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What is a chromosome?
A long length of DNA along which genes are spaced
What is a gene?
A length of DNA that codes for a protein
What is a chromatid?
Two chromosome replicants held together by a centromere
What is a homologous pair?
- A pair of chromosomes in a diploid cell containing the same genes but possibly different alleles
- Form bivalents during meiosis
What is an allele?
An alternate form of a gene created by mutation
What is the locus?
The position a gene occupies on a chromosome
What is the genotype?
The alleles present in a cell
What is the phenotype
The observable characteristics due to the expression of the alleles present in a cell
What is meant by the term: Heterozygous
Different alleles on the chromosome pair (Bb)
What is meant by the term: Homozygous
The same alleles on the chromosome pair (BB)
What is meant by the term: Dominant
- An allele that is expressed even if heterozygous
- Produces a functional protein
What is meant by the term: Recessive?
- An allele that is expressed only if dominant
- Caused by a mutation resulting in the allele producing a non-functional protein
What is meant by the term: Co-dominant?
- Both alleles are expressed in the phenotype if they are both present.
- They both produce functional, but different, proteins
What does a monohybrid cross involve?
A single gene with more than one allele
What does a sex linked cross involve?
- A gene situated on a sex chromosome
- This means that males will express the phenotype differently to females because males have only one X chromosome and therefore only need one recessive allele for it to be expressed