SBI4U (AP Biology) - Molecular Genetics Summary/Test Review
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Course
Biology
Institution
12th Grade
This test review + free Quizlet summarizes the key concepts of biochemistry, as covered by the AP Biology/Ontario Grade 12 Biology curriculum. Some topics it deals with include transcription, translation, basic DNA properties, regulation of gene expression (operons, etc.), biotechnology and more!
Molecular Genetics - Unit Test Review (Quizlet here)
Chapter 16 (Molecular Basis of Inheritance)
1. Introduction to DNA
Deoxyribonucleic Acid: A double-stranded polymer made of nucleotides. The
phosphate group/deoxyribose sugar form DNA’s backbone, with nitrogenous
bases acting as DNA’s ‘rungs’. Adenine + guanine are purines (2 rings), and
cytosine + thymine (or uracil in RNA) are pyrimidines (1 ring)
DNA Structure: DNA strands are antiparallel and have a 5’ (phosphate) and 3’
(hydroxyl from sugar) end - nucleotides are 0.34 nm apart and one turn of the helix
consists of 10 nucleotides
DNA Bonding: The bonds between bases are hydrogen bonds (2 between A/T, 3
between C/G), and nucleotides are linked by phosphodiester linkages (where 1
phosphate creates 2 ester bonds w sugars)
, 2. Important Scientists
Scientist(s) Experiment/Discovery
Frederick Griffith mixed heat-killed pathogenic cells with harmless living cells, and some
Griffith living cells became pathogenic - this meant genetic material could be transferred
(even from dead cells!) through transformation
Alfred Hershey + They labelled the DNA of a T2 bacteriophage with phosphorus and its protein
Martha Chase coat with sulfur, and only found the phosphorous inside infected E-coli cells - this
meant that the injected DNA provided genetic information (at least for this
specific bacteriophage)
Erwin Chargaff Chargaff found that the composition of DNA (levels of each base) varied from one
species to the next - this supported the idea that DNA was genetic material since
it explained differences between species! He also found that there were equal
numbers of complementary bases (A + T and G + C) in DNA (Chargaff’s rule)
Franklin, Franklin used X-ray crystallography to produce the first picture of a DNA
Wilkins, Watson molecule, which Wilkins gave to Watson and Crick who figured out the structure
and Crick of DNA - they also realized that A was paired with T and C was paired with G (this
provided a uniform width for the molecule), explaining Chargaff’s rule
3. Models of DNA Replication
Conservative: The entire DNA double helix is somehow used as a template to
make another complete helix
Semiconservative: The DNA helix’s strands are split, and each individual strand
acts as a template for the complementary strand - each daughter molecule
contains one template strand and one new strand (this was Watson and Crick’s
model)
Dispersive: The new DNA helix is a hybrid of template and daughter DNA, with
bits of both on each strand
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