17.1 Flashcards
Genotype
Genetic makeup of an organism
Alleles it contains
Phenotype
Observable or biochemical characteristic expressed in organism
Interaction between genotype and environment
Gene
length of DNA that is sequence of nucleotide bases that code for particular polypeptide
Locus
position of gene on DNA
Reasons ratio isn’t expected ratio
-fertilisation of gametes is random
-sex-linkage
-co-dominance
-samples taken from small populations
Law of independent assortment
Chromosomes arrange themselves randomly on the equator during meiosis - each fertilisation combination is pure chance
Codominance
Both alleles are expressed in phenotype
Meiosis producing genetic variation
-crossing over between chromatids creates different combination of alleles
- independent assortment
Epistasis
When alleles mask or supress expression of genes at different locus
Sex linkage
Characteristics only coded for by genes found on sex chromosomes
X-linked disorders more common in men
- X chromosome is much longer than Y so has more genes that don’t have homologous conterpart
-Males only have one copy of X chromosome so are more likely to have recessive phenotype
Autosomal linkage
When genes are close together on the same autosome
Autosomal linkage unexpected ratio
-more likely to be inherited together in gametes and offspring
-stay together during independent segregation in meiosis 1
-only 2 outcomes(reduced variation)
Recombinant genes
Only formed by crossing over in meiosis 1
Have a lower frequency
Parental genes
Autosomaly linked genes
Have a higher frequency
Chi squared conditions
1- sample size must be large
2- data must be discrete categories
3- only raw counts not %
4- compare experimental results with theoretical ones
Chi squared fomula
Chi squared = sum of
(observed numbers - expected number)^2 / expected numbers
Significant results
If chi squared is less than critical value
Reject null hypothesis
Null hypothesis
There is no significant statistical difference between the observed number and expected number and it is due to chance
Non-significant results
If chi is greater or equal to critical value
Accept null hypothesis
