1. Reproduction and variation

2. D.S.Q. 1. How often do hens (female chickens) lay eggs?
2. Can these eggs hatch into a chick?
3. Do hens lay eggs without the presence of a rooster (male chicken)?
4. How are chicken eggs fertilized?
5. What happens to the unfertilized eggs?

3. Activity Time

4. Discussion 1. Is a chicken egg an organism, organ, or cell?
2. What function do you think the yolk serves?
3. Do chickens reproduce sexually (DNA is received from both parents) or asexually (only one parent is involved, and the offspring is genetically identical to the parent)?

5. Heredity The passing of traits from parents to offspring
For example: You have blue eyes because your mom does.
However, what if you have blue eyes but both your parents have brown eyes? How does this happen?

6. Gregor Mendel
He performed experiments that helped answer these questions and how inheritance happens.
Mendel is known as the father of genetics
Genetics is the study of how traits are passed from parents to offspring

7. Mendel’s Experiment His experiment was tested on a pea plant.

8. True Breeding PLants
When a true-breeding plant self pollinates, it always produces offsprings with traits that match the parent
Ex. If a pea plant is wrinkled and self-pollinates, then it will only produce wrinkled seeds

9. Mendel’s Results Purple x Purple All white flowers White x White
All Purple Flowers (True-breeding)
White x White
All white flowers

10. All purple flowers (hybrids)
Mendel’s Result
All purple flowers (hybrids)
Purple x White
After doing his experiment, he was wondering why when he mixed purple and white seeds that all of them came out purple flowers.

11. Second Generation (Hybrid) Crosses
A hybrid plant is when a plant is produced from two true breeding plants with different forms of the same trait.

12. Mendel’s Conclusion
There are two genetic factors control each inherited trait
When organisms reproduce, each reproductive cell—sperm or egg—contributes one factor for each trait

13. Dominant & Recessive Traits
All purple flowers (hybrids)
Purple x White
Why didn’t the flowers turn white?
Mendel believed that the purple color is the only factor seen or expressed because it blocks the white factor

14. Dominant and Recessive Traits
A genetic factor that blocks another genetic factor is called the dominant trait
A dominant trait is observed when offspring have either one or two dominant factors
A genetic factor that is blocked by the presence of a dominant factor is called a recessive trait
A recessive trait is observed ONLY when two recessive genetic factors are present in the offspring

15. What is inheritance?
Who do you look like? Your mom, dad, grandma, grandpa?
What features do you have that are similar to them?
A trait is a distinguishing characteristic of an organism
During reproduction, traits are passed from one generation to another

16. What is inheritance?
Inheritance is the passing of traits from one generation to another

17. Inheritance and DNA
Organisms pass inherited traits to their offspring in one of two ways:
Either asexually or sexually
Asexual reproduction pass traits to their offspring by cell division and mitosis and are identical to their parents
Sexual reproduction, produce offspring's that are similar to their parents

18. DNA & Genes
Sexual reproduction requires DNA from a sperm cell and egg cell
DNA is a molecule inside a cell’s nucleus.

19. DNA and Genes
Gene: is a section of DNA that has genetic information for one trait
Genes carry the information in the DNA
IF you were to stretch out the DNA it would be 2 METERS LONG!
Alleles are the different forms
Of a gene

20. DNA and genes
DNA fits in the nucleus because it is tightly coiled with proteins to form chromosomes
A chromosome is a structure made of long chains of DNA

21. Chromosomes The number of chromosomes differ between every species.
Humans have 23 paired chromosomes.
We get 23 from the sperm cell (males) and 23 from egg cells (females)

22. Genotype and Phenotype
What human trait can you observe?

23. Genotype and Phenotype
Phenotypes are known as how a trait appears, or is expressed
Genotype is when the two alleles that control the phenotype of a trait
For example, the white plant in our previous example has two recessive alleles. The two alleles are its genotype and the WHITE flower is its phenotype

24. Symbols for Genotypes Uppercase letters represent dominant alleles
Lowercase letters represent recessive alleles

25. Homozygous and Heterozygous
When 2 alleles are the same, its genotype is HOMOZYGOUS.
For example, AA or aa
If two alleles of a gene are different, its genotype is heterozygous
For example, Aa

26. 2 ways of modeling inheritance
Punnett Squares and pedigree can be used to predict the identify traits among genetically related individuals

27. Punnett Squares
If the genotypes of the parents are known, then the different genotypes and phenotypes of the offspring can be predicted
Punnett Square is a model used to predict possible outcomes for the offspring

28. Punnett Squares