2.1.6 Cell division, cell diversity and cellular organisation Flashcards
What are the three phases of the cell cycle?
interphase, nuclear division (mitosis), Cell division (cytokinesis)
What is the movement from one phase in the cell cycle to another triggered by?
Chemicals called cyclins.
What are the three phases in interphase?
G1, S phase, G2
What happens during G1 in interphase?
The cell grows, new organelles and proteins are made.
What happens in S phase in interphase?
Cell replicates its DNA.
What happens in G2 of interphase?
The cell continues growing and prepares to divide.
Does mitosis occur in all somatic cells?
Yes
How many rounds of division are in mitosis?
One
What is mitosis used for?
growth, repair, asexual reproduction
What type of cells does mitosis produce?
2 identical daughter diploid cells.
How many chromosomes do the cells produced from mitosis have?
46
What type of cells does meiosis produce?
4 non identical daughter haploid cells
How many chromosomes do the cells produced from meiosis have?
23
Are the cells produced by meiosis diploid or haploid?
haploid
Are the cells produced by mitosis diploid or haploid?
Diploid
How many rounds of division are involved in meiosis?
Two
What is meiosis used for?
sexual reproduction, production of gametes
How many checkpoints are there in the cell cycle?
Four
What is the cell checked for in G1?
Damage.
What is the cell checked for in S phase?
Ensure that chromosomes have been replicated.
What is the cell checked for in G2 phase?
Additional check for if DNA damage has occurred.
When are each of the checkpoints in the cell cycle?
G1, S, G2, Metaphase.
What are the stages of mitosis?
prophase, metaphase, anaphase, telophase
What happens in prophase of mitosis?
Chromosomes condense and are visible.
Nuclear envelope breaks down
Spindle fibres begin to emerge
DNA supercoils
What happens in metaphase of mitosis?
chromosomes line up along the equator of the cell
What happens in anaphase of mitosis?
Sister chromatids separate at centromere.
Spindles shorten
Sister chromatids pulled to opposite poles
What happens in telophase of mitosis?
Chromosomes arrive at opposite poles and begin to recompense.
Nuclear envelope reforms
Spindle fibres break down
What happens in cytokinesis?
division of the cytoplasm
How many cells does meiosis produce?
four
How many cells does mitosis produce?
Two
What is the point at which sister chromatids are joined together called?
Centromere
What happens in prophase I of meiosis?
DNA condenses.
Homologous chromosomes line up
Crossing over
Nuclear envelope breaks down
Spindle fibres form
When does crossing over occur in meiosis?
Prophase 1
What happens in metaphase I of meiosis?
Bivalents line up along equator
independent assortment.
At which stage of meiosis does independent assortment occur?
Metaphase I
What happens in anaphase I of meiosis?
Microtubules pull chromosomes to opposite ends of the spindle
Centromeres do not divide
What happens in telophase I of meiosis?
Chromosomes arrive at opposite poles
spindles break down
nuclear envelope reforms
What happens in prophase II of meiosis?
The nuclear envelope breaks down
chrosomes condense
Spindle fibres form at right angles to previous ones
What happens in metaphase II of meiosis?
Chromosomes line up in single file along the equator of the spindle
What happens in anaphase II of meiosis?
Centromeres divide and individual chromatids are pulled to opposite poles.
What happens in telophase II of meiosis?
Nuclear membrane reofrms
What are the three mechanisms of creating genetically different offspring in meiosis?
Crossing over
independent assortment
Random fusion of gametes
What is crossing over?
When non-sister chromatids exchange alleles by getting entangled which places stress on the DNA molecules so a section on one chromosome will join with a section on the other chromosomes.
What is independent assortment?
The production of different combinations of chromosomes in daughter cells due to the random alignment of homologous pairs along the equator of the spindle.
What is random fusion of gametes?
Meiosis creates genetic variation between the gametes produced so every gamete carry’s very different alleles. During fertilisation,any male gamete can fuse with any female one to create a zygote.
What is a stem cell?
a cell that can differentiate and become any type of human cell
What are the three levels of potency?
totipotent, pluripotent, multipotent
What is potency?
the ability of stem cells to differentiate into specialised cells
What is totipotency?
Stem cells which can differentiate into any cell type found in an embryo as well as the placenta.
What is pluripotency?
Embryonic stem cells which can differentiate into any cell type found in the embryo however not the placenta cells.
What is mutlipotency?
Adult stem cells that have lost potency. Can only produce a limited range of cell types e.g blood cells.
Where are adult stem cells found?
bone marrow
How are red blood cells formed?
From adult bone marrow stem cells.
Use of embryonic stem cells?
Huge potential in the treatment of disease.
Use of adult stem cells?
stem cells from healthy persons bone marrow can replace faulty blood cells in patient.
Why is the use of embryonic stem cells controversial?
It involves the destruction of embryos
What shape do red blood cells have?
Bioconcave disc
Function of red blood cells?
transport oxygen around the body.
Which pigment is found in red blood cells?
Haemoglobin
Why do red blood cells have a bioconcave shape?
Increase surface area.
Why is there no nucleus in red blood cells?
Makes more space inside the cell for maximum oxygen carrying capability.
Function of neutrophils.
phagocytosis
What type of nucleus do neutrophils have?
Lobed
Sperm cells function
To fertilise the egg
What does the sperm acrosome contain?
Digestive enzymes to break down the outer layer of egg cell .
What is the mid piece of sperm packed with?
Mitochondria
Function of root hair cell
Absorption of water and mineral ions from soil
Why do root hair cells have a large surface area?
To take up more water by osmosis.
Function of ciliated epithelium
moving substances across the surface of a tissue
Why do ciliated epithelium have cilia?
They beat in a coordinated way to shift material along the surface of the epithelium tissue.
Function of goblet cells?
Secrete mucus.
Function of guard cells
Opening and closing of the stomata to regulate water loss and gas exchange.
