Notes 11/13

a. Polyribosomes
i. Can have a single mRNA that has a whole bunch of ribosomes attached to it at one time in different stages of translating mRNA (picture in notebook)
II. Kinds of mutations
a. Mutation
i. Any change in the DNA sequence of an organism
1. NOT a change in gene expression
ii. They happen because it is impossible to copy that many DNA correctly that many times in such a short period
b. Mutation rate: 1x10^9 bases copied is different from original
c. Point mutations
i. Mutations to DNA that changes just 1 base
ii. Missense
1. Mutation that changes the sequence of DNA, only 1 base, but change enough to change the amino acid sequences of protein
a. Ex. A change to one base in the DNA sequence, as result it changed the mRNA in such a way that there was a difference between the amino acid sequences of the original protein and the mutation protein
iii. Nonsense
1. Mutation to DNA such that the resulting mRNA now has an earlier stop codon than originally, so you have a short protein that is smaller than the original one that resulted

iv. Silent
1. On account of the fact that there are more codons than amino acids (meaning multiple codons per amino acid)– change in the DNA, but it results in NO change of the amino acid sequence of the protein
a. Could happen in a bunch of different places as long as there isn’t a change in the organism
2. Also could be a change in the “crap” part of our sequence that we don’t use because it wouldn’t change the amino acid sequence
d. Frameshift mutations
i. Where we either add or delete 1-2 bases from our DNA
ii. Might be a problem if there was a mutation that from the original sequence a base just isn’t copied at all
1. Would still start at the AUG but would have a different reading frame of 3 bases.
2. Would result in a very different ribosomal result than the previous one did – causing problems

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