Download Genetics Guided Notes

Guided Notes: Simple Genetics
Punnett Squares

In order to determine the ___________ a person might inherit, we use a simple diagram called
a ____________________________
o Give us _________________ of an offspring having particular traits
Pieces of the Punnett Square

Allele: A _____________ form of a ______________
o Humans inherit __________ allele from each parent that determines a ___________
o Ex. Curly/straight hair, tall/short, etc.

Dominant Allele: A ____________allele shows their effect even if there is only ______ copy
of the allele (think strong!)
o Dominant alleles are denoted by a capital letter (Ex. _________)

Recessive Allele: A ___________allele will only show up if no dominant alleles are in place.
(think weak!)
o Recessive alleles are denoted by a lower case letter (Ex. ________)

Dominant and recessive alleles pair together to determine a ___________! (Ex.
___________)

Homozygous: If both letters are ____________ (both dominant (capital) or both recessive
(lowercase)), the alleles are ____________________
o “Homo” means “_________”
o Ex. Let’s say “A” represents the allele for a widow’s peak, and “a” represents the allele
for a straight hairline


A person with “AA” would be called homozygous __________________

A person with “Aa” would be called homozygous __________________
Heterozygous: If both letters are ______________ (one dominant (capital) and one recessive
(lowercase)), the alleles are ______________________
o “Hetero” means “__________________”
o Ex. A person with “Aa” would be heterozygous

Would they have a widow’s peak or a straight hairline?

Genotype: The ________________, _______________ information of an organism
o Example: A person’s genotype is Aa (heterozygous); they can pass on either a
dominant allele or a recessive one

Phenotype: The _____________,_______________ appearance of an organism
o Example: A person has a widow’s peak
Dominant or Recessive?
Heterozygous or Homozygous
Phenotype or Genotype?
A _______________
AA ____________________
She’s homozygous recessive ________
b _______________
Bb ____________________
She has blue eyes _________________
B _______________
cc _____________________
Building a Punnett Square


Consider the following alleles for color of a pea plant:

AA (Yellow-homozygous dominant)

Aa (Yellow-heterozygous)

aa (Green-homozygous recessive)
Problem: Let’s say you had two pea plants, both heterozygous yellow (Aa), and you wanted to
know what color plants would be produced. How would you find out? ____________________
1. Setting up the square
a. What we know: ____________________
b. So, cross _________________ will be carried out in the
Punnett Square
2. Carrying out the square
a. Father’s letters cross to the __________
b. Mother’s letters cross ____________
c. Notice each combination has one allele from dad and one
from mom
3. Interpreting the final square
a. Once the square is finished, determine the _____________
and ____________ ratios of the possible offspring
i. Genotype:
ii. Phenotype:
Tt x tt
What is the probability of producing offspring that have
short whiskers from a cross of two long whiskered seals,
one homozygous dominant and one heterozygous?
Genotype:
Genotype:
Phenotype:
Phenotype:
A Few Notes on Genetics:

Some traits are controlled by _______________________ pair of genes, and so present a
wide range of phenotypes (ex. Skin, hair, eye color)

All traits depend on both _______________ and _____________ factors
o Heredity determines your traits, but the environment may play a role in how they act
Guided Notes: Genetic Diseases
Dominant or Recessive?

If a disease is ___________________, both parents have to pass on a mutated allele to the
offspring
o Those who are heterozygous (Aa) are ____________, meaning they have the mutated
allele and can pass it on, but are ____________ themselves

If a disease is ___________________, only one parent has to pass on the mutated allele for
offspring to have it
o Can a person with a dominant disease be a carrier?
Genetic Diseases
Disease
Cystic Fibrosis
Dominant or Recessive?
Characteristics

Causes __________ buildup in lungs
and digestive system

Those affected have _______________
and ____________________________

Common in those with _____________
ancestry

Life expectancy up to _____ years
thanks to ___________________
Sickle Cell Anemia

Affects a person’s _________________
cells

The “sickle” or bent shape causes the
cells to get stuck in ________________

Common in those with _____________
ancestry

Carriers associated with ____________
resistance
PKU

Stands for _______________________

Missing the ____________to break
down phenylalanine, an amino acid

Results in __________ deterioration

People affected must keep low
____________ diet + inject enzyme
Huntington’s

Affects the _____________ of the body
Disease

Affected will have _________________
decline

Often does not show signs until a
person reaches mid _________
A woman who is a carrier for
Cystic Fibrosis marries a man
who is also a carrier. What is the
probability that they will have a
child with Cystic Fibrosis?
A woman is concerned that she
may develop Huntington’s
Disease because her father has
it. What is the probability that
she has Huntington’s?