7.1 Genetics Flashcards
What is a genotype?
Genetic constitution of an organism including all alleles an organism has.
What is a phenotype?
Characteristics produced by the genotype and the environment.
What is a gene?
A length of DNA made up of a nucleotide sequence
What word is used to describe where a gene is located on DNA?
Locus /loci
What is an allele?
Form of a gene
How many alleles for each gene does a diploid organism with homologous chromosomes have?
2
What are co-dominant alleles?
When both alleles are expressed
What does homozygous mean?
Two copies of the same allele
What does heterozygous mean?
Different alleles for a gene
What does it mean when genes are autosomally linked?
They’re on the same chromosome
(When they are close together they are more likely to be transferred together during crossing over)
What are autosomes?
Chromosomes that aren’t the sex chromosomes
What happens if men (XY) receive a recessive allele that is linked to the X chromosome?
If a recessive gene is inherited on the X chromosome, it will always be expressed in the male phenotype as it is the only allele present.
How are sex chromosomes different to autosomes?
They’re non-homologous
How many alleles can be present in an organism for a gene?
Two
How many alleles can be present for a gene on a population level?
Multiple
What is epistasis?
Epistasis is when a gene at one locus inhibits the expression of a gene at another locus.
What is recessive epistasis?
When the epistatic allele is recessive so two copies of the allele are needed to mask the hypostatic allele
What is dominant epistasis?
When the epistatic allele is dominant so only one copy of the allele is needed to mask the hypostatic allele.
What is the ratio of offspring for recessive epistasis?
9:3:4
What is the ratio of offspring for dominant epistasis?
12:3:1
What does chi-squared test compare?
Observed and expected data
What is the null hypothesis for a chi-squared test?
There is no significant difference between observed and expected data, the difference is due to chance
How are degrees of freedom calculated?
Degrees of freedom = the number of categories − 1.
When do we accept the null hypothesis?
If the chi-squared value is lower than the critical value. The difference between observed and expected data is due to chance.
