Cell Division and Cell Differentiation Flashcards
What are the stages of the Eukaryotic cell cycle?
Gap phase 1 (sometimes gap phase 0)
Synthesis
Gap phase 2
Meitosis
What happens during Gap phase 1?
Cell growth/increase size
Transcribe RNA
Duplicate organelles
Biosynthesis
What happens during synthesis?
DNA replication
commits the cell to completing the cell cycle
Why must synthesis occur very fast?
As DNA is replicate, bases get exposed which are susceptible to mutagenic agents
What happens during Gap phase 2?
Cell growth
Preparation for mitosis
Is it possible to exit the cell cycle if so, how?
Yes
This can happen through a resting phase called Gap phase 0 this is where:
Apoptosis (programmed cell death) can occur
Differentiation - stops dividing
Can stay there indefinitely
What are sister chromatids
Replicated chromosomes
How is the cell cycle regulated
Using checkpoints
Why does the cell cycle need to be replicated?
To prevent uncontrolled division of cells
Detect DNA damage
What happens if checkpoints fail?
Cancer can arise - which is the result of uncontrolled cell division/defects
When do the check points occur
Before synthesis and meitosis
What are the 2 checkpoints
G1/S (Gap phase 1 /Synthesis)
G2/M (Gap phase 2/Meitosis)
Can the cell cycle be reversed?Why?
No - because of the check points
What is the role of the G1/S checkpoint
The cell checks for any damage to the DNA and that the cell is ready to enter S phase- that the cell is the correct size and nutrients/growth factors are present .
What is the role of the G2/M checkpoint?
The cell checks whether the DNA has been replicated without damage and that the cell is the correct size
How many times can DNA be replicated during the cell cycle?
Once
What is G1 S and G2 together known as?
Interphase
What is meitosis?
The division of the cell into 2 genetically identical (diploid) daughter cells
What is meitosis used for?
Growth
Tissue repair
Asexual reproduction
What are the stages of meitosis?
Prophase Metaphase Anaphase Telophase (Cytokinesis)
What happens during Prophase?
Chromosomes condense and supercoil Nuclear envelope divides Centriole divides New centrioles move to opposite poles Spindle forms
What happens during Metaphase?
Sister chromatids attach to the spindle by their centromeres and line up on the equator
What happens during Anaphase?
Centromeres of the sister chromatids split
Motor proteins drag the chromatids towards the poles of the cell
What happens during Telophase?
New nuclear envelopes form around the chromosomes
Cell contains 2 nuclei
What happens during cytokinesis in plant cells?
End plate forms at the equator
New bits of plasma membrane form on either side of the end plate
Forms 2 cells
What happens during cytokinesis in animal cells?
Cell inches off in the middle
Cytoplasm splits
What is meiosis important for?
Sexual reproduction
increases genetic variation by random fertilisation
What are diploid cells
cells containing 2 sets of chromosomes
What are haploid cells
cells containing 1 set of chromosomes
What is random feritlisation
random fusion of nuclei of gametes
Give an example of haploid cell
Gametes (egg cell)
What are homologous chromosomes
one chromosome comes from the mother and one comes from the father containing genes that code for the same thing - can contain different alleles
How many cells produced in meiosis?
4 non-identical haploid cells
What are the stages in meiosis?
Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II
What happens during Prophase I?
Chromosomes condense and supercoil Centrioles divide and move to cell poles Spindle forms Nuclear envelope breaks down Crossing over occurs
What is crossing over in meiosis?
Sister chromatids wrap around eachother, joining at the chiasmata and exchange sections to shuffle alleles
What happens during Metaphase I?
Homologous chromosomes align on the equator and attach to spindle at their centromere
What happens during Anaphase I?
Homologous chromosomes are pulled apart, centromeres don’t divide
What happens during Telophase I?
Two nuclear envelopes form, cytokinesis occurs and brief interphase
Do plants undergo Telophase I
No, they go straight from Anaphase I to Prophase II
What happens during Prophase II?
Newly formed nuclear envelopes break down (animals only)
Chromosomes condense and supercoil
Centrioles divide and move to cell poles
Spindle forms
What happens during Metaphase II?
Sister chromosomes align on the equator and attach to the spindles
What happens during Anaphase II?
Centromeres divide, chromatids are pulled apart
What happens during Telophase II?
