Patterns Of Inheritance Flashcards
What genetic factors lead to variation?
Many versions of alleles, the ones inherited affect genotype
Sexual reproduction -meiosis (crossing over and independent assortment)
And random fusion of gametes in fertilisation
What are 3 examples of environmental contributions to variation?
Diet
Etiolation
Chlorosis
How can diet cause variation?
It affects the body mass of animals
What is chlorosis and what environmental factors cause it?
When a plant can’t produce normal amounts of chlorophyll making the leaves pale and yellow
Caused by
-lack of light - to conserve resources turn of chlorophyll production
- mineral difficiences- lack of iron or magnesium (cofactors for enzymes to make chlorophyll and mg found in chlorophyll molecule
- virus infections-intefere with metabolism of cells so can no longer support chlorophyll production
What is etiolatoion?
When plants don’t get enough light so they grown long and week stems which are yellow in colour
How do you perform a genetic cross?
State the phenotype if the parents State the genotype of the parents State the gametes of the parents Make a punnet square State the proportion of each genotype and corresponding phenotype
What is codominance?
When two alleles for the same gene are equally dominant
What is the expected phenotypic ratio in a dihybrid cross?
9:3:3:1
Why might the ratio of a dihybrid cross differ to what’s expected?
Genes are linked (same chromosome) so if no crossing over occurs they will always be inherited together
Fertilisation is a random process so in a small sample chance events can lead to skewed ratio
What does sexlinkage mean?
When a gene is found on the X chromosome but not on the y so men are more likely to have recessive sex linked conditions
When do you use the chi squared test?
To determine the significance of the difference between observed and expected results
How many genes are involved in phenotypes with discontinuous verses continuous variation?
Very few genes involved in discontinuous variation but many genes involved in continuous
What factors effect evolution?
Mutation
Gene flow
Genetic drift
Natural selection
What is a genetic bottle neck?
When an event happens which causes a large reduction in a population for atleast 1 generation so alleles in new gene pool will have much bigger effect due to small gene pool and low variation
What is the founder effect?
When small populations arise due to establishment of new colonies by a few isolated individuals
Small gene pool and low variation so rarer genes have much larger effect
What is genetic drift,
Or by chance the allele for one genotype gets passed on more often than others
Allele increases in frequency
What is stabilising selection?
When the environment isn’t changing much do individuals with characteristics towards the middle section are more likely to survive and reproduce so these alleles increase in frequency
What is directional selection?
When there’s a change in the environment so individuals with more extreme characteristics are more likely to survive and reproduce so these rarer alleles increase in frequency over time
When does genetic drift have a greater effect?
When there’s a genetic bottle neck
The founder effect
What does the hardy Weinberg principle do?
Predicts that the frequencies of alleles in a population won’t change from one generation to the next
Used to estimate the frequency of particular alleles and geno types in a population
What has to be true when using the Harvey Weinberg principle?
Large populations
No immigration emigration mutations or natural selection
Random mating
What is allopathic speciation?
Speciation by geographical mechanisms
What is sympatric speciation?
Speciation by reproductive mechanisms
Give three examples of sympatric speciation
Seasonal changes- different mating seasons
Mechanical differences- different genitalia
Behavioural- courtship rituals that don’t attract
What is artificial selection?
Breeding individuals with desirable traits
What are the problems with artificial selection?
It reduces the gene pool
So less likely for population to survive a change in environment as can’t adapt quickly enough
Could’ve accidentally lost useful alleles
Important to preserve original wild type organism
How would you use selective breeding in wheat to increase yield?
Cross breed high yielding wheat individuals
Measure the yield
Crossbreed selected high yielding offspring
Over generations
Prevent unwanted pollination
What term describes the random changes in allele frequency in a small population?
Genetic drift
what do you use as degrees of freedom in a chi squared test?
the number of phenotypes/classes minus 1
