Chapter 13

How many possible codons?

64

Enzymes

Ubiquitin ligase, which attaches ubiquitin molecules to a protein, targeting it for destruction

Multiple codons can code for the same amino acid so, we say the genetic code is ___________

degenerate

The code is considered ____________ although there are some exceptions to the rule

universal

T/F: 1. Bacteria have only one kind of ribosome 2. Ribosomes have large and small subunits 3. Eukaryotic ribosomes are assembled in the cytosol 4. Ribosomes are composed solely of rRNAa 5. In eukaryotes, ribosomes found in mitochondria and chloroplasts have a different composition than that of cytosolic ribosomes

1. True 2. True 3. False 4. False 5. True

Determine if the following statements applies to only prokaryotes, to only eukaryotes, or to both: 1. The first tRNA used is charged with a formyl methionine 2. Translation occurs in the cytoplasm 3. Requires a Shine-Dalgarno sequence to be present on the mRNA 4. Translation occurs cotranscriptionally 5. Initiation requires a 7-methylguanosine cap on the mRNA 6. Requires a release factor to terminate translation

1. prokaryotes 2. both 3. prokaryotes 4. prokaryotes 5. eukaryotes 6. both

During the elongation stage of translation, new tRNAs enter at which site?

A site

Movement

Actin assembles and disassembles allowing cells to migrate

Cell shape and organization

MreB, a bacterial protein important for helping maintain the rod-shape of certain bacteria

The initiator tRNA is special because it is the only tRNA that can initially bind at this site in the ribosome.

P site

Genes are used to make RNA and some RNA is used to make proteins. Not all RNAs in the cell are destined to be translated. What RNAs will be translated?

mRNAs

Codons that specify the same amino acid are termed __________

synonymous

Transport

the IP3 receptor, which functions as a calcium channel in the endoplasmic reticulum

The third base in a codon is called the __________ base

wobble

You are studying a protein that contains the amino acid selenocysteine. To understand the protein better, you place the gene for this protein into a plasmid, so that you can control the expression of the gene in cells. When you look at the protein expressed from the plasmid, however, you are surprised to find that the protein encoded from the plasmid is shorter than the protein encoded from the genome. Why?

you forgot to include the SECID, and therefore UGA functioned as a stop codon rather than a codon for selenocysteine