TOPIC: Genetics
AIM: How are traits passed on?
TRAIT
 Characteristics
 Examples – hair color, eye color
GENETICS
 The study of heredity
 ____________________________________________
Gregor Mendel
 Father of Genetics
 Studied how traits are passed on
 Used pea plants
GENES
 Units of heredity, on chromosomes
 ____________________________________________________________________
DOMINANT GENE
 “stronger” gene/trait
 CAPITAL LETTER
 Ex: T = tall pea plant
RECESSIVE GENE
 “weaker” gene/trait
 Lower case
 Ex: t = short pea plant
PHENOTYPE
 physical appearance
 tall, short, blue eyes, brown eyes
GENOTYPE
 Genetic makeup
 Names of genes (what genes do
they have?
GENE COMBINATIONS
1. TT
2. tt
P = ______________________
P = _____________________
G = _______________________
__________________________
G=
___________________________
________________________________
________
3. Tt
P = ______________________ G = ____________________________
TOPIC: Genetics
AIM: How are traits determined by using a Punnett Square?
Probability
The possibility that an event may or may not take place
¼ = _______
2/4 = ______
¾ = ______
4/4 _______
Punnett Squares
Special charts that show possible gene combinations of offspring between 2 organisms
EXAMPLES
1. T = tall
t = short
TT x
tt
2. B= black
b = white
Bb x Bb
3. Red is dominant in flowers & white is recessive. Cross a heterozygous flower with a
homozygous dominant flower.
4. One dog carries heterozygous, black fur traits, and the other carries homozygous
recessive white traits. What are the chances of having a puppy with black fur?
Complete all Punnett Squares on a piece of looseleaf. Indicate the phenotypes
and genetotypes for all problems.
1. T = tall, t = short
Cross a heterozygous tall plant with a short plant.
2. G = green, g = yellow
Cross a pure green plant with a hybrid plant.
3. A man with blue eyes marries a woman who is heterozygous for brown eyes. If brown eyes are dominant, what are the chances
of having a blue eyed child? Also, give the phenotypes and genotyes.
4. Red hair (R) is dominant over blonde hair (r). Make a cross between a heterozygous red head and a blonde. Determine phenotype &
genotype.
5. In tomatoes, red fruit color is dominant to yellow fruit color. Predict the phenotypes and genotypes of the offspring by crossing a
homozygous dominant parent with a homozygous recessive parent.
6. In a certain species of mouse, pointed ears are dominant over round ears. Predict the genotypes and phenotypes of a cross between
two hybrid pointed-eared mice.
7. In a certain species of dog, a black nose is dominant over a pink nose. Predict the genotypes and phenotypes of a
cross between a purebred dominant male dog and a purebred recessive female.
8. Red hair (R) is dominant over blonde hair (r). Make a cross between a heterozygous red head and a blonde.
9. Cross a heterozygous brown haired rabbit with a homozygous recessive white haired rabbit.
10. Black eyes (R) is dominant over red eyes (r) in rats. Make a cross between a homozygous rat with black eyes and a rat with red
eyes.
11. Cross a homozygous dominant long haired guinea pig with a heterozygous long haired guinea pig.
12. Cross a heterozygous wrinkly elephant with another heterozygous wrinkly elephant.
13. The freckles trait is considered to be dominant. A couple a wonders if their children will have freckles. The man has freckles
but his mother did not. The woman in this couple has no freckles. Create a Punnett Square and determine the phenotype
and genotype of their possible offspring.
14. The gene for free ear lobes is dominant. The gene for attached ear lobes is recessive. Show the cross between two heterozygous
parents.
15. I = cleft chin
i = smooth chin
Cross these 2 parents:
Ii x ii
16. A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR).
17. A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant.
18. In pea plants purple flowers are dominant to white flowers. Cross two white flowered plants.
19. A white flowered plant is crossed with a plant that is heterozygous for the trait.
20. Curly hair is recessive, and straight hair is dominant. A woman with curly hair marries a man who is homozygous dominant for
straight hair. Predict the outcomes for their children.
21. Attached earlobes are dominant over free hanging earlobes. Complete the Punnett Square for the following individuals:
Mom=BB and Dad=bb
22. Cross a male with the heterozygous condition for tongue rolling (the ability to roll the tongue is dominant), with
a female who is homozygous recessive.
23. In guinea pigs, black coat color (use B) is dominant over white coat color (use b). Short hair (S) is dominant over long hair (s).
Cross two guinea pigs, both with a heterozygous genotype for each trait.