Genetic Tests

What is dominance?

The relationship between a pair of two alleles (a gene can have more than 2 alleles)

How do you do a genetic test for dominance?

Cross allele #1 w/ allele #2

Alleles “Fight” in F1 generation, and the result on the phenotype shows dominance

Dominance is typically denoted by…

Capital letters (be careful about complete or codominance

How to test for a true breeding organism (hmz)

Do a progeny test

• look at progeny your organism is (A_)

• self pollinate your organism

  • If A_ self cross results in all AA, organism is true breeding (homozygote)

  • if A_ self cross is 3 A_:1 aa, then your organism is not true breeding (heterozygote)

A phenotypic progeny should be __ plants to be statistically satisfactory, how much accuracy does this provide?

16 plants (recommended to overcompensate this a little bit to account for loss)

95% accuracy

What is a test cross?

crossing a plant with a homozygous recessive “tester” parent

Why do a test cross?

• when plants cannot self pollinate (dioecious, self incompatible)

How many plants are needed for test cross confidence?

only 6

because of it’s low amount of plants needed for confidence, what is test crossing especially effective for?

Large, slow growing plants

How to test the # of genes that are influencing a given phenotype via the genetic mapping approach?

Make an F₂ cross, if it is 3:1 there is only one gene, if it is 9:7 or 13:3 it is multiple genes.

Compare each to a chi square test to see if it’s close enough

How to test for complementation?

Cross a plant with a recessive phenotype with another plant that has that recessive phenotype, if it results in plants with the dominant wild-type phenotype, they are different genes (complementation), if it results only in the mutant genotype, it is a result of the same gene.