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Final

EBIO 1210 Study Guide - Final Guide: Dna Replication, Messenger Rna, Central Dogma Of Molecular Biology


Department
Ecology & Evolutionary Biology
Course Code
EBIO 1210
Professor
barbra
Study Guide
Final

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III. Major Topic #3: DNA and its replication
Topic III.A.: The structure of the DNA molecule
Learning Goals for this topic:9
22. Know the basic structure of DNA in terms of the three fundamental building blocks
(nitrogenous base, five-carbon sugar, phosphate group), and how those building blocks
go together to make a polymer.
a. DNA is a double stranded molecule
b. The two strands are complementary, and together wind around to form a
double helix
c. A nucleic acid is a polymer made of nucleotide monomers
d. nucleotide consists of a sugar, nitrogenous base and a phosphate group
e. The base is what varies
f. The sequence of nucleotides with different bases is what forms the code
containing all hereditary information
g. The sugar and phosphate groups are the SAME for all nucleotides
h. There are only four nitrogenous bases & four possible nucleotides
23. Know how hydrogen bonds hold a DNA molecule together and how the pattern of
hydrogen bonding gives rise to Chargaff’s rule.
a. % of Adenine (A) = % of Thymine (T)
b. % of Guanine (G) = % of Cytosine (C)
c. DNA has a sugar-phosphate backbone
d. Around the outside of a double stranded molecule
e. With nitrogenous bases arranged in the middle
f. The phosphate group in a single nucleotide is attached to the 5’ carbon
atom of the sugar
g. Adjacent nucleotides are linked phosphate to 3’ carbon atom. This forms
the “backbone”
h. Antiparallel arrangement allows proper base pairing
24. Understand what is meant by the polarity of a DNA molecule (5’ vs. 3’ ends), and
why we say that two strands of a DNA molecule run “antiparallel” to one another.
a. antiparallel arrangement allows for proper base pairing
b. adjacent nucleotides are linked to 3’ carbon atom, which forms the “backbone”
Topic III. B.: DNA replication
Learning Goals for this topic:
25. List the basic steps that must be accomplished in order to replicate DNA.

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a. Parent molecule → separation of strands → “Daughter” DNA molecules,
each consisting of one parental strand and one new strand,
complementary to template strand
b. During replication:
i. The two strands in the original molecule separate, with each
serving as a template for a newly synthesized strand
ii. EX: Suppose a cell has 6 chromosomes. At the beginning of G1
phase, 6 DNA molecules are present in this cell. At the beginning of
G2 phase, 12 DNA molecules are present in this cell.
C. Helpful to know how Interphase and DNA Replication work simultaneously at
each stage
26. Describe how the DNA molecule itself acts as a “template” for accurate replication.
a. before Replication of DNA template is possible, need:
i. Origin of replication: bubble where DNA replication happens
II. Helicase- unzips the helix
iii. Topoisomerase- relieves tension of the unwinding helix
Iv. RNA Primer, Primase- RNA primer needs to be in place before copying
begins
V. DNA polymerase- enzyme used for copying the template strand,
replaces RNA primer with DNA
VI. Semiconservative model of replication- each replicated double helix
contains one original template
b. DNA Polymerases
c.
i. Match the right monomers with the template
ii. Catalyze formation of new sugar-phosphate bonds
iii. Add 50 (eukaryotes) to 500 (bacteria) bases per second
d. DNA Polymerase “reads” the parental template from 3’ to 5’
e. and adds 5’ to 3’
f. DNA polymerase synthesizes the new strand by building onto the 3’ end of
the RNA primer, or newly made strand, it builds the new strand 5’ to 3’
*building of new, complementary bases will always end in 3'
27. Compare and contrast DNA replication in bacteria vs. eukaryotes.
A. In bacteria: origin of replication, parental (template) DNA strands separate,
bubble grows, replication fork, DNA unwinds, RNA polymerase builds new
(complementary) strands, no RNA processing

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B. In eukaryotes: RNA polymerase + promoter = pre-mRNA, then RNA processing
(splicing and capping) = mRNA, then Translation
28. Describe how consequences—such as differences between “leading” and “lagging”
strands, and the loss of DNA from telomeres—arise from the DNA molecule’s polarity
and the unidirectional synthesis performed by enzymes during replication.
A. Leading strand-is built in one continuous strand
B. Lagging strand- is built in a series of fragments, then joined together by the DNA
ligase
*view slide 23 of DNA replication to see lagging strand building
i. The same process for leading/lagging strands is going on the other strand (on
the opposite side) of the origin of replication
C. Telomeres- the cap ends of our DNA that protect our chromosomes from
deterioration
i. the more rounds of replication that happen, the shorter the DNA molecule
becomes: this could lead to understanding the aging process, as DNA replicates
throughout the lifetime, the DNA molecule shortens, thus causing loss of genetic
material=aging
29. Understand how errors in DNA replication create random mutations; relate these
mutations to Learning Goal #5 (from exam #3).
A. The different forms of mutations are frameshift, substitution, missense,
nonsense, and change.
a. Frameshift is either a deletion or an addition. Its called a frameshift
because the whole entire nucleotide sequence "shifts" with the
deletion or addition of a nucleotide
b. substitution: switching one nucleotide for another cause a different
amino acid to be attached
i. missense→ T instead of C, A instead of G
c. no change:
i. silent→ A instead of G, U instead of C
ii. A mutation that changes a single nucleotide, but does not
change the amino acid created.
d. Nonsense:
i. A type of mutation where a stop codon is added prematurely
IV. Major Topic #4: The Central Dogma
Topic IV.A.: Genes contain the information needed to build and run an organism.
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