Flashcards in Biochemistry L5/6 - Gene structure and function Deck (27):
What type of bonds exist between complimentary bases of the 2 anti parallel DNA strands in a DNA double helix? How do these protect DNA?
They keep the charged phosphate sugar backbone facing the water environment, protecting the bases in the middle.
Which enzyme catalyses the addition of nucleotides during replication of DNA
DNA polymerase III
In what direction does DNA synthesis always occur, and how do you distinguish between the two ends?
5' to 3'. The 5' end is the amino end, while the 3' end features a hydroxyl group from the carboxyl group
Where DNA contains thymine, RNA contains which base?
At which part of a gene is the promoter located?
5' to the transcription start site
What are the two main types of RNA processing (to make mature mRNA)
5' capping, addition of a polyA tail (for nuclear export and stability)
Which amino acid always initiates translation
What are the 3 stop codons and do they code for an amino acid
UAA, UAG, UGA.
Don't code for an amino acid
What end of tRNA is the amino acid attached to and what is tRNA with an amino acid attached referred to as
3' end, aminoacyl-tRNA
What are the four stages of protein synthesis
Amino acid activation, initiation, elongation, termination
What is an example of a general transcription factor
Housekeeping gene. General TF are expressed in all cells
What are the 3 main constituents of a nucleotide
Nitrogenous base, pentose sugar, phosphate
What does a nucleoside consist of
Which two bases are purines
Guanine and adenine
What is the building block of DNA synthesis
Nucleoside triphosphate (dNTP)
What are the 4 steps (include enZymes involved) in synthesis of the lagging strand
Lagging strand synthesis is discontinuous
1. Primase synthesizes RNA primer
2. DNA pol III elongates RNA primers with new DNA a
3. DNA pol I removes RNA at 5' end of neighboring fragment plus fills the gap
4. DNA ligase connects adjacent fragments
What is an exon?
A coding region of DNA, separated from each other by non-coding regions called introns
Do regulatory regions contain information about the structure of a gene product?
No. They contain sequences that are recognised and bound to by proteins that make a gene's RNA, and also by proteins that influence how much of the gene should be made
What is the difference between DNA and RNA sugars?
The ribose sugar has an extra alcohol group where a deoxyribose sugar has a hydrogen
What are Nucleic Acids?
Polymers of nucleotides, linked by phosphodiester bonds
Which bases are pyrimidines and how many rings to they have?
PyCT - pyrimidines are Cytosine and Thymine. These are ONE ringed structures
What is a regulatory sequence?
A binding site for gene regulatory proteins that affects transcription rates. These DO NOT have to be close to promotor regions, and can even be in introns
Do purine bind to other purines, or to pyrimidines and why?
Purines bind to pyrimidines, which keeps an even radius to the DNA double helix - purines are big (double rings) and pyrimidines are small (single rings). This is Complementary Base Pairing - Adenosine binds to Thymine, Cytosine binds to Guanine
What do the terms degenerate, and unambiguous refer to in regards to DNA and amino acids?
Degenerate: every amino acid is coded for by at least one codon
Unambiguous: one codon codes for only one amino acid
What is the charge on a:
1. nucleic acid
2. amino acid
Which enzyme unwinds DNA for replication, and which nucleotides feature strongly in origin of replication regions?