Flashcards
Cell cycle
Cards in this deck (26)
- 1What is the eukaryotic cell cycle?Cells reproduce by duplicating their content and splitting into two
The dividing of chromosomes is called mitosis followed by cytokinesis division =
This is only part of the cell cycle , M , between each M is an interphase, there are check points in the interphase whcih are carefully controlled and ordered - 2What are the cell cycle checkpoints?There are two main check points G1/S also known as restriction and G2/M.
There is another check point halfway through G1.
The purpose of check points is to prevent uncontrollable division
Detect and repair damage to DNA
The specificity is to make sure that the cycle can't be reversed and that DNA only replicates once in each cycle - 3What happens in the M phase?checkpoint chemical triggers condensation of chromatin
Halfway through the cycle, metaphase checkpoint ensures that the cell is ready to complete
Events in the cell:
Cell growth stops
Nuclear division consists of stages
Cytokinesis - 4What happens in G0 phase?A resting phase triggered early in G1 as the restriction point by a checkpoint
Some cells don't have this stage
Events in the cell:
In this phase, cells may undergo differentiation
Some types of cells remain in this phase for a long time or indefinitely - 5What happens in G1 , growth, phase?A G1 checkpoint control mechanism ensures that the cell is ready to enter the S phase and begins DNA synthesis
Events in the cell:
Cells grow and increase the size
transcription of genes to make RNA occurs
Organelles duplicate
The p53 gene helps to control this - 6What happens in the S, synthesis, phase?Because the chromosomes are unwound and the DNA is diffuse, every DNA molecule is replicated. There is a specific sequence of replication
Event in the cells:
Once the cell has entered this phase, the cell is committed to completing the cycle
DNA replicates
When all the chromosomes have been duplicated each one consists of identical chromatids
This phase is rapid and because the exposed DNA base pairs are more susceptible to mutagenic agents - 7What happens in the G2 phase?Special chemicals ensure that the cell is ready for mitosis by stimulating proteins that are involved in making chromosomes condense and form spindles
Events in the cell:
Cells grow - 8Why is mitosis important?It is important for growth and repair
Growth - All multicellular organisms grow by producing more cells that are genetically identical to each other and to the parent cells
Tissue repair - wounds heal when growth factors secreted by platelets and w.b.c and damaged cells of the blood vessel walls - 9What are the stages of mitosis?Prophase, metaphase, anaphase, telephase
- 10What happens in the prophase of mitosis?The chromosomes that have replicated during the S phase of interphase and consist of 2 identical sister chromotids, now shorter and thicker due to supercoiling
The nuclear envelope breaks down
centrioles in animal cells divides into 2 daughter centrioles and move to the poles
Cytoskeleton protein threads forma spindle between the centrioles. The spindle has a 3D structure - 11What happens in the metaphase of mitosis?The pairs of chromatids attach to the spindle threads at the equator region
They attach by their centromeres - 12What happens in the anaphase of mitosis?The centromeres of each pair of chromatids splits
motor proteins, walking along the tubulin threads,pulls each sister chromatid of a pair in opposite directions towards the poles
Because their centromere goes first, the chromotids,now called chromosomes assume a V shape - 13What happens in the telphase 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 from which they arose - 14What is cytokinesis?Once mitosis is complete the cell splits into 2, so each new cell has a nucleus
In the animal cell, the plasma membrane folds inwards and 'nips in' the cytoplasm
In plant cells, an end plate forms where the equator of the spindle was, and new plasma membrane and cellulose cell-wall materials are laid down either side of the end plate - 15Why is mitosis important?Sexual reproduction increases genetic variation because it involves combing genetic material from 2 unrelated individuals by the process of fertilisation
This process increases genetic variation in a species
In many organisms body cells are diploids, for sexual reproduction they need to make haploid gametes
When two gamete nuclei fuse a diploid zygote is produced - 16What are homologous chromosomes?People have 46 chromosomes half from the mother and half from the father, these form matching pairs one maternal and one paternal, these are called homologous chromosomes they have the same genes but may contain different alleles
- 17What are the main stages of meiosis?There are 2 divisions in meiosis each containing 4 stages
Prophase 1 + 2, metaphase 1 + 2, anaphase 1+ 2 and telophase 1 +2 - 18What is prohase 1?The chromatin condenses and each chromosomes supercoils
The nuclear envelope breaks down, spindle threads of tubulin protein form from the centriols in animal cells
The chromosomes come together in their homologous pairs
each member of pair consist of two chromatids
Crossing over may occur where non-sister chromatids wrap around each other and may swap sections so that alleles are shuffled - 19What is metaphase 1 ?The pairs of homologous chromosomes, still in their crossed over state, attach along the equator of the spindle
Each attach to a spindle thread by its centromere
The homologous pairs are arranged randomly, with the members of each pair facing opposite poles. This is independent assortment
The way that they line up determine how they segregate - 20What is anaphase 1?The members of each pair of homologous chromosomes are pulled part by motor proteins that drag them along the tubulin threads of the spindle
The centromeres do not divide, each consist of two chromatids
The crossed over areas separate from each other, resulting in the swapped areas of chromosomes and allele shuffling - 21What is telophase 1?In most animal cells, two new nuclear envelopes for around each set of chromosomse, cell divides by cytokinesis
Each new nucleus contains half the original number of chromosomes but each chromosome consists of two chromatids
In most plant cells, the cell goes straight from anaphase 1 and prophase 2 - 22What is prophase 2?If the nuclear envelopes have reformed then they beak down again
Chromosomes coil and condense, each one consisting of two chromatids
The chromatids of each chromosome are no longer identical
spindles form - 23What is metaphase 2?The chromosomes 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 they separate in anaphase - 24What is anaphase 2?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 - 25What is telophase 2?Nuclear envelopes for around each of the four haploid nuclei
In animal cells the two cells now divide into 4 haploid cells
In plants a tetrad of four haploid cells is formed - 26How does meiosis produce genetic variation?Crossing over during prophase 1 shuffles alleles
Independent assortment of chromosomes in anaphase 1 leads to random distribution of maternal and paternal chromosomes
Independent assortment of chromatids in ananphase 2 leads to further random distribution of genetic material
Haploid gametes are produced, which can undergo random fusion with gametes derived from another organisms of the same species
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- AS level Biology (Cell diversity) Flashcards on Cell cycle, created by Kelsie Hepworth on 18/01/2020.
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