Nuclear envelope forms around the 4 haploid nuclei
In animals - 2 cells divide to from 4
In plants - tetrad structure of 4 haploid cells form
What are the ways in which genetic diversity is created in meiosis?
Crossing over of chromosomes creates different allele combinations
Mutations (in meitosis too)
Dividing the chromosomes and sister chromatids in Anaphase I and II ensures that each of the four daughter cells has adifferent combination of alleles
Define differentiation
the process by which cells, tissue, and organs get specialised features, especially during embryonic development. (switching genes on and off)
Define specialisation
The adaptation of an organ or part to serve a special function.
How can cells differentiate?
Change proportions of organelles in a cell
Vary shape of cell
Vary the cellular contents (e.g. protein content)
What are tissues?
group of cells that work together to perform a common function
What are organs?
group of tissues that work together to perform a common function
What cells make up the cross section of the leaf
Waxy cuticle Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis + guard cell Waxy cuticle
How does the specialisation of palisade cells allow it to complete its function?
Long cylindrical shape, packed vertically in a leaf - maximising light absorption.
Large vacuole which pushes the chloroplast to the edges of the cell - short diffusion distance of CO2.
It has lots of chloroplast which can be moved up or down by motor proteins on cytoskeletal threads depending on the amount of light available
How does the specialisation of guard cells allow it to complete its function?
Contains chloroplasts to turn light energy into ATP which move potassium ions into the guard cell so water enters by a change in water potential
Cell wall is thicker in the middle of the cells than at the end so when turgid the cells bend due to the differences in thickness opening stomata, allowing gases to diffuse through
How does the specialisation of root hair cells allow it complete its function?
Hair like projections increase surface area to absorb more water and minerals from the soil
Many carrier proteins on plasma membrane actively transport mineral ions into the cells
Many mitochondria provide ATP for
active transport
Where can stem cells be found in plants?
In meristem tissue at the root, shoot and cambium of vascular bundles
What are the features/structure of meristem tissue
Thin cell wall
no chloroplast
no large vacuole
Are meristem cells capable of undergoing meitosis
yes
How is the xylem specialised for its function
Contains lignin which strengthens the cell and makes it waterproof
Lignin deposited, causes cells in the xylem tissue to die
Cell walls at the ends break down allowing the xylem vessel to become a continuous column
Contains no organelles for greater water flow
How is the phloem specilised for its function
Contains live cells
Sieve tubes lose most of their organelles and develop sieve plates to allow sugar through
Has companion cells because the cells are still alive but lose its organelles
Companion cells have many mitochondria and provide ATP for loading sugars into sieve tubes
What are pluripotent cells
Cells has the potential to differentiate and specialise into any cell type that that organism can produce.
What are the main plant organs and what are their roles
Flower - reproduction
Stem - support plant and transport things
Leaf - photosynthesis
Root - anchor plant in the ground, storage, absorption of water
Erythrocytes and neutrophils come from stem cells found where
bone marrow
What is the function of Erythrocytes?
Carry oxygen from lungs to respiring cells
Carry carbon dioxide from cells to the lungs
How are erythrocytes specialised for its function
Small - has large surface area to volume ratio
Contains no organelles to maximise space for hb
Has biconcave shape - allows flexibility, to fit through tiny capillaries
What is the function of neutrophils
Ingest invading pathogens
How are neutrophils specialised for its function?
large - 2x RBC
contains many lysosomes
enzymes in lysosomes are specialised to kill microorganisms
How are spematozoa (sperm cell) specialised for its function
Many mitochondria that generate ATP for movement
Sperm head contain (acrosome) specialised lysosomes to break down wall of egg
Small, long and thin to ease movement
Tail helps to propel/move the sperm
Haploid to fulfil role as gamete
What are the function of epithelial cells
lining of airways and intestines
How are epithelial cells specialised for its function
Squamous cells – flattened in shape to maximise surface area
Ciliated cells – have many cilia on cell surface - wafts mucus up the throat
What are the 4 main types of tissue in animals
Muscle
epithelial
Connective
Nervous
What are the 2 types of epithilial tissue
Squamous
Ciliated
How are squamous epithelial tissue specialised for their function
Made almost entirely of closely packed cells with short cell cycles
Line other tissues, vessels and surfaces
Mainly for secretion and protection
How are ciliated epithelial tissue specialised for their function
Made of closely packed cells with short cell cycles
Contain many small projections (cilia or microvilli) at the surface to increase surface area
Mainly for secretion and absorption
