Lecture outline (pages 294-317)

DNA ----> RNA ----> protein

• Transcription
  • an RNA copy is made of the DNA template strand through the process of transcription
  • RNA (ribonucleic acid) differs from DNA- ribose instead of deoxyribose of DNA, four bases of RNA are adenine, cytosine, guanine, and uracil (uracil is used instead of thymine)
  • RNA polymerase separates DNA strands, then hooks together RNA nucleotides to make an RNA copy of the DNA template strand
  • transcription moves from the promoter to the terminator
  • completed RNA copy=transcript, or messenger RNA (mRNA)
  • messenger RNA is processed by addition of a 5' cap and a 3' poly (A) tail, and may be spliced to remove introns
• Translation
  • messenger RNA is translated into protein
  • messenger RNA carries information from the nucleus to the ribosomes
  • transfer RNA (tRNA) brings amino acids to the ribosomes
  • ribosomes are made of RNA (ribosomal RNA) and protein
  • ribosomes are the sites of protein synthesis in the cell, and each ribosome consists of a small subunit and a large subunit
  • during translation, the ribosome moves along the messenger RNA molecule, reading each triplet codon (triplet codon= a sequence of three bases that encodes a specific amino acid), and adding amino acids one by one to a growing chain of linked amino acids
  • start codon=AUG
  • stop codon=UAA, UAG, or UGA
  • release factor allows the ribosome/RNA complex to dissociate when a stop codon is reached
• Some types of proteins in cells
  • structural
  • transport
  • contractile
  • defensive
  • emzymatic
• Some genetic diseases
  • Tay-Sachs disease- caused by a mutation in a gene encoding and enzyme required to break down certain lipids
  • Sickle cell disease- caused by a mutation in the gene encoding hemoglobin
  • Cystic fibrosis- caused by a mutation in a gene encoding a membrane protein that functions in chloride ion transport

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