1. Cell Division: Mitosis vs. Meiosis
Cell division increases the number of somatic (body) cells or produces the sex cells (gametes).
Development/growth
Repair injured cells
Production of sperm or egg
Karyokinesis is division of nucleus.
Mitosis
Results in two daughter cells
Genetically identical to mother cell
Meiosis
Results in four gametes (sex cells)
Not genetically identical to mother cell
Cytokinesis is division of the cytoplasm.

2. Mitosis
With mitosis you get two identical cells from a parent cell
Precisely replicates DNA
Sends a copy of DNA to each pole of the cell
Separates into two daughter cells

3. Chromatin & Chromosomes
Chromatin: thin strands of DNA & protein that are present in nucleus when cell is not dividing.
Chromosomes: coiled, condensed chromatin (DNA) present during cell division.
Humans have 23 pairs of chromosomes. This means you have 46 chromosomes in every cell of your body except the gametes.
Diploid (2n)= nucleus contains 2 of each type of chromosome
Haploid (1n)= nucleus contains 1 of each chromosome

4. DNA: Chromatin & Chromosomes
Our body cells have 46 chromosomes
Our gametes contain 23
In interphase chromosomes cannot be seen, DNA is in chromatin form
During prophase and throughout mitosis chromosomes are visible

5. Chromosomes Each chromosome consist of two sister chromatids
The two chromatids possess identical copies of the chromosomes DNA and are attached at the centromere

6. The Cell Cycle The cell cycle is the life cycle of a cell.
Most of the cell cycle is spent in interphase.
Three stages of interphase:
G1: after a cell divides into 2, cell grows to mature size; cell doubles organelles & gathers materials needed for DNA synthesis. Many cells (muscle, nerve, bone) never leave G1.
S: DNA replication occurs in this phase
G2: cell makes proteins needed for cell division (like protein needed to make microtubules)

7. Cell Division in Prokaryotes
Bacteria have a single chromosome
Divide by binary fission (asexual reproduction)
Parent cell divides to produce 2 identical daughter cells

8. Mitosis
4 phase of mitosis
Prophase
Metaphase
Anaphase
Telophase

9. Prophase Centrosomes move to opposite ends of nucleus
Nuclear envelope disappears
Nucleolus begins to disappear
Spindle fibers appear between centrosomes
Chromosomes become visible

10. Metaphase Chromosomes attach to spindle fibers at centromere
Chromosomes line up at the metaphase plate (middle of cell)

11. Anaphase Centromeres divide
Sister chromatids separate to become daughter chromosomes
Daughter chromosomes move to opposite poles of cell
Daughter chromosomes = 1 centromere + 1 chromatid
Cleavage furrow begins

12. Telophase Spindle fibers disappear Nuclear envelope reassembles
Chromosomes uncoil to become chromatin
Nucleolus reappears
Cleavage furrow deepens
Cytokinesis continues
Two diploid genetically identical daughter cells form

13. Mitosis in PlaNTS Plant cells have no centrioles
Rigid cell wall prevents cytokinesis by furrowing
Cytokinesis involves formation of a cell plate

14. Results of Mitosis
Two new daughter cells that are genetically identical to the parent. (Chromosomes are identical)

15. Meiosis Form of cell division that halves the number of chromosomes
Forms specialized reproductive cells like the gametes or spores
Requires two sets of cell division (Meiosis I & Meiosis II)
Results in 4 haploid daughter cells genetically different from parent cell
Sperm= 23 chromosomes (haploid)
Egg = 23 chromosomes (haploid)
Fertilization restores diploid number of chromsomes (46)

16. Meiosis: A Source of Genetic Variation
Meiosis scrambles the specific forms of each gene that each sex cell (egg or sperm) receives.
This makes for a lot of genetic diversity. This trick is accomplished through independent assortment and crossing-over.
Genetic diversity is important for the evolution of populations and species.

17. Keys to Understanding Meiosis
9/19/2018
Keys to Understanding Meiosis
Chromosomes are paired.
Chromosomes carry genes.
The gene forms on a pair of chromosomes may be identical ..
Brown eyes
Tall
Brown eyes
Blue eyes
Tall
Short
or different.
G. Podgorski, Biology 1010

18. Meiosis
9/19/2018
One Way Meiosis Makes Lots of Different Sex Cells (Gametes) – Independent Assortment
Independent assortment produces 2n distinct gametes, where n = the number of unique chromosomes.
In humans, n = 23 and 223 ≈ 8,000,000.
That’s a lot of diversity by this mechanism alone.
G. Podgorski, Biology 1010

19. Another Way Meiosis Makes Lots of Different Sex Cells – Crossing-Over
9/19/2018
Another Way Meiosis Makes Lots of Different Sex Cells – Crossing-Over
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.
G. Podgorski, Biology 1010

20. Meiosis
9/19/2018
Between Independent Assortment and Crossing-Over, No Two Gametes Are Identical.
G. Podgorski, Biology 1010

