Biology Partnership
(A Teacher Quality Grant)
Genetics I
History, terms, Punnett squares, &
simple inheritance
Nancy Dow
Jill Hansen
Tammy Stundon
January 26, 2013
Gulf Coast State College
Panhandle Area Educational Consortium
5230 West Highway 98
753 West Boulevard
Panama City, Florida 32401
Chipley, Florida 32428
850-769-1551
877-873-7232
www.gulfcoast.edu
Pre-test
Q and A board
What is genetics?
How come some siblings look a lot
alike but others don’t?
Why am I the only person in my
family to have blue eyes?
Florida Next Generation
Sunshine State Standards
BENCHMARK
• SC.912.L.16.1* Use Mendel's laws of segregation and independent
assortment to analyze patterns of inheritance. (HIGH)
• SC.912.L.16.2* Discuss observed inheritance patterns caused by
various modes of inheritance, including dominant & recessive
which are simple inheritance & codominant, sex-linked, polygenic,
and multiple alleles (complex inheritance). (HIGH)
The February session will go into the complex inheritance.
Florida Next Generation
Sunshine State Standards
Benchmark Clarifications
• Students will use Mendel’s laws of segregation and independent
assortment to analyze patterns of inheritance.
• Students will identify, analyze, and/or predict inheritance patterns
caused by various modes of inheritance.
Content Limits
• Items referring to general dominant and recessive traits may
address but will not assess the P and F1 generations.
• Items addressing dihybrid crosses (THIS SESSION) or patterns that
include codominance, incomplete dominance, multiple alleles, sexlinkage, or polygenic inheritance may assess the P and F1
generations (NEXT SESSION).
Florida Next Generation
Sunshine State Standards
Stimulus Attributes
•Inheritance outcomes may be expressed in percent, ratios, or
fractions.
•Scenarios may refer to codominance or incomplete
dominance but not both codominance and incomplete
dominance.
•Punnett squares may be used to predict outcomes of a cross.
Response Attribute
•Options may include codominance or incomplete dominance
but not both (NEXT SESSION)
Karyotype
-display of pairs of chromosomes
For Humans: 23 homologous
pairs; one chromosome form
mom and the other from dad
Autosomes are chromosomes 1-22
Chromosome pair 23 is your sex
chromosomes
Genetics
Vocabulary …Vocabulary… Vocabulary!!!!
Scenarios … Scenarios … Scenarios!!!!
• Gene - heredity code (topic)
• Allele – represents specific info of the gene (affect the
trait which may need several genes)
– Dominant Allele - upper case letter
– Recessive Allele - lower case letter
Genetics
Vocabulary …Vocabulary… Vocabulary!!!!
• Karyotype - the display of the pair of
chromosomes with highlighted alleles
• Phenotype - the physical appearance of the
alleles
• Genotype - genes of an individual Bb, BB,
or bb (B is the dominant allele, b is the
recessive allele)
• Trait - term for distinguishing phenotypic
features
INHERITANCE OF GENES
Maternal
chromosome pair
Paternal
chromosome pair
Gene
Maternal gamete: egg
Paternal gamete: sperm
Gametes unite during fertilization.
Humans have
23 pairs of
chromosomes
(46 individual
chromosomes)
and, thus, two
copies of each
gene.
Each human
gamete has just
one copy of each
chromosome and,
thus, one copy of
each gene.
Child inherits one set of
chromosomes from each
parent and, thus, two
copies of each gene.
ALLELES
What traits will be expressed?
For simple inheritance, you only need ONE Dominant allele
for the Dominant trait to be expressed.
Naturally, the only way for a Recessive trait to be expressed
is if the person has TWO
Recessive alleles.
