Genetic diversity and adaptations Flashcards
Substitution
When a base in a sequence of amino acid is changed.
Deletion
When a base is removed from a sequence of amino acids this changes the sequence and results in the sequence being read differently.
What happens during Meiosis
DNA replication - chromosomes and chromatids
Homologous chromosomes line up in pairs randomly (independent segregation)
Division 1- homologous pairs separate
Division 2- chromosomes and copies split
Gametes formed (haploid)
Gene mutation
Any change to one or more nucleotide bases, or a change in the sequence of the bases in DNA
What are the consequences of substitution
This can result in different amino acids however doesn’t often lead to a mutation as multiple codons code for the same amino acid and might occur in an intron which is non-coding and will be removed during splicing.
What are the consequences of deletion
This will lead to a mutation as the exons will be changed as well as the introns changing the structure of the protein.
- polypeptide will be entirely different and might not function correctly
What are the two types of chromosomal mutation
-changes in whole sets of chromosomes
-changes in the number of individual chromosomes
changes in the number of individual chromosomes
sometimes individual homologous pairs of chromosomes fail to separate during meiosis, this is known as non-disjunction.
non-disjunction
results in gametes having either one more or one fewer chromosomes
How does meiosis produce genetic variation
-independent segregation
-crossing over
Independent segregation
homologous pairs line up randomly
Crossing over
-Chromatids of each pair become twisted around each other
-chromatids break off due to tension
-might re-join with the chromatid of its homologous pair
genetic diversity
The number of different alleles of genes in a population
Natural selection
The process that leads to evolution in population
Describe the process of natural selection
- New alleles for a gene are created by random mutations
- If the new alleles increases the chances of survival in that environment then they are more likely to survive and reproduce
3.This reproduction passes on the advantageous allele to the next generation. - As a result over many generations the new allele increases in frequency in the population
Population
A group of individuals of the same species that live in the same place and can interbreed
Gene pool
The total number of alleles in a particular population at a specific time
Selection
The process in which organisms that are better adapted to their environment tend to survive and breed
Directional selection
Occurs when the environmental conditions change and the phenotypes best suited to the new conditions are more likely to survive. As a result these individuals will breed and produce offspring.
What is an example of directional selection
Bacteria being resistant to antibiotics.
-single bacteria has a mutation meaning it is not killed as it produces the enzyme penicillinase .
-As a result it can grow and populate and the frequency of alleles that enabled penicillinase production increased in population
-Therefore the population moved to have greater penicillin resistance
Stabilising selection
The phenotypes with successful characteristics are preserved and those of greater diversity are reduced. This selection doesn’t occur due to changes in the environment. If the environment stays the same then the individuals closest to the mean are favoured
What is an example if stabilising selection
New born babies weights. Those that have birth weights of around 3kg are more likely to survive than those at the extremes
