Genetic Information and DNA Replication Quiz

Rosalind Franklin probably would have received the prize as well but for her death from cancer in 1958. The Watson-Crick model gave new meaning to the words genes and chromosomes. The genetic information in a chromosome is encoded in the nucleotide sequence of DNA. Checkpoint question: Along one strand of a double helix is the nucleotide sequence G G C A T A G G T. What is the complementary sequence for the other DNA strand?

• C C G T A T C C A

• G G C A T A G G T

• T T A C G C T T A

• A A T G C G A A T

DNA replication is when DNA copies itself to form 2 strands. Replication starts with the separation of DNA strands. Enzymes then use each strand as a template to assemble new nucleotides into a complementary strand. DNA replication follows a semiconservative model. The two DNA strands separate. Each strand then becomes a template for the assembly of a complementary strand from a supply of free nucleotides. Each new DNA helix has one old strand with one new strand which is semiconservative because half of the parental molecule is maintained (conserved) in each daughter molecule. Which model does DNA replication follow?

• Conservative

• Dispersive

• Semiconservative

• Random

The enzyme DNA helicase “unwinds & unzips” or cuts the hydrogen bonds between the two DNA strands and separates them. The enzyme DNA polymerase links DNA nucleotides to a growing daughter strand, the cell synthesizes one daughter strand as a continuous piece. The other strand is synthesized as a series of short pieces as the fork opens up called Okazaki fragments, which are then connected by the enzyme DNA ligase. After the strands are separated, replication proceeds in both directions, creating replication “bubbles”, the parental DNA strands open up as daughter strands elongate on both sides of the bubble. Notice the sugar-phosphate backbones run in opposite directions; as a result each strand has a 3’ (three prime) end and a 5’ (five prime) end. The leading strand is the strand running in 3’ to 5’ direction. The lagging strand is the strand running in the 5’ to 3’ direction. What is the role of enzymes in DNA replication?

• DNA helicase unwinds and unzips the DNA strands.

• DNA polymerase links DNA nucleotides to a growing daughter strand.

• Okazaki fragments are connected by DNA ligase.

• All of the above.

The DNA of a gene — a linear sequence of many nucleotides— is transcribed into RNA, which is translated into a polypeptide. Transcription is the synthesis of RNA under the direction of DNA. Translation is the synthesis of proteins under the direction of RNA. Currently, a gene is defined as a region of DNA that can be expressed to produce a functional product that is either a polypeptide or an RNA molecule. What is the flow of genetic information from DNA to RNA to protein?

• DNA -> RNA -> Protein

• RNA -> DNA -> Protein

• Protein -> RNA -> DNA

• DNA -> Protein -> RNA

The sequence of nucleotides in DNA provides a code for constructing a protein. Translation requires the conversion of the nucleic acid language to the polypeptide language. During translation, there is a change in language from the nucleotide sequence of the RNA to the amino acid sequence of the polypeptide. Experiments have verified that the flow of information from gene to protein is based on a triplet code: The genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as a series of three-base “words” called codons. What is the process of translation from RNA to protein?

• Transcription

• Replication

• Translation

• Mutation

Translate the RNA sequence CCAUUUACG into the corresponding amino acid sequence.

• Proline-Phenylalanine-Threonine

• Glycine-Lysine-Serine

• Histidine-Leucine-Arginine

• Proline-Phenylalanine-Threonine

Which of the following is a property of the genetic code?

• It is universal

• It is ambiguous

• It is not redundant

• It is species-specific

What are the start and stop codons in the genetic code?

• Start codon: AUG, Stop codons: UAA, UAG, UGA

• Start codon: UAA, Stop codons: AUG, UAG, UGA

• Start codon: UGA, Stop codons: AUG, UAA, UAG

• Start codon: UAG, Stop codons: AUG, UAA, UGA

Which of the following describes the 3 steps of transcription?

• Initiation, Elongation, Termination

• Replication, Transcription, Translation

• Binding, Unwinding, Synthesis

• Activation, Elongation, Termination

What role does a promoter play in transcription?

• Initiates the process of transcription

• Terminates the process of transcription

• Elongates the RNA strand

• Modifies the RNA transcript