Chi Square

Molecular Genetics Lab

what are mendels three laws of heredity

1. law of dominance

2. law of segregation

3. law of independent assortment

what is law of dominance

dominant allele is expressed when at least one copy is present; a recessive trait appears only when two recessive alleles are inherited

what is law of segregation

two alleles for a trait separate during gamete formation so each gamete receives only one allele

what is law of independent assortment

alleles of different genes assort independently during gamete formation

what is an allele

alternate form of a gene

what is a genotype

allele combination an organisms possesses

what is a phenotype

observable trait expressed by an organism

what offspring genotype results from crossing PP x pp

all offspring are Pp

what phenotype results from PP x pp is P is dominant

100% dominant phenotype

what is the genotypic ratio of Pp x Pp

1 PP : 2 Pp : 1 pp

what is the phenotypic ratio of Pp x Pp

3 dominant : 1 recessive

what percentage of offspring are homozygous recessive in a Pp x Pp cross

25%

what percentage of offspring display the dominant phenotype in a Pp x Pp cross

75%

what does each gamete receive for a given gene

one allele

how doe you calculate the number of possible gametes

2ⁿ where n = number of heterozygous gene pairs

how many gametes can RrYy produce

4 gametes

what are the gametes produced by RrYy

RY, Ry, rY, ry

how many gametes can AaBbCCDd produce

8 gametes

what is a dihybrid cross

cross involving two different traits

what must be included in every gamete during a dihybrid cross

one allele for each gene

what is the purpose of a test cross

determine whether an individual with a dominant phenotype is homozygous or heterozygous

what genotype is used as the tester in a test cross

homozygous recessive

what chromosomes determine sex in many organisms

X and Y

where are many sex linked genes located

X chromosome

in sex linked inheritance, what important feature does the Y chromosome have

often doesn’t carry the allele being studied

what is the null hypothesis

hypothesis stating no significant difference between observed and expected results

what is the alternative hypothesis

hypothesis stating a significant difference exists between observed and expected results

what does a chi square goodness of fit test evaluate

how well observed data match expected data from a hypothesis

what are observed frequencies

actual counts collected in an experiment

what are expected frequencies

counts predicted if the null hypothesis is true

how are degrees of freedom calculated for a goodness of fit test

number of categories - 1

if there are 3 categories what is the degree freedom

2