MCAT - Biomolecules

In a cross of AaBb x AaBb, what fraction of the offspring can be expected to express one of the two dominant alleles, but not both?

3/8

Hydrogen bonding btwn. separate subunits of DNA polymerase is an example of which structure?

4 degree structure

What are the eukaryotic ribosomal subunits?

60S and 40S

What is an operon?

A unit of DNA containing a cluster of genes under control of a promoter and a repressor

A polypeptide with a net positive charge at physiologic pH (~7.4) most likely contains amino acids with R groups of what type?

Basic R groups

Deacetylation of histones has what effect?

Coiling of the histone structure, preventing it from being accessed by transcriptional machinery

Pyrimidine dimers resulting from UV light damage to DNA are removed from sequences via the action of what class of enzymes?

Endonucleases

What is the role of an activator?

Enhances interaction between RNA polymerase and the promoter

Micro RNA (miRNA) primarily aids in transcriptional and post-transcriptional regulation by what method?

Gene silencing through translational repression or target degradation

Suppose a white-furred rabbit breeds with a black-furred rabbit and all of their offspring have a phenotype of gray fur. What does the gene for fur color in rabbits appear to be an example of?

Incomplete dominance

At what point during normal DNA replication is genetic material lost from the telomeres?

Joining of adjacent Okazaki fragments

The amino acids in hemoglobin (or any protein) uniformly have which configuration?

L

What is the functional relationship between codons and amino acids?

Many different codons may code for the same amino acid

The unique cyclic structure of which amino acid plays a central role in the formation of alpha helices and beta sheets?

Proline

Methylation of CpG islands is essential to what process?

Stable silencing of DNA as cells terminally differentiate

Where within the eukaryotic cell might a drug which exclusively binds to tRNA binding sites exert its effects?

The cytosol

What is the function of the spliceosome?

To cleave introns from RNA and ligate the cut ends

In a bacteria possessing the lac operon, what occurs when glucose is low and lactose is abundant?

Transport of lactose into the cell is enhanced

In the ABO blood group system in humans, if a person of type-B blood has children with a person of type-AB blood, what blood types could their children have?

Type-AB, type-A, and type-B

Which of the following amino acids has a net negative charge at physiologic pH (~7.4)? a. glutamate b. histidine c. asparagine d. lysine

a. Glutamate

What type of side chain does leucine have?

aliphatic

Which of the following properties of a protein is least likely to be affected by changes in pH? a. Tertiary structure b. Primary structure c. Net charge d. Secondary structure

b. Primary structure

Electrophoretic separation of leucine from a protein sample would be least effective at which of the following pH values? a. 1.4 b. 7.4 c. 2.4 d. 0.4

c. 7.4

All hydrophobic amino acids (valine, leucine, isoleucine, etc.) share which of the following properties? a. Polar uncharged R groups b. Basic R groups c. Nonpolar uncharged R groups d. Acidic R groups

c. Nonpolar uncharged R groups

The effect of allolactose is:

conformational change in the repressor protein, inducing the lac operon

What constitutes the phosphodiester bonds in DNA?

covalently linked nucleotides

The alpha helix is an example of which structural property of proteins?

secondary structure