BIOL 110 UNIT 3

Mitosis, Meiosis, Chromosomal Abnormalities

Mitosis: A process of cell division that results in two genetically identical daughter cells, crucial for growth and tissue repair.
Meiosis: A specialized form of cell division occurring in germ cells, leading to the production of gametes with half the chromosome number of the parent cell.
Chromosomal Abnormalities: Variations in the normal structure or number of chromosomes, which can lead to genetic disorders such as Down syndrome (trisomy 21) and Turner syndrome (monosomy X).

1. What is a zygote?
The first cell of an organism formed after fertilization.

2. How many cells are in the human body approximately?
About 100 trillion.

3. What types of cells divide by mitosis?
Somatic (body) cells.

4. What types of cells do NOT divide by mitosis?
Sex cells (gametes).

5. What are the three reasons cells divide?
Growth, repair, replacement.

6. What is the Hayflick limit?
Normal cells can divide about 50 times before stopping.

7. What are the three stages of interphase?
G1, S, G2.

8. What happens during G1?
Cell grows and performs normal functions.

9. What happens during the S phase?
DNA replicates.

10. What happens during G2?
Final preparation for mitosis.

11. What happens during prophase?
Chromosomes condense, spindle fibers form, nuclear envelope breaks down.

12. What happens during metaphase?
Chromosomes line up in the middle of the cell.

13. What happens during anaphase?
Sister chromatids separate and move to opposite poles.

14. What happens during telophase?
New nuclei form and chromosomes uncoil.

15. What is cytokinesis?
Division of the cytoplasm into two cells.

16. How does cytokinesis differ in plant vs. animal cells?
Animals: cleavage furrow.
Plants: cell plate.

17. What are cell cycle checkpoints?
Points that ensure the cell is healthy before moving to next stage.

18. What is G0?
A resting phase where cells stop dividing.

19. What are telomeres?
Protective caps at chromosome ends that shorten each division.

20. What does telomerase do?
Rebuilds telomeres (active in stem/cancer cells).

21. What type of reproduction uses mitosis?
Asexual reproduction.

22. What type of reproduction uses meiosis?
Sexual reproduction.

23. What is the chromosome number of human germ cells?
Diploid (46 chromosomes, 23 pairs).

24. What is the chromosome number of human gametes?
Haploid (23 unpaired chromosomes).

25. What happens to gametes at fertilization?
Fuse to form a diploid zygote (46 chromosomes).

26. How many rounds of division occur in meiosis?
Two (Meiosis I and Meiosis II).

27. What is separated in Meiosis I?
Homologous chromosomes.

28. What is separated in Meiosis II?
Sister chromatids.

29. How many cells are produced after meiosis?
Four.

30. Are the cells identical or different?
All genetically unique.

31. What is crossing over?
Exchange of DNA between homologous chromosomes in Prophase I.

32. What does crossing over create?
Genetic variation.

33. What is independent assortment?
Random arrangement of homologous chromosome pairs during Metaphase I → variation.

34. Where does independent assortment happen?
Metaphase I and Anaphase I.

35. How many chromosome pairs do humans have?
23 pairs (46 total).

36. What is a chromosomal duplication?
A region of a chromosome is copied twice.

37. What is a chromosomal deletion?
A region of a chromosome is lost.

38. What is a chromosomal inversion?
A region flips around in orientation.

39. What is a chromosomal translocation?
A piece of one chromosome attaches to another chromosome.

40. What is polyploidy?
Having three or more copies of every chromosome set (e.g., triploidy).

41. What is aneuploidy?
Having too many or too few of one chromosome (e.g., trisomy 21).

42. What causes aneuploidy?
Nondisjunction.

43. What is nondisjunction?
Failure of chromosomes to separate properly during meiosis.