Exceptions   
Human chromosome sheet
– to practice genotypes
---------
Traits included
Freckles
Ability to taste
Hairline
Disease
-------
Rh factor
Dimples
Earlobes .
f
t
H
d
f
t
H
D
Rh-
Rh-
M
e
M
e
Genetics
More Vocabulary
• Heterozygous - a dominant and a recessive
allele (Bb) (also called hybrid)
• Homozygous dominant - two dominant
alleles (BB) (also called Purebred)
• Homozygous recessive - two recessive
alleles (bb) (also called Purebred)
• Only one dominant allele need to be present
to be expressed
Punnett squares illustrate genetic crosses.
• The Punnett square is a grid system for predicting
all possible genotypes resulting from a cross.
– The axes represent
the possible gametes
of each parent.
– The boxes show the
possible genotypes
of the offspring.
• The Punnett square yields
the ratio of possible
genotypes and
phenotypes.
A monohybrid cross involves one trait.
• Monohybrid crosses examine the inheritance of
only one specific trait.
– homozygous dominant X homozygous recessive
• Genotype: all heterozygous (100%)
• Phenotype: all dominant (100%)
PUNNETT SQUARE:
A Punnett square is a useful tool for determining the possible
outcomesALBINISM
of a cross between two individuals.
Cross 1 (F 1)
MOTHER
albino
homozygous
aa
a
FATHER
pigmented
homozygous
AA
GAMETES
a
GAMETES
A
Aa
Aa
Aa
Aa
A
OFFSPRING Genotype
All heterozygous Aa
Phenotype
All pigmented
– If you cross a heterozygous with a heterozygous (Ff X Ff)
– What is the genotypic ratio of the offspring?
– 1:2:1 homozygous dominant: heterozygous:
homozygous recessive; (25%:50%:25%)
– What is the phenotypic ratio of the offspring?
– 3:1 dominant: recessive (75%:25%)
MOTHER
pigmented
heterozygous
Aa
Cross 2
(F2)
A
FATHER
pigmented
heterozygous
Aa
GAMETES
a
Your
genotype
and
phenotype
results are
presented
separately
GAMETES
A
AA
Aa
Aa
aa
a
OFFSPRING
Genotype
Phenotype
1/4 homozygous dominant AA
2/4 heterozygous Aa
1/4 homozygous recessive aa
3/4 pigmented
1/4 albino
3:1
RATIO
• If you cross a heterozygous with homozygous recessive
(Ff X ff)
• What is the genotypic ratio?
• 1:1 heterozygous: homozygous recessive
• What is the phenotypic ratio?
• 1:1 dominant: recessive
• A testcross is a cross between an organism
with an unknown genotype and an organism
with the recessive phenotype
Why use the
recessive
phenotype to
test an
unknown?
Heredity patterns can be calculated with probability.
• Probability is the likelihood that something will happen.
• Probability predicts an average number of occurrences, not an
exact number of occurrences.
number of ways a specific event can occur
• Probability =
number of total possible outcomes
• Probability applies to
random events such as
meiosis and fertilization.
GENETICS AND PROBABILITY
IF…
The mother is albino, and
the father is heterozygous
aa
Aa
100%
a
50%
a
1.0
A
×
THEN…
There is a 100% chance that
the mother’s egg will carry
the recessive a allele and a
50% chance that a sperm will
carry the recessive a allele
a
0.5
Multiply the two components
together
to determine the overall probability.
AND…
= 0.5 or 50%
chance the
offspring will
be albino.
aa
A Dihybrid cross involves two traits.
• Mendel’s dihybrid crosses with heterozygous
plants yielded a 9:3:3:1 phenotypic ratio.
• Mendel’s dihybrid crosses
led to his second law,
the law of independent
assortment.
• The law of independent
assortment states that
allele pairs separate
independently of each
other during meiosis.
Dihybrid Cross:
a cross that shows the possible offspring for
two traits
Fur Color:
B: Black
b: White
Coat Texture:
R: Rough
r: Smooth
In this example, we will cross a
heterozygous individual with another
heterozygous individual. Their
genotypes will be:
BbRr x BbRr
Dihybrid Cross
BbRr x BbRr
First, you must find ALL possible gametes that
can be made from each parent.
