7.1 Inheritance Flashcards
Define genotype
is 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
two
what is a dominant allele
an allele whose characteristic will always appear in the phenotype, whether one or two are present
what is a recessive allele
an allele whose characteristic only appears in the phenotype if no dominant allele is present, meaning two must be present
codominant allele
two dominant alleles that both contribute to the phenotype, either by showing a blend of both characteristics or the characteristics appearing together
homozygous
both alleles are dominant, or both alleles are recessive
Heterozygous
one allele is dominant, the other is recessive
Monohybrid inheritance
where one phenotypic characteristic is controlled by a single gene
Dihybrid inheritance
where two phenotypic characteristics are determined by two different chromosomes at the same time
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
Which parent do males inherit sex- linked characteristics from
Their mother, since the Y chromosome can only come from their father.
What is meant by autosomal linkage
When two or more genes are located on the same (non- sex) chromosome. In this case, only homologous pair is needed for all four alleles to be present. For genes that aren’t linked, two homologous pairs are needed
What is meant by epistasis
Where two non- linked genes interact, with one gene either masking or suppressing the other gene
Define the two types of epistasis
Recessive epistasis- where two homozygous recessive alleles mask expression of another allele
Dominat epistasis - where one dominant allele masks expression of multiple other alleles
What is a 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
data placed in discrete categories
Large sample size
Only raw count data allowed
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 degree of freedom)
If number greater than or equal to critical value, we conclude there is a sig difference between observed and expected data and that the results didn’t occur due to chance
gene
is a length of DNA, that is a sequence of nucleotide bases that normally code for a particular polypeptide
locus
position of gene on a particular DNA molecule
allele
Is the different forms of a gene
codominance
Is which both alleles are expressed in the phenotype
Multiple alleles
where there are more than two alleles, of which only two may present at the loci of an individual’s homologous chromosomes
females
XX
male
XY
Chi squared equation
X2 = sum of (O -E )^2 / E
degrees of freedom
n-1
characteristics are determined by
genes
In fruit flies, males have the sex chromosomes XY and the females have XX. In fruit flies, a gene for eye colour is carried on the X chromosome. The allele for red eyes, R, is dominant to the allele for white eyes, r.
(a) Male fruit flies are more likely than female fruit flies to have white eyes. Explain why.
males have one allele
Female need two recessive alleles
females are homozygous recessive
female could have dominated and recessive alleles
phenotype def
charactertics due to genetic alleles due to the environment
what is meant by codomiant allele
both alleles expressed in the phenotype
