cell
23 chromosomes
What is the result of mitosis
Two daughter cells that are genetically identical to the parent cell
What are the 3 mitotic cell cycle checkpoints
G1 checkpoint, G2 checkpoint, M checkpoint
What is the G1 checkpoint
Checks for DNA damage, cell size and nutrient availability
Cell enters G0 if not appropriate signals present
What is the M checkpoints
Checks if all chromosomes attatched to spindles
What does meiosis produce
4 haploid gametes (sex cells) with half the number of chromosomes
Genetically different from parent cell
What is synapsis
Two sister chromatids of each pair of homologous chromosomes pair up
What is a tetrad
The 4 chromatids formed from synapsis
What is crossing over
When non-sister chromatids exchange DNA material during prophase i
What is independent assortment
Where chromosomes move randomly to the poles during metaphase i
What is the goal of meiosis i
To separate homologous chromosomes
What is the goal of meiosis ii
To separate sister chromatids
What are the three sources of genetic variation in meiosis
Independent assortment at metaphase i (2^23 possible combinations)
Crossing over at prophase i (~1-3 crossover events per pair)
Random fusion of gametes (2^23 * 2^23 combinations)
