|
Post by lauren on Apr 15, 2012 13:33:31 GMT -5
Hi Miss,
I just wanted to confirm that nothing on the RNA powerpoint will be on the test tomorrow. Also, I was wondering if there will be anything on our test that relates to the Strawberry DNA lab that we did on Thursday. Thanks!
Confirmed. Day 3: RNA will NOT be on the test No. There will NOT be any questions from the lab.
|
|
|
Post by Brittany on Apr 15, 2012 13:36:47 GMT -5
What is the purpose of deoxyribonucleoside triphosphate and how does it attach to the DNA? Thanks We never covered this in class. It will not be on the test.
|
|
|
Post by raygiang on Apr 15, 2012 16:59:33 GMT -5
Hey miss i dont understand why one strand replicates in one direction and the other strand replicates in the opposite direction.
DNA is antiparallel. This means one strand goes from 3' to 5'. The other strand goes from 5' to 3'. When the strands separate, the RNA primer will attach to each strand. This primer is anitparallel to the strand it attaches to. For example: This is the original double stranded helix 5' ATTCCGGGTTTTA 3' 3' TAAGGCCCAAAAT 5'
This is what it will look like when the strands separate and the primers attach 5' ATTCCGGGTTTTA 3' 3' AAT 5'
5' TTA 3' 3' TAAGGCCCAAAAT 5'
New bases are added to the 3' end of the RNA primer. For the strand on top, this is fine. The leading strand runs 5' to 3' which means the RNA primer runs 3' to 5'. The 3' end of the primer faces towards the replication fork (the left side of the screen). So as the DNA unzips, new bases keep being added to the 3' end of the primer (add new bases to the left) on the leading strand. Replication happens in the same direction as the DNA is being unzipped. The strand which runs 3' to 5' has an RNA primer which runs 5' to 3'. This means the 3' end of the primer is facing away from the replication fork. New bases are added to the right. This means replication occurs in the opposite direction of the unzipping. As the DNA continues to unzip, new primers have to keep being added so the freshly unzipped DNA can still be replicated.
oh ok thanks miss
|
|
|
Post by amanda on Apr 15, 2012 17:14:32 GMT -5
Hi Miss,
I have a question regarding DNA replication it was about DNA helicase and your note said that it started unwinding at the origin of replication do we have to know where this is or anything about the origin of replication?? Also the RNA primer signals where replication should start so is this the origin of replication or are they different??
The origin of replication is the area of the DNA where replication begins. This means the DNA helicase will begin to unwind the DNA at this point as well as the RNA primer will attach here. You do not need to know anything more about the origin of replication.
|
|
|
Post by Carly on Apr 15, 2012 19:35:40 GMT -5
Hi, in one of your answers you said that purines are single ring structures? But in my note I wrote down they are double ringed. Did I copy this down wrong?
Your note was right. Purines are double rings. My mistake in the other answer. I will go fix that now.
|
|
seema
New Member
Posts: 15
|
Post by seema on Apr 15, 2012 19:40:07 GMT -5
Hey Miss, I was just wondering if we need to know anything about the order of which DNA helicase, DNA gyrase, RNA primer, DNA polymerase III, and the rest of the enzymes work in during DNA replication ? Like is DNA ligase the last enzyme and then DNA replication is over?
Yes you do need to know the order of the steps of DNA replication. If, for example, I were to ask you to fully explains the steps involved in DNA replication, I would expect them to be in order. And yes, DNA ligase will be the last step.
|
|
|
Post by melanie on Apr 15, 2012 19:58:21 GMT -5
Hi, in one of your answers you said that purines are single ring structures? But in my note I wrote down they are double ringed. Did I copy this down wrong? Carly I'm going to try and answer your question according to the textbook purines are double ringed and pyrimidines are single ringed... i dont think you copied it down wrong Thanks for answering! Yes, as mentioned above, this is correct. My other post was wrong. I posted in the announcements folder about my mistake so hopefully anyone else having this issue will be made aware of my error and the correction.
|
|
|
Post by Carly on Apr 15, 2012 20:13:35 GMT -5
Thanks Mel!
|
|
|
Post by Carly on Apr 15, 2012 20:47:16 GMT -5
Ok thanks Ms! Sorry one more quick question. What is the importance of phosphodiester bonds? (Where is it, what does it do?) Does this have anything to do with the fact that in nucleotides the phosphate group is joined to the 5th carbon by an ester bond and that the nitrogenous base is joined to the 1st carbon by a glycosyl bond?
No apology needed.
The phosphodiester bond is between the 3' carbon (OH group) of one nucleotide and the 5' carbon (phosphate group) of the following nucleotide. When DNA is being replicated, we said that each new nucleotide is added to the 3' carbon. This means that the 3' carbon of the existing nucleotide is forming a bond with the 5' carbon of the newly added nucleotide. These bonds are important because they allow the formation of the DNA strand. Also, remember that hydrogen bonds are formed between the stands.
|
|
|
Post by melanie on Apr 22, 2012 10:35:42 GMT -5
Hi Miss I was just wondering if there is going to be anything that is not from our notes and only in our textbook on the test such as the stuff about the HIV case study, the four levels of control of gene expression in Eukaryotic cells, and the scientist hypothesis from section 5.1 -Thank you
Same rule as last time. If it wasn't in the notes/talked about in class, it will NOT be on my test. Happy studying
|
|
|
Post by rebecca L on Apr 22, 2012 17:04:18 GMT -5
Hi Miss, I was just wondering if you could explain the purpose of pseudogenes? I was looking over my notes and if there was a question on these on the test I'm not sure what I would write to answer it
There is no purpose...or so it would seem. Pseudogenes look like genes (similiar in base sequence), however they do no code for any proteins. It seems as though they do not do anything. Keep in mind, years from now, we could learn that they do have a function though.
|
|
|
Post by brittany on Apr 23, 2012 17:24:03 GMT -5
Would we have to know the exact order and points of the slides that read '10 mark question' and '20 mark question'?
No. I had those slides from when I taught this unit at Brebeuf. For this class, just use them like a recap slide, NOT a memorize slide.
|
|
seema
New Member
Posts: 15
|
Post by seema on Apr 23, 2012 18:30:07 GMT -5
Hey miss, on one of your notes (the second one) it says: "Only the section of DNA coding for the gene to be transcribed unwinds" I don't really understand what you mean by that? Thank you!
Okay well during transcription, the DNA unwinds. But remember the RNA poly II is only transcribing ONE gene. So only the gene being transcribed will be unwound as opposed to the entire piece of DNA.
|
|
|
Post by lauren on Apr 23, 2012 18:39:59 GMT -5
Hey Seema I think I have the answer to your question. Only a small part of the DNA unwinds to code for the mRNA because the mRNA only needs to code for a specific gene. It doesn't have to make a copy of the entire strand of DNA, that would be a waste in energy since not all of the information that on the DNA is needed for the particular amino acid it is coding for. For example, if you are reading an essay on DNA but you only needed to copy a certain paragraph, you cover the parts you don't need with paper and only photocopy the small section you need. You don't need the rest of the essay since you are only interested in the one part. If you photocopied the entire essay you would be wasting paper.
Yes! Perfect!! Hope that helps!
|
|
|
Post by Lisa Kim on Apr 23, 2012 19:02:25 GMT -5
Hi Miss,
Do we need to know about four levels of control in eukaryotic cells, such as transcriptional, posttranscriptional, translational, posttranslational?
No. I know there is a question about this in the review but don't worry about it.
|
|