1. Nucleic Acids and Gene Expression Flashcards
1
Q
Types of nucleic acids
A
- DNA
- RNA
2
Q
DNA
A
Deoxyribonucleic acid
3
Q
RNA
A
Ribonucleic acid
4
Q
Components of nucleotides
A
- 5-carbon/pentose sugar (ribose or deoxyribose)
- nitrogenous base (A,T,G,C,U)
- phosphate group
5
Q
Ribose vs Deoxyribose
A
Ref. to carbon 2 carrying hydroxyl group (-OH) or hydrogen atom
6
Q
Types of nitrogenous bases
A
- purines
- pyrimidines
7
Q
Purines
A
- A, adenine
- G, guanine
8
Q
Pyrimidines
A
- T, thymine
- C, cytosine
- U, uracil
9
Q
Number of C in PURINES
A
5 carbon atoms
10
Q
Number of C in PYRIMIDINES
A
4 carbon atoms
11
Q
Which C is the nitrogenous base attached to?
A
Carbon 1
12
Q
Which C is the phosphate group attached to?
A
Carbon 5
13
Q
Formation of nucleotides
A
- 3 components joined through condensation reactions involving removal of water molecules
- nitrogenous base attached to C1 through a glycosidic bond, forming a NUCLEOSIDE
- pentose sugar attached to C5 through a phosphoester bond, forming a NUCLEOTIDE
14
Q
Formation of nucleic acids from nucleotides
A
- nucleotides added as deoxyribonucleoside triphosphates (dNTPs) / ribonucleoside triphosphates (rNTPs)
- lose 2 phosphate groups (pyrophosphate) in the process
- condensation between 5’ phosphate group of incoming nucleotide and free 3’ -OH group of growing polynucleotide chain; phosphodiester bond
15
Q
Structure of DNA
A
- 2 strands of deoxyribonucleotide chains twisted to form double helix; held by hydrogen bonds between complementary nitrogenous bases (2 in A-T, 3 in G-C)
- uniform diameter of 2.0nm between the 2 sugar-phosphate backbones (as purine always paired with pyrimidine)
- one complete turn of helix consists of 10 base pairs spanning 3.4 nm
- anti-parallel
16
Q
Significance of base pairing in DNA
A
- large number of hydrogen bonds confer stability; template for replication of new DNA strands and transmission of genetic information stored
- deviation of diameter from 2.0nm; anomalies easily detected and allows proofreading during DNA replication
17
Q
Bonds in a DNA molecule
A
- H bonds between complementary base pairs
- hydrophobic interactions between stacked bases
- phosphodiester bonds between nucelotides
18
Q
DNA packing
A
- DNA molecule negatively charged, histones positively charged
- DNA double helix winds around group of 8 histone proteins, forming nucleosomes
- adjacent nucelosomes linked by linker DNA, forming bead-on-string structure
- coils into 30nm thick solenoid, stabilised by H1 histones
- solenoid folds into 300nm thick loop domains, stabilised by scaffold proteins
- further coils and packs into chromosome; 2 sister chromatids joined at centromere
