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DNA RNA Genetics Basics
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1
Question
What is the basic chemical structure of a DNA nucleotide?
Answer
A nitrogenous base, a pentose sugar (deoxyribose), and a phosphate group.
2
Question
Which nitrogenous base is present in DNA but not in RNA?
Answer
Thymine.
3
Question
How are two nucleotides linked in DNA?
Answer
Through a 3'-5' phosphodiester bond.
4
Question
What does Chargaff's rule state?
Answer
The amounts of adenine and thymine are equal, and the amounts of guanine and cytosine are equal, indicating base pairing.
5
Question
Describe features of the DNA double helix.
Answer
Two antiparallel strands, sugar-phosphate backbone, complementary base pairing via hydrogen bonds, right-handed coiling, and uniform base pair spacing.
6
Question
Why is the distance between DNA strands constant?
Answer
Due to the size and pairing rules of purines and pyrimidines, maintaining a uniform helix diameter.
7
Question
What is the role of histones?
Answer
They form nucleosomes by wrapping DNA around histone octamers, aiding in DNA packaging.
8
Question
Difference between a nucleoside and a nucleotide?
Answer
A nucleoside consists of a nitrogenous base and sugar; a nucleotide includes these plus a phosphate group.
9
Question
What is semiconservative DNA replication?
Answer
Each daughter DNA molecule contains one parental strand and one newly synthesized strand.
10
Question
Which experiment proved semiconservative replication?
Answer
Meselson and Stahl’s density gradient centrifugation experiment.
11
Question
Why is DNA more stable than RNA?
Answer
Because DNA lacks the 2'-OH group, making it less reactive and more resistant to hydrolysis.
12
Question
What is the significance of thymine?
Answer
Thymine’s methyl group adds to DNA stability and reduces mutation rates.
13
Question
Which enzyme primarily synthesizes DNA during replication?
Answer
DNA-dependent DNA polymerase.
14
Question
Function of DNA ligase?
Answer
Joining Okazaki fragments on the lagging strand.
15
Question
In transcription, which DNA strand serves as the template?
Answer
The 3'-5' strand.
16
Question
What is the role of a promoter?
Answer
It provides a binding site for RNA polymerase and initiates transcription.
17
Question
Why is only one DNA strand transcribed?
Answer
To produce a specific RNA sequence and prevent formation of double-stranded RNA.
18
Question
Regions in a transcription unit?
Answer
Promoter, structural gene, terminator.
19
Question
Difference between monocistronic and polycistronic genes?
Answer
Monocistronic mRNA encodes one gene; polycistronic encodes multiple genes.
20
Question
Main types of bacterial RNA?
Answer
mRNA, tRNA, rRNA.
21
Question
Why can DNA act as genetic material?
Answer
It can replicate accurately and is chemically stable.
22
Question
Key conclusion of Hershey and Chase?
Answer
DNA, not protein, is the genetic material passed into bacteria.
23
Question
Chemical difference between DNA and RNA?
Answer
DNA has deoxyribose and thymine; RNA has ribose and uracil.
24
Question
Why is DNA less reactive than RNA?
Answer
Absence of 2'-OH group in DNA reduces reactivity.
25
Question
What defines a gene?
Answer
A DNA segment coding for a functional RNA or protein.
26
Question
What are exons?
Answer
Coding sequences in eukaryotic genes that are retained in mature mRNA.
27
Question
Main role of mRNA?
Answer
Template for protein synthesis.
28
Question
How do bacterial RNA polymerases initiate transcription?
Answer
By binding to the promoter and associating with sigma factors.
29
Question
Difference between eukaryotic and bacterial transcription?
Answer
Eukaryotes have multiple RNA polymerases and splicing; bacteria have a single RNA polymerase.
30
Question
What is splicing?
Answer
Removal of introns and joining of exons to produce functional mRNA.