Chapter 17 Test Preparation

A reminder: some students find the Cliffs Note book, and the CD ROM helpful. I would begin first with my lectures and then use the other material as needed. You know your own learning style best. If you have a chance to study with one other person it is always great to quiz one another since information tends to stick better and you often pick up nuances you might otherwise overlook when studying alone.

Know the details of protein synthesis really well- transcription, RNA modification, translation, etc. Be aware that prokaryote and eukaryote protein synthesis are slightly different from one another. Know the similarities and differences.

Know both free response questions 2 &3 very well. Be able to illustrate them. Know them to the detail of my lectures. Be aware that the Cliffs Notes book only has a “P” and “A” site on the ribosome. This is common for many books. Our book has the latest and best material which includes an “E” site. Know about the “E” site since that is what our book has and is the latest information. Check out the CD ROM for nice animations if that helps you learn better.

Understand the basic idea behind the key experiment that linked genes to proteins:
•Beadle and Tatum: One gene- one enzyme
Know the details of the experiment.

Know the difference between an intron and an exon.

Know how DNA and RNA differ from each other.

Think about why tRNA has the shape it does- what causes it to take on its 3D shape?

Understand what a codon is and then realize that the genetic code which we read off the genetic code table is actually what we would see in the mRNA, not the DNA. This can confuse students! Be able to decode a section of a gene from DNA into mRNA and finally into a protein using the Genetic Code Table. Memorize the start codon (AUG). Know why the codon is 3 base pairs and not 2 or 1.

Know the difference between a codon and an anticodon.

Understand that the code is redundant. Know about wobble.

Know what a polyribosome and a polysome are.



Mutations
See my lecture notes. Here is a summary of the ideas.

There are different kinds of mutations but the kind of mutations on the molecular level are called point mutations. They are called this since they simply change one base pair or just a few base pairs in a single gene. They should be distinguished from chromosomal mutations we talked about in a previous chapter.

Effects of mutations:
Somatic cells vs. Gametes (sex cells)
Somatic: Only affect the individual
Gamete: Affect all the offspring- forever and ever!!

Two Categories of Point Mutations:
1. Base-pair substitutions
2. Base-pair insertions or deletions

1. Base pair substitutions
One nucleotide is changed (and therefore its complement) in the DNA

a. Silent Mutation
•No change in amino acid
•Due to redundancy in the code

Change amino acid (Two types)
b. Missense
•Changes one amino acid
•Sometimes not a problem if it isn’t in a critical part of the protein
•If it near the active site of an enzyme this can lead to problems

c. Nonsense
•change in amino acid causes one of the three stop codons to appear.
•BAD!!

2. Base Pair Insertion or Deletion
BAD NEWS!!!
Generally causes a Frameshift mutation. Because the genetic code is read in triplets if you insert or delete one base-pair, everything downstream is different and the protein is nonfunctional unless it happens at the very end of the protein.

Frameshift can cause missense downstream or nonsense downstream.