Homozygous — Science definition
Defined in 2 courses:
- Carrying two identical alleles, such as AA or aa; such a parent produces only one kind of gamete. (Life Science & Scientific Inquiry)
- Having the same allele at both copies of a diploid locus. (Life Science: Biology)
Where it is taught
- Inheritance, Probability & Punnett Squares — Genes, Cell Division & Heredity, Life Science & Scientific Inquiry, Grade 7
- Mendelian Genetics — DNA, Inheritance & Gene Expression, Life Science: Biology, Grade 10
Questions using homozygous
Problem 1
An organism that is homozygous for a trait has
- no alleles for that trait
- two identical alleles (for example BB or bb)
- two different alleles (Bb)
- only one allele in total
Answer and explanation
two identical alleles (for example BB or bb)
Homozygous means the two alleles match (BB or bb); heterozygous (Bb) means they differ.
Problem 2
A test cross with a homozygous recessive individual is used to determine
- whether a trait is inherited
- the genotype of an individual showing the dominant phenotype
- the number of chromosomes
- whether a mutation occurred
Answer and explanation
the genotype of an individual showing the dominant phenotype
Crossing with a homozygous recessive reveals the unknown genotype: any recessive offspring shows that the tested parent carried a recessive allele.