Genetics 3 - Mendelian Genetics Companion Questions

Learning Objectives

Recognize common crosses
P-gen / F1
hybrid x hybrid(Aa x Aa)
- 1:2:1 Genotypic 3:1 phenotypic
hybrid test (Aa x aa)
dihybrid x dihybrid
- 9:3:3:1
dihybrid x test
- 1:1:1:1
Understand how to write / utilize the following allele variance
- incomplete dominance
- multi-allelic (know blood typing alleles)
- codominance
- sex-linked
know what polygenic means
understand what X-inactivation means and what a mosaic is
Understand that epistasis is the masking of a gene (A) by the homozygous recessive genotype of another gene (bb)
Understand that non-disjunction is an error (and therefore unpredictable) in meiosis, leading to too many or too few copies of a chromosome
- know that Down syndrome is an example of a trisomy (3 copies)
Be able to utilize a pedigree to determine unknown genotypes
Be able to use a punnett square to predict outcome probabilities for an individual child (using any allele variance)
Be able to accommodate for conditional probabilities.
- child is a girl / boy (in sex-linked crosses)
- child is know to be unaffected (AA/Aa - eliminate aa)
- Parent is unknown
Be able to use the rules of probability (AND/multiplication & OR/addition rules) to:
- to determine the possible gamete combinations
- determine the probability of multiple children

Terms

Gene/ Trait
allele
Homozygous = Purebred (P-gen)
Heterozygous = hybrid / dihybrid (carrier if recessive trait)
Genotype
Phenotype

1

2

3

4 - please note, there is a typo around the 5:30 mark. In the table of genotypes, it incorrectly has X^HX^h for female with hemophilia. It should say X^hX^h.