Bio

What was Rosalind Franklin's role in the discovery of the structure of DNA?

She carried out X-ray diffracton experiments leading to the determination that DNA is a double helix.

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes (this means not many changes/mutations have been seen). What does this most probably mean?

That the critical function of telomeres must be maintained

What is meant by the description "anti-parallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 3' to 5' direction of the other strand.

Which of the following is true about tRNA attachment to an amino acid?

The amino acid binding site on the tRNA is not part of the loop structures found within the tRNA molecule.

In the Hershey and Chase experiment, which of the following is correct about the phages used?

The phages' protein coat was labelled using the radioactive isotope 35S.

Which of the following is the first event to take place in translation in eukaryotes?

The small subunit of the ribosome recognises and attaches to the initiator codon of mRNA

Which of the following statements describes the tertiary structure of a protein?

The structure forms from interactions between the amino acid side (R) groups.

Which of the following features does not apply to the tRNA-activating enzyme?

The tRNA-activating enzyme binds the amino acid to the corresponding tRNA by adding one phosphate molecule to ADP.

Which of the following is correct about anticodons?

There are no anticodons that complement termination codons found on mRNA.

Modern DNA sequencers make use of the Sanger strategy to learn about the base sequence of DNA. Which of the following is true with regard to the nucleotides used in this strategy?

They are normal DNA nucleotides but lacking the 3' OH group.

Which of the following is correct with regard to the free ribosomes found in eukaryotic cells?

They synthesise proteins for use primarily within the cell.

Which of the following is a function of the signal recognition particle (SRP)?

To help translocate polypeptides across the ER membrane

What is the role of the single strand binding proteins in DNA replication?

To prevent the DNA strands from re-annealing.

Why might a laboratory be using dideoxynucleotides?

To sequence a DNA fragment

Which statement applies to transcription in eukaryotic cells but NOT to prokaryotic cells?

Transcription takes place in the cell nucleus.

DNA methylation and histone acetylation are all examples of:

Transcriptional regulation

A particular triplet of bases in the sense strand of a gene reads 5' AAA 3'. The anticodon on the tRNA that binds the mRNA codon is:

UUU

Transcriptional regulation:

-Be induced by a repressor protein, as highlighted by the lac operon (where genes are switched on or off depending on the availability of lactose in the medium) -Allow the cell to only produce proteins that are needed at the time. -Be highly efficient at completely preventing transcription.

Secondary protein structures are normally stabilised by hydrogen bonds created between:

-NH groups of peptide bonds and -C=O groups of other peptide bonds found in the same chain.

The anticodon loop of the tRNA that will complement the mRNA 5' CCG 3' is:

3' GGC 5'

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%

A polysome is:

A group of ribosomes working on the same mRNA molecule

What is a promoter?

A non-coding region of DNA.

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by:

A signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane

What is the function of DNA polymerase III in DNA replication?

Adds nucleotides to RNA primers.

What is produced during transcription?

All RNA

In response to the presence of certain food sources, prokaryotes can do which of the following?

Alter the level of transcription of certain genes

Which of the following processes describes an event that takes place in translation?

Amino acids join at the P site by a peptide bond.

A biochemist isolated and purified molecules needed for DNA replication. When she added some DNA, replication occurred but the DNA molecules were defective. Each consisted of a normal DNA strand paired with numerous segments of DNA a few hundred nucleotides long. What had she probably left out of the mixture?

DNA Ligase

What makes up a nucleosome?

DNA and histone proteins.

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

DNA contains phosphorus, whereas protein does not.

Which of the following is not needed for transcription?

DNA polymerase

What happens during the formation of Okazaki fragments?

DNA polymerase III adds nucleotides in the 5′→3′ direction.

What is the basis for the difference in the synthesis of the leading and lagging strands of DNA molecules?

DNA polymerase III can only join new nucleotides to the 3' end of the growing strand.

Gene expression might be altered at the level of post-transcriptional processing in eukaryotes and not in prokaryotes because of which of the following?

Eukaryotic exons may be spliced in alternative patterns.

Which of the following statements is true about mRNA?

Every three nucleotides code for one specific amino acid.

Which of the following is not considered a non-coding region of DNA?

Exons

Himalayan rabbits carry the C gene, which is required for the development of pigments in the fur, skin and eyes. The expression of the C gene is regulated by temperature. What can we conclude from this?

External conditions may affect gene expression in some organisms.

How does transcription of RNA in eukaryotes proceed?

From 5′ to 3′ in exons and introns.

Egg thing in nucleosomes

Histone

The amino acids of the protein keratin are arranged predominantly in an alpha helix. This secondary structure is stabilised by:

Hydrogen bonds

Nucleosomes have a role in: I. Supercoiling of chromosomes II. Regulating gene expression III. Regulating translation and transcription

I and II

Which of the following is false about initiator tRNA?

Initiator tRNA carries the amino acid leucine.

What is removed during the formation of mature RNA in eukaryotes?

Introns

Why is mRNA received by eukaryotic ribosomes shorter than the mRNA produced immediately after transcription of DNA?

Introns are removed before the RNA is translated.

Which of the following statements describes a eukaryotic chromosome?

It consists of a single linear molecule of double-stranded DNA plus proteins.

What is the function of the tRNA-activating enzyme?

It links tRNA to a specific amino acid.

What describes a tertiary protein?

It occurs due to the folding of a polypeptide chain.

Which of the following statements is correct with regard to DNA gyrase?

It relieves strain on the strand outside the replication fork.

In DNA replication, which enzymes and structures other than DNA Polymerase are involved in synthesizing the leading and the lagging strand?

Leading DNA primase and one RNA primer Lagging DNA primase and RNA primers

Splicing of mRNA is an important process that takes place in some organisms. Which of the following is not true about splicing?

Modifies the mRNA strand in some prokaryotes.

What will be the consequence if a mutation occurs in a single tRNA molecule such that it still attaches to the same amino acid (phe), but its anticodon loop has the sequence AAU so it binds to the mRNA codon UUA (that usually specifies leucine)?

One mutated tRNA molecule will be relatively inconsequential because it will compete with many 'normal' ones.

Which of the following is NOT correct about polysomes?

Prokaryotic polysomes involve multiple bound ribosomes attached to the same mRNA.

An Okazaki fragment has which of the following components?

RNA primer, DNA fragment

In the gene regulation of the lac operon in prokaryotes, which of the following events take place in the absence of lactose?

Repressor protein prevents binding of RNA polymerase so mRNA is not produced.

Who carried out X-ray diffraction experiments leading to the determination that DNA was a helical molecule

Rosalind Franklin

What aspects of protein structure are stabilised or assisted by hydrogen bonds?

Secondary, tertiary, and quaternary structures, but not primary structures

Which of the following statements about translation is false?

mRNA binds to the large subunit of the ribosome until it reaches the start codon.

During DNA replication:

methylation of DNA doesn't change