KA2.4 - Variation and Inheritance Flashcards
Describe discrete variation?
Discrete variation is seen in characteristics where measurements fall into distinct groups.
E.g. eye colour can be seperated into distinct groups.
Describe continuous variation?
Continuous variation is seen in characteristics where there is a range of values between a minimum and a maximum.
E.g. height has a minimum and maximum value with a huge range of heights in between.
Discrete variation is caused by … gene and is called … gene inheritance.
one … single.
Discrete variation is caused by one gene and is called single gene inheritance. This is why there are distinct groups as one gene can cause much variety.
Characteristics that show continuous variation are controlled by … genes, which is called … inheritance
multiple … polygenic.
Characteristics that show continuous variation are controlled by multiple genes, which is called polygenic inheritance.
What does the term allele mean?
Different forms of a gene.
E.g. there is a gene for hair colour and several forms of this gene which makes the different hair colours.
A … is what the characteristic actually looks like, e.g. brown hair.
Phenotype
State the definition of a genotype?
The alleles that are present.
e.g. Bb or BB
What type of allele is always seen in the phenotype if it is present?
A dominant allele.
These are represented with a capital letter.
An allele which is only seen in the phenotype if there are no dominant alleles present is called …
Recessive.
These are represented with lower case letters.
Describe the term homozygous?
Only one type of allele is present in the genotype, e.g. BB or bb
A genotype is … if there are both dominant and recessive alleles present.
Heterozygous
Why does the predicted number of offspring that have a certain genotype and phenotype not always match the actual numbers seen?
Fertilisation is a random process.
The allele that the parent passes down to their offspring is random so it will not always match the prediction.
