Bio 311C Unit 3 QUESTIONS AND ANSWERS A+ GRADED
How did experiments on transformed pneumonia-causing bacteria and radioactively-labeled bacterial viruses (Hershey & Chase) inform scientists that the genetic material was indeed DNA and not protein?
By using certain enzymes that would break d...
How did experiments on transformed pneumonia-causing bacteria and
radioactively-labeled bacterial viruses (Hershey & Chase) inform scientists that
the genetic material was indeed DNA and not protein?
By using certain enzymes that would break down protein, DNA, or RNA, they saw that
the genetic make-up would only be altered with DNA
Describe the double helix model of DNA, reviewing the evidence that supports
this model. What were some specific types of data used by Watson & Crick to
determine the structure of DNA?
X-ray images and quantitative base pairing to conform the structure of DNA as a double
helix.
Describe the structure of DNA nucleotide components(phosphate, sugar, A T C G
bases), their arrangement in DNA including complementary base pairing, and the
types of bonds(hydrogen or covalent) between various components. What are
3'and 5' ends of DNA? What is meant by the "anti-parallel" structure of DNA?
Sugar and Phosphate create the backbone and the nitrogenous bases crate the base
paring
Covalent bond- phosphate group and sugar
Hydrogen bond- between nitrogenous bases
5' end- phosphate group attached to 5th carbon
3' end- OH on 3rd carbon
Tell what is meant by "semi-conservative replication". How did Meselson & Stahl
use bacteria and heavy N to determine that DNA replication is semi-conservative,
not conservative?
One strand from each DNA
They ran an experiment through a centrifuged and gathered data by the bands that
were present
Describe the steps of DNA replication beginning at the "origin of replication" site,
including the role of these major enzymes (helicase, primase, DNA polymerase,
ligase). Include the role of primers for starting, the use of tri-phosphate
nucleosides as building blocks (& energy), and addition of new nucleotides to the
3' end of the growing strand.
Initiation at the origin of replication, unwinding the DNA, formation of primers, DNA
synthesis, leading of lagging strands, joining Okazaki fragments, Completion
Why does DNA's anti-parallel arrangement require a difference between
replication processes at the leading &lagging strands? What are Okazaki
fragments? Why is DNA ligase needed only in replication on the lagging strand?
1.It is necessary for different replication strategies for leading and lagging strands
2. Okazaki fragments- short pieces formed during lagging strand synthesis
3.DNA ligase is needed to join these segments together on lagging strand
Name two ways in which RNA differs chemically from DNA.
1. RNA has sugar ribose/ DNA had deoxyribose
2. RNA has Uracil while DNA has Thymine
, RNA polymerase always begins transcription of a gene at a DNA sequence called
what? It will stop transcription at a place on the DNA known as what?
Compare/contrast each pair of terms: (a) action of DNA polymerase vs RNA
polymerase action, (b) primer vs promoter; (c) replication vs transcription
Promoter
Terminator
A. DNA does replication and RNA involves in transcription
B. Primer starts DNA synthesis, Promoter signals where transcription begins
C. Identical vs copying parts of DNA for complementary RNA molecule
Explain what is meant by a "triplet code". Examine the mRNA codon chart and
explain what is meant by the term "redundant code". From a mRNA sequence,
how do you use the codon chart to translate the mRNA into a protein?
Code where a sequence of three nucleotides bases in DNA or RNA specifies a amino
acid into protein
Tell how a point mutation like a base substitution or insertion/deletion can affect
the resulting protein. What's an example of a frameshift mutation? Distinguish
these: silent mutation, missense mutation, nonsense mutations
Silent- does not alter
Missense- creates different amino acids
Nonsense- creates stop codon
Frameshift- base gets inserted causing rest of code to shift over
In what three ways do eukaryotic cells modify the messenger RNA (pre-mRNA)
after transcription? Tell the main function of the 3' poly-A tail and the 5' cap
adding a 5' cap, splicing out introns, and adding a 3' poly-A tail
5 Cap- initiation of translation by allowing ribosomes to bind to mRNA
3 Cap- Protects mRNA from degradation
What are introns and exons? What complex of proteins & snRNA's splices introns
out of the mRNA? Does this splicing occur in the nucleus or in the cytosol? How
can alternate mRNA splicing allow different cells to make slightly different
proteins from one gene?
Intron- cut out- exon- expressed
Spliceosomes
In the Nucleus
By selectively choosing exons to include in final mRNA
Distinguish the functions of each of the following types of RNA: rRNA, tRNA,
mRNA, snRNA. Remember that each is made in the nucleus by transcription from
the DNA.
rRNA- create shape/function of ribosome
tRNA- transports specific amino acid to mRNA in ribosome
mRNA- Contains code for protein
sRNA- part of splicing
What is the general function of a tRNA? How does a tRNA become bonded to its
specific amino acid? Does this occur at the mRNA or before the tRNA arrives at
the mRNA? How do the mRNA codon and the tRNA anticodon interact with each
other?
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