Cell Cycle And Division Flashcards
What are the stages of the cell cycle?
-interphase
-prophase
-metaphase
-anaphase
-telophase
-cytokinesis
What are the three stages within interphase?
-G1 Phase
-S Phase
-G2 Phase
What stage is the majority of the life of the cell spent in?
Interphase G1
What happens in the G1 Phase?
Cells increase in size/volume and new biomass is made (proteins)
What happens in the S phase?
DNA replication by semiconservative DNA replication
What happens in the G2 phase?
So prepared for division, synthesis& & stores of ATP and new organelles synthesised
What is nuclear division?
Period when the nucleus divides into two (mitosis) or four (meiosis)
What is cytokinesis?
-division of the cytoplasm which follows nuclear division and produces two new genetically identical cells (mitosis) or four new genetically identical cells (meiosis)
Typically, how long does a mammalian cell take to complete a cell cycle and how much of this is interphase?
-takes 24 hours
-90% is interphase
How is genetic information carried?
In the form of genes
What is a gene?
A section of DNA that causes for one specific polypeptide
What is a chromosome?
An independent DNA molecule which has been super coiled into a condensed form
Draw an unduplicated chromosome
Draw a duplicated chromosome
How is a chromosome made?
-during semiconservative DNA replication, 2 genetically identical copies of the DNA molecule made
- they remained attached at a central point called the centromere
-each of the DNA copies now supercoils (using histones proteins to help them coil into eukaryotes)
-when they are still joined, the two condensed DNA molecules are called identical sister chromatids
-the whole structure is called a chromosome
What is the number of chromosomes possessed by an organism known as and what is it represented by?
-chromosome number
- represented by n
What is a homologous chromosome?
Have the same gene in the same gene Loki but have many different alleles.
What are diploid cells?
-Body cells have their chromosomes in homologous chromosomes.
-These somatic cells are called diploid cells
What is the number of homologous chromosomes in a diploid cell?
2n
What are haploid cells?
-cells with only one copy of each chromosome
-these are the gamete’s (sex cells)
Why is it important to have haploid cells?
To restore the species chromosome number when gametes fuse to make a zygote
Are somatic cells such as skin cells and liver cells diploid or haploid ?
Diploid (2n)
Are gametes such as sperm cells diploid or haploid?
Haploid (n)
What is mitosis used for?
-increasing cell numbers and growth of an organism
-Repair of damaged tissues (not cells)
-Replacement of worn out/dead cells
In mitosis, what types of cells are produced?
Two genetically identical daughter cells
These are clones
No variation occurs
In what types of environments do some organisms use mitosis for asexual reproduction?
In favourable, stable environment environments (where there is no environmental change)
Draw the stages of mitosis
How to remember the order of mitosis
Pro Met Ana on the Telophone
Interphase
Prophase
Metaphase
Anaphase
Telophase
What happens during prophase in mitosis?
- The nuclear membrane starts to breakdown
- The centrioles start to move to the poles of the cell and make spindle fibres
-The chromosomes super coil and condensed/shorten/thicken and become visible
-each chromosome appears as two identical sister chromatids joined at the centromere
What is the easiest way to spot prophase during mitosis?
You first see the chromosomes PROperly = PROphase
What happens during metaphase in mitosis?
-The centrioles complete the production of spindle fibres
-The chromosomes are attached to the spindle fibres by their centromere
-The chromosomes align down the equator of the cell
What is the easiest way to spot metaphase during mitosis?
The chromosomes look like they lineup in the Middle= Metaphase
What happens during anaphase in mitosis?
-The spindle fibres contract/shorten
-The centromere splits
-The identical sister chromatids are pulled to opposite poles
-making a ‘V’ shape
What is the easiest way to spot anaphase during mitosis?
Chromosomes are pulled apart=anaphase
What happens during telophase in mitosis?
- A nuclear membrane starts to reform around each set of chromosomes
-The chromatids/chromosomes unwind/coil/become longer/thinner and become invisible
What is the easiest way to spot telophase in mitosis?
The chromosomes has split and clustered into Two nuclei =Telophase
What is an allele?
