1. Chapter 8 Cell Reproduction
Section 1 Chromosomes

2. Chromosome Structure
Chromosome- rod-shaped structure made of DNA and proteins
If DNA were stretched out, it would be 6 feet long!!
How does it fit into the nucleus of a cell?

3. Histone proteins DNA is tightly coiled around histone proteins
*These proteins help maintain the shape of chromosomes
The red structures are histone proteins

4. DNA molecules are coiled on many levels to form chromosomes

5. Chromatid-each identical half of a chromosome

6. Centromere-a structure that holds two chromatids together

7. chromatin
-less tightly coiled DNA; DNA exists as chromatin when it is not coiled into chromosomes

8. Prokaryotic DNA…
…is a circle and consists of one chromosome

9. Every species has a unique number of chromosomes…
How many do we have?
46 chromosomes
Or 23 pairs of chromosomes

10. Does the number of chromosomes indicate the complexity of an organism?
Adder’s tongue fern
1,262
Carrot 18
Cat 32
Chimpanzee 48
Dog 78
Earthworm 36
Fruit fly 8
Organism
Number of Chromosomes
Garden pea 20
Gorilla 48
Horse 64
Human 46
Lettuce 18
Orangutan
Does the number of chromosomes indicate the complexity of an organism?

11. Types of chromosomes XX XY
We have 1 pair or 2 chromosomes
They are X and Y XX XY
1. Sex Chromosomes-chromosomes that determine the sex of an individual

12. 2. Autosomes-They control everything about us except for our sex
Ex. Eye color
We have 22 pairs or
44 autosomes

13. The Structure of a Chromosome
Two
Chromosomes
similar in size and shape
that make up a pair are called
Homologous
chromosomes

14. Here is a picture of someone’s chromosomes…
Do you see the autosomes?
Do you see the sex chromosomes?

15. A picture of a person’s chromosomes…
Which one is male and which one is female?
is called a karyotype

16. What info. is given by a karyotype?
Missing parts of chromosomes
Extra chromosomes
Sex of offspring
Down Syndrome-caused by 3 chromosomes
#21

17. Diploid and Haploid Cells
Diploid- a full set of chromosomes from both parents (2n)
Haploid- one set of chromosomes (1n)
Egg and sperm cells are haploid; all other cells are diploid

18. Cell Division
25 million cells are produced by an adult human body every day
Growth and development are achieved by cell division

19. The division of prokaryotic cells
Binary fission- the division of a prokaryotic cell into two offspring cells

20. Mitosis Results in two identical cells from a parent cell
Occurs for development, cell repair, or asexual reproduction

21. Meiosis- the production of egg and sperm cells
Allows chromosome number to be reduced to half. In us, 23 chromosomes are contained in our sex cells
Meiosis produces gametes which are sex cells

22. The Cell Cycle-repeating set of events in the life of a cell
Includes interphase, mitosis and cytokinesis

23. The Cell Cycle
Interphase- a cell spends most its time in interphase G1- offspring cells grow to mature size S- DNA is copied (synthesized) G2- cell prepares to divide

24. Continued…
Mitosis
Prophase
Metaphase
Anaphase
Telophase

25. prophase telophase metaphase interphase anaphase 1 2 3 4 5
What type of cell is shown; plant or animal? How do you know?
interphase
anaphase

26. Cytokinesis- the division of the cytoplasm and organelles; begins with a cleavage furrow in animal cells and a cell plate in cell walls