Cell Division And Specialisation Flashcards by Tom Ridsdale

What are chromosomes composed off

Two identical chromatids connected at a centromere with DNA wrapped around histones and telomeres at the end

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How many chromosomes does a human have

46 23 pairs

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What stage does the cell spend longest in during the cell cycle

Interphase

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What happens in g1 interphase

Growth of cell and duplication of organelles

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What happens in s phase

DNA is duplicated (chromosomes duplicated)

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What happens in G2

Cell increases more in size and DNA is checked

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What happens in interphase

DNA I could and becomes visible
DNA replicates and checks
Centrioles replicate
Cytoplasm increased
new organelles produced
Cell is active and uses lots of atp

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What happens in prophase

Chromosomes become more visible by supercooling
Centrioles move to opposite poles
Microtubules form pole to pole forming spindle fibres
Nuclear envelope dissolves
Nucleolus dissapears

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What happens in metaphase

Centrioles reach 2 poles
Chromosomes line up across equator
Spindle fibres attach at centromeres helping to arrange them

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What happens in anaphase

Centromeres divide
Chromatids are pulled apart centromere leading by the shortening of spindle fibres (contracting)
Chromosomes at opposite poles

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What happens in telophase

Nucleolus reappears
Nuclear envelope reforms
Chromosomes uncoiled to form chromatin

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What happens on cytolkinesis of an animal cell

Involves furrowing and cleavage of cytoplasm which starts on the outside of the cell
Two new cells formed

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What happens in cytokinesis of an animal cell

Cell plate forms
This starts from middle of cell
Two daughter cells formed

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What’s the importance of mitosis

Replacement of cells
Repair of tissues
Asexual reproduction
Growth in multicellular organisms

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What are the purposes of checkpoints in the cell cycle

Monitor wether each stage is completed correctly before continuing
Prevents uncontrolled division leading to tumors
Detect and repair dna damage
Ensure cell cycle isn’t reversed
To make sure dna is only copies once to form two diploid cells with the correct number of chromosomes

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What is checked for at g1 checkpoint

Nutrients
Growth factors
DNA damage

G2 purpose

Check for correct dna replication
Any dna damage
Cell size

G2 purpose

Check for correct dna replication
Any dna damage
Cell size

Purpose of spindle assembly checkpoint

To ensure spindle fibres attach to chromosomes

What are stem cells

Undifferentiated cells that can undergo cell division and have the potential to differentiate

What are totipotent cells

Can differentiate into any type of cells

What are pluripotent cells

Can form all tissue types but not a whole organism

What are multipotent cells

Multipotent cells can form any type of cells in a specific type of tissue

What are unipotent cells

Unipotent cells can only form one type of cell e.g muscle cells

What are some medical uses of stem cells

Heart disease - can be used in repairing damaged tissue after a heart attack Type 1 diabetes - can form artificial insulin producing cells to keep patient alive Parkinsons - caused by death of dopamine so cells can replace damaged cells in tissue in the brain Alzheimer’s - brain cells destroyed so can be replaced by stem cells Spinal injuries - can help for nerve cells to restore motor function Artificial organs can be made for research

What happens during meiosis interphase

DNA replicates so each chromosome has two sister chromatids which contain the same alleles that contain the same genes

What happens in early prophase 1

Chromosomes uncoil to become visible Nucleolus dissapears and nuclear envelope dissolves Centrioles migrate to poles and form spindle fibres

What happens in late prophase 1

Homologous chromosomes pair up to form a bivalent One chromosome is paternal the other maternal Recombination occurs where chromosome pairs cross over at chiasmata swapping sections of dna This forms recombinant chromatids The genes exchanged may be of different alleles of the same genes resulting in genetic variation

What happens in metaphase 1

Bivalents randomly line up across equator independent assortment of chromosomes Spindle fibres attach to centromeres

What happens in anaphase 1

Homologous chromosomes of each bivalent are pulled apart centromere leading towards the poles The chiasmata are pulled separate Centromere isn’t pulled apart so each chromosome still has two chromatids

What happens in telophase 1

In animal cell nuclear envelope reappears and there may be a short interphase Cytokinesis may occur

What happens in prophase 2

Everything now happens in two separate nuclei Chromosomes reondense and have two chromatids Nuclear envelope disintegrates Centrioles replicate and spindle develops perpendicular to previous plane of division

What happens in metaphase 2

Chromosomes randomly line up on equator in depends assortment of chromatids ( happens due to dna swapping at chiasmata during prophase 1 ) Spindle attaches to centromeres

What happens in anaphase 2

The chromosomes are pulled apart at the centromere Pulled towards poles centromere leading

What happens in telophase 2

Chromatids now chromosomes condense Nuclear envelope reforms to form 4 separate nuclei

What happens In cytokinesis

Cell may divide Forms 4 haploid cells that are genetically different