DNA Structure & Replication
The type of bond that holds base pairs together in DNA.
What are hydrogen bonds?
- Hydrogen bonds form between complementary bases (A-T has 2 bonds, C-G has 3 bonds) and help stabilize the double helix.
In eukaryotic cells, transcription occurs in this organelle.
What is the nucleus?
- In eukaryotes, transcription happens in the nucleus before the mRNA is transported to the cytoplasm for translation.
The site of protein synthesis.
What is the ribosome?
- Ribosomes are responsible for translating mRNA into proteins by linking amino acids together.
What is a mutation that changes an amino acid but does not stop translation?
What is a missense mutation?
- Missense mutations replace one amino acid with another, which may alter protein function but does not stop translation.
What organelle is responsible for breaking down waste and cellular debris?
What is the lysosome?
- Lysosomes contain digestive enzymes that break down waste, old organelles, and foreign material.
The direction in which DNA is synthesized.
What is 5’ to 3’?
- DNA polymerase can only add nucleotides to the 3’ end of a growing DNA strand, making synthesis occur in the 5’ to 3’ direction.
The process of making an RNA copy of DNA is called this.
What is transcription?
- Transcription is when RNA polymerase reads the DNA sequence and synthesizes mRNA.
What does tRNA use to recognize codons in mRNA?
What is an anticodon?
- The anticodon of a tRNA molecule binds to the complementary mRNA codon, ensuring the correct amino acid is added.
Which repair mechanism corrects replication errors that escaped proofreading?
What is mismatch repair?
- Mismatch repair corrects errors that escaped DNA polymerase proofreading, ensuring proper base pairing.
What structure allows mRNA to exit the nucleus?
What is the nuclear pore?
- Nuclear pores allow processed mRNA to exit the nucleus and enter the cytoplasm for translation.
The enzyme responsible for synthesizing the complementary DNA strand during replication.
What is DNA polymerase III?
- DNA Polymerase III is the main enzyme that adds nucleotides to form the new DNA strand in prokaryotic cells.
What is the role of general transcription factors in eukaryotic cells?
What is they help RNA polymerase bind to the promoter?
- General transcription factors assist RNA polymerase II in recognizing the promoter region and starting transcription.
What happens when a stop codon is reached during translation?
What is a release factor binds and terminates translation?
- Release factors recognize stop codons (UAA, UAG, UGA) and cause the ribosome to release the newly made protein.
What mutation type results in a premature stop codon?
What is a nonsense mutation?
- Nonsense mutations introduce a stop codon too early, leading to an incomplete and usually nonfunctional protein.
What cellular structure assembles microtubules?
What is the centrosome?
- The centrosome organizes microtubules, which are essential for cell shape and chromosome movement in mitosis.
What makes the leading strand different from the lagging strand?
What is it is synthesized continuously?
- The leading strand follows the replication fork and is synthesized continuously, while the lagging strand is synthesized in fragments (Okazaki fragments).
What is the function of the 5’ cap and poly-A tail?
What is mRNA stability and translation initiation?
- The 5’ cap helps the ribosome recognize the mRNA, while the poly-A tail protects it from degradation and assists with nuclear export.
What part of the ribosome catalyzes peptide bond formation?
What is rRNA?
- Ribosomal RNA (rRNA) acts as a ribozyme that catalyzes peptide bond formation, linking amino acids together.
What does base-excision repair fix?
What is damaged or incorrect single bases?
- Base-excision repair (BER) removes single damaged bases and replaces them with the correct ones using DNA polymerase.
What process do cells use to engulf large particles?
What is phagocytosis?
- Phagocytosis is a form of endocytosis where the cell engulfs large molecules or microbes for digestion.
What prevents the separated DNA strands from reannealing during replication?
What are single-strand binding proteins (SSBs)?
- SSBs bind to the separated DNA strands, keeping them apart so that replication can proceed efficiently.
What type of RNA can inhibit gene expression by binding to mRNA?
What is microRNA (miRNA)?
- miRNA can bind to mRNA and prevent translation by blocking ribosome binding or degrading the mRNA.
What is wobble base pairing?
What is flexibility in the third codon position that allows one tRNA to recognize multiple codons?
- Wobble base pairing allows some tRNAs to recognize multiple codons by tolerating mismatches in the third base, reducing the number of tRNAs needed.
What happens if homologous recombination repair fails?
What is increased genetic instability and possible cancer?
- Homologous recombination accurately fixes double-strand breaks, and failure to repair these breaks can lead to mutations and cancer.
What is the main purpose of the smooth ER?
What is lipid synthesis and detoxification?
- The smooth endoplasmic reticulum (ER) makes lipids and steroids and detoxifies harmful substances in cells.