Genetic Diversity Can Arise As A Result Of Mutations Or Duing Meiosis Flashcards
What are the two types of mutations
Gene mutations
Chromosome mutations
What are the three types of gene mutations
Substitution
Deletion
Insertion
What are the two types of chromosome mutations
Chromosome structure
Chromosome number
What does degeneracy mean
There is more genetic information than what’s needed
Where does degeneracy happen in genetic code
Within the third base of each codon which usually codes for the same amino acid
Why does degenerate mutations not always matter
Because two or more codons can code for 1 amino acid
What is a substitution mutation
When one amino acid is replaced.with a different base
What effect does a substitution mutation have
-If it’s the third base of a codon then there may be no effect due to degenerate codes (silent mutations)
- if a mutation leads to a premature stop codon then the protein will be incomplete and non functional (nonsense mutation)
What is substitution/deletion
When a base is deleted or inserted into the genetic information
The effect of substitution/deletion
It causes a frame shift mutation (changing the codon reading frame)
A single deletion or insertion mutation will cause all of the coded amino acids afterwards to be different
A deletion and insertion will cancel each other out
Why do lots of mutations not have an effect on our phenotype
Because they occur in non coding DNA
The mutation doesn’t change the amino acid
The steps in mutations in DNA changing the cells phenotype
-change in base of DNA
-Different codon
-Different amino acid in protein
-change in primary structure of protein
-Change in secondary and tertiary structure of protein
-Change in protein function
-Change in cell function
What are mutations caused by
Mutagens
A physical or chemical agent that changes the genetic material of an organism, increasing the frequency of mutations above the natural background level
Examples of mutagens
X-ray
UV rays
What is nondisjunction
A chromosome mutation that changes the number of chromosomes in a cell
When/how does nondisjunction happen
In either anaphase I or anaphase II of meiosis when chromatids remain stuck together, this results in some gametes having extra or missing chromosomes
If an abnormal gamete is fertiliser what would the zygote show
Polysomy (eg.down syndrome)
Monosomy (eg.turner syndrome)
What are the three ways we form new alleles for genetic variation
Independent segregation
Crossing over
Random fertilisation
What is independent segregation/assortment
During the first meiotic division, homologous chromosomes form bivalents and line up either side of the equator
The assortment of maternal and paternal chromosomes on either side of the equator is random
What is crossing over
When the homologous chromosomes and bivalent, sections of the chromosomes are swapped with corresponding sections of the other pair
The point at which the chromosomes swap over is called the chiasma
What does crossing over produce
It means the maternal and paternal alleles can be combined
