3 genetics questions, need help please!

[dab33r]

1- After bacteria are grown for many generations on a medium containing normal, nonradioactive phosphorous (P), some are transferred to a medium where all the phosphorous in the form of its radioactive isotope, P32. The bacteria use this P32 to synthesize the deoxyribonucleotides they need for DNA replication. The bacteria grow on this P32 for three generations and a sample of bacteria is removed at the end of each round of replication. DNA duplexes from these samples are isolated and analyzed for P32 content.

 

a. For each of the three samples of bacteria, estimate the proportion of duplexes that would have (1) all of their nucleotides containing P32, (2) some of their nucleotides containing P32 and some containing normal P and (3) all of their nucleotides containing normal P.

 

b. For the duplexes that have some nucleotides containing P32 and some containing normal P, estimate the proportion of P32 nucleotides in these duplexes.

 

2-Assume that the transcription and translation of a polypeptide that is routinely synthesized in humans and secreted by a certain type of glandular cell has been studied.

a. The polypeptide’s unit of transcription consists of 5318 base pairs. How many bases will occur in the primary mRNA transcript produced from this transcription unit?

b. During its post-transcriptional modification, the length of this mRNA transcript is increased by several hundred nucleotides. What is added to contribute to this increase in length?

c. At the end of its post-transcriptional modification, the length of this mRNA, now designated as mature mRNA, consists of 1222 nucleotides. What has been responsible for decreasing the length of the transcript?

d. The polypeptide consists of 262 amino acids. How many of the nucleotides present in the mature mRNA strand are required to code for these amino acids?

 

3- A number of antibiotics have been identified that block the process of polypeptide synthesis. Several of these are listed along with the component of the polypeptide-synthesizing system that they affect. For each compound, indicate the stage of polypeptide synthesis (that is, initiation-complex formation, chain initiation, chain elongation or chain termination) that is disrupted or blocked by the antibiotic. Explain your answer.

a. Sparsomycin inhibits the action of the enzyme peptidyl transferase.

b. Puromyocin acts like an amino acid-tRNA complex. It can occupy the A site and receive the growing amino acid chain from a tRNA molecule, but it lacks a terminal carboxyl group.

c. Tetracycline binds to the small ribosome subunit and blocks the A site.

d. Aurintricarboxylic acid prevents the joining of mRNA molecules to the ribosome.

 

 

Thanks in advance for your help!

[Sayonara]

We aren't just going to do your homework for you. You need to tell us which parts you understand and which parts are giving you problems, so that we can help you figure out how to solve it.

[dab33r]

Sayonara, I am really confused in all parts of these questions and really have no clue in even how to begin them.

 

I dont want just answers if you could also explain and help me learn I would appreciate it thank you!

[jimmydasaint]

dab33r - You need to read up on the following:

 

DNA Replication (Semi Conservative method); http://www3.interscience.wiley.com:8100/legacy/college/boyer/0471661791/animations/replication/replication.swf

 

Transcription http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html

 

Translation.

http://www.johnkyrk.com/DNAtranslation.html

 

Then come back.