Topic 8.2 Transfer of genetic information Flashcards
Define genotype
The genetic constitution of an organism
Define phenotype
The expression of an organism’s genetic constition with its interaction with the enviroment
What is an allele?
Different froms of a particular gene, found at the same locus (position) on a chromosome. A single gene could have many alleles.
What is meant by a dominant allele?
An allele whose charecterisitic will always appear in the phenotype, whether one or two are present.
What is meant by a recessive allele?
An allele whose charecterisitc only appears in the phenotype if no dominant allele is present, meaning two must be present.
What is meant by codominant alleles?
Two dominant alleles that both contrubute to the phenotype, either by showing a blend of both charecteristics, or the charecteristics appering together
What is meant by homozygous?
Both alleles are dominant, or both alleles are recessive.
What is meant by heterozygous?
One allele is dominant, the other is recessive.
What is Mendal’s first law, segregation?
States that an individual can pass only one allele for a characteristic into a gamete. In a heterozygote there will be an equal probability of this being either of their two alleles.
What is meant by multiple alleles?
A gene with more than two alleles
How are non-interacting, unlinked genes inheritited?
Can be monohydrid of dihybrid.
- Monohybrid = a phenotypic charecterisitic is contolled by a single gene
- Dihybrid = two phenotypic charecterisitics are controlled by two different genes present on two different chromosomes
What is meant by autosomal linkage?
Where two or more genes are located on the same (non-sex) chromosome. In this case, only one homologous pair is needed for all four alleles to be present. For genes that aren’t linked, two homologous pairs are needed.
What is Mendal’s second law
States that the inheritance of one charecterisitic will have no effect on the inheritance of another. However it has become clear that this only applies when genes are not linked on the same chromosome
Give an example of autosomal linkage
Drosophila (fruit flies); colour and wing length are autosomally linked, meaning they are inherited in pairs
Explain why autosomally linked genes are inherited in pairs, referring to mitosis.
Genes on the same chromosome, particularly those closest together, are unlikely to undergo recombination during meiosis. Therefore they are inherited as if they were the same gene.
