1. Making predictions about future generations…
Genetics Basics
Making predictions about future generations…

2. Objective
I will be able to use Punnett squares to predict the genotype and phenotype of offspring.

3. Gene vs. Allele
Gene: A specific region of the DNA that codes for a particular trait
Allele: Any of the alternative versions of a gene that occur at specific locations on a chromosome
Example: The alleles for pea flowers are purple and white
What are some alleles for eye color?

4. Introducing the Father of Genetics…
Gregor Mendel!
A monk that lived in Austria in the 1860s
Mendel bred peas to study inheritance.
He discovered the founding principles of heredity.

5. The technique…

6. The results… X Experiment 1 Purple and white makes…? Purple!
Purple and purple makes…?
Purple and white! X

7. The discovery…
The dominant allele, is fully expressed in the organism’s appearance.
Shown with a CAPITAL LETTER
The recessive allele, has no noticeable effect on the organism’s appearance.
Shown with a lowercase letter
Purple = dominant = P
White = recessive = p

8. Two Alleles for Each Trait
For each trait, an organism inherits two alleles
One from MOMMY one from DADDY
Homozygous: When the two alleles are the same
AA or aa
Heterozygous: When the two alleles are different: Aa Aa AA aa

9. Genotype vs. Phenotype
Genotype: all the organism’ genetic information that codes for traits
“what’s in the DNA”
Example: BB, Bb, bb
Phenotype: the organisms physical characteristics
“what it looks like”
Example: Brown or blue eyes

10. Vocab. Practice…
1. If T = tall and t = short, what is the genotype of each of these:
Homozygous dominant:
Homozygous recessive:
Heterozygous:
2. What is the phenotype for each of these?
TT =
Tt =
tt = TT tt Tt
tall
tall
short

11. More practice: N = Straight hair, n = curly hair
3. A man that is heterozygous for straight hair, marries a woman who is homozygous recessive for curly hair.
Man genotype:
Man phenotype:
Woman genotype:
Woman phenotype: Nn
Straight hair nn
Curly hair

12. B = brown eyes, b = blue eyes
One more:
B = brown eyes, b = blue eyes
4. A man with blue eyes marries a woman who is homozygous dominant for brown eyes.
Man genotype:
Man phenotype:
Woman genotype:
Woman phenotype: bb
Blue eyes BB
Brown eyes