DNA Structure
Phosphodiester bonds
Which of the following would be found as heterochromatin, not euchromatin?(multiple answers are correct)
A) Heteromeres
B) Telomeres
C) Centromeres
D) Highly expressed regions of DNA
E) Mitotic chromosomes
(B, C, and E)
What is the main word that describes how DNA replication takes place?
I.E: DNA replication is ____________
DNA replication is SEMICONSERVATIVE
What are the 3 main incidences that occur that need repairing in our DNA?(Bonus points if you can explain them)
1.) Depurination: loss of purine bases(A and G)
2.) Deamination: Loss of amino group on cytosine producing uracil
3.) Double strand breaks: both strands of the double helix break in the same spot
What are the 2 main aspects that differ in DNA and RNA?
1.) RNA nucleotides are ribonucleotides that contain a ribose sugar instead of deoxyribose sugar
2.) RNA nucleotides include uracil instead of thymine
Across the rungs of the DNA ladder, nitrogenous bases are ALWAYS bound in what fashion?
Purines are always bound to pyrimidines
What is the difference between interphase and mitosis?
Interphase duplicates chromosomes, mitosis segregates these duplicated chromosomes into daughter cells.
What are replication origins typically composed of?(bonus point if you can tell me why?)
Replication origins are rich in AT base pairs because AT pairs are double bound, rather than triple bound like CG pairs, making them easier for enzymes to pull apart at the start of replication
What damage does UV radiation promote in DNA?
UV radiation promotes a covalent bond to form between 2 pyrimidine bases forming thymine dimers
What is the main difference between functioning of RNA Polymerase and DNA polymerase?
RNA polymerase does not need a primer to initiate transcription
What type of bond holds the 2 DNA strands of the double helix together?(Bonus point if you can tell me why?)
H bonds, because they are weak individually it makes it easier for enzymes to pull the strands apart during replication.
What characteristic of DNA allows each strand of the molecule to act as a template that specifies the exact sequence of nucleotides to the other strand?
The complimentarity of the bases
(A with T, U with G)
What 3 enzymes are typically involved in DNA repair?(NOT a double stranded break, that repair mechanism is different)
1.) Nucleases: recognize and remove damaged DNA
2.) Repair polymerase(DNA Pol. 1): fills the gap made by nuclease
3.) Ligase: Seals nick between old and newly synthesized DNA
What sequences tell RNA when to start and stop transcription?
Promoter and terminator sequences
In what fashion must strands be oriented in the DNA double helix?
Strands must be oriented in an Antiparallel fashion(5' end lines up with 3' end)
What is the order of DNA folding in mitosis?
What differentiates the 3' end of DNA from the 5' end of DNA?
The 3' end contains a hydroxyl group while the 5' end contains a phosphate group
What are the 2 methods used to repair a double stranded DNA break?(bonus point if you can explain why one method isn't as effective compared to the other)
1.) Non-homologous end joining(not as effective due to chewing of broken ends which can cause loss of nucleotides and gene disruption)
2.) Homologous recombination
What 4 types of RNA are produced during transcription?(bonus if you can tell me what each type is used for)
1.) mRNA: direct protein synthesis
2.) rRNA: Form structural and catalytic components of ribosomes
3.) tRNA: Directs amino acids to ribosome for incorporation into proteins
4.) miRNA: Regulate gene expression
What proteins are present in the histone octamer in the nucleosome?
2 H2A, 2 H2B, 2 H3, 2 H4
What are the 2 modifying enzymes that change nucleosome structure to allow for access to DNA?
1.) Chromatin Remodeling Complex: uses atp to change position of DNA wrapped around nucleosomes
2.) Histone-Modifying Enzymes: Catalyze addition of an acetyl group, phosphate group, or methyl group to histone tails
Name the function of each of these enzymes:
1.) Primase
2.) Nuclease
3.) Ligase
4.) Helicase
5.) Topoisomerase
6.) DNA Pol. III
7.) DNA Pol. I
1.) Primase creates the RNA primer that allows DNA Pol. III to bind to a double helix
2.) Nuclease cleaves the primer from the strand and degrades it
3.) Ligase seals the nick left from RNA primer in newly synthesized DNA via phosphodiester bonds
4.) Helicase unwinds the DNA during replication
5.) Topoisomerase relieves tension caused by unwinding by placing nicks on single strands and sealing them
6.) DNA Pol. III synthesizes new strands of DNA using the template strand via phosphate hydrolysis
7.) DNA pol. I, the repair polymerase, replaces RNA with DNA
What are the 4 steps of homologous recombination?
1.) Nuclease chews back 5' ends of both broken strands
2.) 3' end invades homologous double helix to search for its complimentary sequence
3.) Repair DNA Pol.(DNA Pol. I) elongates damaged 3' end using complimentary sequence on the homologous DNA
4.) Newly elongated strand rejoins original partner strand and additional DNA is synthesized at 3' ends followed by ligation
What assists RNA Pol. in binding and initiating transcription?
General transcription factors
Specifically TFIID that binds to TATA box and distortsthe double helix and TFIIH that phosphorylates the tail fo RNA Pol releasing it from the promoter and dissociating the complex