DNA and Chromosomes
What region of DNA is tightly wound not allowing transcription factors in?
Heterochromatin
What is the Replisome?
The replisome is the replication machine that contains all the proteins required for DNA replication.
When is an mRNA considered mature?
After it has gone through 5' capping, the addition of a poly A tail, and RNA splicing.
What do ubiquitin chains do when added to proteins?
ubiquitin chains degrade proteins into amino acids
What is the start codon?
AUG
What does the Histone protein H1 do?
Helps pack the “beads” into a tight structure. 30 nm fiber.
What Direction does DNA Polymerase Synthesize?
3' to 5'
Only add nucleotides to the 3' end.
What do sigma factors tell the cell in bacterial transcription?
Sigma factors tell RNA Polymerase where to bind on the promoter region to start transcription.
Deacetylation of histones has which of the following effects?
a) Uncoiling of histone structure, preventing it from being accessed by transcriptional machinery
b) Uncoiling of histone structure, allowing it to be accessed by transcriptional machinery
c) Coiling of the histone structure, allowing it to be accessed by transcriptional machinery
d) Coiling of the histone structure, preventing it from being accessed by transcriptional machinery
Coiling of the histone structure, preventing it from being accessed by transcriptional machinery
What are the 8 histone proteins that make up the nucleosome?
2 molecules of H2A
2 molecules of H2B
2 molecules of H3
2 molecules of H4
How many hydrogen bonds are between A-T and G-C? and why is this important?
there are 2 hydrogen bonds between A-T and 3 hydrogen bonds between G-C. This is important because 2 hydrogen bonds are easier to break than 3 hydrogen bonds.
How many RNA primers does the leading strand need vs the lagging strand?
Only one RNA primer is needed for the leading strand and there are many needed for the lagging strand.
What is the purpose of aminoacyl-tRNA synthetases?
to create a high-energy bond between amino acid and tRNA.
What do RISC and DICER do?
DICER: Cuts double-stranded RNA into shorter segments
RISC: Processed them so they become single-stranded RNA molecules.
This process of RNA interference will allow the single-stranded RNA to search for foreign Double-stranded RNA and will degrade it.
In what phase do most of our cells spend time in?
G0
How many pairs of homologous chromosomes are in the cell?
22 homologous Pairs
What is special about DNA Polymerase?
DNA Polymerase can proofread its work to check for errors. This process occurs from the 3' to 5' direction.
What do transcription factors TFD II and TF IIH do?
TFDII: will bind to the TATA box which allows RNA polymerase II to bind
TFIIH: will act as helicase
How is transcription controlled in eukaryotes
Repressor and activators
Intron splicing
Addition of 3’ polyadenylated tail
Addition of 5’ cap
What are the origins of replication (ORI's)? and how many eukaryotic cells have?
The site where DNA first opens up. Eukaryotic cells have many sites.
what does the chromatin remodeling complex do?
Use energy to loosen or tighten DNA for accessibility.
Explain homologous vs. non-homologous end joinign
Non-homologous end joining does not use homologous chromosomes. Nuclease removes some of the nucleotides, and then DNA Ligase glues the strand back together. This is a quick and easy process, and it is normally okay because most of our DNA is Intergenic.
Homologous Recombination is a more complex process. A process called strand invasion happens when a homologous strand invades the chromosome and it will be used as a template. This process is much slower but way more accurate than non-homologous end joining.
Explain the EPA sites on the Ribosome and how they help create a peptide chain.
the 5' mRNA will look for, AUG, the start codon, and once found it will bind to the P site. A new tRNA will bind to the A site and the growing peptide chain will release from the P site to the A site forming a peptide bond with the amino acid in the A site. After this happens the reading frame will shift over, so what was in the P site is not in the E site where it wall exits the ribosome.
How does the shap of the untranslated region determin wheathe a gene gets expressed?
Untranslated regions can change their shape so transcription factors cannot bind and the proteins do not get made.
How does the leading strand differ from the lagging strand?
The leading strand can be directly synthesized by DNA Polymerase and only has one RNA primer but the lagging strand can only be synthesized in small fragments called the Okazaki fragments. The lagging strand has many Okazaki fragments.