Unit 1: Nucleic acids Flashcards
What is a nucleic acid ?
A long repeating chain of nucleotides
Give 2 examples of nucleic acids
- DNA
- RNA
What are the 3 components of a nucleotide ?
- 3 phosphate groups
- A central sugar ring
- A nitrogenous base
What is a nucleoside ?
Contains a sugar and a base without the phosphate groups
What is the sugar in DNA ?
Deoxy-ribose
What direction are the carbon atoms always numbered in ?
Clockwise
What are the 4 bases in DNA ?
- Cytosine
- Thymine
- Adenine
- Guanine
What are the 2 categories of nucleotide bases ?
- Pyrimidines
- Purines
Which 2 bases are in the pyrimidines ?
- Cytosine
- Thymine
Which 2 bases are in the purines ?
- Adenine
- Guanine
What is a good way of remembering which bases fit into which category ?
- Smaller 2 bases (C and T) are in the longest word (Pyrimidines)
- Larger 2 bases (A and G) are in the shortest word (Purines)
What is a dNTP ?
A deoxyribose + adenine + triphosphate
What is the nucleotide for adenine ?
Deoxy-adenosine triphosphate
What is the nucleotide for guanine ?
Deoxy-guanosine triphosphate
What is the nucleotide for cytosine ?
Deoxy-cytidine triphosphate
What is the nucleotide for thymine ?
Deoxy-thymidine triphosphate
What is directionality in reference to DNA ?
That DNA is read in the 5’ to 3’ direction (From left to right)
Where are new nucleotides added to a strand of DNA ?
At the 3’ end
What is chargaffs rule ?
That in double stranded DNA, there is a 1:1 ratio of purine molecules to pyrimidine molecules
Why is bonding between G and C stronger than between A and T ?
- Between C and G is 3 H bonds
- Between A and T is 2 H bonds
- Between G and C there is a higher affinity, they are more stable and therefore harder to separate
What protein structure is a DNA helix an example of ?
A secondary structure
What are the 3 key differences between DNA and RNA ?
1) RNA is single stranded
2) RNA contains ribose as opposed to deoxyribose
3) RNA contains uracil in place of Thymine
Why is ribose very reactive and less stable than deoxyribose ?
As ribose has an extra O on its C2’
What is the job of mRNA?
Codes for cellular proteins
What is the job of tRNA ?
Involved in bringing amino acids to the ribosome
What is the job of rRNA?
Structural RNAs that contribute to the ribosome
What is the job of snRNA?
Involved in the mRNA splicing in the nucleus
How can RNA give rise to a secondary structure ?
As base paring can occur between nucleotides in a single RNA strand
How can RNA give rise to a tertiary structure ?
Due to further 3 dimensional folding
