Chapter 3 Learning Curve

Which DNA molecules would be more stable under conditions of increasing temperature?

A DNA molecule that has more guanine and cytosine nucleotides

The bases in the nontemplate DNA strand of a particular prokaryotic gene include 10% of thymine. What percentage of the primary transcript synthesized from this gene is uracil?

10%

A lariat is a loop and tail of RNA formed during RNA splicing.

True

What is the backbone of DNA?

The phosphodiester bond and (5' phosphate group) and the nucelotide

During the early days of deciphering the human genome, scientists were surprised to find that the number of genes appeared to be significantly fewer than what had been predicted on the basis of the estimated numbers of different proteins required by our cells. What aspect of nucleic acids and transcription can help explain this discrepancy?

Alternative slicing means a gene can produce more than one protein product.

Only the extracts from heat-killed cells treated with protease are unable to transform nonvirulent bacteria into virulent bacteria.

Only the extracts from heat-killed cells treated with protease are unable to transform nonvirulent bacteria into virulent bacteria.

Promoters of many genes have mostly adenines and thymines. What is the most likely reason for this high proportion of adenines and thymines?

This is the region where template and nontemplate strands separate, and A-T base pairs require less energy to separate than G-C base pairs.

Consider Griffith's experiment. If he observed healthy mice after injecting these animals with dead virulent and live non-virulent bacteria, what could he have concluded?

Genetic information cannot be transferred between bacteria.

α helices are coils with how many amino acids per complete turn?

3.6

An operon is a group of functionally related genes transcribed as a polycistronic mRNA from a single promoter to a single terminator.

true

A portion of a polypeptide with a particular three-dimensional structure, relatively independent of the rest of the molecule, is a:

folding domain

Secondary structures are stabilized by which type of interaction?

hydrogen bonding

Spider silk is a material made of proteins that has a strength per gram that is five times that of steel. One feature of some of the toughest spider silks is a high proportion of β sheets that stack tightly together to form crystal-like arrays. Which amino acids would you expect to be common in such crystalline stacks and why?

glycine and alanine, because the R groups are small, allowing close stacking

5'—AUG—3' specifies amino acid

methionine

Amino acid sequences evolve through:

mutation and selection

As translation proceeds, energy is required to power the stepwise movement of the ribosome along the mRNA. This energy comes from the breaking of high energy bonds in _____ that is bound to _____.

GTP; elongation factors

Which of the events is a possible function of a protein-folding domain?

facilitation of interactions between proteins

transport of molecules across a membrane

catalysis

The tRNA that binds the start codon has the sequence _____ at its _____.

3′—UAC—5′; anticodon