Gene And Chromosomes


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Gene And Chromosomes

  2. 2. Key vocabulary  Nucleoid/ nucleosomeNucleoid/ nucleosome  ChromatinChromatin  Scaffold proteinScaffold protein  Histone/ non histoneHistone/ non histone  CentromereCentromere  TelomereTelomere  KaryotypingKaryotyping
  3. 3. Organization  Highly dependent on the type of org.Highly dependent on the type of org.  Prokaryotic vs Eukaryotic org.Prokaryotic vs Eukaryotic org.  Different technique used to visualise.Different technique used to visualise.
  4. 4. Precise location   Such a compact space. Question arises on how key activities inSuch a compact space. Question arises on how key activities in protein synthesis can take place within this limited space.protein synthesis can take place within this limited space.
  5. 5. Closer view..
  6. 6. Chromatin Chromosome discovered by W. Waldeyer. Euchromatin –Fibers less packed, disperse–Fibers less packed, disperse appearance occupying most of the nuclearappearance occupying most of the nuclear region.region. Heterochromatin- More dense area, found atMore dense area, found at centromeres.centromeres.
  7. 7. Chromosome number. Diff. org = diff. no.  Man 23 pairs =Total 46.  22 pairs of autosomes  2 sex chromosomes.  Cht. size shape + pattern,  Numbered in order of size. Different cell diff number eg. Liver cells 92.
  8. 8.  Varies among species.Varies among species.  Unrelated to the size or biological complexityUnrelated to the size or biological complexity of an org.of an org.  An asian deer = 3.An asian deer = 3.  Diploid – 2 of the chromosome in a set.Diploid – 2 of the chromosome in a set.  Tetraploid – 4 of each chr.Tetraploid – 4 of each chr.  Octaploid – 8 of each chr.Octaploid – 8 of each chr.
  9. 9. G-bands  Certain Tx/ staining techniques (Eg. Giemsa)Certain Tx/ staining techniques (Eg. Giemsa) will allow chromosomes to have striations.will allow chromosomes to have striations.  Large structures containing approx 10Large structures containing approx 1077 bp DNAbp DNA  chromosomes can be id by cht. bandingchromosomes can be id by cht. banding pattern- Used for karyotyping –pattern- Used for karyotyping –  Translocations can be id. by comparing to theTranslocations can be id. by comparing to the original diploid set.original diploid set.
  10. 10. Homologous pairs..Homologous pairs..
  11. 11. Homologous contd..  Notice that the size, order of bands, and shape is the same for both chromosomes.  Carry the same genes in the same order.
  12. 12. Human chromosomes..
  13. 13. Human Karyotype Sex chromosomes
  14. 14. Chromosomes and genes..  The dark lines represent bands.  Each chromosome, bears a particular set of genes, these genes are arranged in a specific order.
  15. 15. Typical metaphase chromosome i.i. Contains a DNA replication origin  ii. A centromere to attach the DNA to the mitotic spindle.  iii. A telomere located at the end.  DNA needs to be condensed.  Chromosomes with AT/ GC base pair specific dyes. When stained.  Mitotic chromosomes have a banded structure . ? Methaphase and not other stages?
  16. 16. Basic units of a chromosome  i.  i.  DNA (2.2m = Massive folding + coiling)  ii. Proteins (Histones, scaffold p, polymerase)  iii.Small amounts of RNA.
  17. 17.  Complex between histones + DNA = chromatin.  Nucleosome = basic structure of chromatin (beaded appearance)  Scaffold protein = non-histone p. Nucleosome coils aound it.  Polymerases = enzymes involved with a)transcription of the gen. information during protein synthesis b)replication of the DNA prior to the division of chromosomes.
  18. 18. Nucleosome..  Contains 200 bp DNA.Contains 200 bp DNA.  Subunit of chromatinSubunit of chromatin composed of short DNAcomposed of short DNA wrapped around histonewrapped around histone  8 histone molecules =8 histone molecules = octamer.octamer.  Nucleosome fibre is tightlyNucleosome fibre is tightly coiled and looped aroundcoiled and looped around non-histone proteinsnon-histone proteins  Nucleosomes are packedNucleosomes are packed together = compact.together = compact.
  19. 19. Placement of genes  Gene = A region of DNA Gene = A region of DNA  that that controls hereditary  info   specifiying the  sequence of a particular  protein. .   Carries biological info Carries biological info  that must be copied and that must be copied and  transmitted to its transmitted to its  progeny.progeny.  Can be as short/long.Can be as short/long.  2001: 30,00/40,000 2001: 30,00/40,000  genes.genes.
  20. 20.  Color BlindnessColor Blindness  Muscular DystrophyMuscular Dystrophy  Fragile X syndromeFragile X syndrome  HemophiliaHemophilia