What were the main theories of ineheritance
blending inheritance - offspring have traits that are intermediate to their parents
Inheritance of an acquired traits - favorable traits acquired by parents are passed on to offspring
Directed evolution - the use and disuse of body parts would impact their presence in the next generation.
why does the blending inheritance theory not work
because if blending inheritance was the mechanism, then variation would be reduced over time, this doesn’t reflect the constant presence of variation that is observed in populations.
Who was Gregor Mendel
- he tested the hypothesis of blending inheritance and particulate inheritance
- to do so he used true-breeding varieties of peas
what was different about mednel’s experiments
- used true breeding plants which had homozygous genotypes
- focused on one single and simple trait at a time
- counted the progeny which allowed him to use quantitative analysis
in mendel’s experiments what was the genotype of the parents?
homozygous
What does Po mean
parental generation
what does F1 mean
the first fillial generation (comes after the parental generation). he would self-fertilize this generation
Define the difference between dominant and recessive alleles
dominant alleles susually code for a functional protein whereas the recessive alleles don’t.
describe mednel’s principle of segregation
each organisms has two alleles. homozygous means that the two alleles are the same and therefore will only produce one type of gamete. Heterozygous means that the two alleles are different and which produce different gametes.
How to determine if you have a heterozygous organism
you perform a test cross. mating with an individual with a homozygous recessive genotype. if the original organism was heterozygous then you would see a 1-1 ratio of dominant and recessive phenotypes, whereas if the original organism was homozygous all phenotypes would be dominant.
what were mendel’s main ideas
- all adults carry two copies of factors (genes) that govern the inheritance of a character/trait
- dominant alleles mask recessive ones
- you get one allele from each parent according to his laws of segregation.
What is the product rule
when looking at the probability of two independent events occurring in succession, then you must multiply individual probabilities.
what is the sum rule
says that the probability of an outcome that can be achieves by two or more mutually exclusive events is the sum of their individual probabilities. Individual probabilities are added.
What is a monohybrid cross
a cross between two heterozygotes
what is incomplete dominance
the presence of an intermediate phenotype that kind of mixes the dominant and recessive ones. superscripts are used to label alleles.
what is codominance
when both alleles are expressed fully.
Are there always only up to 2 alleles per gene?
no you can have more as some genes are multi allelic/polymorphic. for example the alleles for the MHC gene
how does mendelian segregation preserve genetic variation?
- solves darwin’s conundrum of how genetic variation is passed down generations, this establishes a mechanism for inheritance.
How can mendilian traits be made more realistic?
mendel described discrete traist which is where you have one gene two alleles, each phenotype is consistent with a genotype. this is a bit different from the real world as we see multiple genes with multiple alleles and there is variation is phenotype. –> continous variation of traits.
Is it possible for two individuals to have the same phenotype but different genotypes?
yes this is possible as Rr will have the same effect as RR
Is it possible for two individuals to have the same genotype but different phenotypes
yes as dominant and recessive alleles just refer to the ability of that gene to make a protein, other factors that can influence phenotype from the same genotype is the regulation of that genotype. There is also variation that can be caused by environmental and nutritional factors.
