DNA

The figure above shows the structure of--

• A DNA molecule

• An amino acid

• An RNA molecule

• A protein

The X in the diagram above represents:

• A gene

• A protein

• A nucleotide

• A chromosome

DNA and RNA differ in all but one of the following ways:

• DNA is double-stranded, while RNA is single-stranded

• RNA uses the sugar ribose in its backbone, while DNA uses deoxyribose.

• DNA contains the base uracil, while RNA contains the base thymine instead.

• DNA is found in the chromosomes in the nucleus, while RNA can move around the cell.

A scientist is purifying DNA from a bacterium. During the purification process, a preparation is obtained that contains only 4 nucleotides. Some components of these are listed in the table above. Which of the following is the DNA?

• Molecule 1

• Molecule 2

• Molecule 3

• Molecule4

The diagram above shows the first step of protein synthesis, which is called ___ and takes place in the ___.

• Transcription; nucleus

• Transcription; ribosome

• Translation; nucleus

• Translation; ribosome

Put the following events in the correct order.

1. mRNA leaves the nucleus and goes to the ribosome.
2. The ribosome moves along the chain of amino acids, creating a polypeptide.
3. Amino acids attached to anticodons are carried to the mRNA.
4. mRNA is transcribed from DNA.

• 1, 2, 3, 4

• 4, 2, 3, 1

• 4, 3, 1, 2

• 4, 1 , 3, 2

A section of one DNA strand has the sequence of ACC GAG GTT. What is the sequence of mRNA transcribed from this section of DNA?

• ACC GAG GUU

• TGG CTC CAA

• UGG CUC CAA

• ACC GAG GTT

Genes for medically important proteins can be cloned and inserted into bacteria, as shown in the diagram. Why can bacteria recognize a human gene and then produce a human protein?

• DNA replication in bacteria and humans is the same.

• Bacterial cells contain the same organelles as human cells.

• The basic components of DNA are the same in humans and bacteria.

• Bacterial cells and human cells contain the same kind of chromosomes.

A scientist studies the effect of exposing DNA to various wavelengths of UV light and determined the number of copying errors made after exposure. The graph shows the scientist's experimental results. At which of these UV wavelengths would a mutation in a skin cell most likely occur?

• 225 nm

• 250 nm

• 265 nm

• 300 nm

During transcription the DNA base sequence is transcribed into a complementary mRNA sequence. A codon table like the one shown below lists the amino acids coded for by particular triads of mRNA bases. A segment of DNA has undergone a mutation in which one nucleotide has been changed. The original sequence was ACG and the new sequence is ACA. Use the codon table to determine whether or not this mutation will cause a change in the phenotype of the organism.

• Yes, the phenotype of the organism would change because a new amino acid will be coded for.

• Yes, the phenotype of the organism would change because any change in the DNA sequence will cause a change in phenotype.

• Even though the DNA sequence changed, the sequence still codes for the same amino acid, so no change in phenotype will occur.

• It is impossible to determine if a change in phenotype will occur using only the DNA sequence.