Heredity Flashcards
Describe Mendel’s pea plant experiment and the results that occurred.
The parental generation of Mendel’s pea plants were yellow (AA) and green (aa). The next generation received ‘A’ from yellow parent and ‘a’ from green parent (Aa - heterozygous).
In the next generation, half the gametes were ‘A’ and the other half ‘a’. Th probability of being homozygous = 0.5 x 0.5 = 1/4.
Therefore, 1/4 will be AA, 1/4 will be aa, and 1/2 will be Aa.
The 1/4 of plants that are AA and the 1/2 that are Aa will be yellow. The 1/4 that are aa will be green. So there is a 3:1 ratio.
What does independent segregation mean. Refer to Mendel’s pea plants.
It means that traits travel separately down the generations. So genes for plant colour and plant texture are on different chromosomes. During meiosis, selection is done independently for each chromosome.
How do serious Mendelian diseases maintain a high frequency?
- the phenotypic effect only occurs after reproduction even though it is dominant and lethal.
- If the recessive allele is in a heterozygous individual who then reproduces with another heterozygous individual, 2 recessive alleles will be passed down to the next generation.
What does the Hardy-Weinberg theory state?
Allele and genotype frequencies will remain stable form generation to generation when there are no evolutionary influences.
Describe the neutral theory of molecular evolution.
Most evolutionary changes happen at the molecular level. Most of the variation within and between species is due to random genetic drift of mutant alleles that are selectively neutral.
Define ‘heritability’.
The proportion of observed phenotypic variation that is accounted for by genetic variation.
What is the coefficient of relatedness? What is the coefficient of relatedness between parents and siblings?
The coefficient of relatedness describes how much variation is accounted for by genetics and environment. If it is closer to 1 then more phenotypic variation is described by genetics. it is 0.5 to your parents and siblings.
Describe Falconer’s estimate of heritability.
It estimates the relative contribution of genetics vs environment to variation in a trait. It is based on twin correlations.
