Chapter 4 : DNA and RNA Flashcards
Why are DNA and RNA so important.
They are able to carry genetic information
What are the three components of nucleic acids ?
- 5 carbon sugar
- nitrogenous base
- phosphate group
What are the two types of nitrogenous bases ?
- Pyrimidine
- Purine
What is the difference between pyrimidines and purines ?
Pyrimidines contain one ring while purines contain two rings
What is the similarity between pyrimidines and purines
Both are insoluble in water and have a planar structure
Which bases are pyrimidines ?
Cytosine, Uracil and Thymine
Which bases are purines ?
Adenine and Guanine
What are some other purines not commonly used ?
- hypoxanthine
- xanthine
- uric acid
What are nucelosides ?
Contains a nitrogenous base and a sugar ( ribose or deoxyribose )
What is the difference between a nuceloside and a nucleotide
Nucleotides contain a phosphate group and nucleosides don’t
How are nucelosides named ?
Add - idine to the root name if it’s a pyrimidine an - osine if it is a purine
What carbon is the phosphate located on the nucleotide ?
The 5th carbon
True or false, nucleotides are weak polyprotic acids
False, nucleotides are strong polyprotic acids. They can dissociate 3-4 protons from their phosphate groups
Phosphate anions form stable complexes with divalent cations. Which one is most common?
Complexes with Mg(2+)
Nucleic acids are the polymers of ______
nucleotides
What kind of bonds connect nucleic acids together ?
phosphodiester bonds
Where is a phosphodiester bond created ?
Between the C3 ( OH) of one nucleotide and the C5 phosphate of the next nucleotide
What is the difference between the 5’ direction and the 3’ direction
Phosphate on the C5 indicates the 5’ end . -OH on C3 indicates the 3’ end
DNA has what type of backbone ?
sugar phosphate backbone
Adenine binds with
Thymine
Cytosine binds with
Guanine
Thymine can bind with either
Adenine or Uracil
How many hydrogen bonds are between C and G ?
3
How many hydrogen bonds are between A and T
2
Why does DNA have a helical structure
DNA is double stranded
The sequence of bases also indicates the sequence of
amino acids in proteins
How is DNA size indicated
By the number of base pairs
True or False, the two strands of DNA have an anti- parallel orientation .
True, one strand has the 5’ to 3’ end while the other strand is the 3’ to 5’ end
What makes the double helix of DNA so stable ?
- Hydrogen bonding between the bases
- Hydrophobic effect from structure of bases
- Stacking effect of bases
What are the 3 different conformations of DNA?
A , B, and Z
B DNA
The most common form of DNA. Termed the right handed helix . The major groove is wide while the minor groove is narrow, both intermediate size.
A DNA
- Formed when DNA is dehydrated
- found in some DNA- RNA hybrids
- Longer right handed helix
- Major groove is narrow and deep while minor groove is broad and shallow
Z DNA
- biological role is unknown
- binds to some viral proteins
- Left handed helix
- Methylation of C can change Z to B form
- Major groove is flattened out and the minor groove is narrow but deep
How are stem loop structures formed?
Single stranded nucleic acids fold back on themselves
Examples of stem loop structures
ssDNA and RNA
What makes up the stem in the stem loop structure
Base pairs
What makes up the bulge of the stem loop structure ?
mismatched or unmatched bases
How can DNA be denatured?
- Heat or UV radiation
- pH extremes
Tm or Melting temperature is dependent on what ?
% of GC content and % of AT content
If DNA is removed from denaturing effects, , can the strands renature ?
Yes through a process known as renaturation
Renaturation is dependent on what ?
DNA concentration and time
The rate of renaturation indicates
How complex the DNA is. The more repeated DNA is , the faster it will reform compared to unique sequences. It also indicates length.
Why does DNA have a major groove and a minor groove ?
Since DNA is anti- parallel, the nucleotides are placed at an angle instead of directly across. This can cause the strand’s backbone to be closer or father apart from each other
When DNA is denatured, what bonds are being broken between the bases ?
Hydrogen bonds
Why does DNA with a higher GC content require a higher temperature to be denatured ?
More hydrogen bonds to break
What are the three types of RNA
mRNA , rRNA , and tRNA
mRNA
Messenger RNA : The RNA copy of the DNA base sequence which is used for protein synthesis.
- Also contain a poly A tail an a 5’ cap
rRNA
Ribosomal RNA : Major component of ribosomes. It contains two subunits of different sizes
tRNA
Transfer RNA : carries the appropiate amino acid to the polypeptide chain
What kind of secondary structure does tRNA form
Cloverleaf structure that contains acceptor stem, anti-codon loop , D-loop, Tψ loop, and variable
loop
