17 - Inherited change Flashcards
Define an allele.
One of a number of alternative forms of a gene.
Define a gene.
A section of DNA on a chromosome coding for one or more polypeptides.
Define a dominant allele.
An allele always expressed in the phenotype of an organism.
Define a recessive allele.
The effect of the allele is apparent in the phenotype of a diploid organism only in the presence of another identical allele.
Define heterozygous.
The condition where the alleles of a particular gene are different.
Define homozygous.
The condition where the alleles of a particular gene are identical.
Define phenotype.
Expression of the genetic constitution and its interaction with the environment.
Define genotype.
The genetic composition of an organism.
Define a chromosome.
A thread-like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next.
Define an autosome.
A chromosome which is not a sex chromosome.
What is a locus? (inheritance)
The position of a gene on a particular DNA molecule.
What is it called when two alleles are expressed in the phenotype?
Codominant
What is the F1 generation?
Name given to the first generation resulting from a homozygous dominant individual being crossed with a homozygous recessive individual.
What sex chromosomes does a male human have?
XY
Is the X or Y chromosome larger?
X
What is autosomal linkage?
When genes appear on the same, non-sex chromosome. (No independent assortment)
What is epistasis?
When the allele of one gene affects or masks the expression of another in the phenotype.
How is the degrees of freedom determined?
Number of classes - 1
Give four causes of genetic variation.
Crossing over
Independent segregation
Random fertilisation
Mutation
In genetic crosses, the observed phenotypic ratios obtained are not often the same as expected. Why (5 reasons)
Small sample size
Random fertilisation of gametes
Linked genes
Epistasis
Lethal genotypes
What is meant by codominant alleles?
Both alleles expressed in phenotype
Two genes are linked. Explain what this means.
On same chromosome
Which statistical test should the scientist use to determine whether his observed results were significantly different from the expected result? Why? (2)
Chi squared
Categorical data
