Cell Division Flashcards
State what the cell cycle is.
A process involving the GROWTH of the cell and REPLICATION of the genetic material to make 2identical daughter cells
Name the stages of the cell cycle.
Interphase
Prophase
Metaphase «< Mitosis
Anaphase
Telophase
Cytokinesis (cytoplasmic division)
Explain why the cell cycle doesn’t occur in some cells.
Some cells (e.g. neurons) don’t have the ability to DIVIDE after DIFFERENTIATION.
What is the difference between the cell cycle and mitosis?
Cell cycle is the growth period between divisions.
Mitosis is only 10% of the cycle and is just nuclear division.
State the purpose of mitosis.
Produces 2 genetically identical daughter cells for:
Growth
Cell replacement / tissue repair
Asexual reproduction
Name the stages of mitosis.
P = Prophase
M = Metaphase
A = Anaphase
T = Telophase
What types of organism undergoes either cell cycle or binary fission or viral replication?
Eukaryotes undergo cell cycle.
Prokaryotes undergo binary fission.
Viruses undergo viral replication.
How many pairs of chromosomes do human cells contain?
23
How many chromosomes does a human cell have?
46
What are diploid cells?
Cells that contain chromosome PAIRS - 46 total.
What are haploid cells?
A cell that contains a single set of chromosomes - 23 total.
What is cytokinesis?
When a diploid cell divides to form 2 IDENTICAL daughter cells.
What occurs in the mitotic phase during the cell cycle?
Nucleus divides into 2 daughter nuclei. (mitosis)
Cell divides into 2 daughter cells with a nucleus. (cytokinesis)
What’s the difference between mitosis and cytokinesis?
Mitosis divides the nucleus.
Cytokinesis divides the cell cytoplasm.
What does the mitotic phase consist of?
Mitosis
Cytokinesis
What is chromatin?
Combination of DNA and proteins that make up chromosomes.
What are replicated chromosomes called?
Sister chromatids
What is the point where sister chromatids are joined called?
Centromere
During interphase. the chromosomes are…
not visible as distinct structures in the nucleus - not condensed.
Describe the interphase stage of the cell cycle.
1~ DNA is DECONDENSED so chromosomes are not visible
2~ DNA replication and replication of ORGANELLES occurs
3 ~ Protein synthesis.
Describe the prophase stage in mitosis.
1~ Chromosomes CONDENSES & become VISIBLE in the nucleus.
2~ Nucleolus disappears, nuclear envelope breaks down.
3~ CENTRIOLES move to opposite poles of cell, and produces SPINDLE fibres.
4~ Spindle attaches to CENTROMERE of each chromosome.
Describe the metaphase stage in mitosis.
1~ Spindle fibres line up the chromosomes along the EQUATOR / centre of the cell.
Describe the anaphase stage in mitosis.
1~ Spindle fibres shorten.
2~ This SEPARATES the sister chromatids as they are pulled to opposite poles of the cell.
Describe the telophase stage in mitosis.
1~ Spindle breaks down.
2~ Chromosomes DECONDENSE & become invisible again.
3~ 2 new NUCLEAR ENVELOPES form and the nucleolus reappears in each nucleus.
Describe what happens during the cytokinesis phase in the M (mitotic stage).
1~ The cytoplasm separates and the cell divides into two.
What are the differences in mitosis of animal and plant cells?
PLANT CELLS =
> Don’t have centrioles so cannot form spindles.
> A new cell wall also forms down the centre.
What do centrioles do?
Form spindle fibres.
What are spindle fibres made up of?
Microtubules
Describe three functions of mitosis in multicellular organisms [3 marks]
Growth of tissues
Repairs damaged tissue
Asexual reproduction
Production of new stem cells
Proliferation of white blood cells
Producing gametes from haploid cells
Development of body plan
What is meant by chromosomes?
Long strands of DNA made up of genes.
What is meant by chromatids?
1 of the 2 identical halves of a chromosome that has been replicated for cell division.
What are histones?
Proteins that hold DNA.
What does it mean when DNA condenses?
Chromosomes fold around histones to become coiled, making them appear SHORTER and THICKER, so they are visible.
What does it mean when DNA decondenses?
Chromosomes aren’t coiled around histones so they appear LONG and THIN, and cannot be seen through a light microscope.
When can chromosomes be seen through a light microscope?
When they are condensed.
Visually map this in your head, but what counts as a chromosome?
A single chromosome strand. ( I )
Sister chromatids ( 𝑥 )
What happens to the mass when a chromosome is doubled?
The mass is doubled.
How many hours does it take for our body cells to divide?
Every 24 hours
Why does the nuclear envelope break down? [1 mark]
To release chromosomes
Why do the chromosomes condense? [2 marks]
To allow the chromosomes to attach onto spindle fibres without becoming TANGLED or broken.
Why do the chromosomes decondense? [2 marks]
To protect the DNA sequence so GENE EXPRESSION doesn’t take place for PROTEINS to be made.
You don’t want other things to be made while making DNA.
Why are chromosomes visible when they condense?
They are shorter and thicker
Q1 = The total cell cycle of Cell X takes 10 hours. 300 of these cells are observed under the microscope.
Interphase 80
Prophase 15
Metaphase 1
Anaphase 2
Telophase 2
(a) How long does interphase take?
(b) How long does prophase take?
(c) How long does metaphase take?
(d) How long does anaphase take?
(e) How long does telophase take?
(f) How long does mitosis take?
(a) 8 hours
10 hours x 0.8 (80%) = 8
(b) 1.5 hours
10 hours x 0.15 = 1.5
(c) 0.1 hours
10 hours x 0.01 = 0.1
(d) 0.2 hours
10 hours x 0.02 = 0.2
(e) 0.2 hours
10 hours x 0.02 = 0.2
(f) 2 hours
1.5+0.1+0.2+0.2 = 2
Q2 = The total cell cycle of Cell Y takes 23 hours. 200 of these cells are observed under the microscope.
Interphase 170
Metaphase 2
Anaphase 4
(a) How long does interphase take?
(b) How long does metaphase take?
(c) How long does anaphase take?
(d) How long does mitosis take?
(a) 19.55 hours
170/200 = 85%
23 hours x 0.85 = 19.55
(b) 0.23 hours
2/200 = 1%
23 hours x 0.01 = 0.23
(c) 0.46 hours
4/200 = 2%
23 hours x 0.02 = 0.46
(d) 0.69 hours
0.23+0.46 = 0.69
TURN THEM INTO PERCENTAGES FIRST
Describe the behaviour of chromosomes during mitosis.
Explain how this results in the production of two identical daughter cells [6 marks]
1~ In prophase, chromosomes condense and coil.
2~ In metaphase, chromosomes line up at the equator of the cell.
3~ In anaphase, sister chromatids separate and are pulled towards opposite poles of the cell.
4~ In telophase, chromatids reach the poles and decondense.
5~ Cytokinesis
6~ Each daughter cell inherits ONE HALF of the sister chromatids.
