42 Questions
What are the structural elements of nucleic acids?
Nucleotides and nucleosides
Which atoms are present in the composition of nucleotides?
C, H, N, and P
What is the primary structure of DNA?
Sequence of nucleotides linked by phosphodiester bonds
What are the types of RNA mentioned in the chapter?
Messenger RNA, ribosomal RNA, transfer RNA
What does the genetic information in DNA molecules primarily reside in?
Bases of DNA molecules
Apart from carrying genetic information, what other role do sugar and phosphate groups play in DNA molecules?
Perform a structural role
What did Chargaff discover about the base ratios in DNA?
The number of adenine residues is the same as thymine residues
What is the primary structure of RNA composed of?
Ribose and A, U, C, G bases
Which form of DNA is favored in solutions devoid of water?
A form
How is the complementary strand synthesized during DNA replication?
By adding nucleotides according to Chargaff's rules
What is responsible for the secondary structure important for the function of the RNA molecule?
Double helix region (hairpin)
Which scientist studied the DNA structure using x-ray technology to study DNA fibers?
Rosalind Franklin
What holds the double helix structure of DNA together?
Base-stacking interactions
What did Watson and Crick's double helix model suggest about the transmission of genetic information?
It suggested the complementarity of the two DNA strands is essential for transmission
What happens when DNA strands are denatured by high temperature?
Hydrogen bonds are broken causing unwinding of the double helical structure
In eukaryotes, what is found at the 5'-end of mRNA?
Methyl-guanosine + a triphosphate group: CAP
What type of RNA contains different structures including loop and double helix region (hairpin)?
Transfer RNA (tRNA)
What does chromatin condensation involve?
Association of DNA with special proteins called histones
Which molecule lacks an oxygen atom that is present in ribose?
Deoxyribose
What is the correct composition of a nucleoside?
Nitrogenous base + Pentose
Which of the following is a purine?
Adenine
What is the name of the bond that links a nitrogenous base to a pentose in a nucleoside?
N-glycosidic bond
Which nucleotide is not found in RNA?
Deoxythymidine 5’-monophosphate
What compound forms highly energetic bonds between other phosphate groups to form diphosphate and triphosphate nucleotides?
ATP
In ATP, where is the most common site of esterification in naturally occurring nucleotides?
Hydroxyl group attached to C-5 of the sugar
Which molecule participates in Redox reactions by transferring H+ and electrons from one substrate to the other?
FAD
Which organic compound is essential in small quantities and acts as coenzymes or forms part of them?
Vitamins
'ACGT' represents the sequence of bases in DNA from which end to which end?
'ACGT' from 5’ end to 3’ end
'ACGT' from adenine to thymine end represents the sequence of bases in which part of DNA?
'ACGT' from adenine to thymine end
Which molecule participates in the transfer of chemical groups by transferring acetyl groups to other substrates?
Coenzyme A (CoA-SH)
What is formed when cAMP undergoes ester bonds with -OH at position 3'?
Intramolecular bridge
In eukaryotes, what is the primary role of the poly A tail in mRNA molecules?
To avoid degradation and drive the RNA molecule migration from nucleus to cytoplasm
What is the main function of tRNA in protein synthesis?
Transporting amino acids to the ribosomes
What is the distinctive feature of mature tRNA molecules that enables them to bind to specific codons in the ribosome?
The presence of a triplet of bases called anticodon
What is the primary function of ribosomal RNA (rRNA) in protein synthesis?
Forming part of the ribosomes and contributing to specific sites for mRNA and tRNA binding
What is the primary function of nucleolar RNA in a eukaryotic cell?
Forming nucleoli in association with proteins
In molecular terms, what does a gene consist of?
Entire nucleic acid sequence necessary for one functional molecule and inherited
What distinguishes genes in eukaryotes from those in prokaryotes?
Presence of introns and monocistronic nature in eukaryotes
What is the main difference between prokaryotic and eukaryotic transcription units?
Eukaryotic units include introns and have alternative splicing
What is the primary role of double-stranded RNA (dsRNA) in eukaryotic cells?
Regulating gene expression by interfering with mRNA translation
What is a distinct characteristic of genes in prokaryotes compared to those in eukaryotes?
Polycistronic nature and absence of introns
What is the primary role of iRNA (double-stranded RNA) in eukaryotic cells?
Preventing gene expression regulation by interfering with mRNA translation
Study Notes
Nucleic Acids Structure
- Nucleic acids are composed of nucleotides, which are made up of a sugar molecule, a phosphate group, and a nitrogenous base.
- The primary structure of DNA is a double helix, where two complementary strands are twisted together.
Composition of Nucleotides
- Atoms present in the composition of nucleotides include carbon, nitrogen, oxygen, and phosphorus.
DNA Structure
- The genetic information in DNA molecules primarily resides in the sequence of nitrogenous bases.
- Sugar and phosphate groups play a crucial role in holding the double helix structure of DNA together.
- The primary structure of DNA is favored in solutions devoid of water in the B-form.
RNA Structure
- The primary structure of RNA is composed of a single strand with a ribose sugar molecule and a phosphate group.
- RNA contains different structures, including loop and double helix regions (hairpin).
DNA Replication
- During DNA replication, the complementary strand is synthesized by the enzyme DNA polymerase.
RNA Function
- The secondary structure of RNA molecules is important for their function.
- The primary function of tRNA in protein synthesis is to carry amino acids to the ribosomes.
- The distinctive feature of mature tRNA molecules is their ability to bind to specific codons in the ribosome.
- The primary function of rRNA in protein synthesis is to form part of the ribosome.
- The primary function of nucleolar RNA in a eukaryotic cell is to synthesize rRNA.
Gene Structure
- A gene consists of a sequence of nucleotides that code for a specific protein or RNA molecule.
- Genes in eukaryotes are distinguished from those in prokaryotes by the presence of introns and exons.
Gene Expression
- The primary role of double-stranded RNA (dsRNA) in eukaryotic cells is to regulate gene expression.
- The primary role of iRNA (double-stranded RNA) in eukaryotic cells is to interfere with gene expression.
Discoveries
- Chargaff discovered that the ratios of adenine to thymine and guanine to cytosine are equal in DNA molecules.
- Watson and Crick's double helix model suggested that genetic information is transmitted from one generation to the next through the replication of DNA.
- Rosalind Franklin and Maurice Wilkins used x-ray technology to study DNA fibers.
Other
- High temperature can denature DNA strands, causing them to separate.
- In eukaryotes, a cap structure is found at the 5'-end of mRNA.
- ATP is a molecule that participates in Redox reactions by transferring H+ and electrons from one substrate to the other.
- Coenzyme A is an organic compound essential in small quantities that acts as a coenzyme or forms part of them.
- 'ACGT' represents the sequence of bases in DNA from the 5'-end to the 3'-end.
Test your knowledge on the structure and function of DNA, including the specific DNA sequence, polynucleotide chain directionality, and the types of DNA. Explore the primary and secondary structure of DNA and learn about the scientists who contributed to our understanding of DNA's molecular structure.
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