Cell division and dna


Published on

Published in: Education
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Cell division and dna

  1. 1. Chapter 8 Cell DivisionBy Mr. “4 weeks” Chapman
  2. 2. Cell Division What is cell division? Is how a cell reproduces, makes a copy of itself. Is how living things grow and make sex cells.
  3. 3. Why do we need new cells??? Need new cells to grow, repair scratches and tears (scar).
  4. 4. Cell Division 2 Types of Cell Division 1. Mitosis – process of making new somatic (nonsex) cells like skin cells (clones).
  5. 5. Cell Division 2. Meiosis – process of making new sex cells (gametes) like sperm and egg (23 chromosomes).
  6. 6. Nucleic Acid 2 types of Nucleic Acids: 1. DNA 2. RNA
  7. 7. Nucleic Acids Function of DNA – Store and transmit hereditary information DNA – Deoxyribose nucleic acid Has 2 strands
  8. 8. DNA Structure DNA is made out of 2 long chains of nucleotides. 4 Types of nucleotides:  Adenine (A)  Guanine (G)  Cytosine (C)  Thymine (T)
  9. 9. Structure of Nucleotides Nucleotides are made out of 3 molecules: 1. deoxyribose – sugar molecule 2. phosphate group – contains phosphate (P)
  10. 10. Nucleotide Structure 3. Nitrogen base – contains nitrogen (N)  Adenine (A)  Guanine (G)  Cytosine (C)  Thymine (T)
  11. 11. Nucleotide
  12. 12. DNA The DNA molecule model was proposed by James Watson and Francis Crick.
  13. 13. Double Helix Complementary Base Pairing: certain bases always pair with each other  A with T  G with C
  14. 14. DNA Replication Replication of DNA: DNA unwinds and Helicase (enzyme) breaks apart the 2 strands. Each strand serves as a template for the new DNA
  15. 15. DNA Replication DNA polymerase: (enzyme) that adds nucleotides to each strand of DNA. Many polymerases attach at the same time.  On a fruit fly DNA replication starts at 6,000 different places
  16. 16. DNA Replication According to the base pairing rules, what would the new stand of DNA be if the original strand was A – T – T – C – C- G
  17. 17. DNA Replication Accuracy and Repair DNA is copied with a high degree of accuracy Mutation: change in the nucleotide sequence of DNA; it can have serious effects on the organism.  Can be harmful or beneficial
  18. 18. DNA Replication Environmental factors can damage DNA  Ex. Ultraviolet radiation from the sun, enzymes work to repair the damaged DNA What do you think would happen if the repair enzymes weren’t working properly?
  19. 19. Cell Division Now you know what DNA is…… how does the cell organize DNA for Mitosis.
  20. 20. Cell Division Chromosomes – tightly coiled  Strands of DNA wrap packages of DNA; they are rod around proteins called shaped and proteins hold them Histones. together.
  21. 21. Cell Division Chromatid – half of a chromosome; forms as DNA copies itself before cell division Centromere – holds the chromatids together until they separate
  22. 22. Important Words  How many chromosomes do humans have? Each species has a unique number of chromosomes.  46 chromosomes or 23 pairs.
  23. 23. Types of Chromosomes 2 Types of Chromosomes: 1. Sex Chromosomes – are the chromosomes that determine the sex of an organism. Female: XX Male: XY 2. Autosomes – all other chromosomes  Humans: 44 autosomal chromosomes
  24. 24. Chromosomes Homologous chromosomes – two copies of each autosome (maternal and paternal) Homologous chromosomes are the same size, shape, and carry genes for the same trait.
  25. 25. Chromosomes Karyotype – is a picture of the chromosomes in a dividing cell. 22 homologous pairs of autosomes. 2 sex chromosomes
  26. 26. Chromosomes Diploid (2n)– cells have two sets (maternal and paternal) of chromosomes.  Has all 46 chromosomes. Haploid (n)– cells have one set of chromosomes.  Has 23 chromosomes.  Gametes
  27. 27. Chromosomes Examples of haploid cells? Gametes - sperm and egg cells; they have 23 chromosomes Fertilization 23 in sperm + 23 in egg = 46
  28. 28. Cell Division Where do new cells come from? All cells came from preexisting cells. Why do cells divide? 1. Increase Cell volume 2. Growth 3. Repair tissue and organs 4. Reproduce
  29. 29. Cell Division Prokaryotes – cell division by:  Binary Fission  DNA copied, cell grows, cell splits in two. Eukaryotes – cell division by 2 ways: Mitosis  new cells have identical genetic material; produces clones. Meiosis  reduces chromosome number in half, makes sex cells (gametes).
  30. 30. Cell Cycle The Cell Cycle – a repeating set of events that make up the life of a cell. There are 3 steps to the cell cycle.
  31. 31. Cell Cycle 1. Interphase – the longest phase, in between cell division  G1 phase – growth of cell  G0 phase – inactive stage.  S phase – DNA is copied (“S” synthesis of DNA)  G2 phase – growth of cell; prepares for cell division *G0 phase – non dividing state after the G1 phase;  Ex. Many cells in human body – nervous system cells
  32. 32. Mitosis 2. Mitosis – division of the nucleus; a continuous process divided into 4 phases  1. Prophase  2. Metaphase  3. Anaphase  4. Telophase 3. Cytokinesis – division of the cytoplasm  The chromosomes start to uncoil and become less dense  Two new, identical cells are formed
  33. 33. G1 phaseM phase S phase G2 phase
  34. 34. Cell Mitosis (M Phase) The many stages of the cell life cycle can be seen in the image to the right The process of cell reproduction includes prophase, metaphase, anaphase, and telophase
  35. 35. Mitosis 1. Prophase Chromosomes appear The nucleolus disappears The nuclear membrane begins to break down
  36. 36. Mitosis 2. Metaphase Chromosomes align along the equator of the cell Spindles Fibers that are attached to the poles connect to the centromeres
  37. 37. Mitosis 3. Anaphase Chromosomes are pulled to the pole by the contraction of the spindle fibers Sister chromatids are separated at the centromere
  38. 38. Mitosis 3. Anaphase (Late) Chromosomes begin to congregate at the poles.
  39. 39. Mitosis 4. Telophase The new cell wall begins to form so the two cells can separate The chromosomes begin to form a nucleus. See cleavage (animal) and Cell plate (plant) cells.
  40. 40. Cytokenisis
  41. 41. What are the phases?Interphase Prophase Prometaphase
  42. 42. What are the phases? Anaphase Telophase/Metaphase Cytokenisis
  43. 43. What stage of Mitosis?
  44. 44. DNA (Double Helix) Transcription – process of turning DNA into RNA Translation – process of using RNA to make protein. DNA has 2 strands RNA has 1 strand.