3 Main Questions:
- What is true breeding?
Refering to plants that produce offspring of the same variety when they self-pollinate.
- What is trait?
Any detectable variant in genetic character.
- What is hybridization?
In genetics, the mating, or crossing, of two true-breeding varietites.
5 Main Facts:
- An organism that has a pair of identical alleles for a character is said to be homozygous.
- An organism that has two different alleles for a gene is said to be heterozygous.
- Because of the different effects of dominant and recessive alleles, an organisms's trait do not always reveal its genetic composition.
-Alleles can show different degrees of dominance and recessiveness in relation to each other.
- We can not predict with certainty the exact numbers of progeny of different genotypes resulting from a genetic cross.
Diagram:
Group F2 offspring from a cross for flower color according to phenotype results in the typical 3:1 phenotypic ratio. In terms of genotype, however there are actually two categories of purple flowered plants, PP(homozygous) and Pp(heterozygous), giving a 1:2:1 genotypic ratio.
Summary:
The explaination of heredity most widely in favor during the 1800s was the "blending" hypothesis, the idea that genetic material contributed by the two parents mixes in a manner analogous to the way blue and yellow blend to make green.
Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned experiments. The results of Mendel's dihybrid experiments are the basis for what we now call the law of independent assortment, which states that each pair of alleles segregates independently of each other pair of alleles during gamete formation.
Video:
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