Nucleaic Acids Flashcards
What are the three components of a nucleotide?
A phosphate group, a pentose sugar (deoxyribose in DNA), and a nitrogenous base.
Which nitrogenous bases are purines, and which are pyrimidines in DNA?
Purines: Adenine (A) and Guanine (G); Pyrimidines: Cytosine (C) and Thymine (T).
Describe the structure of the DNA double helix.
DNA consists of two antiparallel strands forming a double helix, with complementary base pairing (A pairs with T, and G pairs with C) held together by hydrogen bonds.
What type of bond forms between nucleotides in a DNA strand?
Phosphodiester bonds link the phosphate group of one nucleotide to the hydroxyl group of the pentose sugar of the next nucleotide.
What is the role of DNA helicase in DNA replication?
DNA helicase unwinds the DNA double helix and separates the two strands by breaking the hydrogen bonds between base pairs.
How does ATP differ structurally from a DNA nucleotide?
ATP (adenosine triphosphate) consists of the nitrogenous base adenine, the sugar ribose, and three phosphate groups, whereas a DNA nucleotide has deoxyribose sugar and one phosphate group.
What is the significance of ATP in cellular activities?
ATP serves as the primary energy carrier in cells, providing energy for various biological processes such as muscle contraction, nerve impulse propagation, and chemical synthesis.
Explain the process of ATP hydrolysis.
ATP hydrolysis involves the breakdown of ATP into ADP (adenosine diphosphate) and an inorganic phosphate (Pi), releasing energy that can be used by the cell.
What is complementary base pairing, and why is it important?
Complementary base pairing refers to the specific pairing of nitrogenous bases in DNA: adenine pairs with thymine, and guanine pairs with cytosine. This ensures accurate replication and transcription of genetic information.
How do the structures of DNA and RNA differ?
DNA is double-stranded with deoxyribose sugar and contains thymine, while RNA is single-stranded with ribose sugar and contains uracil instead of thymine.
What are the three main types of RNA, and what are their primary functions?
The three main types of RNA are:
• Messenger RNA (mRNA): Carries genetic information from DNA to the ribosome for protein synthesis.
• Transfer RNA (tRNA): Brings specific amino acids to the ribosome during protein synthesis.
• Ribosomal RNA (rRNA): Combines with proteins to form ribosomes, the site of protein synthesis.
How does the sugar component of RNA differ from that of DNA?
RNA contains ribose sugar, which has a hydroxyl (-OH) group on the 2’ carbon, whereas DNA contains deoxyribose sugar, lacking the hydroxyl group on the 2’ carbon.
Which nitrogenous base is unique to RNA, and which base does it replace compared to DNA?
RNA contains uracil (U), which replaces thymine (T) found in DNA.
Describe the structure of a tRNA molecule.
A tRNA molecule has a cloverleaf structure with:
• An amino acid attachment site at the 3’ end.
• An anticodon loop that pairs with the complementary codon on mRNA during translation.
What is the role of mRNA in protein synthesis
mRNA carries the genetic code transcribed from DNA, specifying the sequence of amino acids in a protein, from the nucleus to the ribosome.
How does RNA’s single-stranded nature influence its function?
Being single-stranded allows RNA to fold into various shapes, enabling it to perform diverse functions such as catalysis (in the case of some rRNAs) and regulation.
What is the significance of the anticodon region in tRNA?
The anticodon region of tRNA contains a sequence of three nucleotides that are complementary to an mRNA codon, ensuring the correct amino acid is added during protein synthesis.
How does rRNA contribute to the structure and function of ribosomes?
rRNA molecules combine with ribosomal proteins to form the two subunits of ribosomes, providing a framework that facilitates the alignment of mRNA and tRNAs during protein synthesis.
In what cellular locations can RNA be found?
RNA can be found in both the nucleus and cytoplasm. mRNA is synthesized in the nucleus and then transported to the cytoplasm, where rRNA and tRNA function in protein synthesis.
What is the role of small nuclear RNA (snRNA) in the cell?
snRNA is involved in the splicing of pre-mRNA, removing introns and joining exons to form mature mRNA.
What is the role of DNA helicase in DNA replication?
DNA helicase unwinds the DNA double helix and separates the two strands by breaking the hydrogen bonds between complementary base pairs.
How are the two strands of DNA kept separate during replication?
Single-strand binding proteins attach to the separated strands to prevent them from reannealing.
What is the function of DNA polymerase in DNA replication
DNA polymerase synthesizes new DNA strands by adding nucleotides complementary to the template strand, working in a 5’ to 3’ direction.
Why is one of the new DNA strands called the leading strand?
The leading strand is synthesized continuously in the same direction as the replication fork movement.
What characterizes the synthesis of the lagging strand during DNA replication?
The lagging strand is synthesized discontinuously, forming short DNA segments known as Okazaki fragments.
What enzyme joins Okazaki fragments on the lagging strand?
DNA ligase joins Okazaki fragments by forming phosphodiester bonds between adjacent nucleotides.
What is the role of RNA primers in DNA replication?
RNA primers provide a starting point for DNA synthesis by DNA polymerase, as it cannot initiate synthesis de novo.
How are RNA primers removed and replaced during DNA replication?
RNA primers are removed by exonuclease activity, and the resulting gaps are filled with DNA nucleotides by DNA polymerase.
What does it mean that DNA replication is semiconservative?
Semiconservative replication means that each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.
Why is DNA replication important for cell division?
DNA replication ensures that each daughter cell receives an exact copy of the genetic material, maintaining genetic continuity.
What is transcription in the context of protein synthesis?
Transcription is the process by which a segment of DNA is used as a template to synthesize a complementary strand of messenger RNA (mRNA), which then carries genetic information from the nucleus to the cytoplasm for protein synthesis.
Which enzyme is responsible for synthesizing mRNA during transcription?
RNA polymerase is the enzyme that synthesizes mRNA by adding RNA nucleotides complementary to the DNA template strand during transcription.
Describe the role of RNA polymerase in transcription.
RNA polymerase binds to the promoter region of the gene, unwinds the DNA strands, and synthesizes a complementary mRNA strand by adding RNA nucleotides in the 5’ to 3’ direction.
What is the function of the promoter region in DNA transcription?
The promoter region is a specific DNA sequence that signals RNA polymerase where to bind and initiate transcription
What modifications occur to pre-mRNA before it becomes mature mRNA in eukaryotic cells?
Pre-mRNA undergoes splicing to remove introns, and a 5’ cap and a poly-A tail are added to enhance stability and facilitate translation.
What is translation in the context of protein synthesis?
Translation is the process by which ribosomes synthesize proteins using the sequence of codons in mRNA to assemble amino acids into a polypeptide chain.
How does tRNA contribute to translation?
Transfer RNA (tRNA) molecules transport specific amino acids to the ribosome, where their anticodons pair with complementary codons on the mRNA strand, ensuring the correct sequence of amino acids in the growing polypeptide chain.
What is a codon, and what is its role in the genetic code?
A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid or a stop signal during protein synthesis.
Explain the concept of the genetic code being degenerate.
Explain the concept of the genetic code being degenerate.
What does it mean that the genetic code is universal?
The genetic code is universal, meaning that the same codons specify the same amino acids across nearly all organisms, highlighting a common evolutionary origin.
