Section 2 Flashcards
A ___________ amount of DNA encoding genes are the sequences that go on to make proteins.
a) very small
b) very large
c) large
A very small amount
Which of the RNAs are coding RNAs vs non-coding?
mRNA is a coding RNA (translated into protein)
tRNA and rRNA are non-coding RNAs
Describe each of the non-coding RNAs
Transfer RNA (tRNA): present during translation
Ribosomal RNA (rRNA): present during translation
Long Non-Coding RNAs (lncRNA): can be important regulatory RNAs
Small Nuclear RNAs (snRNAs): play a role in gene regulation (splicing “snurps”)
MicroRNAs (miRNAs): limit translation by binding to the 3’-end of target mRNAs
Small Interfering RNAs (siRNAs): can inhibit transcription of certain genes and viral DNA
Small Nucleolar RNAs (snoRNAs): are involved in the processing of rRNAs
Catalytic RNAs: for example, ribozymes
What is the primary role of mRNA (messenger RNA)?
mRNA is primarily responsible for carrying the encoded genetic information from the nucleus to the ribosomes for protein synthesis.
Is mRNA the only type of coding RNA?
Yes, mRNA is the only type of coding RNA. It carries the genetic code that specifies the amino acid sequence of a protein.
How do mRNA molecules determine the amino acid sequence of a protein?
The coding sequence of mRNA determines the amino acid sequence of the protein it encodes. Each set of three nucleotides in the mRNA, called a codon, corresponds to a specific amino acid.
What is the role of mRNA’s 3D structure, and why does it vary among different mRNA molecules?
Different mRNA molecules can adopt various 3D structures based on what is energetically favorable. This structural variability can influence how efficiently the mRNA is translated and can also have regulatory implications.
What distinguishes RNA from DNA?
The pentose sugar group in RNA is ribose, while DNA contains deoxyribose.
Ribose is a five-carbon sugar with a hydroxyl group at the 2’ carbon, which allows for additional hydrogen bonding, contributing to the stabilization of RNA’s 3-dimensional folding.
The pentose sugar RNA differs from DNA in which way:
* Ribose lacks a hydroxyl group on the 2’ carbon.
* Ribose possess a hydroxyl group on the 2’ carbon.
* Deoxyribose is a five carbon sugar, while ribose is a four carbon sugar.
* The ribose in RNA attaches to the nitrogenous base through the 2’ carbon, while deoxyribose
attached through the 1’ carbon.
Correct answer: Ribose has a hydroxyl group on the 2’ carbon and deoxyribose does not
What are the nitrogenous bases that compose RNA, and how does base pairing in RNA differ from classic Watson-Crick base pairing?
RNA consists of the nitrogenous bases A, U, G, and C. While classic Watson-Crick base pairing involves C pairing with G and A pairing with T in DNA, RNA base pairing doesn’t strictly adhere to these rules. RNA often features interspersed base pairs like A-A and G-U. “WOBBLE base pairing”
Additionally, RNA’s secondary structure allows unpaired nucleotides in one region to interact with noncontiguous sequences, which stabilizes its three-dimensional folding. These interactions create a compact shape with surfaces capable of binding other molecules. Noncontiguous sequences are those that lack a common border and are not adjacent to each other.
What is wobble base pairing?
Non-Watson Crick base pairing.
Involves interspersed base pairs like A-A and G-U.
Additionally, RNA’s secondary structure allows unpaired nucleotides in one region to interact with noncontiguous sequences, which stabilizes its three-dimensional folding. These interactions create a compact shape with surfaces capable of binding other molecules. Noncontiguous sequences are those that lack a common border and are not adjacent to each other.
Increase flexibility of RNA?
What accounts for the difference in stability between RNA and DNA under alkaline conditions, and why is RNA more sensitive to alkaline conditions?
RNA is less stable in alkaline conditions because the 2’-hydroxyl group on ribose sugar in RNA can interact with hydroxide ions (OH-), leading to phosphodiester bond hydrolysis. DNA is more stable as it lacks this 2’-hydroxyl group. RNA’s relative instability serves a purpose in gene expression; it allows for dynamic synthesis and degradation of RNA molecules, while DNA is maintained during cell division and extended periods in non-replicating cells.
What are some common RNA secondary structure features?
- Helical Structures: Forming right-handed helices with antiparallel paired strands dominated by base-stacking interactions, similar to DNA.
- Internal Loops: Occurring when double-stranded RNA separates due to a lack of Watson-Crick base pairing, with special cases like bulges where one strand has an unpaired base.
- Hairpin Loops: Common RNA secondary structures, where an RNA strand folds back onto itself, creating an unpaired loop at the end of a stem region. Nucleotides within the loops maximize hydrogen bonding and base stacking for thermodynamic stability.
What factors influence the stability of RNA structures, especially in terms of weak interactions and metal ions?
- Weak interactions, such as hydrogen bonding and van der Waals interactions, often involving the 2’-OH group in the ribose sugar.
- Binding of metal ions to specific sites to shield the negative charge of the backbone, promoting tight packing of RNA.
- The number of G-C versus A-U (and G-U) base pairs.
- The number of base pairs in a stem region.
- The number of base pairs in a hairpin loop, as forming loops with more than 10 or fewer than 5 bases requires more energy.
- The number of unpaired bases, as unpaired bases decrease the stability of the RNA structure.
Which one is resistant and which one is degraded in alkaline conditions?
DNA
RNA
DNA: resistant to alkaline conditions
RNA: degraded in alkaline conditions
