28 Questions
What is the term used to describe the smallest part of DNA that may represent a gene?
Cistron
What is the role of the initiator tRNA in the translation process?
It attaches the first amino acid (methionine) to the ribosome
What is the name of the site on the ribosome where the initiator tRNA first binds?
P site
What is the role of the anticodon on the incoming tRNA during translation?
It pairs with the next mRNA codon at the A site
Which of the following is NOT a component of the ribosome?
mRNA
What is the term used to describe the closer loops of DNA material?
Plasmids
What is the relationship between the number of purine and pyrimidine bases in DNA according to Chargaff's rule?
The number of purine bases is equal to the number of pyrimidine bases.
What is the primary function of DNA?
To store information about the proteins that make up the organism.
Which of the following is the functional unit of inheritance in DNA?
Gene
What is the purpose of telomeres in chromosomes?
To prevent problems during cell division.
Which of the following terms refers to the less densely packed form of DNA?
Chromatin
What is the difference between the p arm and q arm of a chromosome?
The p arm is the short arm, and the q arm is the long arm.
What does the codon AUG represent?
Start codon
Which of the following statements about the genetic code is incorrect?
The code overlaps, and codons are not read sequentially.
What is the primary role of tRNA/soluble RNAs in protein synthesis?
To transport individual amino acids to the ribosomes based on the codon sequence
Which of the following codons represents a stop/termination codon?
UAA
In the process of protein synthesis, what happens when an amino acid combines with ATP?
An amino acyl adenylate is formed.
What is the function of mRNA?
Carries the genetic code to the cytoplasm for protein formation
During protein synthesis, what is the role of tRNA?
Transfers amino acid molecules to ribosomes
What is the primary function of rRNA in protein synthesis?
Constitutes 40-50% of ribosomes
Which enzyme is responsible for catalyzing transcription in protein synthesis?
DNA-dependent RNA polymerase
What is the function of DNA ligase in protein synthesis?
Joins Okazaki fragments together
How many codons make up a coding triplet in the genetic code?
64
What event causes protein synthesis to stop?
The ribosome reaches a stop codon on mRNA
When the ribosome shifts by one codon, where does the tRNA previously at the A site move to?
P site
Where does the peptide bond formation occur during protein synthesis?
A site
What is the role of guanine and cytosine in protein synthesis?
Forming peptide bonds with amino acids
Which tRNA site contains the amino acid that participates in forming the peptide bond?
A site
Study Notes
Central Dogma and Protein Synthesis
- Anticodon: a set of nucleotides used in the formation of a polypeptide chain
- Cistron: the smallest part of DNA that represents a gene
- Intron: smaller sub-units of DNA that cannot represent a gene
- Plasmids: closed loops of DNA material
Ribosomes and mRNA
- Ribosomes consist of a small subunit and a large subunit
- Initiator tRNA binds to the P site on the small subunit
- mRNA binds to the ribosome at the A site
- The large subunit joins the small subunit to form a functional ribosome
Codons and Amino Acids
- Codons: sequences of three nucleotides that specify an amino acid
- Initiator codon (AUG) starts protein synthesis
- Stop codons (UAA, UAG, UGA) terminate protein synthesis
- The first two bases of a codon are more significant and important
Characteristics of the Genetic Code
- Universal: all organisms have the same codon for each amino acid
- Degenerate code: more than one codon can specify the same amino acid
- Continuous: the code is read sequentially, with no overlap
Protein Synthesis Stages
- Transcription: generating mRNA from DNA
- Translation: decoding mRNA to form a polypeptide chain
- Formation of a Polypeptide Chain: amino acids are activated and transported to the ribosomes
Transcription
- Enzyme-dependent process of generating mRNA from DNA
- Catalyzed by a DNA-dependent RNA polymerase enzyme
- Three phases: initiation, elongation, and termination
Translation
- Process by which ribosomes translate/decode the information carried by mRNA
- Production of 20 amino acids
- mRNA leaves the nucleus and goes to the cytoplasm (ribosomes)
The Genetic Code
- Codons/Coding triplet: groups of three adjacent bases that specify an amino acid
- 64 codons in the genetic code
- Most amino acids are coded for by more than one codon
Test your knowledge on DNA base pairing, including the significance of A=T and G=C in Chargaff's Rule, and the functions of DNA in storing genetic information. Explore concepts like genes, chromosomes, and chromatin.
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