NAME:___________________________________
Introduction to Genetics Guided Notes
1. Basic Terms
Heredity:
Genetics:
Traits:
Gametes:
Fertilization:
2. The Work of GREGOR MENDEL
Who is Gregor Mendel?
An Austrian Monk who carried out the first important studies on _________________.
Mendel carried out experiments using the _________________. Mendel was the 1st person to predict
how traits are transferred from one generation to the next.
3. Mendel’s First Cross
His first cross was a ______________________ (“mono” meaning ________ thus monohybrid
means a cross of _____________________)
The first trait Mendel wanted to analyze was _______________. To do this he selected a
_________________________ and a ______________________. The plants Mendel selected were
known as _____________________, because they came from generations of plants that were the same
height (all tall or all short). Thus this cross is called a ___________________because it is done with two
purebred organisms.
Using his cross pollination, Mendel performed the following genetic cross:
Cross #1: Tall Pea Plant x Short Pea Plant
Results: _________ Pea Plants

Parent Generation (______)

First offspring (________________)
Next he took all of the tall pea plants from the first generation and crossed them.
Cross #2: Tall (____) x Tall (_____)

Results:_______________________________
First offspring (________________)

Second Offspring (_________________)
4. Mendel made some observations
Mendel determined that each organism must have 2 factors (one from ___________and one
from______________) that determine the organism’s traits. These factors are known as
_______________, and each are located on the ______________________________.
Each gene can exist in alternate forms, such as __________________________________. These
alternate or different forms are called _________________________________.
Organisms usually have 2 alleles for each trait. One allele from the _______________________
and the other allele from the _____________________________.
5. Mendel’s Principles
a. Principle of Segregation (Separation): explains how _______________________ for a trait but
only donates _____________________ to their offspring _____________________.
-Describes _______________________________
b. Principle of Independent Assortment:
c. Principle of Dominance: There are ____________________ alleles-one is______________ and
the other called _____________________. Geneticists represent alleles by letters.
Dominant Trait:
Dominant Alleles Represented by _____________________:
Recessive Trait:
Recessive Alleles Represented by _____________________:
6. Representing Traits as Letters
Genotypes:
Examples of Genotypes:
7. Types of Genotypes
a. Homozygous:
Examples:
b. Heterozygous:
Examples:
8. Determining how an organism looks
Phenotype:
Examples of phenotypes:
Practice
1.
2. Genotypes in which the dominant trait is expressed: AA
Dd
EE
ff
Jj
RR
3. Genotypes in which the recessive phenotype is expressed:
aa
Gg
Ff
KK
rr
4. Examine the following Punnett squares and circle those that are correct.
5. What do the letters on the outside of the Punnett square stand for? ___________________________
6. What do the letters on the inside of the Punnett square stand for? ____________________________
7. In guinea pigs, short hair, H, is dominant to long hair, h. Complete the following Punnett squares
according to the directions given. Then, fill in the blanks beside each Punnett square with the correct
numbers.
a.
One guinea pig is Hh and one is hh.
P1 = _________ x __________
b.
Both guinea pigs are heterozygous for short hair.
P1 = _________ x __________
8. In humans, being a tongue roller (R) is dominant over non-roller (r). A man who is a non-roller
marries a woman who is heterozygous for tongue rolling.
Father’s phenotype ________
Father’s genotype ________
Mother’s phenotype _________
Mother’s genotype _________
What is the probability of this couple having a child who is a tongue roller? ________