Download Figure 14.0 Painting of Mendel

Genetics
Chapter 8
Gregor Mendel: Father of Genetics

Genetics: study of
heredity

Heredity: passing
traits from parent to
offspring

Used peas to study
heredity
Why Peas?



1. Several Traits
2. Control mating
3. Small, grow easily, and matures
quickly
Alleles: Different versions of a gene
Ex: White and Purple Flowers
Mendel’s Experiment

Monohybrid Cross: One pair of contrasting
traits.


Ex: Mating a plant with purple flowers with white
flowers
True-breeding: All offspring would have
only one form of the trait

Ex: Purple-flowering plant only has purpleflowered offspring
Mendel’s Experiments
Vocabulary


Dominant: (A)
 Expressed in appearance when the individual has
one copy
Recessive: (a)
 Not noticeable in appearance when individual has
one copy
 Individual must have two copies of recessive
allele to express the trait

Homozygous: AA or aa

Heterozygous: Aa
More Vocabulary

Genotype: Genetic make up (ex: Pp)

Phenotype: Physical Appearance (ex: Purple
flowers)
Punnett Square-predicts outcome of
a cross 1 pair of contrasting traits
btwn 2 individuals
Ratios
Test Cross
Law of Segregation

Alleles for a trait
separate when gametes
are formed

50% chance that one
allele will go into a
gamete
Law of Independent Assortment
Alleles of
different genes
separate
independently
of each other
during meiosis

Dihybrid Cross: Cross that involve two traits