BIOLOGY 154 Lecture Notes - Lecture 2: Guanine, Cytosine, Chromosome
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15 Sep 2016
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2 Molecular Biology
Genome
●the complete set of genes or genetic material in a cell or organism
●how life stores information
DNA
●molecule that carries genetic information for most of life
○only exception is viruses
●composed of four different chemical units called nucleotide bases
○adenine
○guanine
○cytosine
○thymine
○A-T and C-G pairs
●sequence and pattern of DNA bases carries genetic information
○nucleotide bases linked together by enzyme DNA polymerase
●two DNA strands twist around each other to form double helix
Proteins
●make up all the structural parts of life
●machinery that gets everything done
○making more DNA
●a life form is mostly protein and water
●genes are coding units for proteins
Roles of DNA in cell
1. Replication
a. used as template to make more DNA
b. inheritance
c. DNA replication generates mutations
c.i. leads to vaccine and drug challenges
c.ii. HIV does it differently than we do
c.ii.1. opportunities for new drug targets
2. Transcription
a. used to make an RNA copy of its genetic information (not make RNA)
b. make functional, non-coding molecules
Note
●Both replication and transcription depend on complementarity
○complementarity is the chemical affinity between bases such that the most stable
chemical form of a DNA double is is A-T and C-G
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●DNA replication consists of enzymes (proteins) splitting apart the double helix and then using
the pattern of bases as a template to create the other strand
○old strand used as template
○if sequence of one strand of the DNA double helix know, then can predict the
complementary strand
○end up with two helices from one helix
Polymerase Chain Reaction (PCR)
●PCR uses complementary base pairs and DNA replication to isolate and amplify specific DNA
sequences
●Pull out specific gene / DNA sequence from a very small source (hair or drop of blood)
○can be used to find the very small amounts of HIV genome that is present in an infected
person’s blood
●PCR is multiple rounds of DNA replication
○melts the helix apart at high temperature
■becomes single stranded
○cool so primer starts replication in the area of interest
■primer is the “hook” that is complementary to piece of DNA that you want to
pull out
■taq polymerase extends
○allow extension of new complementary strand until you have a new double stranded
region
○melt and start all over again until amplified the region millions of times
●Primer 1 and 2 for each strand and copies only in between where the two primers are
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