Topic 2.6 Cell Division And Cell Diversity Flashcards
(22 cards)
State the Prophase stage of mitosis
Chromosomes that have been replicated condense and coil
Nuclear envelope breaks down
The centriole in animal cells divides and two centrioles move to opposite ends
Tubulin threads form a spindle between centrioles
What happens in metaphase stage in mitosis
The pairs of chromatids attach to the spindle threads at the equator region
They attach by their centromeres
What happens in anaphase stage of mitosis
The centromere of each pair of chromatids splits
Motor proteins pull each sister chromatid of a pair toward opposite poles
Because centromeres move first chromatids form a V shape
What happens in telophase stage of mitosis
The Separated chromosomes reach the poles
A new nuclear envelope forms around each set of chromosomes
The cell now contains two nuclei each genetically identical to each other and to the parent cell
Why is A sexual reproduction significant of mitosis in the life cycle
Single celled protoctists divide by mitosis to produce new individuals
What does growth have to do with mitosis
All multi cellular organisms grow by producing more cells that are genetically identical to each other and to the parent cell from which they arose by mitosis
What does Tissue Repair have to do with Mitosis
Wounds heal when growth factors are secreted by white blood cells
What happens in M phase of interphase
Cell growth stops
Nuclear division (mitosis) begins
What happens in the G0 phase of interphase
In this phase cells may undergo Apoptosis (programmed cell death), differentiation of senescence
Some types of cells (neurones) remain in this phase indefinitely
What happens in the G1 phase of mitosis
At G1 checkpoint control mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis
Cells grown and increase in size
Transcription of genes to make RNA occurs
Organelles duplicate
Biosynthesis (DNA replication, protein synthesis)
The p53 gene helps control this phase
What happens in S phase of interphase
Once the cell has entered this phase, it is committed to completing the cell cycle
DNA replicates
Each chromosome that has been duplicated has an identical sister chromatid
This phase is rapid due to the exposed DNA bases, reducing the chance of mutation
What happens in G2 phase of interphase
Cells grow
What is the significance of Meiosis in life cycles
It increases genetic variation
For this it requires haploid gametes in sexual reproduction
What happens in Prophase 1 in Meiosis?
The Chromatin Condenses and each chromosome supercoils
The nuclear envelope breaks down, and spindle threads of tubulin protein form from the centriole in animal cells
The chromosome come together in their homologous pairs
Each member of the pair consists of two chromatids
Crossing over occurs where the chromatids wrap around each other and swap alleles
What happens in Metaphase 1 of Meiosis
The pairs of homologous chromosomes (still crossed over) attach along the equator of the spindle
Each attaches to a spindle thread by its centromere
The homologous pairs are arranged randomly, with the members of each pair facing the opposite poles of the cell. This is independent assortment
What happens in Anaphase 1 of Meiosis
The member of each pair of homologous chromosomes are pulled apart by the motor proteins that drag them along the tubulin threads of the spindle
The centromeres do not divide, and each chromosome consists of two chromatids
The crossed over areas separate from each other, resulting in swapped areas of chromosomes and allele shuffling
What happens in Telophase 1 of meiosis
In most animal cells, two new nuclear envelopes form around each set of chromosome and the cell divides by cytokinesis
There is a short interphase where chromosomes uncoil
Each new nucleus contains half the original number of chromosomes, but each new chromosome consists of two chromatids
What happens in Prophase 2 in meiosis
If the nuclear envelopes have reformed, then they now break down
The chromosomes now coil and condense, each one consisting of two chromatids
The chromatids of each chromosome are no longer identical, due to crossing over in prophase 1
Spindles form
What happens in metaphase 2 of meiosis
The chromosome attach, by their centromere, to the equator of the spindle
The chromatids of each chromosome are randomly arranged
The way that they are arranged will determine how the chromatids separate during anaphase
What happens in Anaphase 2 of Meiosis
The centromeres divide.
The chromatids of each chromosome are pulled apart by motor proteins that drag them along the tubulin threads of the spindle, towards the opposite poles
The chromatids are therefore randomly segregated
What happens in telophase 2 in meiosis
Nuclear envelopes form around each of the four haploid nuclei
In animals, the two cells now divide to give four haploid cells
In plants a reread of four haploid cells is formed
How does Meiosis produce genetic variation?
Crossing over during prophase 1 shuffles alleles
Independent assortment of chromosomes in Metaphase one leads to random distribution of parent chromosomes
Independent assortment of chromatids in metaphase 2 leads to further random distribution of genetic material
Haploid gametes are produced, which can undergo random fusion with gametes derived from another organism of the same species
