1. Introduction to Genetics

2. Gregor Mendel Gregor Mendel is the “father of modern genetics”
Austrian monk who did genetic experiments with pea plants
Defined basic units of heredity

3. Mendel used pea plants to conduct experiments
Mendel used pea plants to conduct experiments. He concentrated on petal color and shape of peas.
Experiments led to basic genetic understandings such as:
What happens when two different plants breed?
How traits are passed from parents to offspring?
Basic understandings of dominant and recessive traits?

4. Different traits Mendel observed:

5. Why Peas? Mendel could do two experiments a year
Lacked modern technology
Today scientists use organisms that reproduce quickly such as drosophila (fruit fly) which reproduces in 2 weeks or bacteria such as E. coli which reproduces within hours.

6. Genetics DNA are the blue-prints of all of your genetic information.
DNA is tightly wound into chromosomes
Your genetic information is on genes
Genes are located on chromosomes

7. Your Genes and DNA You are a combination of your parents.
You have ½ of your mom’s and ½ of your dad’s DNA
Remember Meiosis?
You have 23 pairs (one from each parent) to make a total of 46 chromosomes.

8. Human Chromosomes

9. Genetic Traits
Genes you get from your dad are “paternal” and genes you get from your mom are “maternal”
These make up your traits.
Trait: characteristic determined by genes
Example: I have the trait for blue eyes

10. Alleles Each trait is carried on a chromosome stripe.
These stripes are called alleles.
Allele: form of a gene on a specific region of a chromosome

11. Alleles for flower color
Maternal
Chromosome
Paternal
Chromosome

12. Which of Your Parents Traits Will You Get?
Based on probability
For example, eggs have X chromosomes and sperm have either X or Y chromosomes.
XX= girl
XY= boy
What is the probability offspring will be a girl?

13. Boy or Girl 50% chance or 1 out of 2 Only two different combinations!
XX or XY
Determining the sex of a baby is one example of probability.
But…it doesn’t always work that way…

14. Dominant Alleles vs. Recessive Alleles
Certain traits are stronger then others. This means that they will more likely be expressed.
For example: If I mix black paint with white paint, what color will paint most likely be?
Black! It is a “stronger color”.
Dominant allele: one that is expressed physically (what organism looks like)

15. Dominant Alleles vs. Recessive Alleles
What about the white paint?
Recessive allele: one that is masked or hidden by the dominant allele.
White paint would be an example of the “recessive color”. There is still white paint in the mixture, but it looks black.

16. Terms To Know Genotype: combination of two alleles
Homozygous: When the genes are
identical
Heterozygous: When the genes are
different
Phenotype: The observable trait
(the trait you see)

17. Boy: XY Girl: XX What is the genotype for girl?
Is boy homo or heterozygous?
Heterozygous XY (different letters)
Homozygous XX (same letters)
What is the dominant allele (X or Y?) Y
How do you know?
Wherever Y is means a boy will form

18. How genes are expressed
If an organism carries any combination of dominant genes, it will be expressed in an organism.
Recessive genes are only expressed when there are two recessive genes
Example XX in girls