1. Inheritance of Traits
Genetics

2. Genetics: The study of how traits are passed from parents to offspring
Chromosomes are long structures found in the nucleus of a cell
Chromosomes are actually coiled up DNA molecules
Genes are specific sections on chromosomes
Each gene determines a specific trait of an organism

3. Traits Traits are specific characteristics of an organism
Examples include: eye color, hair color, shape of body parts, whether one can taste a yucky tasting compound or not, certain chemical processes in the body
Organisms have thousands of traits
Genetics can also be looked at as the study of how genes control the traits

5. Genes are arranged on a chromosome, one next to the other
Each chromosome has different genes, that control different traits

7. Passing Traits to Offspring
When the sperm fertilizes the egg, DNA from the mother is combined with DNA from the father
The offspring now has a complete but unique set of DNA
It is a combination of the mother’s and the father’s but it is completely unique compared to both of them

8. Dominant and Recessive Genes
Genes come in pairs (because chromosomes come in pairs)
Some genes mask the expression of their counterpart
These are called dominant genes
Example: If one parent gives the gene for attached earlobes and the other gives the gene for free eat lobes, the child will have free earlobes. The gene for free ear lobes is dominant. It masks the expression of the attached ear lobe gene
The gene that gets masked is called recessive

9. Heterozygous and Homozygous
An organism with two dominant genes for a trait is called pure dominant (homozygous dominant)
An organism with two recessive genes for a trait is called pure recessive (homozygous recessive)
An organism with a dominant gene and a recessive gene is called heterozygous. In this case, the individual will only express the dominant trait even though it carries the recessive trait.

10. Predicting the Gene Combinations Using a Punnett Square
A Punnett square is used to predict the possible gene combinations that offspring may have based on the parent’s genes
In the example of the earlobes, free lobes was the dominant trait and attached was the recessive trait. We use one letter to represent these traits.
We use the first letter of the dominant trait. Uppercase letters fro dominant and lower case for recessive. So…
F = free and f = attached

11. Example I’ll show you one and you do the rest.
Say one parent is pure dominant (homozygous dominant) and the other is heterozygous
We set up the Punnett square like this

12. Then we bring the letters on the left over to the boxes next to them and the letters in the top down.
Always right any upper case letters first
It should look like this

13. With this information we can now see that there are only two possible combinations for offspring from these parents
So we can say there is a 50% chance of getting an offspring that is pure dominant and a 50% chance of getting an offspring that is heterozygous
What kind of earlobes will the offspring have?

14. Genotype and Phenotype
Genotype is just a fancy word for the genetic makeup of something
For example, we talked about attached and free earlobes. If your earlobes are free your genotype is Ff or FF. If your lobes are attached your genotype is ff.
Phenotype is a fancy word for the actual, physical trait. So, the phenotypes are attached ear lobes or free ear lobes.
Genotype controls phenotype!!! (the genes control what traits will be expressed.)

15. You Try It! Complete Punnett Square for Each of the Following Scenarios
Use earlobes again.
Both parents are heterozygous
Possible outcomes:
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16. Tasting the PTC is dominant to not tasting
Parent 1 is heterozygous
Parent 2 is homozygous recessive
Possible outcomes:
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