mendelian genetics Flashcards
What are the three postulates of inheritance Mendel proposed?
In a diploid individual, genes have two alleles, each on a chromosome of the homologous pair.
In the pair of alleles for a single characteristic in an individual, one allele is dominant and the other is recessive.
The two alleles of a single gene separate independently during gamete formation.
State the law of segregation
When an organism makes gametes, each gamete receives just one gene copy, which is selected randomly.
Explain how a test cross can be used to determine whether an organism with a dominant phenotype is homozygous or heterozygous
In a test cross, the organism with the dominant phenotype is crossed with an organism that is homozygous recessive.
If the organism with the dominant phenotype is homozygous, then all of the F1 offspring will get a dominant allele from that parent, be heterozygous, and show the dominant phenotype. If the organism with the dominant phenotype organism is instead a heterozygote, the F1 offspring will be half heterozygotes (dominant phenotype) and half recessive homozygotes (recessive phenotype).
The fact that we get a 1:1 ratio in this second case is another confirmation of Mendel’s law of segregation.
State the law of independent assortment
the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
