Genetics Flashcards
Define gene
Seq. of bases on DNA that codes for protein
Define allele
Diff. version of a gene
Define genotype
Genetic makeup of an organism
Define phenotype
Expression of genotype + it’s interactions w/ the env
Define dominant
Allele whose characteristic appears in phenotype even when there’s only 1 copy
Define recessive
Allele whose characteristics appear if 2 copies are present
Define codominant
Alleles both expressed in the phenotype
Define locus
Fixed position of a gene on c’some
Define homozygote
Organism that carries same allele
Define heterozygote
Organism that carries 2 diff alleles
Define carrier
Person carrying allele which is not expressed in phenotype but can be passed onto offspring
Humans are diploid organisms. What does this term mean?
2 alleles for each gene
What is the phenotypic ratio in a monohybrid btw homo dom + homo rec? (RR x rr)
3:1
Dominant : Recessive
What is the phenotypic ratio in a dihybrid btw hetro? (RrYy x RrYy)
9 : 3 : 3 : 1
Dom : Hetro : Hetro : Rec
When are characteristics described as sex-linked?
Allele that codes for characteristic is located on sex c’some
What are the sex c’somes in females?
XX
What are the sex c’somes in males?
XY
Outline a diff. btw Y c’somes and X c’somes
Y is smaller so carriers fewer genes
Why are males more likely to show recessive phenotype for sex-linked genes?
Males only have one X c’some, often have 1 allele so express characteristic even if recessive
Define autosome
C’somes that aren’t sex c’somes
Why are genes on the same autosome said to be linked?
Same autosome stay together during independent segregation + passed onto offspring
When are autosomes not linked?
When crossing over occurs
When are autosomal genes said to be more closely linked?
Closer together two genes are on autosome bc crossing over is less likely to split them up
Define epistatis
Allele of one gene masks the expression of the alleles on the other genes
What is the chi-squared test used for?
Test to compare the goodness of fit of observed + expected results
Chi-squared value is larger than or equal to critical value
- Significant diff.
- Less than 5% probability diff. due to chance
- Reject null
Chi-squared value is smaller than or equal to critical value
- No significant diff.
- More than 5% probability diff. due to chance
- Accept null
How do you work out the chi-squared value?
(O-E)2 / E
- O = observed
- E = expected
After working out the chi-squared value, what do you do?
- Degrees of freedom - no. classes minues 1
- Critical value at probability of 0.05
- Compare critical w/ chi-squared value
