DNA and Proteins

Nuclear DNA is a double stranded nucleic acid molecule. in a double stranded DNA molecule the

• number of G bases is = number of C bases

• number of T bases is twice number of C bases

• number of all 4 bases are equal

• A bases and U bases are equal

A single DNA nucleotide contains

• ribose sugar, phosphate and thymine

• deoxyribose sugar, phosphate and uracil

• ribose sugar, phosphate and uracil

• deoxyribose sugar, phosphate and thymine

The diagram represents part of a DNA molecule. A feature of DNA that can be seen in the diagram is

• the anti-parallel arrangement of the two strands of nucleotides

• the process of semi- conservative replication

• its ribose sugar-phosphate backbone

• its double-helix structure

The codon GGA codes for the amino acid glycine. It is reasonable to conclude that

• the DNA segment that acts as the template for the codon is CCU

• the tRNA anticodon with which this codon pairs will have the sequence CCT

• the codon GGA may also code for other amino acids

• codons other than GGA may code for glycine

During RNA processing in the nucleus

• introns are retained and exons are removed

• a poly-A tail is added to the 5' end of the pre-mRNA

• exons are retained and introns are removed

• the positions of introns and exons are arranged

The structural order within a gene on prokaryotic DNA is

• promoter, operator, genes

• genes, operator, promoter

• promoter, genes, operator

• operator, promoter, genes

The promoter region of a gene is needed to

• promote the translation of the gene into a functioning protein

• allow RNA polymerase to recognise the region and bind so the process of transcription can occur

• identify the intron and exons across a piece of DNA for splicing

• enable a repressor protein to bind so that the gene is not transcribe

A prokaryotic cell found itself in an environment lacking tryptophan. This resulted in

• the trp operon being turned off by a repressor protein because the production of these enzymes was not required

• an increase in cell mass because it could n0t excrete the by product of its metabolism

• the trp operon being free of repressors so that the enzymes required to synthesise tryptophan could be produced

• no significant changes to the metabolic processes occurring in the cell

The diagram shows

• Production of repressor proteins to reduce synthesis of the enzymesto make trp amino acid

• in low levels of tryptophan, trp repressor cant bind to the DNA and enzymes required for the production of tryptophan can be transcribed and translated

• DNA polymerase can bind to the trp operon so that replication of this operon can occur

• the trp operon can be translated by RNA polymerase adn then transcribed into tryptophan

Which of the following is true of a protein's primary function

• it is formed by hydrogen bonds between neighbouring amino acids

• it may include a combination of alpha helices and beta pleated sheets

• involved peptide bonds between neighbouring amino acids

• determined by the properties of the amino acids R groups