Cell Cycle and Cell Division Flashcards
Chromosomes, The cell cycle, Mitosis, Cancer, Bianry fission in bacteria, Virus replication, Meiosis, Crossing over, Independent segregation
What is genetic information carried in the form of?
Genes
What is a gene?
A section of DNA coding for one polypeptide
What is a chromosome?
It is an independent DNA molecule which has been supercoiled into a condensed form. Chromosomes contain many different genes
What happens during semi-conservative replication?
. Two genetically identical copies of the DNA molecules are made
. They remain attached at a central point called the centromere
. Each copy of DNA supercoils (using histone proteins to help them fold)
. While they are still joined the two DNA molecules are called ‘sister chromatids’
. The whole structure is the chromosome
What is the chromosome number?
It is the number of chromosomes possessed by an organism and is represented a ‘n’
What is a diploid cell?
They have their chromosomes in homologous pairs
How is the number of homologous pairs of a chromosomes represented?
2n - 2 x The number of chromosomes possessed by an organism
What is a haploid cell?
They have one copy of each chromosome and are gametes
Why is it important gametes are haploid?
It restores the chromosome number when gametes fuse to make a zygote
What is the loci of a gene?
The location of the gene on the chromosome
What is an allele?
The variant form of a gene (e.g. Alelle for blue eyes and the allele for brown eyes)
What are the stages of the cell cycle?
I - Interphase P - Prophase M - Metaphase A - Anaphase T - Telophase C - Cytokinesis
What happens during interphase?
Cell spends the majority of it’s time in interphase so during this time the cell performs it’s normal function.
At G1 phase the cell increases in size and a new biomass is made
At S phase the DNA replicates
At G2 phase the cell gets ready for division, it makes stores of ATP and new organelles
What is nuclear divison?
The period when the nucleus divides into two
What happens during prophase?
The chromosomes supercoil and become visable
What happens during metaphase?
Chromosomes line up at the equator of the cell
What happens during anaphase?
Spindle fibres get shorter and the centromere splits. The identical chromatids seperate
What happens during telophase?
Two nuclei form
What happens during cytokinesis?
The cell divides into two, each daughter cell receiving one of the nuclei
What is mitosis used for?
. Increasing cell numbers and growth of an organism
. Repair of damaged tissue
. Replacement of dead cells
What is produced in mitosis?
Two genetically identical daughter cells
What is the definition of cancer?
Cells that undergo uncontrolled mitosis and from tumours that spread into the tissue
What is one method used to treat cancer?
Drugs that can stop cell division
These drugs could stop: DNA replication, spindle formation, cytokinesus or other processess linked to mitosis
How do prokaryotes reproduce?
Asexually through binary fission
What does binary fission in bacteria involve?
. The DNA (which is often attached to a fold at a fold of the cell membrane) must be replicated before cell division
. The cell elongates, separating the DNA
. A new cell wall is formed down the middle which eventually meets, dividing the cell into two
How do virus’ reproduce?
They cannot undergo cell division, however they reproduce inside host cells
What is the first step in viral replication?
The protein molecules on the capsid attach to the cell surface membrane of the host cell
What is the second step in viral reproduction?
The virus enters the cell
What is the third step in viral reproduction?
The viruses DNA in encorporated into the host cells DNA
What is the fourth step in viral reproduction?
The viral DNA is transcribed and translated into proteins
What is the fifth step in viral reproduction?
The cell copies the viral DNA
What is the sixth step in viral reproduction?
The genetic material and proteins coats are assembled into virions
What is the seventh step in viral reproduction?
Eventually these virions burst out of the cell, destroying the host cell
What kind of cells are produced through meiosis?
Four genetically different daughter cells, that are haploid gametes
Why is meiosis important?
Without meiosis gametes would have 2n and when two gametes fuse they would form a cell with 4n, double that of a normal organsim
What is the process of meiosis
The chromosomes go through two divisions
In the first meiotic division, the homologous chromosomes pair up and are separated
In the second division, the chromatids are separated
Random fertilisation
Haploid gametes produced by meiosis cause variation in a population
Crossing over
During prophase and metaphase of the first division:
1. The homologous pairs associate (Bivalent)
2. Chiamata form
3. Equal lengths of chromatids are exchanged
4. Producing new alleles
All the cells at the end are genetically different
Independent segregation
During metaphase of the first division, the homologous chromosomes attach to the spindle fibres and they pair up and are reshuffled in any combination
To calculate the number of different combinations of chromosomes use 2^n
