Inheritance Flashcards
Define gene.
A sequence of bases on a DNA molecules that codes for a protein which results in a different characteristic. Eg eye colour.
Define genotype.
The genetic constitution (makeup) of an organism.
It describes the alleles the organism has - eg BB, Bb or bb for eye colour.
Define phenotype.
The expression of genetic constitution and its interaction with the environment.
An organisms characteristics - e.g. brown eyes.
Define dominant.
An allele whose characteristic appears in the phenotype even when there’s only one copy.
They’re shown by a capital letter.
Define recessive.
An allele whose characteristic into appears in the phenotype of two copies are present.
They’re shown by a lower case letter.
Define codominant.
Alleles that are both expressed in the phenotype - neither one is recessive. Eg the alleles for haemoglobin.
Define locus.
The fixed position of a gene of a chromosome. Alleles of a gene are found at the same locus on each Chris one in a pair.
Define homozygote.
An organism that carries two copies of the same allele (eg BB or bb).
(Possessing the same alleles of genes at the same locus on homologous chromosomes).
Define heterozygote.
An organism that carries two different alleles eg Bb.
(Possessing different alleles of genes at the same locus on homologous chromosomes).
Define carrier.
A person carrying an allele which isn’t expressed in the phenotype but that can be passed on to the offspring.
What are genetic diagrams used for?
Genetic diagrams can be used to predict the genotype and phenotype of the offspring produced if two parents are crossed (bred).
What is monohybrid inheritance?
The inheritance of a characteristic which is controlled by a single gene.
What is dihybrid inheritance?
Two characters, determined by two different genes located on different chromosomes are inherited.
When codominance occurs, how can both alleles be expressed in the genotype.
Where instead of one allele being dominant and the other recessive, both alleles are equally dominant. This means that both alleles of a gene are expressed in the phenotype.
Define multiple alleles.
Where there are more than two alleles, of which only two may be present at the loci of an individual’s homologous chromosome.
