Topic 7 Content Flashcards
What is the genotype?
- The genotype is the genetic constitution of an organism.
What is the phenotype?
- The phenotype is the expression of the genetic constitution and its interaction with the environment.
What are alleles?
- Alleles are different forms of the same genes.
What is the dominant allele?
- The allele that if present is expressed in the phenotype, even if there is only 1 copy.
What is the recessive allele?
- The allele that appears in the phenotype if 2 copies are present.
What is the co-dominant allele?
- Alleles that are both sharing dominance.
What is monohybrid inheritance?
- The inheritance of one single characteristic controlled by a single gene.
What is dihybrid inheritance?
- The inheritance of two characteristics controlled by 2 genes.
- It involves 2 genes on 2 different characteristics.
What is sex-linkage?
- Gene found on sex chromosome is said to be ‘sex linked’.
What is the trend of sex linked genes?
- Most genes are found on the X chromosome, and with males being XY they only have one sex linked allele.
What are carriers?
- Females who have faulty recessive alleles but are heterozygous due to the presence of a dominant allele which cancels out the recessive allele.
What is epistasis?
- Where the expression of one gene is affected by the expression of one or more independently inherited genes.
What is an example of epistasis?
Petal colours being controlled by the presence of different enzymes.
Why is chi squared used?
- Used to compare the goodness of fit of observed phenotypic ratios with expected ratios.
- Used to see if there is dihybrid cross with linkages or no linkages.
How do you carry out chi squared?
- Find the chi squared value using the equation.
- Compare with the critical value (found by doing number of samples - 1)
- If chi squared is the same or exceeds the critical value then we reject the null hypothesis.
What is a population?
- A group of organisms of the same species occupying a particular space at a particular time that can breed with one another to produce fertile offspring.
What is a gene pool?
- the different variety of alleles in a population
What is allele frequency?
- The number of times alleles appear in the population.
What is the Hardy-Weinberg principle?
- The mathematical principle which states that the frequency of alleles in a population won’t change across generations.
What is P+Q=1 used for?
- Used for allele frequency.
What is P^2+2pq+Q^2=1 used for?
- Used for the frequency of individuals
What are the assumptions that Hardy Weinberg principle?
- No natural selection
- No gene flow ( no emigration of different genes)
- Large population
- No mutations (no new alleles in the population)
- Random mating (alleles aren’t selective)
What is disruptive selection?
- Where individuals with extreme characteristics are more likely to survive and reproduce.
What is selection pressures?
- The ability to avoid predators depending on your characteristic.
- Example: Squirrels with short tails are harder to be caught due to predators not being able to grasp onto their tails, and squirrels with large tails can stay more balanced on trees.
What is evolution?
- Evolution is the change in allele frequency in a population.
How do new species develop?
- From a common ancestor
How does speciation process?
1) Part of the population becomes separated and reproductively isolated.
2) Each population finds itself in a different environment, and so experience different selection pressures.
3) Different alleles have different advantages so natural selection occurs.
4) Allele frequencies change the gene pool.
5) The populations cannot interbreed to produce fertile offspring.
What is allopatric speciation?
- The physical reproductive isolation by a geographical barrier.
What is sympatric speciation?
- Other reasons for reproductive isolation such as mutations and behaviour.
What is genetic drift?
- The change in allele frequencies due to chance.
- Not every individual will have the same number of offspring.
- Greater impact on smaller populations due to individauls making up a greater proportion of the population.
What is primary succession?
- The change in an ecosystem over time
What are pioneer species?
- Species that are able to survive in extreme, hostile conditions.
Why are pioneer species important?
- They change the environment to make abiotic conditions less hostile.
How do pioneer species make abiotic conditions less hostile?
- They do this by eroding rocks, releasing minerals, adding more humus when they are killed and increasing the nitrogen oxide content.
What happens when new species arise in the community?
- They change the environment, making it less hostile for them and less suitable for the previous species.
What happens when succession occurs over a longer period of time?
- Different organisms that are better adapted to the improved conditions outcompete those already there.
- The arrival of new species increases the biodiversity.
What happens at the end of succession?
- The largest and most complex community will form called a climax community.
What happens during secondary succession?
- The climax community is cleared in some way (E.G Forest fire)
- Succession will have to restart but at a much greater rate as the community won’t start at an extremely hostile condition.
Why do we conserve?
- We conserve to prevent succession from continuing which will preserve the ecosystem in its current state.
- We do this because if another species arrived and dominated, existing species would be outcompeted and would die out, and we want to keep biodiversity high.
How do we conserve
- We conserve by grazing, where we remove the growing tips from plants such as tree samplings or shrubs, so that they don’t develop.
- We can also manage fires to wipe out all species which will force secondary succession to happen.
What is autosomal linkage?
Autosomal linkage is when genes that are close to one another on a chromosome are likely to be inherited together.
