4.3 Genetic Diversity: Mutations & Meiosis Flashcards
What is a substitution mutation?
When one base is changed for another
What is an insertion/addition mutation?
When one or more nucleotides are added into the DNA
What is a deletion mutation?
When one or more nucleotides are deleted from DNA
What is a point mutation?
When a single base pair is altered
What is a frameshift?
A knock on effect causing every amino acid after to be incorrect
Why are frameshifts caused?
Bases are read 3 at a time in a non-overlapping frame
What is the result of a frameshift?
The bonds will form in different places and the tertiary structure of the protein will be incorrect
What is meant by a silent mutation?
No change has been made to the primary structure
How can a mutation be silent?
Degenerate code means multiple codons can code for the same amino acid
What is a mutagen?
Something that increase chances of a mutation
What is in cells to help prevent mutations?
Enzymes that check the DNA after replication
What will happen to the cell of a healthy person if there is a mistake in DNA?
Apoptosis - programmed cell death
OR
There are enzymes that can fix small mistakes
What is apoptosis?
Programmed cell death
What is the consequence of cancer patients who don’t have the working enzymes to cause programmed cell death?
Cell will not undergo apoptosis
Means uncontrolled cell division and tumour growth
Give examples of mutagens.
Alcohol
Benzene
UV light
x-rays
What is the role of meiosis?
Create gametes
What is started with in meiosis?
Germ line cells
How many chromosomes do germ line cells have?
46
What is a homologous pair of chromosomes?
Chromosomes that code for the same gene
Where does each chromosome in an homologous pair come from?
One from each parent
Are homologous chromosomes identical?
No they can contain different alleles (different versions of the same gene)
How do chromosomes line up during the first division of meiosis?
In their homologous pairs down the centre of the cell
Why is it important homologous pairs line up the centre of the cell during the first stage of meiosis?
As one from each pair needs to end up in a daughter cell
What process can occur when homologous pairs are lined up in pairs during the first stage of meiosis?
Crossing over when chromosomes in homologous pairs can swap one or more alleles
Why does crossing over increase variation?
Creates new combinations of alleles
What has happened by the end of division one in meiosis?
DNA chromosomes have been halved from 46 to 23
How does the amount of gametes produced in parents create increased variation?
Random fertilisation
What is random segregation?
The allocation of gene copies is random with one of two gene copies being distributed to each gamete