Remember, each gamete must have one B and
one R.
You will combine your genotype and
phenotype results (heterozygous fur color)
Dihybrid Cross
BbRr x BbRr
Possible gametes:
BR
Br
bR
br
Next, arrange all possible gametes
for one parent along the top of your
Punnett Square, and all possible
gametes for the other parent down
the side of your Punnett Square…
Dihybrid Crosses:
a cross that shows the possible offspring for two traits
BbRr x BbRr
BR
Fur Color:
B: Black
b: White
BR
Coat Texture:
R: Rough
r: Smooth
Br
Then, find the
possible
genotypes of
the offspring
bR
br
Br
bR
br
Dihybrid Crosses:
a cross that shows the possible offspring for two traits
BR
Br
bR
br
BR
BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
bR
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
BbRr x BbRr
Fur Color:
B: Black
b: White
Coat Texture:
R: Rough
r: Smooth
How many of the offspring
would have a black, rough
coat?
BR
Br
bR
br
BR BBRR
BBRr
BbRR
BbRr
BBRr
BBrr
BbRr
Bbrr
How many of the offspring
would have a white, rough bR
coat?
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
How many of the offspring
would have a black,
Br
smooth coat?
How many of the offspring
would have a white,
smooth coat?
Fur Color:
Coat Texture:
B: Black
R: Rough
b: White
r: Smooth
How many of the offspring
would have black, rough
coat?
BR
Br
bR
br
BR BBRR
BBRr
BbRR
BbRr
BBRr
BBrr
BbRr
Bbrr
BbRR
BbRr
bbRR
bbRr
BbRr
Bbrr
bbRr
bbrr
How many of the offspring
would have a black, smooth
Br
coat?
How many of the offspring
would have a white, rough bR
coat?
How many of the offspring br
would have a white, smooth
coat?
Phenotypic Ratio
9:3:3:1
Fur Color:
Coat Texture:
B: Black
R: Rough
b: White
r: Smooth
More practice…work within your quad
Selected Traits in Cats – Study this table then determine the crosses below
Trait
Dominant Allele
Recessive Allele
Coat Length
Short Hair (H)
Long Hair (h)
Tabby Stripes
Tabby (T)
Stripeless (t)
Colorpt (markings on the nose, Normal (N)
ear, paws, and/or tail)
Color point (n)
(no colorpt)
Show the results of the following crosses; give the info for the amount of
genotypes/phenotypes
1. Heterozygous short hair and Heterozygous short hair
2. Heterozygous tabby and stripeless
3. Colorpoint and homozygous normal
4. Homozygous short homozygous colorpoint and Homozygous long
homozygous normal
Heredity – biological means of
obtaining your genes
Theory of Blending Inheritance – people up
through the 1800s believed that people are a
blending mixture of the mom and dad
- support – facial features appear
- But you are not an average of your parents
– not an average of their height, hair color,
eye color, etc.
MENDEL’S RESEARCH APPROACH
Gregor Mendel
(1822–1884)
Three features of Mendel’s
methodical research were
critical to its success.
THE ‘FATHER OF GENETICS’. 1800s A monk in modern day Czech
republic. He was the first to apply math to inheritance, however, he did
not know about DNA. His work is the mechanism that supports
Darwin’s Natural Selection Theory.
Why was Mendel so successful?
1. Preliminary investigations were carried out to obtain
familiarity with the experimental organism.
2. All experiments were carefully planned.
3. Meticulous care was taken in carrying out all techniques.
4. Accurate records were kept of all the results.
5. Sufficient data were obtained to have statistical significance.
As Mendel stated, "The value of utility of any experiment are
determined by the fitness of the material to the purpose for
which it is used."
