Nucleic Acids

The diagram shows a typical portion of the DNA molecule of the chromosome. Which of the following is NOT represented by the region labelled X?

• Hydrogen bonds between base pairs

• Two anti-parallel strands

• Pyrimidine to pyrimidine base pairing

• One complete turn of the double helix

Which of the following events occurs in transcription as well as in replication of DNA?

• Free nucleotides bond to the DNA strand

• Two new DNA molecules are produced

• Uracil nucleotides bond to adenine on the DNA strand

• Only part of the DNA molecules containing a gene unwinds

The amino acid sequence leucine-lysine-valine occurs in a portion of a polypeptide molecule. The table below shows the DNA codes for these amino acids.

• GAA - TTT - CAA

• GAA - UUU - CAA

• CUU - AAA - GUU

• CUU - UUU - GUU

One structure that may be observed in animal cells during mitosis but is NOT seen in plant cells is

• spindle fibres

• centromeres

• centrioles

• chromatids

The following are events in transcription.

• V-I-III-II-IV

• V-II-III-I-IV

• V-II-I-IV-III

• V-II-IV-I-III

The diagram shows a segment of a strand of DNA. The base X is

• cytosine

• guanine

• uracil

• adenine

The sequences of bases in one strand of DNA from part of a gene is ACC CCA TTT CAT CCA. The table below shows the anticodons of some tRNA molecules and the specific amino acids each would carry. Which of the following is the amino acid sequence coded for in this part of the gene?

• valine-glycine-tryptophan-glycine-lysine

• tryptophan-glycine-lysine-valine-glycine

• lysine-valine-lysine-valine-glycine

• glycine-tryptophan-lysine-valine-glycine

What type of bonds are used to link nucleotides together to form a polynucleotide?

• Peptide

• Glycosidic

• Hydrogen

• Phosphodiester

Why is the copied portion of the DNA longer than that of the functional mRNA molecule produced from it?

• The DNA portion contains many genes

• The DNA portion contains a promoter region

• Only exon portions are included in the mRNA

• Only intron portions are included in the mRNA

Which of the following types of bonds holds together the two strands of nucleotides in a DNA molecule?

• Carbon

• Peptide

• Hydrogen

• Glycosidic