Topic 1 & 2
Describe how nucleotides pair in DNA (which nucleotides bond and what bonds form... be specific!)
C triple bonds with G (hydrogen bonds)
A double bonds with T (hydrogen bonds)
Which type of RNA carries genetic info from the nucleus to the cytoplasm?
mRNA
What does it mean if a tRNA molecule is "charged?"
it is carrying an amino acid
What is the physical process that gives an organism its shape during embryonic development in eukaryotic cells?
differentiation
A point mutation that changes the 3rd nucleotide from an A to a G occurs in the following DNA template strand: 3' - CCA GGT TGC - 5'.
What type of point mutation is this?
Silent - it does NOT change the protein
A strand of DNA consists of 17.5% adenine. What percent of cytosine would you expect?
32.5%
Are promoters upstream or downstream from the desired gene transcribed? Explain why
promoters are upstream so the RNA polymerase can bind and begin transcribing downstream
P site (all other tRNA go to the A site first)
The E. coli lac operon is classified as which type of operon?
Inducible operon
What procedure allows scientists to amplify DNA?
PCR
Why do Okazaki fragments form?
The lagging strand of DNA is synthesized discontinuously in short segments, as DNA polymerase can only move in the 3' to 5' direction, leading to the necessity of synthesizing the lagging strand in a series of short fragments.
Describe the consequences of a chemical that prevents modifications on pre-mRNA in eukaryotic cells.
mRNA degradation - it won't be able to leave the nucleus to be translated
List and briefly describe the 3 sites on the large ribosomal subunit.
A site - amino acid site (holds the next tRNA carrying an amino acid)
P site - polypeptide site ( holds the tRNA carrying the growing polypeptide chain)
E site - exit site (polypeptide chain exits here)
list and briefly describe the three parts of an operon
promoter - where RNA polymerase can attach
operator - the on/off switch
genes - code for related enzymes in pathway
Why does DNA move toward the positive electrodes during gel electrophoresis?
The phosphate groups on DNA are negatively charged, which attracts it to the positive electrodes.
A section of reads 3' - ACTGATCTAAGC - 5'
Primase places an RNA primer starting at the bolded nucleotide. What would the primer sequence be?
5' - UAGAUUCG -3'
How does initiation during transcription differ between prokaryotes and eukaryotes?
For RNA polymerase to bind in eukaryotic cells, transcription factors must first bind.
In prokaryotes, RNA polymerase can bind directly to the DNA.
If a tRNA holds the anticodon CAA, what amino acid would it also carry?
mRNA = GUU
Amino Acid = Val
Briefly describe the difference between Repressible and Inducible operons.
Repressible - transcription is normally on but can be turned off
Inducible - transcription is normally off but can be turned on
Describe how a point mutation could affect the activity of an enzyme.
If a point mutation changes the amino acid or causes an early stop codon, it could reduce the functionality of the enzyme.
Researchers are experimenting with a new cancer therapy drug that works by causing the DNA strands to rebond together after they have been separated by helicase. What would be the most directly affected by this drug when DNA replicates? (Hint: an enzyme or protein that aids in DNA replication)
SSBPs (single-stranded binding proteins)
How does termination in transcription differ between eukaryotes and prokaryotes?
Prokaryotes - RNA polymerase transcribes through a termination sequence, which causes the RNA polymerase to detach from the DNA and release the mRNA transcript. mRNA is ready for translation
Eukaryotes - RNA polymerase transcribes through a polyadenylation signal sequence. mRNA must go through modifications before it is ready for translation.
Describe what needs to happen for a polypeptide chain to be released during the termination stage of translation.
A stop codon in the mRNA will reach the A binding site of the large ribosomal subunit. This stop codon signals for a release factor that will hydrolyze the bond that holds the peptide to the P site, thereby releasing it.
list and briefly describe the two ways in which chromatin structure can be modified in eukaryotic cells
Histone acetylation - adds acetyl groups to histones which loosen DNA strands
DNA methylation - adds methyl groups to DNA which causes chromatin to condense
Differentiate between transformation and transduction.
Transformation - when bacteria uptake DNA from their surroundings
Transduction - when a virus injects its DNA into a bacterial cell (sometimes bacterial DNA is incorporated into the viral DNA)