1. How do organisms create offspring through sexual reproduction?

2. What is Sexual Reproduction?
It involves the joining of two cells to begin the
development of a new individual.
These special cells are called: Sex Cells (Gametes)

3. What are the names of these sex cells?
Egg cell
(Female)
Sperm Cell
(Male)
The joining of a sperm cell with
an egg cell is called fertilization.

4. How many chromosomes do we have in our cells?
We have 46 chromosomes
in each our body cells.
We can also say that we
have 23 pairs of
chromosomes
Karyotype

6. Why do we have 2 of each chromosome?
We get one chromosome from each parent
Each pair of chromosomes are called:
Homologous Chromosomes

7. Homologous Chromosomes:
Gene
Mom
Dad
Eye Color B G
Part of a
chromosome
that codes for
a trait B
Hair Color R
Have genes that code for the same trait, but may
have different versions of that trait

8. How are chromatids different than homologous chromosomes?
Chromatids are exact
duplicates of each other
Homologous chromosomes
have genes that code for
the same trait, but they may
code for different versions
of that trait

9. How many chromosomes do the offspring have after mitosis?
46X
Mitosis
46X
46X

10. Do our sex cells have 46 chromosomes?
NO!!!

11. What would happen if our sex cells did have 46 chromosomes?92 +
Offspring
Egg
Sperm
The offspring would have 92 chromosomes

12. Sexual Reproduction: 23 23 46 + Offspring Egg
A fertilized egg cell is called a Zygote
Sperm
Characteristics of Sexual Reproduction:
1) Is the creation of a new individual from parents. 2
2) Offspring are not genetically to the parents.
identical

13. Sex Cells (Gametes) Sex Cells: SPERM and EGG
Sex cells should have 1/2 the normal number of chromosomes

14. Chromosome Number
Diploid cells: (2n) normal number of chromosomes (Body Cells)
Haploid cells: (n) ½ the normal number of chromosomes (Sex Cells)

15. Diploid vs Haploid
Movie Clips

16. Meiosis
The process by which haploid (sex) cells are produced with half the number of chromosomes.

17. What is the end result of meiosis?
46X
Meiosis
23X
23X
23X
23X

18. Where does meiosis occur?
Gonads – Ovaries and Testis

19. Why is meiosis important?
Maintains the number of chromosomes from generation to generation
Provides genetic variation
Only during fertilization (union of sperm and egg) is the full (diploid) set of chromosomes restored.

20. Practice Problems: