Mendelian Inheritance: Alleles

Overview

Recall questions on Alleles.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define the term allele.

   Model answer

   An allele is one of the alternative forms of a gene found at the same locus on homologous chromosomes.

2. 2

   What is meant by the locus of a gene?

   Model answer

   It is the fixed position that the gene occupies on a particular chromosome.

3. 3

   Distinguish between genotype and phenotype.

   Model answer

   The genotype is the alleles an organism carries, whereas the phenotype is the observable characteristics produced by those alleles and the environment.

4. 4

   What does it mean to be heterozygous at a locus?

   Model answer

   The organism carries two different alleles of that gene.

5. 5

   Explain how a recessive allele can be present in an organism without being expressed.

   Model answer

   In a heterozygote the dominant allele is expressed and masks the effect of the recessive allele.

6. 6

   State Mendel's first law.

   Model answer

   The two alleles of a gene separate during gamete formation, so each gamete receives only one of them.

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