Top Posters
Since Sunday
5
o
5
4
m
4
b
4
x
4
a
4
l
4
t
4
S
4
m
3
s
3
A free membership is required to access uploaded content. Login or Register.

genetics pse

Uploaded: 5 years ago
Contributor: a123k456b789
Category: Developmental Biology
Type: Assignment
Rating: N/A
Helpful
Unhelpful
Filename:   PSE1 .doc (33.5 kB)
Page Count: 3
Credit Cost: 1
Views: 213
Downloads: 2
Last Download: A year ago
Description
genetics hw
Transcript
All answers must be typed and in bold so we can distinguish your answers from the questions. If you use more than one page they must be stapled together or points will be deducted. 1. A virus contains 14% adenine, 36% cytosine, 35% guanine and 15% uracil. Is the genetic material in this virus double -stranded DNA, single -stranded DNA, double stranded RNA or single stranded RNA? Explain the reasoning that supports your answer. This genetic material is double stranded RNA. I know it is RNA because of the uracil nitrogenous base; only DNA has thymine whereas only RNA has uracil. One can tell it is double stranded because the complementary nitrogenous bases have equal percentages; A=14% and U=15%, while C=36% and G=35%. Since the complementary base pairs have equivalent percentages that means that it is double stranded, because there needs to be equal amounts of the complementary base pair in order to have a boned double stranded molecule. Also, we know some viruses can be double stranded, even though RNA is typically single stranded. 2. An alternative to semi-conservative replication is conservative replication in which the parent strands come apart only temporarily to serve as templates for synthesis of daughter strands but then come back together again as they were originally and the two new daughter strands then also form a duplex molecule. What single feature of the Meselsohn Stahl experiment allowed this conservative replication hypothesis to be rejected? (Hint:To answer this question you can consider the banding pattern produced on the cesium chloride density-gradient centrifugation following one round of replication in the Meselsohn Stahl experiment.) The Meselson Stahl experiment supported that DNA replicates semi-conservatively; showing that newly synthesized DNA consists of one old strand and one new strand. In their experiment, they grew E. Coli cells in an 15N medium, and allowed it to replicate for 3 generations. Generation 1 had 15N/14N, and it was present in a single band of intermediate density (expected result for semi-conservative replication). In conservative replication, the two distinct bands would occur. After two cell divisions DNA samples showed 2 density bands; one intermediate and one light. Similar results occurred in generation 3, except the proportion of the lighter band increased, which is consistent with semi-conservative replication. 5’ TAAGCGTAACCCGCTAA CGTATGCGAAC GGGTCCTATTAACGCAC 3’ 3’ ATTCGCATTGGGCGATT GCATACGCTTG CCCAGGATAATTGCGTG 5’ 3. Imagine that the double-stranded DNA molecule shown above was broken at the sites indicated by spaces in the sequence and that before they were repaired, the italicized DNA fragment between the breaks was reversed. What would be the base sequence of the repaired molecule? Show the sequence, label the 5’ and 3’ ends and briefly explain the reasoning supporting your answer. 5’ TAAGCGTAACCCGCTAA CAAGCGTATGC GGGTCCTATTAACGCAC 3’ 3’ ATTCGCATTGGGCGATT GTTCGCATACG CCCAGGATAATTGCGTG 5’ Since the complementary base pairs are still in line, the DNA fragments will remain reversed. DNA polymerase I repairs mismatched nucleotides, not DNA sequences. 4. Consider a hypothetical phage whose DNA replicates exclusively by rolling circle replication. A phage with radioactive DNA in both strands infects a bacterium and is allowed to replicate in a nonradioactive medium. Assume that only daughter DNA from the elongated branch ever gets packaged into progeny particles. Consult the website http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter13/animation_quiz_6.html for a nice picture of the rolling circle model which will help you in formulating your answer to the questions below. What fraction of the parental radioactivity will appear in the progeny phage? ½ or 50% of the parental radioactivity will appear in the progeny phage. How many progeny phage will contain radioactive DNA? All of the progeny phages will contain radioactive DNA, because all the daughter DNA will have the radioactivity, and those are the ones being packages into progeny particles. What Is the fundamental difference of theta replication and that of the rolling circle. Rolling circle replication breaks the outer strand and the free 3’ OH strand is extended by DNA polymerase. The 3’ end on the circle is lengthened while the growing point rolls around the circular template. The 5’ end is displaced and forms a tail of single stranded DNA. Theta replication produces only two circular DNA molecules, whereas rolling circular replication produces multiple. 5. A bacterium synthesizes DNA at each replication fork at a rate of 1500 nucleotides per second. If this bacterium completely replicates its circular chromosome by theta replication in 20 minutes, how many base pairs of DNA will its chromosome contain? ((1500 nucleotides / 1 second) x 2 forks) x (60 seconds/ 1 minute) x 20 minutes = 3,600,000 nucleotides 6. Assume that the sequence of bases given in this problem is present on one nucleotide chain of DNA duplex and that the chain has opened up at the replication fork. Synthesis of an RNA primer occurs on this template starting at the base that is underlined. a) If the RNA primer sequence consists of eight nucleotides, what is its base sequence? 5’ ACCTAAGT 3’ 3’ TGGATTCA 5’ b) In the intact RNA primer, which nucleotide has a free 3’-OH terminus? Thymine has a free 3’ OH terminus (the last nucleotide in the sequence) 3’…..GGCTACCTGGATTCA….5’

Related Downloads
Explore
Post your homework questions and get free online help from our incredible volunteers
  1115 People Browsing
Your Opinion
Which industry do you think artificial intelligence (AI) will impact the most?
Votes: 308