DNA/RNA Structure
What are the three parts of a nucleotide?
Phosphate group, nitrogenous base, sugar (deoxyribose/ribose)
Why is DNA replication a semi-conservative process?
Each new DNA molecule produced consists of one parental strand from the original DNA molecule and one strand newly synthesized through replication
Name and describe the function of the three classifications of RNA.
mRNA: delivers instructions provided by DNA from nucleus to ribosome
tRNA: Uses complimentary anticodons to recruit the correct amino acid during protein synthesis
rRNA: Functional building blocks of the ribosome
What is the main difference between prokaryotic and eukaryotic translation? Why do they have this difference?
Pro = transcription and translation can occur simultaneously due to the lack of nucleus/organelles
In prokaryotes, what do we call blocks of proteins that are involved in the same biochemical pathways?
Operons
Define plasmid. What role do they typically play in prokaryotes?
Extrachromosomal circular molecules of DNA; aid in antibiotic resistance
Which enzyme is responsible for adding nucleotides to the growing DNA strand complementary to the template strand?
Describe the difference between the template strand and the coding strand.
Template strand is read by RNA Pol = complementary to mRNA transcript
Coding strand is not read by RNA Pol = identical (with U replacing T) to mRNA transcript
Explain the connection between the genetic code and evolution.
Nearly all living organisms follow genetic code = evidence for a common ancestor
Describe the difference between positive and negative regulators within operons.
Negative = expression silenced, positive = expression activated/increased
What proteins act as "spools" for the DNA, condensing and winding chromatin into chromosomes?
Histones
What is the function of the RNA primer?
Provides a free 3'-OH group for DNA Pol to add a 5' phosphate group to begin replication
What three components must be present for transcription to occur?
RNA Polymerase, Transcription Factors, Promoter Sequence
Describe the three steps of translation.
Initiation = AUG starts polypeptide with Met
Elongation: tRNA recruits amino acids as determined by the mRNA transcript to be added to the polypeptide
Termination: rRNA recognizes one of three stop codons, signaling the polypeptide to be released from the ribosome
Explain the function of the trp operon when tryptophan is present vs. when tryptophan is absent.
Trp present = repressor bound to operator, transcription does not occur, expression is silenced
Trp absent = repressor free, RNA Pol can bind and transcribe, expression turned on
What classification of bond is found between adjacent nucleotides? What classification of bond is found between complementary nitrogenous bases?
Phosphodiester; Hydrogen
What are the roles of DNA helicase and topoisomerase?
DNA Helicase unwinds the double helix to form the replication fork while topoisomerase travels ahead of the fork, relaxing supercoiling
Identify and explain three requirements that need to be completed for pre-mRNA to become mature mRNA?
poly-A tail: sequence of adenines added to 3' end, aids in stability and transportation
GTP Cap: Functional group added to 5' end, protects from degradation and aids in ribosomal recognition
Splicing: removing introns and reconnecting exons
Would a substitution, insertion, or deletion be the most detrimental mutation within a DNA sequence?
Deletion because it is loss of genetic material; no protein being made is more likely to have a negative impact than an incorrect protein
Describe eukaryotic epigenetic control.
Histones can move along DNA to expose or block different genes to promote or prevent transcription
Adenine and guanine are (purines/pyrimidines) with a (single/double) ring structure. Thymine, cytosine, and uracil are (purines/pyrimidines) with a (single/double) ring structure.
A/G = purines w/ double ring
T/C/U = pyrimidines w/ single ring
Why does eukaryotic replication involve telomerase while prokaryotic replication does not?
Prokaryotic DNA is not linear; eukaryotic DNA has protective ends (telomeres) on linear chromosomes which telomerase attaches
The human TPM1 gene encodes members of the tropomyosin family of cytoskeletal proteins. Which of the following best explains how different proteins can be made in different cell types from the one TPM1 gene?
Varied exons retained/spliced during RNA processing
How does mutation influence evolution?
Mutation = new phenotypes introduced; natural selection will favor advantageous traits and select against negative traits
Explain the role of lactose and the cAMP + CAP complex in regards to lac operon function.
Lactose must be present for expression to turn on (when absent, repressor is bound); cAMP + CAP complex binds to promoter to stimulates RNA Pol activity, increasing transcription