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Gene Organization & Chromosome Structure.

Section 5.8: Nelson Biology 12: Pages 266-267. Gene Organization & Chromosome Structure. . Chromosomes. In the nucleus, the human genome is organized into chromosomes . Chromosomes consist of a complex of protein & DNA called chromatin . Chromosomes.

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Gene Organization & Chromosome Structure.

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  1. Section 5.8: Nelson Biology 12: Pages 266-267 Gene Organization & Chromosome Structure.

  2. Chromosomes • In the nucleus, the human genome is organized into chromosomes. • Chromosomes consist of a complex of protein & DNA called chromatin.

  3. Chromosomes • If the nucleotides of all chromosomes in a genome could be stretch out in one long double helix, they would measure 1.8 meters in length. • An individual nucleus is only 5 micrometers (micrometers = one millionth of a metre!) • So, DNA has to be very carefully intertwined to fit in the minute space of a cell’s nucleus!

  4. DNA is ORGANIZED HIERARCHICALLY • 1. Every 200 nucleotides, the DNA is coiled around a core group of eight stabilizing proteins known as histones.

  5. Histones & Nuclesomes • The positively charged histones are STRONGLY attached to the negatively charged DNA. • The complex of histones enveloped by coiled DNA is called a nucleosome.

  6. DNA is ORGANIZED HIERARCHICALLY • 2. A series of nucleosomes coil into chromatin fibres. • 3. Lastly, these chromatin fibres fold into the final chromatin structure by means of a higher level of coiling. • Supercoiling!!

  7. Human Chromosomes • Humans: • 46 chromosomes • 23 pairs (23x2 = 46 total) • 44 (22 pairs) = somatic chromosomes • 2 (1 pair) = sex chromosomes. • Chromosomes vary in size and have been numbered 1 – 22, according to their size. • Chromosome #1 = largest

  8. Wow! So much non-coding! • Only a fraction of the human genome is known to code for specific proteins. • Currently, we estimate that 42,000 genes exist within a very small percentage of DNA coding for proteins. • More than 95% of the human genome is noncoding!!

  9. Variable Number Tandem Repeats • Non coding regions are filled with variable number tandem repeats (VNTRs), also known as microsatellites. • These are sequences of base pairs that repeat over and over again. • “TAGTAGTAGTAGTAG...” • These sequences vary among individuals. • Length of microsatellites • Position of microsatellites

  10. Telomeres • The ends of chromosomes have long sequences of repetitive non-coding DNA, known as telomeres, that protect cells from losing valuable genomic material during DNA replication.

  11. Pseudogenes • The genome also contains pseudogenes. • A pseudogene has a nucleotide sequence similar to a functioning gene but does not seem to express any RNA or protein.

  12. Two Types of Psuedogenes • Type #1: LINEs • LONG • INTERSPERSED • NUCLEAR • ELEMENTS • Type#2: SINEs • SHORT • INTERSPERSED • NUCLEAR • ELEMENTS • The function of LINEs & SINEs is not clear.

  13. Wow! • In the last century, we have discovered a great deal about the human genome, but we are still only scratching the surface. • In the next chapter, biotechnological techniques are discussed that promise to reveal even more about the structure, function and organization of our genome and its relationship to normal and abnormal physiological development.

  14. HOMEWORK: Page References: Section 5.8 - Mutations (Pages 266-267) Homework: Page 267 # 2, 3

  15. DON’T UNDERSTAND EVERYTHING? Check This Out! Chromosomal Structure: http://www.dnatube.com/video/47/3D-structure-of-chromosome The Human Genome Project: http://www.genome.gov/10001772

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