1. How were genetics involved?
(3 – 5 sentence answer)

2. Why do you look like you look? What made you the way you are?
Heredity
Why do you look like you look? What made you the way you are?
All of your genetic information is contained on your
CHROMOSOMES!!
GENES are on your chromosomes!!
DNA is found on your genes!!

3. Different organisms contain different numbers of chromosomes!!
Dogs - 78
Cats – 38
Human body cells
46 chromosomes
23 from mom
23 from dad
23 pair of chromosomes
Each pair has a number
from 1-23.
Chromosome 1 from dad/mom
have similar
genetic information.
This is also true for the other
22 pairs.

4. These chromosome pairs are called
HOMOLOGOUS CHROMOSOMES
Genes that determine a specific trait are found in the same location on that pair of chromosomes
Example: the gene that determines ear shape is located in
same place on
2 homologous
chromosomes.

5. Sex Chromosomes In humans, females have 2 “X”
chromosomes. So, each egg contains one
“X” chromosome.
Males have both an “X” and a “Y”
chromosome. Each sperm cell contains
either an “X” or a “Y” chromosome.

6. Those homologous chromosomes carry the genes that make you—YOU!!
Those two make up your
GENOTYPE
Genes passed to offspring.
Genotype determines
Phenotype.
PHENOTYPE
Actual (expression)
Physical appearance.

7. Dominant and Recessive Alleles
Different forms of same gene
are called
Trait
Trait Made By
Dominant
Allele
Recessive
Hair
Type
Curly or
Wavy
Straight
Color
Dark
Light
Earlobe
Free
Attached
Dimples
Present
Not
ALLELES
Alleles will be either:
Dominant = Stronger Trait
Recessive = Weaker Trait
Many traits are controlled by a single gene.
Look at the table to the right
for examples of human traits.

8. Identifying Genotypes and Phenotypes
Genotype trait is written as
2 letters.
Dominant Allele--
Capital Letter
Recessive Allele--
Lowercase Letter
The allele that causes free earlobes
is dominant over the allele for
attached earlobes.
So F is used for free earlobe gene.
What do you think is used for
attached earlobe gene?
Lowercase f

9. ff Ff Homozygous genotypes FF a.k.a--Hybrid
Offspring receive 2 copies of each gene-1 from each parent.
3 possible genotypes
FF, ff, or Ff
The 2 alleles are the exact same--
“Homo” ---“the same.”
Homozygous genotypes
Homozygous Dominant-- FF ff
Homozygous Recessive--
a.k.a--purebred
“Hetero” --- “different.”
Heterozygous genotype
1 dominant allele and
1 recessive allele-- Ff
a.k.a--Hybrid

10. Punnett Squares are used to predict results of genetic crosses.
Mating of 2 parent
organisms
Punnett Squares are used to
calculate probability of genotypes/phenotypes
in offspring.

11. Let’s make a Punnett Square with the information below.
Predict outcome of crossing tall pea plant with short pea plant.
First, we must know the genotype of each parent plant.
There are 3 possible genotypes : TT, Tt, and tt
Genotype of pure tall plant : TT <---- It has 2 dominant alleles
Genotype of pure short plant : tt <--- It has 2 recessive alleles.
To make a Punnett Square, 1st separate the parent alleles.
Place 1 pair across top of square, and other pair down the left side. t t
Genotype –
Genes/letters Tt Tt T
tall
tall
Phenotypes –
physical Tt Tt T
tall
tall
Dominant Gene always 1st in genotype

12. T t TT Tt T Tall Tall Tt tt t Tall Short TT, Tt, tt
Let’s consider a cross between 2 plants with heterozygous genotypes : Tt (mom) x Tt (dad) T t
Probability
of tall
plants? TT Tt T
Tall
Tall
3 out of 4,
or 75%. Tt tt
Probability
of short
plants? t
Tall
Short
How many possible genotypes here?
1 out of 4,
or 25%.
TT, Tt, tt
How many phenotypes?
Tall , Short

13. We’re done! Let’s answer some questions.
1. 2 different forms of the same gene are called
A. phenotypes. C. dominant traits
B. genotypes. D. alleles
2. An organism’s expressed traits make up its
A. recessive traits C. phenotype
B. genotype D. alleles
3. A pea plant that is homozygous dominant for seed color is crossed with a pea plant that is homozygous recessive for seed color. Since yellow is the dominant color, the letters Y and y represent the genes for seed color. What cross represents these 2 plants? A. Yy x Yy C. YY x yy B. YY x Yy D. Yy x yy

14. 4. Suppose you crossed a pea plant that has round seeds (R)
with a pea plant that has wrinkled seeds (r). If 50 percent of
the offspring have round seeds and 50 percent of the
offspring have wrinkled seeds, what are the genotypes of the parent plants? Make a Punnett Square to help you
answer the question.
5. You meet a person and notice that she has dimples. What can you say for sure about the phenotypes of her parents? A. At least 1 of her parents has dimples. B. Both of her parents have dimples. C. Neither parent has dimples. D. 1 of her parents does not have dimples