Biology 4502-Molecular Cell Biology
1. Describe and/or illustrate how renaturation of genomic DNA reveals different classes
of DNA sequences in eukaryotic genomes. How does the renaturation of eukaryotic
DNA compare with the renaturation of prokaryotic (viral or bacterial) DNA (4 points)?
Answer: When denatured DNA from eukaryotic genomes is reannealed the curve
shows three distinct steps that correspond to the three classes of DNA, namely highly
repeated, moderately repeated, and nonrepeated. The classes reanneal at different rates
because they differ as to the number of times their nucleotide sequence is repeated
within the population of fragments. Prokaryotic DNA does not have distinct classes of
DNA and the time required to fully reanneal the DNA is dependent on the size of the
genome.
2a. What are the three possible fates following a gene duplication event (3 points)?
Both copies retain original function
Diverge-acquire different functions
One copy loses function-becomes pseudogenJanuary 12 Lecture
e
b. Describe a mechanism that can result in a gene duplication (or deletion) (3 points)
Unequal Crossing Over: Misalignment of homologous chromosomes followed
by crossing over can result in deletion on one chromosome and addition to other
chromosome.
3. What type of RNAs are transcribed by the following polymerases (3 points)?
RNA Polymerase I
Large SSU rRNA (28S, 18S, 5.8S)
RNA Polymerase II Text-Page 447
mRNA, small nuclear RNAs
RNA Polymerase III
tRNA, small rRNA (5S)
4. You form a hybrid between hnRNA transcribed from the gene for the enzyme
“midtermin” and a DNA fragment from the gene itself. The structure formed is a
continuous double-stranded DNA-RNA hybrid. Next, you form a hybrid between the
mature mRNA for “midtermin” and the same DNA fragment from the gene mentioned
above. What do you see in the electron microscope when you examine this hybrid (4
points)?
Answer: When the processed mRNA is hybridized to the genomic (gene) DNA, the
genomic DNA(double stranded) corresponding to the intron sequence will loop out
since it does not have a complementary sequence in the mRNA to anneal with.
1. Describe and/or illustrate how renaturation of genomic DNA reveals different classes
of DNA sequences in eukaryotic genomes. How does the renaturation of eukaryotic
DNA compare with the renaturation of prokaryotic (viral or bacterial) DNA (4 points)?
Answer: When denatured DNA from eukaryotic genomes is reannealed the curve
shows three distinct steps that correspond to the three classes of DNA, namely highly
repeated, moderately repeated, and nonrepeated. The classes reanneal at different rates
because they differ as to the number of times their nucleotide sequence is repeated
within the population of fragments. Prokaryotic DNA does not have distinct classes of
DNA and the time required to fully reanneal the DNA is dependent on the size of the
genome.
2a. What are the three possible fates following a gene duplication event (3 points)?
Both copies retain original function
Diverge-acquire different functions
One copy loses function-becomes pseudogenJanuary 12 Lecture
e
b. Describe a mechanism that can result in a gene duplication (or deletion) (3 points)
Unequal Crossing Over: Misalignment of homologous chromosomes followed
by crossing over can result in deletion on one chromosome and addition to other
chromosome.
3. What type of RNAs are transcribed by the following polymerases (3 points)?
RNA Polymerase I
Large SSU rRNA (28S, 18S, 5.8S)
RNA Polymerase II Text-Page 447
mRNA, small nuclear RNAs
RNA Polymerase III
tRNA, small rRNA (5S)
4. You form a hybrid between hnRNA transcribed from the gene for the enzyme
“midtermin” and a DNA fragment from the gene itself. The structure formed is a
continuous double-stranded DNA-RNA hybrid. Next, you form a hybrid between the
mature mRNA for “midtermin” and the same DNA fragment from the gene mentioned
above. What do you see in the electron microscope when you examine this hybrid (4
points)?
Answer: When the processed mRNA is hybridized to the genomic (gene) DNA, the
genomic DNA(double stranded) corresponding to the intron sequence will loop out
since it does not have a complementary sequence in the mRNA to anneal with.
