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DIRECTIONS- WEEK 3

• Fill in the attached notes pages as you follow along with the PowerPoint slides.•Keep the 2 notes pages for next week. You will be using them on more activities next week.

CELL DIVISIONT H E C E L L C Y C L E A N D M I T O S I S

WHAT IS DNA?

• Double-stranded molecule made of nucleotides that stores genetic information(double helix)

• How does it store it?• As a long, continuous thread that consists of

numerous genes

DNA: DIFFERENT STAGES-DIFFERENT SHAPES

• Chromatin: loosely compacted single strand

• Chromatid: tightly compacted, one of a pair • Chromosome: two tightly compacted sister

chromatids joined at the centromere• Always paired with an identical copy of itself

SISTER CHROMATIDS

CHROMATID

2 TYPES OF CHROMOSOMES

Humans have 23 pairs of chromosomes(total 46 chromosomes)

•Autosomes• Chromosome pairs 1-22• Contain genes not directly related to the sex of an

organism

• Sex Chromosomes• 23rd pair of chromosomes• Control the development of sex characteristics

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GENES FROM YOUR PARENTS

Everyone gets 2 sets of genes, one from mom and one from dad• Females: have two X chromosomes (XX)• Larger, can hold more information

• Males: have one X chromosome and one Y chromosome (XY)• Smaller, sex-linked information only

TYPES OF CELL DIVISION

• Asexual: offspring are identical to parents (like a clone of the original cell)• Examples: Budding (yeast) and Binary

Fission (bacteria)

• Sexual: offspring have a combination of genetic information from 2 parents (sperm and egg)• Examples: animals and plants

2 TYPES OF CELLS FOUND IN THE BODY

Gametes• Sex cells• Female (egg)

• Male (sperm)

* DNA in gametes is passed on to offspring

Somatic Cells• Body Cells• Make up tissues

and organs

* DNA is NOTpassed to offspring through cell division

THE CELL CYCLE

• The Cell Cycle is a regular pattern of growth, DNA replication and division that occurs in eukaryotic cells

•Why do cells need to divide?• Growth• Reproduction

• Repair

Cell Cycle’s 3 main Stages

1. Interphase• Where DNA replicates and forms

chromosomes

2. Mitosis• Where chromosomes• Divide and separate from each other

3. Cytokinesis• Cytoplasm divides into two daughter cells

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CELL CYCLE

1. Interphase• Chromosomes appear as

threadlike coils (chromatin)• 90% of the cell cycle• Three phases• G1- Growth• S- DNA Replication (DNA doubles to

form sister chromatids)• G2- Growth (prepares to divide)

CELL CYCLE

2. Mitosis• (1 cell becomes 2 cells)• Both new cells are identical to the original• ALL cells except sperm and eggs do this

• Occurs in 4 stages• P. M. A. T.

CELL CYCLE: MITOSIS

PROPHASE (“before”)• First stage of Mitosis• Chromatids become Chromosomes (X)

• Nuclear membrane breaks down

CELL CYCLE: MITOSIS

METAPHASE (“middle”)• Chromosomes line up in the middle of the cell• Spindle fibers attach to the centromere of each chromosome

CELL CYCLE: MITOSIS

ANAPHASE (“anti”)• Spindle fibers shorten and pull sister chromatids apart• Chromatids get pulled to opposite sides of the cell

CELL CYCLE: MITOSIS

TELOPHASE (“two”)• New nuclear membranes begin to form around chromosomes (one for each new cell)• Chromosomes begin to uncoil• Spindle fibers fall apart

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CELL CYCLE

3. Cytokinesis•Cytoplasm splits into 2 cells• Animal cells: cleavage

• Plant cells: cell plate forms

• Full stage of the cell cycle is now complete

END RESULT

•Mitosis is carried out by all cells (somatic cells) EXCEPT sperm and egg cell (gametes are not identical)•Mitosis forms 2 “daughter cells”• Daughter cells are IDENTICAL to original cell• Daughter cells are half the size of the original

What Stages of Mitosis can you find?

Cell Cycle Review Sheet 1. What is stored within DNA? _________________________________________

2. A _______________ is DNA that is tightly compacted and only 1 of a pair.

3. A _______________ is a pair of tightly compacted DNA.

4. _________________ is a loosely compacted single strand of DNA.

5. How many pairs of chromosomes do humans have? ______________

6. Do we have MORE autosomal or sex chromosomes? ____________________

7. If chromosome pair #23 is XX, is this a male or female? _______________ How about someone with XY

in the #23 pair? ____________

8. _______________ reproduction results in a cloned organism that is identical to its parents.

9. _______________ reproduction results in an organism that is a genetic combination of its parents.

10. What kind of somatic cells do females have?_______________ males? __________________

11. Somatic cells are the cells that make up the __________________ and __________________ of your body.

12. _____________________ is the stage of the cell cycle when the cytoplasm divides.

13. _____________________ is the stage of the cell cycle where DNA replicates (copies) and chromosomes

form.

14. _____________________ is the stage of the cell cycle when chromosomes divide and separate from each

other.

15. Cells spend 90% of their life in which stage of the cell cycle? __________________

16. Does mitosis create somatic (body) cells or gamete (sex) cells? _____________

17. How many cells are created by mitosis? ________ Are these cells identical or different? _______________

Match the name of the step where the described action happens.

Interphase: G1, G2, or S

18. ________________ Growth.

19. ________________DNA is replicated (copied) to double the amount.

20. ________________More growth preparing to divide.

Mitosis (Prophase, Metaphase, Anaphase, Telophase) or Cytokinesis stages

21. ________________ Chromatids get pulled to opposite sides of the cell when the spindle fiber shorten.

22. ________________ Chromosomes line up in the middle of the cell where spindle fibers attach to them.

23. ________________Cytoplasm splits into 2 cells.

24. ________________ Chromatids become chromosomes and the nuclear membrane breaks down.

25. ________________ Nuclear membranes reform and chromosomes uncoil.