DNA, RNA, Protein Synthesis — Practice Quiz

A Biology cheat sheet for DNA, RNA, Protein Synthesis — every key formula with its symbols defined — plus a medium-level practice quiz to test recall.

Formulas & key concepts

<b>Double Helix</b>: Two strands of nucleotides twisted. <b>Nucleotide</b>: Deoxyribose sugar + Phosphate + Nitrogenous Base. <b>Base Pairing</b>: Adenine (A) = Thymine (T), Cytosine (C) = Guanine (G).

DNA Structure

<b>Semiconservative</b>: Each new DNA has one old and one new strand. <b>Helicase</b>: Unzips DNA. <b>DNA Polymerase</b>: Adds nucleotides. <b>Telomerase</b>: Adds DNA to chromosome ends to prevent loss. <b>Leading Strand</b>: Continuous. <b>Lagging Strand</b>: Discontinuous (Okazaki fragments).

DNA Replication

<b>mRNA</b> (Messenger): Carries instructions from DNA to ribosome. <b>tRNA</b> (Transfer): Carries amino acids to ribosome; matches <b>Anticodon</b> to mRNA <b>Codon</b>. <b>rRNA</b> (Ribosomal): Forms ribosome subunits.

RNA Types & Functions

Synthesis of mRNA from DNA template. <b>RNA Polymerase</b> binds to <b>Promoter</b>. <b>Processing</b> (Eukaryotes): Introns removed, Exons spliced together (<b>Alternative Splicing</b> allows 1 gene -> multiple proteins), 5' Cap and Poly-A Tail added.

Transcription

<b>Codon</b>: 3-base sequence on mRNA codes for 1 amino acid. <b>Start Codon</b>: AUG (Methionine). <b>Stop Codons</b>: UAA, UAG, UGA. Code is universal.

The Genetic Code

Protein synthesis at Ribosome. mRNA codons match tRNA <b>Anticodons</b>. tRNA brings amino acids. Peptide bonds form between amino acids to build Polypeptide chain.

Translation

Information flows from <b>DNA</b> &rarr; <b>RNA</b> &rarr; <b>Protein</b>. (Exception: Retroviruses use Reverse Transcriptase to go RNA &rarr; DNA).

Central Dogma

Changes in genetic material. <b>Point Mutation</b>: Substitution (e.g., Sickle Cell). <b>Frameshift</b>: Insertion/Deletion (shifts reading frame, changing all subsequent amino acids).

Mutations

<b>Prokaryotes</b>: <b>Operons</b> (e.g., Lac Operon - Repressor blocks Operator until Lactose binds). <b>Eukaryotes</b>: <b>TATA Box</b> marks start. <b>Transcription Factors</b> bind DNA to control expression. <b>Epigenetics</b>: Methylation silences genes.

Gene Regulation

<b>miRNA/siRNA</b>: Small RNA molecules. <b>Dicer</b>: Enzyme cuts RNA loops. <b>Silencing Complex</b>: Destroys target mRNA, stopping translation (gene silencing).

RNA Interference (RNAi)

<b>Differentiation</b>: Cells become specialized. Controlled by <b>Homeotic Genes</b> (e.g., <b>Hox Genes</b>) which determine body plan. Environmental factors (temp, nutrients) can influence expression (e.g., Metamorphosis).

Development & Differentiation

<b>Mutagen</b>: Chemical/physical agent causing mutation. <b>Polyploidy</b>: Extra chromosome sets (common in plants). <b>Genome</b>: Full set of genetic info. <b>Polypeptide</b>: Chain of amino acids.

Key Terms

Practice quiz

  1. If a $DNA$ sample contains $20\%$ Adenine, what percentage of Guanine would be present?

    • $20\%$
    • $30\%$
    • $40\%$
    • $50\%$

    Answer: $30\%$

  2. Which enzyme is primarily responsible for adding new nucleotides during $DNA$ replication?

    • Helicase
    • $DNA$ Polymerase
    • Telomerase
    • $RNA$ Polymerase

    Answer: $DNA$ Polymerase

  3. Which type of $RNA$ is responsible for carrying specific amino acids to the ribosome during protein synthesis?

    • $mRNA$
    • $tRNA$
    • $rRNA$
    • $siRNA$

    Answer: $tRNA$

  4. In eukaryotes, which of the following processes occurs during $mRNA$ processing before translation?

    • $DNA$ unzipping by Helicase
    • Addition of Okazaki fragments
    • Removal of introns and splicing of exons
    • Binding of $tRNA$ to the promoter

    Answer: Removal of introns and splicing of exons

  5. The $mRNA$ codon $AUG$ typically codes for which amino acid and also serves as a start signal?

    • Tryptophan
    • Glycine
    • Methionine
    • Alanine

    Answer: Methionine

  6. If an $mRNA$ codon is $UAC$, what would be the corresponding anticodon on the $tRNA$ molecule that brings the amino acid?

    • $AUG$
    • $UAC$
    • $ATG$
    • $AUGC$

    Answer: $AUG$

  7. According to the Central Dogma of molecular biology, what is the correct flow of genetic information?

    • $RNA \rightarrow DNA \rightarrow Protein$
    • $Protein \rightarrow RNA \rightarrow DNA$
    • $DNA \rightarrow RNA \rightarrow Protein$
    • $DNA \rightarrow Protein \rightarrow RNA$

    Answer: $DNA \rightarrow RNA \rightarrow Protein$

  8. A mutation that involves the insertion or deletion of one or two nucleotides in a gene sequence is most likely to cause a:

    • Point mutation
    • Silent mutation
    • Frameshift mutation
    • Missense mutation

    Answer: Frameshift mutation

  9. In prokaryotes, a group of genes that are regulated together and include a promoter, operator, and structural genes is known as a(n):

    • Exon
    • Intron
    • Operon
    • Plasmid

    Answer: Operon

  10. What is the primary function of $miRNA$ and $siRNA$ in the process of $RNA$ interference ($RNAi$)?

    • To synthesize new $DNA$ strands
    • To carry amino acids to the ribosome
    • To destroy target $mRNA$ molecules
    • To form peptide bonds between amino acids

    Answer: To destroy target $mRNA$ molecules

Select a subject

Select a subject from the left panel to begin exploring formulas.