Ch. 3 Flashcards
Which bases are purines?
Adenine and guanine
Which bases are pyrimidines?
Cytosine, thymine, and uracil
How many rings does purines have?
2 rings
How many rings do pyrimidines have?
1 ring
Why is RNA more unstable than DNA?
RNA has ribose which has a 2’ OH
What are the 3 types of DNA structures?
A-DNA, B-DNA, and Z-DNA
What is the most stable DNA structure?
B-DNA
Which DNA structure is common in cells?
B-DNA
What form is DNA usually in?
B-DNA
Which DNA structures can sometimes be in the same molecules?
B-DNA and Z-DNA
What does it mean if Z-DNA is next to B-DNA?
Transcription of the B-form is about to occur
Which DNA structure(s) is/are right handed?
A-DNA and B-DNA
Which DNA structure(s) is/are left handed?
Z-DNA
How are the base pairs in DNA similar to the hydrophobic effect in membranes?
- Nitrogenous bases in DNA are hydrophobic so they interact primarily with each other but not water
- Water doesn’t have to be organized around them
What is Chargaff’s rule (concept and equation)?
- A-T means A binds to T and G-C means G binds to C (Watson-Crick base pairs)
- [A+T]/[G+C] is characteristic of different species
What affects DNA stability?
Base stacking stabilizes the helix via van der Waals interactions and hydrophobic effect
What are the functions of DNA?
- Genetic material of most organisms and some viruses
- Inheritance
- Gene expression (template for transcription of RNA)
- Sequences surrounding a gene regulate gene expression
- More stable than RNA
What are the functions of RNA?
- Genetic material of some viruses
- Gene expression (translation)
- Determines which proteins are present
What are the functions of nucleotides?
- Drive endergonic reactions
- Cell signaling (activators, secondary messengers, allosteric regulation of enzymes, phosphorylation of enzymes for regulation)
Why is supercoiling needed?
Keep DNA inside cells
What induces supercoiling?
DNA replication and transcription
What relieves supercoiling?
Topoisomerases I and II
What does topoisomerase I do?
Cleaves 1 DNA strand at a time
What does topoisomerase II do?
Cleaves 2 DNA strands at a time
What is the coding strand?
The same sequence as mRNA but T is replaced with U
What is the template strand?
The DNA strand that is copied
What is the start codon nucleotide sequence in the template strand?
3’ - TAC - 5’
