Chapter 33 The Structure of Informational Macromolecules:DNA and RNA Flashcards
What does the Adenine structure look like?
It has the purine base( hexagon connected to a pentagon) and then a NH bonded to the H on top that turns into a NH2
What does the Guanine structure look like?
It has the purine base( hexagon connected to a pentagon) and then A oxygen double bonded to the top
What does the Cytosine structure look like?
It has a pyrimidine base( A hexagon) and a NH2 bonded to the top
What does the Uracil look like?
It has a pyrimidine base( A hexagon) and a oxygen double bonded to the top
What does the Thymine structure look like?
It has a pyrimidine base( A hexagon) and a oxygen double bonded to the top and a CH3 single bonded to the right of the oxygen
What are Nucleosides?
Riboses with a 1’-nitrogenous base
Whats the difference in ribose and deoxyribose structure?
In ribose there is an OH at the 2’ spot and in deoxyribose there is only a H at the 2’ spot
What is a Bets-Glycosidic Linkage in a Nucleoside?
It is a bond between the anomeric carbon and the nitrogen
What is a Adenosine?
It is a local hormone and neuromodulator
Ribose + Adenine=
Adenosine
Ribose + guanine =
Guanosine
Ribose + Cytosine=
Cytidine
Ribose + Uracil=
Uridine
Ribose + Hypoxanthine=
Inosine
Deoxyribose + Thymine=
Thymidine
Deoxyribose + Adenine =
Deoxyadenosine
Deoxyribose + Guanine
Deoxyguanosine
Deoxyribose + Cytosine=
Deoxycytidine
What is a Nucleotide and what is the structure of it?
A nucleotide = Nucleosides+phosphate. The structure includes Ribose-5’-phosphate+Nitrogenous base.
What are cAMP and cGMP and what do they do?
They are second messengers and are important in intracellular “signal transduction”
What are Nucleic Acids composed of ?
They are long, linear polymers constructed from four types of monomers.
What is each monomer consist of in a Nucleic Acid?
They consist of sugar, a phosphate and a base
What is the information content of the Nucleic acid?
The sequence of the bases is the information content
What does the backbones of DNA and RNA consist of?
The sugars linked by phosphodiester bridges between the 3’-hydroxyl of one sugar and the 5’-hydroxyl of an adjacent sugar
Bases are attached to ________________ in the _______
carbon atom 1’,sugar
What do the Phosphodiester bonds link?
The 3’ OH to the 5’ OH
What do the backbone and side chains of a nucleic acid consist of?
Backbone=Sugar-Phosphate
Side chains=Bases
Where are the sugar phosphate backbones and the bases located on the helix?
The sugar phosphate backbones are on the outside of the helix and the bases are on the inside of the helix
The bases are nearly ___________________ to the axis of the helix with the ___________ bases separated by ______
perpendicular, adjacent, 3.4 angstrom
How wide is the Helix
Approximately 20 angstrom wide
What is the double helix stabilized by?
By hydrogen bonds between base pairs as well as by hydrophobic interactions and van Der Waals forces called stacking forces, between adjacent bases
What contributes the most to the stability of the double helix?
The base stacking
Why are G-C pairs stronger than A-T bond?
Because G-C has 3 hydrogen bonds but the A-T only has 2 hydrogen bonds
What is the difference between the A and B form of the double helix ?
The A form is shorter and Widder the the B form, with the bases at an angle rather than perpendicular to the helix axis.
What is the Z form DNA?
It is a left handed helix in which backbone Phosphoryl groups zigzag
What are Palindromes?
This is when the DNA strands read the same forward and backward.
The unwound DNA and the supercoiled form are _______________________ of each other.
Topological isomers
Linear DNA molecules can also form superhelices when packaged into _________________
Chromosomes
There are ___ meters of DNA in a human cell, packaged into __ chromosomes
3.6 , 46
What helps with the compacting of the DNA
the supercoiling and some compaction occurs by binding certain proteins to the DNA
What is a chromatin?
It is the entire complex of a cell’s DNA and its. associated proteins.
Which highly basic proteins are components of chromatin?
Histones
What is a Nucleosome composed of?
Two copies each of histones H2A,H2B,H3,H4 and 200 base pairs of DNA
Nucleosomes are joined by _____________, to which ______________ binds, so that the histone-DNA complex has the appearance of beads on a string
Linker DNA, Histone H1
What is a RNA structure composed of ?
Its usually single stranded and usually a right handed helix
How are most genes regulated?
This happens when the RNA comes and bind to the DNA
In Eukaryotes, DNA is made and stored where?
Nucleus
Where is the DNA information transcribed into RNA?
Nucleus
In eukaryotes, where are proteins made?
In the cytoplasm according to information stored in the DNA
What is a Monocistronic?
RNA that encodes 1 polypeptide
What is a Polycistronic?
RNA that encodes 2 or more polypeptides
what helps carry the amino acids to the mRNA for protein assembly?
Transfer RNA
What is the catalytic component of the Ribosome and what does it help with?
Ribosomal RNA and it is a machine for assembling proteins
What is MicroRNA?
About 22 base pairs, double stranded RNA molecules that regulate the expression of mRNA.
What is Long non coding RNA-IncRNA?
Longer RNA transcripts that regulate gene transcription.
What happens to the DNA double helix at a high temperature or extremes of pH?
It denatures, H-bonds are broken, bases unstack , and the strands separate.
What is Hyperchromicity ?
This is when Denaturation is detected by an increase in uv absorption of the single strands.
What is Hypochromicity?
This is when Renautration of the double helix causes a decrease in uv absorption.
Why do G-C bonds denature at a higher temperature compared to A-T bonds in DNA
its because of the 3 hydrogen bonds in G-C and A-T has only 2 hydrogen bonds
If DNA contained U instead of T, how would enzymes react?
IF they find a U they convert it back to T, aka deamination
What is Depurination?
It is when it repairs the damaged DNA by looking at the complimentary strand to check what is suppose to be in the first strand.
How does the UV light damage the DNA structure?
It causes the two same nucleotide bases to form covalent bonds and it causes kinking in the DNA
