Inheritance Flashcards
Define genotype.
The genetic constitution of an organism.
Define phenotype.
The expression of an organism’s genetic
constitution, combined with its interaction
with the environment
What is an allele?
Different forms of a particular gene,
found at the same locus (position) on a
chromosome. A single gene could have
many alleles.
How many alleles per gene do diploid
organisms carry?
2
What is meant by a dominant allele?
An allele whose characteristic will always
appear in the phenotype, whether one or
two are present.
What is meant by a recessive allele?
An allele whose characteristic 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 contribute
to the phenotype, either by showing a
blend of both characteristics, or the
characteristics appearing together.
What is meant by homozygous and
heterozygous?
Homozygous= both alleles are dominant,
or both alleles are recessive.
Heterozygous= one allele is dominant,
the other is recessive.
Define monohybrid inheritance.
Where one phenotypic characteristic is
controlled by a single gene.
Define dihybrid inheritance
Where two phenotypic characteristics
are determined by two different genes
present on two different chromosomes at
the same time.
draw punnet squares!! and maths link and genetic diagrams
What is meant by sex-linkage?
Where an allele is located on one of the
sex chromosomes, meaning its
expression depends on the sex of the
individual.
Why are males more likely to express a
recessive sex-linked allele?
Most sex-linked alleles are located on the X
chromosome. Therefore males only get one
copy of the allele, so will express this
characteristic even if it’s recessive. Since
females get two alleles, this is less likely.
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Which parent do males inherit sex-linked
characteristics from?
Their mother, since the Y chromosome can
only come from their father. Therefore if the
mother is heterozygous for sex-linked
alleles, she is a carrier and may pass on
the trait on.
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.
Define the two types of epistasis.
Recessive epistasis= where two
homozygous recessive alleles mask
expression of another allele.
Dominant epistasis= where one dominant
allele masks expression of multiple other
alleles.
What is meant by epistasis?
Where two non-linked genes interact, with
one gene either masking or suppressing
the other gene.
What is the chi-squared test?
A statistical test to find out whether the
difference between observed and expected
data is due to chance or a real effect.
What are the criteria for the chi-squared
test?
What are the criteria for the chi-squared test?
● Data placed in discrete categories
● Large sample size
● Only raw count data allowed i.e. not
percentages
● No data values equal zero
How is a chi-squared test performed?
The formula results in a number, which is then
compared to a critical value (for the corresponding
degrees of freedom). If the number is greater than or
equal to the critical value, we conclude there is a
significant difference between the observed and
expected data and that the results did not occur due to
chance.
How can we use a chi-squared test in
relation to the content of this topic?
We can compare expected phenotypic
ratios with observed ratios to test our
understanding of how different genes and
alleles are inherited.
