IB Biology HL

What contribution did the X-ray diffraction conducted by Rosalind Franklin make to our understanding of DNA?

• It identified DNA as the genetic material.

• It indicated the helical shape of the molecule.

• It showed that the DNA of eukaryotes was associated with histone proteins.

• It showed that replication was a semi-conservative process.

The image shows a polysome in a bacterial cell. How many genes have been transcribed?

• 1

• 2

• 3

• 4

Tags

NGSS.HS-LS1-1

Hershey and Chase used a bacteriophage (a virus that infects bacteria) to investigate the chemical nature of genes.

The sulphur in the protein and the phosphorus in the DNA of the bacteriophage were radioactively labelled. The data obtained after bacterial infection and centrifugation are shown in the table.

What did Hershey and Chase conclude from their experiment?

• DNA was mainly outside the bacterial cells.

• Viruses infect bacterial cells with proteins.

• Viral DNA was found within the bacterial cells.

• Neither protein nor DNA were chemicals making up genes in viruses.

Current understanding of DNA is an example of the accumulated discoveries of many scientists. Which scientists are credited with establishing that DNA is the genetic material?

• Franklin and Wilkins

• Watson and Crick

• Meselson and Stahl

• Hershey and Chase

What are polysomes?

• Strings of amino acids

• Packages of eight histones with DNA

• Many ribosomes joined to one mRNA

• Complexes of tRNA with amino acids

What are the functions of DNA primase and DNA polymerase I in DNA replication?

• A

• B

• C

• D

A nucleotide containing dideoxyribose is shown.

• Nucleotides cannot form 5′ to 3′ linkages with dideoxyribonucleotides.

• Nucleotides cannot form base pairs with dideoxyribonucleotides.

• Dideoxyribonucleotides cannot form hydrogen bonds with deoxyribose.

• Dideoxyribonucleotides do not have all four nitrogenous bases.

What applies to DNA base sequences?

I. Some genes do not code for proteins.

II. Promoters are transcribed along with the gene.

III. Introns are only found within genes coding for proteins.

• I only

• II only

• II and III only

• I, II and III

Tags

NGSS.HS-LS3-1

What does eukaryotic DNA have that is missing from prokaryotic DNA?

• Uracil

• Promoter DNA

• Introns

• Coding sequences

Which letter (A–D) indicates where a new nucleotide would attach?

• A

• B

• C

• D

Tags

NGSS.HS-LS1-1