Genetics and Populations Flashcards
Define Diploid
A cell or organism that has a pair of homologous chromosomes
What is a gene?
A sequence/section of DNA that codes for a particular protein
Define Allele?
A version of a gene
What is a Genotype?
The combination of alleles within an organism
What is a phenotype?
The physical expression of a genotype
What does it mean if an allele is dominant?
An allele that is always expressed
What is a recessive allele?
It is only expressed when homozygous
What results from co dominance?
Both alleles are expressed in the phenotype
What is the locus?
The position of a gene on a chromosome
What is dihybrid inheritance?
Inheritance of 2 characteristics controlled by separate genes
What is the expected phenotypic ratio of the F2 generation?
9:3:3:1
What is monohybrid inheritance?
Inheritance of characteristics controlled by a single gene
What percentage of a F1 generation would be heterozygous?
100%
What is the expected retail of genotypes in the F2 generation?
1:2:1
What would be the expected percentage of different phenotypes in the F2 generation?
3:1 (75% to 25%)
What is epistasis?
An interaction between genes where the expression of one gene suppresses the expression of another gene
What is an autosome?
Any chromosome that is not a sex chromosome eg) 44 autosomes
How are autosomes linked?
If they are on the same autosome they will stay together during independent segregation - meaning they will be inherited together
How does autosomal linkage affect phenotypic ratios?
Because they are inherited together more offspring have the same phenotype as their parents
What else can affect autosomal linkage?
Cross over
Species
A group of similar organisms that can breed and produce fertile offspring
Population
All the organisms of a single species in one place at the same time
Community
All organisms in one place in one time
Gene pool
All the alleles present in a population
Allele frequencies
How common the allele is
Evolution
Change in allele frequencies over time
Differential reproductive success
Organisms with a phenotype better adapted to their environment have a selective advantage, more likely to survive breed and pass on their genes
Speciation
The formation of a new species
What are the predictions of Hardy-Weinberg principles?
The frequency of alleles of a gene will stay constant over generations
What assumptions are made for a Hardy Weinberg calculation?
No mutation takes place No selection Random mating Large population No genetic drift Population is genetically isolated
What is intraspecific variation?
Individuals of the same species have the same genes but different alleles (phenotypes)
What is interspecific variation?
Individuals of different species have different genes/ live in different environments ( have different phenotypes)
Define continuous variation. What graph would be used?
Variation is smooth/ continuous eg) height/weight Line graph
Define discontinuous variation. What graph would be used?
Individuals fall into discrete groups with no intermediates eg) blood groups Bar chart
Why would discontinuous variation take place?
It is controlled by a single gene or a few alleles
What are genetic causes of variation?
Mutation Meiosis (cross over/ independent assortment) Random fertilisation
What are environmental examples of variation?
Accent Siamese cat fur ( sensitive to temp.)
What are examples of both genetic and environmentally caused variations.?
Height Both nutrition and genetics
What is speciation?
The forming of a new species
What is allopatric speciation?
Speciation caused by geographic isolation
What is sympatric speciation?
Not geographically isolated but are reproductively isolated Eg) morphological, seasonal, behavioural, hybrid sterility
How does speciation occur?
There is no gene flow between/ within the population(s) Variation exists in the population(s) due to mutation There are different selection pressures (allopatric) This results in directional selection of phenotypes There is differential reproductive success Over several generations there is a change in allele frequencies
What is genetic drift?
Change in allele frequencies over time, caused by random chance and is not reliant on environment Eg ) random fertilisation Affects small populations
Describe directional selection
Caused by a change to environment The extreme phenotype is selected for Eg) antibiotic resistance
Describe stabilising selection
The mean of the Pop. is selected for Eg) birth weight
Describe disruptive selection
Both phenotypic extremes are selected for Contributes to sympatric speciation
What is abundance?
The number of individuals of a single species in and ecosystem
What is distribution?
Where an organism is found in an ecosystem/ habitat
What is intraspecific competition?
Competition within a species, individuals occupy the same niche so compete for food, mates and shelter etc)
What is the carrying capacity?
The maximum stable pop an ecosystem can support
Define limiting factor
The thing that limits pop. size
Define interspecific competition
Competition between different species Between species that have similar niches
Define niche.
The role an organism plays in an ecosystem
What may result of complete niche overlap
One would either die or adapt
What results from partial niche overlap?
Interspecific competition
What type of organisms are studied using transects or quadrats?
Slow moving or stationary organisms eg) plants
What type of sampling is a transect used for?
Systematic
Describe a line transect
Run tap between two points and record all species that touch the tape
Describe a belt transect
Use quadrats along the length of the transect
Describe an interrupted transect
Quadrats are used at fixed intervals along the transect
What is a quadrat
A square frame - can be divided into squares
What does mud can easily cover solid concrete stand for?
Migration, colonisation, establishment, competition, stabilisation, climax
Equation for population size (mark release recapture method)
(total caught 1st x total caught in second sample)/ total recaptured
