Topic 4B - Diversity And Selection Flashcards
What is a mutation
A change in the base sequence
Usually occurs during DNA replication
Why might mutation not lead to change in the amino acid sequence
Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet
Mutation may have occurred in intron
What is a substitution mutation
When a nucleotide in the DNA sequence is replaced by another
More likely that no change occurs in amino acid sequence
What is a deletion mutation
When a nucleotide in DNA sequence is lost. More likely to be harmful and significant, as it leads to frame shift which means the entire amino acid sequence will be different
What is a mutagenic agent
Factors that increase the rate of gene mutation
X-rays, UV light
What is a polyploidy chromosome mutation
Where an individual has three or more sets of chromosomes instead of two
What is chromosomes non-disjunction
When chromosomes fail to seperate correctly in meiosis, resulting in gametes with one more or less chromosome than normal
How does meiosis differ from mitosis
Produces 4 genetically different cells with half the number of chromosomes as the parent cell
Mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cell
What is genetic diversity ?
Number of different alleles of genes in a species or population
Why is genetic diversity important?
If a population has a low genetic diversity, it might not be able to adapt to a change in the environment and the whole population could be wiped out
How can genetic diversity in a population be increased (2)
Mutations in a DNA forming new alleles
Different alleles being introduced into a population when individuals from another population migrate into it and reproduce - gene flow
What is a genetic bottleneck?
An event that causes a big reduction in a population
What are the effects of a genetic bottleneck?
Number of different alleles in a gene pool decreases, so it decreases genetic diversity.
The survivors reproduce and a larger population is created from a few individuals
What is the founder effect?
Describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool.
What can cause the founder effect to occur?
Result of migration leading to geographical seperation or if a new colony is separated from the original production
Describe the process of natural selection (5)
- Individuals with the advantageous allele increase their chances of survival, they survive and reproduce, passing on their advantageous allele - this means there are less individuals with the less advantageous allele
- This means there is a greater proportion of the next generation inherits the beneficial allele
- This in return means they are mire likely to survive, reproduce and pass on the genes
- The advantageous allele increases in frequency from generation to generation
- Over generations this leads to evolution as the advantageous allele become more common in the popualtion
What are the 3 different types of adaptations?
Behavioural
Physiological
Anatomical
What are behavioural adaptations?
Way an organism acts that increase its chances of survival
What are physiological adaptations?
Processes inside an organisms body that increase its chances of survival
What is the anatomical adaptations?
Structural features of an organisms body that increase its chance of survivcal
What are the different types of selection (2)
Directional
Stabilising
What is directional selection ?
Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce. This could be in response to an environmental change
What is stabilising selection?
Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce. It occurs when the environment isn’t changing, and it reduces the range of possible characteristics