21. Meiosis Following a Single Chromosome Pair
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Meiosis Following a Single Chromosome Pair
Crossing over
G. Podgorski, Biology 1010

22. Meiosis
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The Key Difference Between Mitosis and Meiosis is the Way Chromosomes Uniquely Pair and Align in Meiosis
Mitosis
The first (and distinguishing) division of meiosis
G. Podgorski, Biology 1010

23. Meiosis
9/19/2018
The Key Difference Between Mitosis and Meiosis is the Way Chromosomes Uniquely Pair and Align in Meiosis
Mitosis
The first (and distinguishing) division of meiosis
G. Podgorski, Biology 1010

24. Boy or Girl? The Y Chromosome “Decides”
Meiosis
9/19/2018
Boy or Girl? The Y Chromosome “Decides”
X chromosome
Y chromosome
G. Podgorski, Biology 1010

25. Boy or Girl? The Y Chromosome “Decides”
Meiosis
9/19/2018
Boy or Girl? The Y Chromosome “Decides”
G. Podgorski, Biology 1010

26. Oogenesis – A Path of Meiosis in Humans
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Oogenesis – A Path of Meiosis in Humans
Woman are less busy in meiosis than men – meiosis produces only a few hundred mature eggs over a lifetime.
G. Podgorski, Biology 1010

27. Spermatogenesis – Another Path of Meiosis in Humans
9/19/2018
Spermatogenesis – Another Path of Meiosis in Humans
Men are always doing meiosis, producing roughly 250,000,000 sperm per day.
G. Podgorski, Biology 1010

28. “Putting It All Together” - Fertilization
Meiosis
9/19/2018
“Putting It All Together” - Fertilization
G. Podgorski, Biology 1010

29. Meiosis
9/19/2018
What Meiosis is About
Meiosis allows the creation of unique individuals through sexual reproduction.
G. Podgorski, Biology 1010

30. Mutations
A mutation is any change in the DNA sequence.

31. The chromosome number has been reduced by the END of MEIOSIS I
9/19/2018
The chromosome number has been reduced by the END of MEIOSIS I
Each daughter cell now has only 23 chromosomes (haploid)
G. Podgorski, Biology 1010

33. Mutations in Reproductive Cells
Only in gametes could be passed on to offspring

34. Mutations in Body Cells
Somatic (normal/non-sex cells)
cannot be passed on to offspring

35. Types of Mutations
Gene mutations- changes to a specific gene. (DNA base pairs)
Chromosomal mutations- changes to a portion of the chromosome
Can effect many genes

36. Different Types of Gene Mutations
Point mutation-a change in a single base pair in the DNA.
THE DOG BIT THE CAT
THE DOG BIT THE CAR
THE DOG BAT THE CAR
THE DIG BAT THE CAR

38. Point Mutation

39. Frameshift Mutation
a single base pair is added or deleted, causing a shift in how the strand will be read.
THE DOG BIT THE CAT
THE DO BIT THE CAT
THE DOB ITT HEC AT

40. Chromosome Mutations
Deletion-part of a chromosome is left out.

41. There is a small section of chromosome #5 that has been deleted

42. Insertion-part of a chromatid breaks off & attaches to its sister chromatid.

43. Inversion-part of a chromosome breaks off & reinserts backwards.

44. Translocation-part of one chromosome breaks off & is added to a different chromosome.

45. Karyotype A photographic inventory of an individual’s chromosomes
Chromosomes are arranged in pairs starting with the longest
Used to detect abnormalities in chromosome #

46. Nondisjunction- have an abnormal number of chromosomes
Caused by errors in Mitosis or Meiosis
Most die before birth
Results in either monosomy or trisomy

48. Down’s Syndrome Traits
Down’s Syndrome is an example of nondisjunction
Results from trisomy of the 21st pair of chromsomes (3 chromosomes)
Mental retardation, short stature, heart defects, most are sterile, and other problems

49. There is an extra chromosome on the 21st pair
Down’s Syndrome
There is an extra chromosome on the 21st pair

50. Abnormal Sex Chromosome Numbers
Klinefelter syndrome : extra X sex chromosome (XXY)
male sex organs but sterile(testes small)
Breast enlargement with other female characteristics
Turner syndrome: missing X sex chromosome (XO)
Short stature, web of skin extending between neck & shoulders
Sterile with immature sex organs
Poor development of breast and secondary sex characteristics

51. Turner’s Syndrome Traits
Turner’s Syndrome occurs only in females
Results from monosomy X
People with syndrome are sterile
Secondary sex characteristics don’t develop

52. What causes mutations? spontaneous mistakes environment
any agent that can cause a change in DNA is called a mutagen. (x-rays, UV light, asbestos)

53. DNA Repair
enzymes in our cells remove the incorrect nucleotides & replace them with the right ones.
this works well, but is not perfect