Mendelian Inheritance: Dominance, Segregation, and Independent Assortment

All flashcards

What is a gene?

An inherited unit carried on a chromosome that contributes to a characteristic.

How do genotype and phenotype differ?

Genotype is the alleles an organism carries; phenotype is its observable characteristic, often influenced by the environment.

What does dominance describe?

The relationship in which one allele determines a heterozygote’s phenotype while the other is not visibly expressed.

What is the law of segregation?

The two alleles for a gene separate during gamete formation, so each gamete receives one.

What is independent assortment?

The sorting of alleles for one gene does not influence the sorting of alleles for another gene when they assort independently.

Quiz questions

1. During which meiotic event do homologous chromosomes separate, providing the physical basis for allele segregation?Answer: The first division of meiosis
2. For a cross between two heterozygous plants, $Yy \times Yy$, what genotypic ratio is expected?Answer: $1\,YY:2\,Yy:1\,yy$
3. A plant with a dominant phenotype is crossed with a homozygous recessive plant. If the unknown plant is heterozygous, what phenotypic ratio is expected?Answer: A $1:1$ ratio of dominant to recessive phenotypes
4. Assuming independent assortment, what is the probability that an $RrYy$ plant produces a gamete carrying $Ry$?Answer: $\frac{1}{4}$
5. For a cross between two $RrYy$ plants, with complete dominance at both genes and independent assortment, what phenotypic ratio is expected?Answer: $9:3:3:1$