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Chapter 5


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York University
Administrative Studies
ADMS 1000

BIOL 1500 CHAPTER 5 {DNA, GENE EXPRESSION, AND BIOTECHNOLOGY} MAY 27, 2012 C HAPTER NOTES … 5.2  Deoxyribonucleic Acid (DNA) is a macromolecule that stores information o Nucleotidemolecule of sugar, a phosphate group, and a nitrogen-containing molecule called a base  Double helix o Two sugar-phosphate strands spiral forming the backbone of DNA o Bases attached to the sugar molecules bond to those other attached to the other strand to form the rungs  Sugar is always deoxyribose and the phosphate molecule stays the same  Adenine & Thymine connect with 2 hydrogen bonds  Guanine & Cytosine connect with 3 hydrogen bonds 5.3  DNA is the universal code for all life on earth, embodying the instructions for building the cells and structures for virtually every single living cell  The full set of DNA in an individual organism is called its genome o In prokaryotes the information is contained within circular pieces of DNA o In eukaryotes the information is contained within linear longer strands of DNA in the nucleus- chromosomes o Humans have 46 chromosomes and 6 billion base pairs in every cell o A gene is a sequence of base pairs in a DNA molecule carrying information to make proteins  The alternative versions of a gene that code for the same feature are called alleles o Any single characteristic or feature of an organism is referred to as a trait  Trait= eye colour  Allel= blue 5.5 Two birds, one with white feathers and another with red feathers mate. The offspring has red feathers and one gene for white feathers and one gene for red feathers. What is the genotype of the baby bird? Red and whiteare the genes an organism carries What is the phenotype of the baby bird? Redwhat you see and how you perceive the trait BIOL 1500 CHAPTER 5 {DNA, GENE EXPRESSION, AND BIOTECHNOLOGY} MAY 27, 2012 5.6 Transcription  Single copy of one specific gene within the DNA is made  Like copying a single recipe from the cookbook onto an index card 1. Recognize and bind a. A large molecule, the enzyme RNA polymerase binds to the DNA molecule at the promoter site, unwinding to allow reading of one strand of DNA 2. Transcribe a. As DNA strand is processed through the RNA polymerase it builds a copy-a transcript of the gene from the DNA molecule b. This copy is called messenger RNA (mRNA) as after creation it can move elsewhere in the cell and its message translated into a protein i. mRNA is constructed from four different molecules called ribonucelotides ii. each ribonucleotide pairs with an exposed base iii. thymine – adenine iv. adenine – uracil v. guanine – cytosine vi. cytosine – guanine 3. Terminate a. As RNA polymerase encounters the termination site, it stops transcription and releases the mRNA transcript 4. Capping and Editing a. In most eukaryotes the transcript must first be edited. A cap and tail are added to protect the mRNA from damage, and help the protein making machinery recognize the mRNA. Non- coding bits of DNA-introns- are snipped out. It then leaves the nucleus and into the cytoplasm 5.7 Translation  The information carried by the mRNA is read and are used to produce a protein. The following must be present in the cytoplasm for translation to occur: o Must be large amounts of free floating amino acids o Ribosomal subunits where amino acids are linked together in the proper order to produce the protein BIOL 1500 CHAPTER 5 {DNA, GENE EXPRESSION, AND BIOTECHNOLOGY} MAY 27, 2012 o Transfer RNA (tRNA) interpret the mRNA code and link specific base sequences on the mRNA with specific amino acids  Attachment sites consist of a base sequence that matches up with a three-base sequence on the mRNA transcript. Each three-base sequence, a codon, matches with a tRNA that carries one particular amino acid 1. Recognize and initiate protein building a. The start sequence of the mRNA transcript – “A, U, and G” is recognized by a corresponding tRNA molecule and the two ribosomal subunits. The ribosomal subunits assemble around them b. Methionine corresponds to the AUG codon, and is the initiator tRNA molecule 2. El
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