Multiple Choice:

1. An mRNA molecule is synthesized in a process called

b) Translation

c) Mutation

d) Transcription

2. The DNA in a prokaryote is the shape of a

b) Closed circle

c) Open circle

d) None of the above

3. Which type of RNA possesses anticodons?

b) mRNA

c) rRNA

d) dRNA

4. The universal start codon is

b) UAG

c) AAU

d) GUA

5. _________ are portions of DNA molecules that do not code for proteins.

b) Introns

c) Mutagens

d) Okazaki fragments

6. There are ________ different kinds of amino acids.

b) 36

c) 20

d) over 100

7. Amino acids make

b) Chromosomes

c) Uracil

d) Protein

8. Which of the following statements is true?

b) mRNA has a non-coding trailing sequence at its 5’end.

c) The tRNA holding the growing peptide chain occupies the A site of the ribosome.

d) Promoter sequences are not transcribed.

9. A mutagen __________.

b) is an enzyme that fixes mutations.

c) causes mutations.

d) None of the above.

10. Of the following bases, which one is not a pyrimidine?

b) Cytocine

c) Adenine

d) Uracil

True Or False

1.Bacterial mRNA is used immediately after transcription without further processing.

2. During elongation a peptide bond forms between two tRNA molecules.

3. tRNA brings amino acids to the ribosomes during transcription.

4. Tanslation takes place in the nucleus.

5.The lactose repressor protein in encoded by a regulator gene.

6. lac z codes for beta-galactosidase which converts lactose into glucose and galactose.

7. A base substitution mutation is the simplest type of mutation.

8. Elongation is the addition of nucleotides to the forming polypeptide chain.

9. Genes with related functions are clustered into units called operons.

10. Protein coding information in mRNA is specified by codons, which are combinations of three amino acids.

Short Answer Questions

1. Explain what occurs in E.Coli when no glucose is present but lactose is readily available.

-lactose binds to repressor protein, Lacl

-Lacl no longer fits in operator region because lactose changed its shape

-Lacl and lactose complex falls off DNA

-RNA polymerase can now transcribe lac operon to produce enzymes used to break down lactose into glucose and galactose

2. List four differences between prokaryotes and eukaryotes.

-prokaryotes have no nucleus

-prokaryotes have circular DNA/eukaryotes have chromosomes

-prokaryotes do not have introns

-ribosomes are smaller in prokaryotes than in eukaryotes

-translation starts with formylmethionine in prokaryotes… methionine in eukaryotes

-absence of operons in eukaryotes/ presence of operons in prokaryotes

3. Which of the two types of mutations, point or frameshift is more serious and why?

A frameshift mutation is normally worse because it usually produces a completely non-functional protein. If one nucleotide is deleted, the following nucleotides will be misread by the ribosome and the wrong amino acids will be used. A point mutation causes one nucleotide to be substituted for another. This may not change the sequence of amino acids.

4. Messenger RNA passes through the nucleus into the cytoplasm. It joins to a small ribosomal subunit at a special recognition sequence near the 5’ end. Continue the process.

-tRNA attaches to mRNA at the P site with amino acid methionine because it corresponds with start codon AUG

-large ribosomal subunit attaches itself

-another tRNA joins at A site, carrying another amino acid

- two amino acids form a peptide bond

- first RNA leaves and methionine stays with other amino acid

- ribosome shifts over and second tRNA is now in t P site, leaving A site free

-another tRNA places itself at A site... another amino acid bonds with the others and the process continues.

-ribosome reaches stop codon, no amino acid for this codon

-ribosomal subunits come apart and leave

-the polypeptide chain folds up into its specific shape and does its job

-a protein is now formed

Major concept Question