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BCH 5413 EXAM PREP WITH COMPLETE SOLUTION
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BCH 5413 EXAM PREP WITH COMPLETE SOLUTION
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BCH 5413 EXAM PREP WITH COMPLETESOLUTION
1.In the experiment described that supports DNA as the genetic material:
a.Why does the mouse die if the researcher mixes dead pathogenic strain with live non-
pathogenic strain bacteria and then inject it into the mouse? - =The mouse dies because the
DNA in the S strain transforms the R strain into becoming pathogenic
b.What was the only scenario in which the mouse lives? Why? - =The mouse lived when the
DNA was destroyed because the S strain could not transform the R strain.
Based on the carbon numbering system for the sugar (1 -5) that makes up DNA, describe the
main component that is attached to each sugar and why it is important to the structure of DNA
- =The 1 carbon of the sugar has the nitrogenous base and the 5 carbon has the phosphate. The
bases are important because they form the sequences of DNA. The phosphate is important
because it forms the backbone of DNA and makes it negative and hydrophilic so it can bind with
water.
Describe why DNA has directionality. - =DNA has directionality so that there can be
complementary base pairing. This is essential for replication and transcription.
What is the meaning of the term antiparallel in the structure of DNA? - =It means that one
strand runs 3-5 and the other runs 5-3 so they run antiparallel to each other.
What does the Meselson and Stahl experiment
confirm? - =It confirmed that DNA replicates semi-conservatively
T/F Most biological DNA is positively supercoiled - =False, it is negatively supercoiled
T/F GC rich DNA has a lower melting temperature than AT rich DNA - =False, it would be higher
because it has 3 hydrogen bonds instead of 2 between the bases
,T/F Chargaff's rule: A=G andT=C - =False, A=T and C=G
T/FIncreased salt concentration increases the stability of complimentary base pairing - =True
A/Z which is right handed helix - =A
A/Z Which ones has 12 bp per helical - =Z
A/z which is the dehydrated form - =A
Describe three similarities between DNA and RNA. - =-Both use pyrimidines and purines as
bases
-Both a part of the central dogma
-Can have secondary structures
What is the central dogma? - =The central dogma is the concept that DNA-RNA-protein.
Give two examples of RNAs that are
exceptions to the central dogma. - =Two examples of exceptions are mRNA that is turned into
DNA by reverse transcriptase and RNA can also undergo RNA processing and simulate DNA
transcription
What are the two functions of DNA in cells? - =-gene expression
-DNA replication
diploid - =two complete sets of chromosomes with one from each parent
, allele - =an alternative form of a gene that can be inherited
heterozygous - =two different alleles for a gene
meiosis - =reproduction that results in haploid cells like in sex chromosomes
What is the difference between and intron and an exon? - =Introns are non-coding sections and
exons are coding sequences.
How can one stretch of DNA be used to create more than one protein? - =It can undergo
alternative splicing and create different protein products.
What is the meaning of the term exon shuffling? - =Exon shuffling is when an exons from
different genes are brought together or the same exon is duplicated.
How is this process related to the development of new proteins? - =This process is essential for
the development of new proteins because it alters the existing structure and allows the exons
to code for a new protein.
After isolating intact chromatin from cells, lightly digesting it with micrococcal nuclease and
running it on an agarose gel, you see a banding pattern of repeating 200bp fragments (200,
400, 600 etc). Explain this result. - =This is because part of the DNA is protected from
degradation by the nuclease by the nucleosome.
Explain the role of each of the histones in the formation of chromatin? - =Histones interact with
each of the 14 minor grooves of DNA and the DNA wraps around them.
-H4/H2a/2b/H3 (core) are all wound up with DNA and they help expose the DNA for
transcription.
-H1 leads to more complex nucleosomal DNA. Ultimately will result in up-down structure where
it is very organizes and DNA is 7 fold more compact where it can be inside the nucleus. H1 leads
to next level of chromatin structure.
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