1. Cell Division
Mr. Hamilton
Biology

2. Chromosomes Gene: Segment of DNA that codes for a protein.
Chromosomes: Coiled structures that contain DNA and proteins.
Humans have 46 chromosomes (23 Pair)
Composed of chromatids attached by centromeres.
Formed from DNA, Before cell division.

3. Chromosomes Homologous Chromosomes—Similar in shape and information
Sister Chromatids—Occur in pairs
22 pair are autosomes (responsible for traits such as hair color, eye color, etc.)
1 pair of sex chromosomes (determines the sex of the offspring)
Male—X Y
Female—X X

4. Chromosomes
Homologous Chromosome
Sister Chromatids

6. Types of Division
Binary fission: Occurs in Prokaryotes, because they don’t have a nucleus
When dividing, the cell just pinches into two separate cells
This is asexual reproduction.

7. Types of Division
Eukaryotes must undergo mitosis because they have a nucleus
Cell Cycle: Process of growth and development in eukaryotic cells. Includes: Interphase, Mitosis and Cytokinesis.

8. Cell Cycle
Interphase: 90% of time is spent here. Normal activities of cell.
Mitosis: Division of nucleus
Cytokinesis: Division of cytoplasm.

9. Segments of DNA that code for a protein…
Chromosome
Chromatid
Centromere
Gene

10. How many chromosomes do we get from each parent?12 23 24 46 15

11. How many sex chromosomes do humans have?2 4 23 46 15

12. Bacteria divide by…
Binary fission
Cell cycle
Mitosis
Meiosis 15

13. Why do eukaryotes go through mitosis and not binary fission?
They don’t have a nucleus
They have a nucleus
They are multicellular
They are unicellular 20

14. Stages of Mitosis (Duplicates Cell)
Interphase:
The cell spends the majority of its time in this stage.
Performs tasks that prepare the cell for cell division
Chromosomes are not yet present.

15. Stages of Mitosis Prophase: Metaphase: Nuclear membrane disappear.
Spindle fibers form—these help pull chromosomes apart.
Chromosomes become visible
Metaphase:
Meta means middle
Chromosomes line up in the middle/equator.

16. Stages of Mitosis (cont.)
Anaphase:
Centromeres duplicate
Chromosomes are pulled apart to opposite poles.
Telophase
Nuclear membranes reappear.
Spindles dissolve
Cytokinesis begins
Chromosomes uncoil

18. Where do cells spend the majority of their time
Anaphase
Interphase
Metaphase
Telophase 20

19. How many chromosomes will a cell have after mitosis if the original cell has 20?10 20 23 46 20

20. Checkpoints The cell has checkpoints during growth and division.
These help ensure that
things are running smoothly.
Changes or problems could result in the body’s immune system destroying cells.
When problems are not caught, uncontrolled growth of cells results.

22. Chromosomal mutations
Mutation: Any change in DNA.
Two types:
Somatic mutations: Occur in body cells after birth. Ex: Mutations causing cancer.
Germ cell mutations: Occur in sperm/egg. Passed on to offspring. Ex: Down syndrome

23. Cancer Uncontrolled, rapid growth of unspecialized cells.
Can be caused by both genetic and environmental factors.
Tumors are not always cancer (malignant). Some are benign.
A cancer causing agent is called a carcinogen.

24. Carcinoma: A type cancer that can form in epithelial tissue (skin).
Sarcoma: Cancer that can form in connective tissue. (Muscle, bone, etc.)
Leukemia: Cancer that invades blood forming tissue.

25. What is the correct order of Mitosis?
Anaphase—Metaphase—Telophase—Prophase
Anaphase—Metaphase—Prophase—Telophase
Prophase—Metaphase—Anaphase—Telophase
Telophase—Anaphase—Metaphase--Prophase 30

26. Which of the following occur because of mitosis?
A cut will heal
Bacteria will divide
Sperm is produced
Pollen is spread 20

27. UV rays cause DNA to be changed in the skin which results in rapid growth of cells. This could become…
Dermatitis
Eczema
Ringworm
Skin cancer 20

28. Meiosis
Cuts chromosome number in half and creates haploid gametes (sex cells).
Gametes are cut in half—after fertilization you have 46.
Phases are same as Mitosis but they go through them twice.

29. Products of Meiosis
Males: The process of Spermatogenesis produces 4 sperm cells.
Each male produces million sperm/day
2-5 ml of semen is released/ejaculation with million sperm/ml
Infertility occurs with as few as 20 million/ml
Females: The process of Oogenesis produces 1 ovum and 3 polar bodies. In animals—these die. In plants—these form endosperm which nourish the seed until germination.

32. Types of Reproduction
Asexual: Produces exact genetic copies of organisms. No joining of sperm/egg. Occurs in: bacteria and other microbes, hydra, rare in animals.
Sexual: Produces offspring from joining sperm and egg. This can be external or internal fertilization.

33. Why sexual reproduction?
Provides a blending of genes
Too many of the same type of genes causes problems.
Nature ensures that organisms are genetically stronger through sexual reproduction.

34. Genetic Variation
Independent assortment: Chromosomes separate independently of one another. There are about 8 million possibilities.
Crossing-over: Exchange of information between homologues during Prophase I.
Random fertilization: The gametes that join are random and independent.
64 trillion possibilities from one couple.

35. Which of the following is asexual reproduction?
Baby being born
Bacteria dividing
Chicken laying eggs
Pollen being spread 20

36. An organism has 30 chromosomes in their body cells
An organism has 30 chromosomes in their body cells. How many will be in their gametes? 10 15 30 60 20

37. What does meiosis produce?
1 egg and 1 sperm
1 egg and 4 sperm
4 eggs and 1 sperm
4 eggs and 4 sperm 20

38. What is the benefit of sexual reproduction?
To provide a blending of genes
To produce a lot of offspring quickly
To produce clones of organisms
To produce twins and triplets 20

39. Which type of division has more stages?
Binary fission
Meiosis
Mitosis
All have the same 20