Different version of the same gene
What is a gene?
Section of DNA on a chromosome coding for one or more polypeptide
What is a chromosome?
Independent DNA molecule in a condensed form which contains many genes (using histones)
What does the term sister chromatid mean?
One of the two strands of a replicated chromosome that are joined together by a single centromere prior to cell division
What does the term haploid mean?
Cells that contain only a single copy of each chromosome (i.e gametes)
What does the term diploid mean?
Cell in which the nucleus contains two set of homologous chromosomes
What is a somatic cell?
A normal body cell
What is a homologous chromosome?
Same genes are in the same location
What do tumour suppressor genes do?
Code for proteins that slow down the cell cycle
What do proto-onco genes do?
Code for proteins that speed up the cell cycle
What happens if a mutation occurs in the tumour suppressor genes or the proto onco genes?
- cell division continues uncontrolled
-It is often rapid
-Cells produced are abnormal
-Tumour develops
-If the cell spread into the surrounding tissues, this is cancer
Give one way in which cancer can be treated
-Giving drugs that inhibit cell division (mitosis)
-these drugs may stop the DNA replication, spindle formation and cytokinesis
What does binary fission in prokaryotic cell involve?
- replication of the circular DNA and of plasmids
- Division of the cytoplasm to produce two daughter cells each with a single copy of the circular DNA and a variable number of copies of plasmids
Is binary fission a type of mitosis?
No
how do viruses replicate? (7)
-attachment proteins on the virus attach to receptors on the cell
-The virus nucleic acid enters the cell cytoplasm
-* reverse transcriptase makes DNA from viral RNA*
-The viruses DNA is inserted into the host cells own nuclear DNA/genome
-The viral DNA is transcribed(viral mRNA) and translated into viral proteins (enzymes/attachment proteins)
-The cell replicates the viral DNA
-The genetic material and protein coats are assembled into virions
-Eventually these virions burst out of the cell, often destroying the host cell
How do mitochondria and chloroplasts replicate?
Binary fission
What is the formula for calculating mitotic index?
What is the equation for calculating the length of time for each stage of mitosis?
What is the calculation for dilution series?
What is meiosis?
-A form of cell division used by diploid organisms to produce haploid gametes for sexual reproduction.
-This increases variation within the population
-It results 4 genetically different daughter cells
Why is meiosis important?
-increases variation within the population
-Halves the chromosome number (ensuring each egg or sperm cell only has one copy of each chromosome) before fertilisation to restore the full chromosome number at fertilisation 2n
What happens during meiosis 1?
P1 & M1- chromosome supercoil, condense (around histones) and become visible. Homologous pairs of chromosomes form a bivalent and align along the equator. Spindle fibres attached at the centreomere.
A1- spindle fibres contract and separate homologous chromosome pairs, pulling one of each pair to the opposite poles of the cell
T1-nuclear membrane forms around the separated homologous chromosomes
-Each daughter is now a haploid
What happens during meiosis 2?
P2-each daughter cell only contains one chromosome from each homologous pair (haploid)
M2-chromosomes align along the equator
A2-non-chromatids are split by their centromere and pulled to opposite poles of the cell
T2- nuclear membrane reforms
-4 genetically different haploid daughter cells are produced
What happens in crossing over?
-homologous chromosomes associate/bivalent is formed
-chiasma(ta) form
-Equal lengths of non-sister chromatids/alleles are exchanged
-Producing new combinations of alleles
Show what chromosomes would look like before and after crossing over
When does Independent segregation take place?
In metaphase one
What is independent segregation of homologous chromosomes?
During metaphase one, the homologous chromosomes attatch to the spindle fibres and they pair up side-by-side and can be reshuffled in any combination
How can you calculate the possible number of different combinations of chromosomes following meiosis without crossing over?
Describe the process of crossing over and explain how it increases genetic diversity (4)
-Homologous chromosomes associate/bivalent is formed
- chiasma(ta) form
-Equal lengths of non-sister chromatids are exchanged
-Producing new combinations of alleles
Contrast mitosis and meiosis
