What does each eukaryotic chromosome contain?
What does the centromere do?
Hold the chromosome together
What are telomeres?
The ends of DNA which need to be protected because when DNA gets damaged cells have mechanisms to repair it and so need to recognise blunt ends, important do not try to repair natural ends of chromosomes
Why do telomeres need to be protected?
To prevent cells trying to repair natural ends of chromosomes, they recognise blunt ends
What is the process of DNA replication?
1) Strand unwinds and hydrogen bonds connecting bases are broken
2) RNA primer initiates DNA synthesis
3) DNA polymerase copies the information and makes a complimentary strand (daughter strand on each new DNA)
4) Lagging strands need to be initiated by RNA primer and connected by DNA ligase
In what direction does DNA polymerase add new nucleotides?
5' to 3' direction
What are okazaki fragments?
The sections of DNA present on the lagging strand that need to be connected
How much base pairs are lost during mitosis and why?
100 base pairs are lost each time due to the gap at the end of the lagging strand due to the primer
What happens when chromosomes become to short due to bases being lost during each mitosis cycle?
They are recognised by telomerase and become extended
What is mitosis?
Cell division that results in two daughter cells that have the same number of chromosomes as the parent cell
What are the phases of mitosis?
What happens during prophase?
Nuclear membrane disapears
Spindle fibres form from the centriole
What happens during metaphase?
Chromosomes aligned at the equator of the cell
Attached by fibre to each centriole
Maximum condensation of chromosome
What happens during anaphase?
Sister chromatids seperate at centromere
Move to opposite ends of the cell
What happens during telophase?
New nuclear membrane forms
Each cell contains 46 chromosomes (diploid)
What happens during cytokinesis?
Two new daughter cells
During what phase are chromosomes most condensed?
In what phase can chromosomes be seen?
What is the spindle made from?
What do centromeres do during mitosis?
Join sister chromatids and bind to microtubules
What is the site of kinetochore?
What are centromeres composed of?
Repeated DNA sequences known as satellite DNA
What is satellite DNA?
DNA that does not code, but forms the site of kinetochore
What is kinetochore?
Multiprotein complex that attaches to microtubules from each pole
What do both sides of kinetochore need to be captured?
So that each daughter cell has the same amount of chromosomes
What are the 2 forms of chromatin?
Which is heterochromatin and euchromatin is condensed with silent genes and open with active genes?
Heterochromatin is condensed with silent genes
Euchromatin is open with active genes
What is chromatin?
The part of a chromosome that contains the coding information
Why can euchromatin code for proteins?
Open structure can be accessed by RNA polymerase
How many base pairs are there in our genome?