DOMINANT AND RECESSIVE TRAITS
Mendel
crossed
truebreeding
1 purpleflower
D
plants with
trueTrue-breeding
breeding
purple-flower
whiteplant
flower
Studied
pea plants and their
plants.
r
True-breeding
white-flower
plant
reproduction
•Forced cross pollination
•Isolated certain traits (color, height)
Why did he need to
“force” cross
pollination?
How to plants do this
naturally?
What is a vector?
DOMINANT AND RECESSIVE TRAITS
1
‘P’ OR
PARENTAL
GENERATION
Mendel crossed
true-breeding
purple-flower
plants with truebreeding whiteflower plants.
True-breeding
purple-flower plant
F 1 OR
FILIAL
GENERATION
The purple-colored
flower is the
dominant trait,
while the whitecolored flower is a
recessive trait.
2
Then, Mendel
crossed two of
the purple-flower
offspring.
True-breeding
white-flower plant
All offspring have purple flowers.
DOMINANT AND RECESSIVE TRAITS
The purple-colored
flower is the dominant
trait, while the whitecolored flower is a
recessive trait.
All offspring have purple flowers.
Then, Mendel
2 crossed two of
the purpleflower
offspring.
Most offspring have purple flowers,
but some have white flowers.
F2
GENERATION

The recessive trait for the white-colored
flower must have been lurking in the previous
generation, even though it is not visible.
MENDEL’S 2 LAWS:
1ST LAW : LAW OF SEGREGATION
According to Mendel’s law of segregation, only
one of the two alleles for a gene is put into a
gamete. At fertilization, offspring receive from
each parent one allele for each gene.
Heterozygous
pea plant
Two different
alleles
(white, purple)
for the same
gene
(flower color)
MEIOSIS Each gamete gets one copy of each gene.
Heterozygous
pea plant
1.
MENDEL’S LAW OF SEGREGATION
FERTILIZATION Each fertilized egg gets two copies of each gene.
Homozygous Heterozygous
recessive
Heterozygous Homozygous
dominant
A PUNNETT SQUARE IS A TOOL USED TO SHOW THE PROBABILITY
OF THE OFFSPRING FROM FERTILIZATION
MENDEL’S LAW OF INDEPENDENT ASSORTMENT
Mendel’s law of independent assortment states that one trait does not
influence the inheritance of another trait.
MOTHER
albino
homozygous aa
dimpled chin
homozygous DD
Cross 1
a
FATHER
pigmented
homozygous AA
non-dimpled chin
homozygous dd
D
GAMETES
a
D
A
d
Aa
Dd
Aa
Dd
Aa
Dd
Aa
Dd
A
d
OFFSPRING
Genotype
All heterozygous Aa
All heterozygous Dd

Phenotype
All pigmented
All dimpled chin
In this example, having a dimpled chin does
not affect which alleles are inherited for skin
pigmentation.
MENDEL’S LAW OF INDEPENDENT ASSORTMENT
Mendel’s law of independent assortment states that one trait does not
influence the inheritance of another trait.
MOTHER
pigmented
heterozygous Aa
dimpled chin
heterozygous Dd
Cross 2
A
FATHER
pigmented
heterozygous Aa
dimpled chin
heterozygous Dd
D
GAMETES
a
D
A
D
AA
DD
Aa
Dd
Aa
Dd
aa
dd
aA
d
OFFSPRING
Genotype
1/4 homozygous dominant AA
1/4 homozygous dominant DD
2/4 heterozygous Aa
2/4 heterozygous Dd
1/4 homozygous recessive aa
1/4 homozygous recessive dd
Phenotype
3/4 pigmented
3/4 dimpled chin
1/4 albino
1/4 non-dimpled chin
Investigating Genetics
Corn Lab
http://www.genome.gov/
Tons of activities… from the Human Genome Project.
http://learn.genetics.utah.edu/content/begin/tour/
Interactive activities!
http://www.sciencesupport.net/geneticstutorial.html
http://biology.clc.uc.edu/courses/bio105/geneprob.htm
- A case problem
Follow up
•Q & A
•Post Test