Unit 2 - Inheritance Flashcards
What is a phenotype and what is it determined by?
The particular version of a characteristic seen in an individual is described as their phenotype and is determined by the genes on the chromosomes they inherited from their parents.
What is variation?
Characteristics such as eye colour, height and body mass differ between individuals in a population. These differences are called variation.
What is discrete variation?
Characteristics controlled by a single gene (one copy inherited from each parent) tend to have phenotypes that fall into separate categories. They show discrete variation.
Give an example of discrete variation.
Left or right handed.
Ability to roll tongue.
Eye colour.
etc.
What is it called when characteristics are controlled by more than one gene?
Polygenic.
What is continuous variation?
Polygenic characteristics have phenotypes that can show a wide range of values, with each value following on from the value before. This is described as continuous variation.
Give an example of continuous variation.
Height.
Weight.
Hand span.
Etc.
What is an organisms characteristics controlled by?
The genes it inherits from its parents.
What are alleles?
Different versions of a gene.
What is it called if the two alleles of a particular gene are identical?
Homozygous.
What is a heterozygous characteristic?
If the two alleles of a particular gene are not the same.
What is a dominant allele?
An allele that always expresses itself whether it is partnered by a recessive allele or by another like itself.
What is a recessive allele?
Describes the variant of a gene for a particular characteristic which is masked or suppressed in the presence of the dominant variant. A recessive gene will remain dormant unless it is paired with another recessive gene.
What is a Punnett square?
A grid that shows the possible combinations of alleles that can result at fertilisation.
Give an example of a Punnett square.
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