Biology Genetics Notes
For Mendelian Inheritance you need; traits with only two alleles true-breeding plants (produce offspring of the same variety when they self-pollinate) hybridization- mating of two contrasting true-breeding (homozygous) varieties creating the P generation.
The hybrid offspring of the P generation= F1 (first fillial) generation.
F1 individuals self-pollinate= F2 generation.
Mendel's Four Laws 1st- variation is due to alternative versions of genes called alleles. The location of the gene is called locus. 2nd- for each character an organism inherits two alleles, one from each parent 3rd- if the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive allele) has no noticeable effect on appearance. 4th- (law of segregation) the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes.
How can we tell the genotype of an individual with the dominate phenotype? Do a test cross (breed the unknown with a homozygous recessive) if any offspring display the recessive phenotype, the mystery parent must be heterozygous.
The multiplication rule- probability that two or more independent events will occur together (look for the word AND)
The rule of addition- probability that any one or two or more exclusive events will occur (look for the word OR)
Exceptions to Mendelian Genetics when alleles are not completely dominant or recessive (example-codominance) when a gene has more than two alleles (AKA multi-allelic) when a gene produces multiple phenotypes
Complete dominance- regular
Incomplete dominance- the phenotype is between the phenotypes of the two parental varieties=blending (red+white=pink)
Codominance- two dominant alleles affect the phenotypes in separate, distinguishable ways=see both, like spots or patches
Dominant alleles are not necessarily more common in populations than recessive alleles. For example, one baby out of 400 in the US is born with extra fingers or toes (polydactylism)
Multiple alleles- more than two alleles