Topic 7 Flashcards
What is genotype
Genotype: the genetic constitution of an individual (what genes they have)
What is phenotype
Phenotype: the expression of this genetic constitution and its interaction with the environment (what genes are expressed)
What are alleles
Genes can have different versions, called alleles
normally there are two alleles of a gene, but sometimes there can be more
Alleles can be either …
Dominant or recessive
Outline dominant alleles
Dominant alleles will always be expressed if they are present while it takes two copies of a recessive allele to allow it to be expressed
What is a condiment allele
When there are two alleles for a certain characteristic that is dominant
And if they are both present,they both will be expressed
Give an example of co dominant alleles
In humans, blood type is determined by genes: Io is the allele for blood type O, Ia is the allele for blood type A, and Ib is the allele for blood type B.
Blood type A and type B is dominant
Blood type O is recessive
What will the blood type be if both Alleles lb and la were present
Blood type AB
What is a monohybrid cross
Monohybrid cross: when the inheritance of only one characteristic is studied
What is a dihybrid cross
Dihybrid cross: when the inheritance of two characteristics is studied.
What is sex linkage
Sex linkage is when the two genes are on the same sex chromosome (X or Y) so they tend to be linked to the sex of the offspring
What is autosomal linkage
Autosomal linkage is when the two genes are on the same autosomal chromosome (any of the other chromosomes) so they tend to be inherited together
What is epistasis
Epistasis is when one gene affects the expression of the other
What is chi squared and what is it used for
The Chi-squared test is a statistical test used to see if the results of an experiment support the expected result.
The test tells you if you can reject the ‘null hypothesis’
What is a null hypothesis
which is that there is no significant difference between the expected data and observed data
If you reject the null hypothesis, it means that there is a significant difference between the expected and observed data.
Use this formula to work out the test statistic:
Find the right critical value from the chi-squared table:
Work out the degrees of freedom (number of classes - 1) and the probability level (p-value) you are using (usually 0.05)
Look in the corresponding row and column of the table to find the critical value
Compare the critical value and the test statistic
If the test statistic is > or = to the critical value, there is a significant difference between the observed and the expected results, so the null hypothesis can be rejected
If the test statistic is < the critical value, there is no significant difference and the null hypothesis cannot be rejected
What is a population
A population is a group of organisms of the same species occupying a particular space at all and that can potentially interbreed.
What is the gene pool
The gene pool is the complete range of alleles present in a population
What is allele frequency
Allele frequency is how often an allele occurs in a population
What is the hardy Weinberg principle used for
The Hardy–Weinberg principle provides a mathematical model, which predicts that allele frequencies will not change from generation to generation.
When is hardy Weinberg principle applied
principle only is used under certain conditions
population is large
no immigration or emigration
no mutations
no natural selection
random mating
What are the two equations used for hardy Weinberg principle
P+Q=1
P squared +2PQ + Q squared = 1
p = allele frequency of the dominant allele q =the allele frequency of the recessive allele
Why may Individuals within a population of a species show a wide range of variations in phenotype.
Due to genetic and environmental factors
When does genetic variation occur
Genetic variation stems from mutation, meiosis, and random fertilisation of gametes
When does environmental variation occur
Environmental variation is due to environmental factors such as climate, lifestyle, and food availability
Which cause evolution genetic variation or environmental
Genetic
What is evolution
Evolution is a change in allele frequency over time
What is natural selection
Natural selection is one method by which evolution occurs but it can also occur due to artificial selection
What is the steps for natural selection
1.There is variation amongst individuals in a population due to different individuals having different alleles
2.Selection pressures such as predation, competition, and disease, create a struggle for survival
3.The individuals that are best adapted to the selection pressures survive
4.They then pass their alleles to their offspring
5.This results in a greater proportion of the population having the more desirable alleles
6.Over time, the frequency of the desired allele increases, which is evolution.
What are the three types of selection
Selection can be stabilising, directional, or disruptive
When does speciation occur
When a new species forms from an existing species
Due to reproductive isolation
What are the two types of speciation
Allopatric and sympatric
Outline allopatric speciation
Population of species is trapped in an isolated area with different environmental factors e.gclimate
Population would adapt to the new climate and leading to a change in allele frequency
Then change to phenotype
Outline sympatric speciation
Where new species evolve from a single ancestral species when inhabiting the same geographic region
E.g chromosomal error during cell division or mutation
Leading to reproductive isolation
What is a community
All living things in a particular area
