Download Bio 200- Lab Lecture 6

Bio 200- Lab Lecture 7
Mendelian Genetics
Mendel’s Principles
Diploid cells: two sets of homologous chromosomes.
Homologous chromosomes carry genes that govern the same traits.
Alleles: Dominant
Recessive
Homozygous vs. heterozygous
Genotype: genetic make-up
Phenotype: outward appearance.
Genetic traits are passed from one generation to the next through
reproduction.
Gamete production: result of meiosis in animals.
In plants, meiosis produces spores that become the plants that
produce the gametes.
Gametes are haploid cells: each contains only one member of each
pair of homologous chromosomes => one allele for each gene.
Principle of allele segregation:
The 2 alleles of a gene separate from each other during gamete
formation. Each ends up in a different gamete.
Predicting the outcome of a monohybrid cross:
First step:
Determining the gametes produced by the parents and their
proportions.
Monohybrid cross: only one trait is followed.
By convention:
P: Parental generation
F1: First generation of offspring
F2: Second generation of offspring
e.g. If R: tongue-rolling ability in humans.
R dominant over r.
If P: RR x rr
F1 :
Punnett square :
F2:
F2 Ratio in monohybrid crosses: 3:1
Chromosomal Basis of Independent Assortment:
Principle of independent assortment:
Unliked genes segregate independently during meiosis
If 2 genes A and B are found on different chromosomes, their
alleles can be found in any combination in the gametes.
Predicting the outcome of a dihybrid cross:
First step:
Determining the different types of gametes produced by each
parent and determining their proportions.
e.g. If A gene determines the arch of the feet
A: normal arch
a: flat feet
RrAa x RrAa  9:3:3:1 phenotypic ratio.