1. Chromosomes & Mitosis and Meiosis
Chapter 7
Chromosomes
&
Mitosis and Meiosis

2. DNA Coiled around Proteins
Chromosomes
DNA coiled around proteins forms chromosomes
DNA Double Helix-
DNA Coiled around Proteins
Chromatid
Super Coil
Chromosome

3. DNA Coiling

4. Parts of a Chromosome Each half of a chromosome is called a chromatid
Chromatids are held together at a point called the centromere

5. Genes Genes are segments of DNA in chromosomes that code for proteins
Each chromosome contains hundreds of genes

6. Gametes Gametes are an organisms sex cells or reproductive cells
Male gamete = sperm
Female gamete = egg
Each gamete only contains half the number of chromosomes of regular cells

7. Sets of Chromosomes
Humans have 23 pairs of chromosomes, 46 total chromosomes
Humans have 2 copies of each chromosome
2 exact copies of a chromosome are called Homologous Pairs

8. Fertilization
Fertilization is the joining of male and female gametes, egg + sperm

9. Haploid & Diploid Cells
Haploid Cells(n) - have ½ the number of chromosomes of other cells (egg&sperm)
Diploid Cells(2n) - have 2 copies of all chromosomes (regular human cells)
- Sperm haploid(n)
Egg – haploid(n)
- Fertilized Egg Diploid(2n)

10. Types of Chromosomes
Autosomes- the 22 pairs of chromosomes that do NOT determine the sex of an organism
Sex Chromosomes- the 23rd pair of chromosomes that determines the sex of an individual (X & Y chromosome)
XX = female
XY = male

11. Changes in Chromosome #
If an individual has more or less than 46 chromosomes, a genetic disorder may result
Ex: Trisomy-21 (Down Syndrome)
- a person with trisomy-21 has 3 copies of chromosome #21
- Mutations in chromosomes may also cause genetic disorders

12. Trisomy-21

13. Karyotype A karyotype is a picture of an organisms chromosomes
Karyotypes can be used to detect genetic disorders and chromosome abnormalities

14. The Cell Cycle
The cell cycle is a repeating process in which a cell grows, copies it’s DNA, and then divides

15. Cell Cycle Diagram G1- cell grows S- DNA is copied
G2- growth & preparation for mitosis
M- cell divides
Cytokinesis- point when 2 new cells split apart
Apoptosis- cell death
G1 (gap 1)
- Cell Growth
S (synthesis)
- DNA Synthesis
Cytokinesis
G2 (gap 2)
- Cell Growth
M (mitosis)
- Cell Division

16. Cancer
Normal body cells that begin to grow & divide uncontrollably become cancer cells
Carcinogen- a substance that causes cancer
Ex: radiation(x-ray, UV-rays), chemicals, viruses

17. * * Mitosis Mitosis is the process of making exact copies of cells
Phases of Mitosis:
Prophase - * *

18. Phases of Mitosis
2) Metaphase- - * *

19. Phases of Mitosis
3) Anaphase- - * *

20. Phases of Mitosis
4) Telophase- -

21. Cytokinesis
2 exact copies of the original are formed

22. Interphase
Interphase is the phase when a cell is resting and growing, not dividing
Cells spend most of their time in interphase

24. Meiosis Meiosis is the process of forming sex cells (gametes)
Gametes: Male = sperm
Female = egg
Meiosis produces haploid(n) cells, cells that have only one copy of each chromosome
Egg & Sperm cells only have 23 chromosomes each

25. Spermatogenesis Spermatogenesis makes 4 sperm cells in males
Diploid(2n)Parent Cell
Meiosis I
Immature Sperm Cells
Meiosis II
Haploid(n) Sperm Cells

26. Oogenesis Oogenesis makes egg cells in females makes 1 egg
Diploid(2n)Parent Cell
Meiosis I
Polar Body
Secondary Egg Cell
Meiosis II
Polar Bodies
Haploid(n) Egg Cell
* All Polar Bodies Die

27. Genetic Recombination
Often during meiosis pairs of homologous chromosomes exchange pieces of DNA before they separate into daughter cells
This exchange of genetic material is called Crossing Over
Crossing over results in variation in the traits passed on to offspring

28. Crossing Over

29. END OF CHAPTER 7 NOTES