IB Topic 11 Biology

Meselson and Stahl investigated DNA replication by first feeding bacteria with bases containing 15N (heavy), and then with bases containing 14N (light). The results are shown in the photographs.

From this information, what would be the composition of the DNA in generation 3?

• There will be a single 14N band.

• There will be a single 15N band and a single 14N band.

• There will be a darker 14N band and a lighter hybrid band.

• There will be a single 15N band, a single hybrid band and a single 14N band.

A short sequence of nucleotides reads GGACAGAGCGCAGACGA. In which type of molecule could this sequence be found?

• DNA molecule only

• RNA molecule only

• Both in a DNA and an RNA molecule

• In double-stranded DNA only

Which type of bond is identified by the arrow?

• Phosphate

• Hydrogen

• Covalent

• Peptide

What is required to replicate DNA?

• Temperature of 37 °C

• Free nucleotides carrying A, C, G and T bases

• Plasmids

• Endonuclease

Which points to the 3′ end of a strand of DNA?

• I

• II

• III

• IV

Which of the following statements is/are correct for DNA replication?

I. It occurs during interphase.

II. It is semi-conservative.

III. It is a stage in protein synthesis.

• I only

• II only

• I and II only

• I, II and III

Which enzyme catalyzes the elongation of the leading strand?

• RNA polymerase

• Helicase

• DNA polymerase

• Ligase

The percentage of thymine in the DNA of an organism is approximately 30 %. What is the percentage of guanine?

• 70 %

• 30 %

• 40 %

• 20 %

The image shows a DNA nucleotide.

Which correctly identifies the parts labelled I and II?

• I phosphate; II base

• I ribose; II uracil

• I deoxyribose; II base

• I ribose; II base

What is amplified using the polymerase chain reaction (PCR)?

• Large amounts of RNA

• Small amounts of DNA

• Small amounts of protein

• Large amounts of polymers