Nucleic acids Flashcards
What is DNA?
Double stranded polymer of nucleotides which carry the info for protein synthesis
What pentose sugar does DNA contain?
Deoxyribose
What is RNA?
Single stranded polymer of nucleotides
What sugar does RNA contain?
Ribose
What is a polynucleotide?
Polymer of nucleotide monomers covalently bonded together
What is an organic nitrogenous base?
An organic compound containing nitrogen, which is part of all nucleotides
What is a nucleotide made up of?
A phosphate, 5-carbon sugar, and a nitrogenous base
Why is the pentose sugar called 5-carbon sugar?
Either a ribose or deoxyribose molecule, both of these contain 5 carbon atoms
What are the organic nitrogenous bases?
A - adenine C - cytosine G - guanine T - thymine U - uracil
What are the complementary base pairs?
All teachers care gently
a - t
c- g
a - u
In which type of nucleic acid is the base Pais a with u instead of t?
RNA
What are the two types of bases?
Pyrimidines and purines
How many carbon-nitrogen rings does pyrimidine bases consist of?
1
How many carbon-nitrogen rings does purine bases consist of?
2
Which bases are pYrimidines?
ThYmine (Also have Y)
CYtosine (Also have Y)
Uracil (replaces T)
Which bases are purINE?
AdenINE
GuanINE
How is a polynucleotide formed?
The phosphate group of one nucleotide bonds to the sugar molecule of another, forming one long continuous polynucleotide (half a DNA strand)
How do we go from a polynucleotide to the nucleic acid - DNA?
Two polynucleotide chains join together with hydrogen bonds between both polynucleotides nitrogenous bases (hydrogen bonds)
After two polynucleotide chains have joined to form the nucleic acid, how does it fully become DNA?
Once it contains a sugar deoxyribose and the base thymine
What is complementary base pairing?
A will only pair with T (forming two hydrogen bonds), and C will only pair with G (forming three hydrogen bonds)
What is important about complementary base pairing?
Molecule will become very stable and same width all the way down the chain (due to bases holding backbone same width apart)
Describe antiparallel in terms of DNA?
The two polynucleotides and in opposite directions top one another so that the bases meet and bond together in the middle
What is semi-conservative replication?
Each new DNA molecule is made up of 1 conserved stand from original template, and 1 new strand of nucleotides
What does the enzyme DNA helicase do in the first stage of DNA semi-conservative replication?
Unwinds and unzips the double stranded helix, breaking the hydrogen bonds, leaving 2 individual strands
Into what shape is the now 2 singular strands of nucleotide, unzipped into?
A fork, one end becomes the leading strand and the other, the lagging strand
Which strand is the lagging strand?
The one the wrong way up
How does complementary base pairing occur once unzipped, in the second stage of S-CR?
New and free nucleotides in nucleus attach to exposed bases, forming hydrogen bonds
What does DNA polymerase do?
Catalyses the condensation reaction which covalently bonds the new nucleotides to the adjacent base
In stage 3 of S-CR what happens to the leading strand?
DNA polymerase zooms down the strand (in same direction as unzipping) , base pairing is an efficient and continuous process
In stage 3 of S-CR what happens to the lagging strand?
Due do DNA polymerase moving in opposite direction to unzipping, process is a lot slower
What is the triplet code?
The three nitrogenous bases read along the DNA strand that code for DNA
What is the definition of transcription?
The process of exactly copying the genetic code to form a template of mRNA
What is the genetic code?
The triplet code, 3 bases coding for an amino acid
How is mRNA structured?
Single stranded, contains ribose (instead of deoxyribose) and contains uracil instead of thymine
What are the two processes in protein synthesis?
Transcription and translation
What is a gene?
A short length of DNA, a sequence of bases that code for the amino acids which make up an individual protein
What are the two separate strands in a gene?
The coding strand and the template strand
Why does protein synthesis occur?
When the cell needs to produce a specific protein
What is the first stage of protein synthesis?
Enzyme RNA polymerase binds to the gene and unzips the two DNA strands
What direction does the RNA polymerase move?
In the 3’ to 5’ direction
What is the second thing the RNA polymerase does in protein synthesis?
Pairs free RNA nucleotides with complementary nucleotides on the DNA template strand (covalently linked by phosphodiester bonds)
How is the mRNA formed from the RNA?
The complementary RNA nucleotides covalently link to those on the template strand by phosphodiester bonds, making a polynucleotide chain, growing in the 5’ to 3’ direction
Whats the first stage of translation?
mRNA leaves the nucleus via the nuclear pore with small sub unit of ribosome and act as a template for proteins to be synthesised
What is a codon?
A triplet
What is an anticodon?
The complementary triplet to the mRNA codon
What is a tRNA molecule?
Transfer molecule, has an anticodon one end, the sugar-phosphate backbone, and the other is the region for the particular amino acid to attach
What happens after tRNA molecules attach to a ribosome?
The anti codon which is complementary to the codon, pair up on the mRNA
What happens to amino acids transported by tRNA?
They join together by a condensation reaction forming peptide bonds
When does translocation stop?
When tRNA molecules go back to cytoplasm, ribosome has moved along whole mRNA strand and all amino acids have joined, ending with a stop codon
What is rRNA (ribosomal)?
Site of protein synthesis, when RNA molecules are attached to ribosomal protein molecules
Whats the helical structure of RNA?
A polynucleotide chain twists into helix and coils back on itself, some sections of the chain join to other parts for tRNA/mRNA, however mRNA is linear
