Chapter 9 - Genetic diversity and adaptation Flashcards
What is genetic diversity
Variation in alleles of genes
Variation in chromosome numbers/structures
Forms the basis of selection
What are the sources of genetic diversity
Mutations (9.1)
Meiosis (9.2)
Mate selection
Random fertilisation
what is gene mutation
Change in the base sequence of an allele or chromosome
Arise spontaneously/randomly
Occur during DNA replication during Interphase
Can be harmful, neutral or beneficial
Rate of mutation can be increased by mutagenic agents e.g. ionising radiation, x rays, UV light, carcinogens (cigarette smoke)
What are the two types of mutation
Base deletion and base substitution
what is base deletion
When a nucleotide and therefore a base is lost from DNA
All bases after the deletion then shift to the left so all subsequent triplets are read differently (frame shift)
Leads to a change in amino acid sequence (primary structure) so a change in H bonds/ionic bonds and tertiary structure and a non-functioning protein
The position of the deletion on the gene determines the impact. If the base is deleted at the start of a gene then the effect will be more drastic than if the base is deleted near the end.
example of base deletion
What is base substitution
When a nucleotide is replaced and therefore a base is altered
example of base substitution
what are the characteristics of base substitution
only affects one triplet
due to the genetic code being degenerate not all substitutions change the amino acid produced
can lead to non-functioning proteins
can be a problem is start or stop codons are affected
amino acid name table
what is a chromosome mutation
when the structure or number of chromosomes are altered
what is non-dysjunction
occurs during meiosis when chromosomes fail to separate
what is meiosis
genetic replication what produces 4 haploid daughter cells that are genetically different from each other
Replication followed by two nuclear divisions
(genetic material is halved)
what is the importance of meiosis
It produces haploid gametes so diploid number can be restored at fertilisation
It introduces genetic variation
diagram of meiosis
differences between meiosis and mitosis
how does genetic diversity arise from meiosis
due to the random arrangement of chromosomes along the equator during metaphase 1
what are the steps in crossing over between homologous chromosomes
Homologous chromosomes form a bivalent
Chiasmata form
Exchange of alleles between non-sister chromatids
Producing new combinations of alleles
diagram of crossing over between homologous chromosomes
how does genetic diversity arise from sexual reproduction
Mate selection – which 2 organisms mate together.
Random fertilisation – which two gametes fuse.
number of combinations is shown by the equation 2n^2
life cycle of a plant
life cycle of an animal
What is genetic diversity
the number of different alleles of genes in a population
what is the definition for population
group of individuals of the same species living in the same place at the same time
Each species has the same genes
What is the gene pool
all of the alleles in a population
The greater the number of alleles for a gene, the greater the genetic diversity
The greater the genetic diversity, the more likely individuals (and therefore a species) will survive environmental change
what is evolution
the change in allele frequency in a population or species over time
what are the steps in natural selection
- Random mutations can result in new alleles of a gene
- Some mutations are harmful but some are advantageous in certain environments (selection pressure)
- The advantageous mutation leads to increased reproductive success
- Advantageous allele is inherited by members of the next generation
- Over many generations, the new allele increases in frequency in the population
example of natural s
election in giraffes
what are the 3 types of adaptation
Anatomical
Physiological
Behavioural
what is anatomical adaptation with an example
Anatomical - physical features
Shorter ears and thicker fur for arctic foxes compared to warmer climates
what is physiological adaptation
Physiological - Internal body processes
oxidising of fat rather than carbohydrates to produce additional water for kangaroo rats in a warm environment
What is behavioural adaptation
Behavioural - Things organisms do
autumn migration of swallows.
what are the two types of selection
directional selection
stabilising selection
what is the graph that show variation in a population called
a normal distribution curve
what is directional selection
directional selection results in phenotypes at one extreme of the population being selected for and those at the other end of the extreme being selected against.
what is stabilising selection
If the environmental conditions remain stable the individuals with the phenotype closest to the mean are favoured and therefore these individuals are most likely to pass on their alleles to the next generation
graph displaying directional selection
graph displaying stabilising selection
