Intro to Genetics!!!
We have Arrived!
 Genetics-
study of heredity
 Punnett Squares
 Human Genetics
 Pedigree
 Blood Typing
 Forensics
 Gregor
Mendel- Austrian Monk, 1850’s
 Studied pea plants
 Father of Genetics
 Lived in a monastery and studied to be a
priest
The type of experiment that Mendel carried out, investigating just a single
characteristic, is called a monohybrid cross.
There are two alleles controlling pea shape. This means there are three
possible genotypes that the F2 generation of plants could inherit, leading to
two possible phenotypes.
Genotype
Phenotype
homozygous dominant
SS
smooth
homozygous recessive
ww
wrinkly
heterozygous
Sw
smooth
The likelihood of a trait being produced during a monohybrid cross can be
mapped out using a Punnett Square.

Heredity- passing of genes from parent to
offspring.

Traits- characteristics that can be passed from
parent to offspring.

Examples
 Tongue rolling
 Widows peak
 Earlobes
 Hitchhikers Thumb
 Bent Little Finger
 Dimples

 Genes-
part of the chromosome that
contains the hereditary information.
 Sexual
Reproduction- two parents give
genetic material to produce offspring that is
genetically different from the parents.
 Advantages
of Sexual Reproduction
 Genetic variation/diversity
 More likely to survive environmental change
 Genes
Affecting Traits
 Phenotype- traits that are shown.
 Genotype- genetic composition for a trait.
 Dominant-
Gene that is expressed when
present. Blocks out a recessive gene.
Represented by capital letters.
 Recessive-
Gene that is not expressed when
in the presence of a dominant gene.
Represented by lower case letters.
 Homozygous-
identical pair of genes for a
trait.
 Heterozygous- mixed pair of genes for a
trait.



Homozygous Dominant- RR
Homozygous Recessive- rr
Heterozygous- Rr
 *LETTERS
BE USED
DO NOT MATTER. ANY LETTER CAN
 Punnett
Square- predicts the probability
that certain traits will be inherited by
offspring.
 Punnett
Square Ratios
Genotypic Ratio
Phenotypic Ratio
 ______%

Homozygous
Dominant
______%
Heterozygous
______%

 ______%

 ______%

Homozygous
Recessive
 Polygenic
Traits- traits affected by more
than one gene which leads to mixtures.
 Example-
Height
Hair Color, Eye Color, Skin Color,
Special Genes
Multiple Alleles- more than one form of a gene for a trait.
Ex. Blood types.
Practice Problems
Blood Type
A
B
AB
O
Genotypes
IAIA or IAi
IBIB or IBi
IAIB- Universal Receptor
ii- Universal Donor
Sex-Linked Traits- traits caused by genes that are located on the
sex chromosomes.
Ex. Color Blindness, Pattern Baldness, Hemophilia
Why Males are affected more than females
X chromosome is larger than Y chromosome so it holds more genes.
Both X’s must have gene to be expressed in females whereas only
one X in a male must have gene to be expressed.
Polygenic Traits- traits affected by more than one gene which
leads to mixtures.
Example- Hair Color, Eye Color, Skin Color, Height