chapter 6 chromosomes and cell reproduction l.
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Chapter 6 Chromosomes and Cell Reproduction - PowerPoint PPT Presentation


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Chapter 6 Chromosomes and Cell Reproduction. Section 6-1. Cell division (cell reproduction) Occurs in humans and LT at diff times in their life Formation of gametes (egg/sperm) involves special types of cell ÷ (this will be covered in chapter 7) When cells ÷, DNA is 1st copied and then ÷.

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slide2

Section 6-1

  • Cell division (cell reproduction)
  • Occurs in humans and LT at diff times in their life
  • Formation of gametes (egg/sperm) involves special types of cell ÷ (this will be covered in chapter 7)
  • When cells ÷, DNA is 1st copied and then ÷
slide3

Section 6-1

  • Prokaryotic (Bacteria) Cell Reproduction:
  • Binary fission:
  • Form of asexual reproduction in bacteria cells that produces identical offspring
  • Binary fission occurs in 2 stages: 1st, DNA is copied, then cell ÷, eventually the ÷ prokaryote is pinched into 2 independent cells
slide4

Section 6-1

  • Eukaryotic Cell Reproduction:
  • Gene: piece of DNA that codes for a protein or RNA
  • As eukaryotic cell prepares to ÷, DNA and proteins associated w/ DNA coil into chromosomes
  • Chromatids: 2 exact copies of DNA that make up each chromo
  • Centromere: where 2 chromatids of chromo are attached
slide5

Section 6-1

  • Homologous chromosomes: chromo similar in size, shape, genetic content
  • Each homologue in a pair of homologous chromosomes comes from 1 of the 2 parents
  • 46 chromosomes in human somatic (body) cells are actually two sets of 23 chromosomes (23 from mom, 23 from dad)
  • Diploid: cell w/ 46 chromo (23 from mom, 23 from dad)
  • Haploid: cell w/ only 23 chromo, such as gametes
  • Zygote: fusion of 2 haploid gametes (fertilization) to form 1 diploid fertilized egg cell (mom’s 23 w/ dad’s 23 = 46)
slide6

Section 6-1

  • Autosomes: chromo not directly involved in determining sex (gender) of an individual; pairs #1-22
  • Sex chromosomes: 1 pair of chromo in humans, contain genes that determine sex of individual; pair #23 referred to X and Y; XX = female, XY = male
slide7

Section 6-1

  • Change in Chromo #:
  • Humans missing 1 of 46 chromosomes usually don’t survive
  • Trisomy: more than 2 copies of a chromosome, will not develop properly; 3 copies of #21= Down’s Syndrome
  • Karyotype:photo of chromo in a dividing cell showing chromo arranged by size
slide8

Section 6-1

  • Change in Chromo Structure:
  • ∆ in organism’s chromo structure are mutations
  • Breakage of chromo can lead to 4 types of mutations:
  • 1. deletion mutation: piece missing
  • 2. duplication mutation: piece added
  • 3. inversion mutation: piece turned upside down
  • 4. translocation mutation: piece from chromo is put on a different chromo
slide9

Section 6-2

  • Cell Cycle:
  • Repeating sequence of cellular growth/÷ during life of organism
  • Interphase:
  • 1st 3 phases of cell cycle, 90% of cell’s time is in this phase
slide10

Section 6-2

5 Phases of Cell Cycle:

1. 1st growth (G1) phase: cell grows rapidly and carries out routine functions

2. Synthesis (S) phase: DNA is copied

3. 2nd growth (G2) phase: preparations made for nucleus to ÷

4. Mitosis: nucleus of cell ÷ into 2 nuclei

5. Cytokinesis: cytoplasm ÷

slide11

Section 6-2

  • Control of Cell Cycle:
  • Checkpoints at which feedback signals from cell can trigger or delay next phase of cell cycle
  • 1. Cell growth (G1) checkpoint makes decision of whether cell will ÷
  • 2. DNA synthesis (G2) checkpoint DNA replication is checked by DNA repair enzymes
  • 3. Mitosis checkpoint triggers exit from mitosis
slide12

Section 6-2

  • When Control Is Lost: Cancer!
  • If a gene that controls cell growth/÷ is mutated, then regulation of cell growth/÷ can be disrupted = cancer and uncontrolled cell growth results!

Bladder cancer

slide13

Section 6-3

  • Mitosis - Division of the Nucleus in 4 phases:
  • 1. Prophase: Nuclear envelope dissolves; spindle forms
  • 2. Metaphase: Chromo move to center and line up along the equator
  • 3. Anaphase: Centromeres ÷; chromo move to opposite ends of cell
  • 4. Telophase: Nuclear envelope forms around chromo at each pole; Mitosis is complete
slide14

Section 6-3

  • Cytokinesis – Division of the Cytoplasm:
  • As mitosis ends, cytokinesis begins
  • Cytoplasm of cell ÷ in 1/2, cell membrane grows to enclose each new cell, forming 2 separate genetically identical cells from 1 cell