ap bio unit 6: gene expression and regulation

What are the key structural differences between DNA and RNA?

DNA is double stranded with deoxyribose sugar and uses thymine (A-T), while RNA is single stranded with ribose sugar and uses uracil (A-U).

What are the main roles of mRNA, tRNA, and rRNA in protein synthesis?

mRNA carries the genetic code to the ribosome, tRNA transfers amino acids to the ribosome, and rRNA makes up the ribosome that builds proteins.

Describe the process of DNA replication.

DNA replication occurs in the S phase of the cell cycle, where helicase unwinds DNA, primase adds RNA primers, DNA polymerase adds nucleotides in the 5' to 3' direction, and ligase seals Okazaki fragments on the lagging strand.

What is the difference between prokaryotic and eukaryotic transcription?

In prokaryotes, transcription occurs in the cytoplasm and several genes can be transcribed simultaneously; in eukaryotes, it occurs in the nucleus and typically one gene is transcribed at a time with modifications made to the primary transcript.

What role do introns play in gene expression?

Introns may regulate gene activity by allowing a single gene to produce multiple protein variants through alternative splicing.

What is the function of the operon system in prokaryotes?

The operon system regulates gene expression, allowing bacteria to control the production of enzymes based on environmental conditions.

What is the significance of histone acetylation in gene regulation?

Histone acetylation acts as an 'on switch' for gene expression, allowing genes to be transcribed when histones are loosely wrapped around DNA.

What are point mutations and their types?

Point mutations are changes in a single nucleotide, including missense mutations (alter amino acid), nonsense mutations (create a stop codon), and silent mutations (no change in amino acid sequence).

Describe the process of RNA splicing.

RNA splicing involves the removal of introns and joining of exons in the pre-mRNA, facilitating the production of a mature mRNA molecule that exits the nucleus.

What is the purpose of the 5' cap and poly(A) tail in mRNA processing?

The 5' cap protects mRNA from degradation and assists ribosome binding, while the poly(A) tail aids in nuclear export and stability of the mRNA.

What is transcription in molecular biology?

Transcription is the process of synthesizing RNA from a DNA template.

What enzyme is responsible for RNA synthesis during transcription?

RNA polymerase is the enzyme that synthesizes RNA during transcription.

What are the three main stages of transcription?

The three main stages are initiation, elongation, and termination.

Where does transcription occur in prokaryotic cells?

In prokaryotic cells, transcription occurs in the cytoplasm.

Where does transcription occur in eukaryotic cells?

In eukaryotic cells, transcription occurs in the nucleus.

What is the primary role of tRNA in translation?

tRNA's primary role is to transfer specific amino acids to the ribosome during protein synthesis.

What is the genetic code?

The genetic code is a set of rules that defines how sequences of nucleotide triplets (codons) correspond to specific amino acids.

What is a codon?

A codon is a sequence of three nucleotides on an mRNA that specifies a particular amino acid.

What is the role of ribosomes in protein synthesis?

Ribosomes are the molecular machines that assemble amino acids into proteins based on the sequence of m