Card Set Information
Biology Inheritance camturnbull
AQA BIOL4 Inheritance
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