Biology 103 Practice Exam 3: Information Flow Within Cells- Replication, Transcription, Translation and Biotechnology Fall 2024

Similar Structural Elements of DNA and RNA

• Sugar Phosphate Backbone (Negative Charge)

• Polarity to Strand (5’ end to 3’ end)

• A,C, and G bases in common

Structural Differences in DNA and RNA

• DNA is double stranded, RNA is single stranded and may have tertiary structures

• T in DNA U in RNA

• Deoxyribose in DNA and Ribose in RNA

LG: 3-1 Intra/Intermolecular mRNA

Transcription termination signal is a hairpin loop in mRNA transcript

LG: 3-1 Intra/Intermolecular tRNA

“3 leaf clover” structure with anticodon on one end and amino acid binding site on other

LG: 3-1 Intra/Intermolecular rRNA

intramolecular H-bonds help create active sites within ribosomal complex

LG: 3-1 Intra/Intermolecular End-Key

Allows for tRNA to act as an adapter between nucleotide code and amino acid sequence

Major Function of mRNA

Dictates primary protein sequence

Major Function of tRNA

”Adapter” molecule- connects amino acid to specific nucleotide sequence through anticodon

Major Function of rRNA

Catalyzes peptide bond formation to build protein primary sequence (ribosome)

What type of RNA molecule do you expect to act as a catalyst and why?

rRNA is a catalyst, snRNPs that do mRNA splicing are also catalytic

Topoisomerase

Prevents supercoiling

DNA polymerase III

Adds nucleotides to 3’ end of existing chain, error checking

Ligase

Seals gaps in DNA backbone

Primase

Creates RNA primer for replication

SS DNA binding proteins

Stabilize opened strand

Helicase

Opens the DNA helix at origin of replication

DNA polymerase I

Replace RNA primers with DNA, error checking

List the proteins above in the order that you expect them to act in the process of replication.

Helicase and topoisomerase, ssDNA binding proteins, Primase, DNA polymerase III, DNA polymerase I, Ligase

Identify a cell type that needs telomerase and explain why it is needed in that cell type

Rapidly dividing cells need telomerase- stem cells in lining of digestive tract, skin

DNA polymerase I and III perform mismatch repairs.

True

When a mismatched base is replaced, ligase helps seal gaps in DNA backbone.

True

The error rate of bacterial polymerases is lower than that of eukaryotic polymerases.

False

What determines when transcription will stop?

mRNA transcript forms a hairpin loop

What do you need to do to ensure that the protein will indeed be transcribed by the bacterial cell machinery?

Include a bacterial promoter (-35 and -10 box), so sigma factor can bind an start transcription

List one significant advantage and one significant disadvantage of mRNA processing in eukaryotes

Advantage- provides flexibility- more proteins from a set of genes

Disadvantage-errors contribute to cancer and other illnesses

Primarily performed in tubes

PCR

Performed in living cells

CRISPR-Cas9

Produces high volumes of DNA with identical sequences

PCR

Causes mutation in specific gene

CRISPR-Cas9