AP Biology - Unit 6: Gene Expression and Regulation

Flashcards covering key concepts from AP Biology Unit 6: Gene Expression and Regulation.

What are the three components of a nucleotide?

A phosphate group, a deoxyribose sugar, and a nitrogenous base.

What are the four nitrogenous bases in DNA?

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

What type of bond holds base pairs together?

Hydrogen bonds (A-T has 2 bonds, G-C has 3 bonds).

What enzyme unwinds the DNA double helix?

Helicase.

What enzyme adds new nucleotides to the growing DNA strand?

DNA Polymerase.

What is the role of single-stranded binding proteins (SSBs) in DNA replication?

They stabilize the unwound DNA strands to prevent reannealing.

What enzyme relieves tension in the DNA strand ahead of the replication fork?

Topoisomerase.

What is the function of primase in DNA replication?

It synthesizes an RNA primer to provide a starting point for DNA polymerase.

How does the leading strand differ from the lagging strand in DNA replication?

The leading strand is synthesized continuously, while the lagging strand is synthesized in Okazaki fragments.

What enzyme joins Okazaki fragments together?

DNA Ligase.

Where does transcription occur in eukaryotic cells?

In the nucleus.

What enzyme synthesizes mRNA from a DNA template?

RNA Polymerase.

What is the function of the promoter region in transcription?

It signals the RNA polymerase where to begin transcription.

What is the function of the TATA box?

It is a conserved sequence in the promoter region that helps RNA polymerase bind.

What are the three steps of transcription?

Initiation, Elongation, and Termination.

What happens during RNA processing in eukaryotes?

Addition of a 5’ cap, addition of a poly-A tail, and splicing of introns.

What is the function of the 5’ cap and poly-A tail?

They protect mRNA from degradation and help in ribosome binding.

What is the difference between introns and exons?

Introns are noncoding sequences that are removed; exons are coding sequences that remain in mRNA.

What molecule carries out RNA splicing?

The spliceosome, composed of snRNPs and proteins.

Where does translation occur in eukaryotic cells?

In the cytoplasm on ribosomes.

What are the three major types of RNA, and their functions?

mRNA (carries genetic information), tRNA (transfers amino acids), rRNA (part of ribosome structure).

What are the three steps of translation?

Initiation, Elongation, and Termination.

What is the function of tRNA in translation?

It carries amino acids to the ribosome and matches codons with anticodons.

What are codons and anticodons?

Codons are three-nucleotide sequences on mRNA that code for amino acids; anticodons are complementary sequences on tRNA.

What are the three sites of a ribosome, and their functions?

A site: Holds incoming tRNA with an amino acid. P site: Holds the growing polypeptide chain. E site: Exit site for used tRNA.

What signals termination of translation?

A stop codon (UAA, UAG, or UGA) in the mRNA.

What is an operon?

A group of genes that are regulated together in prokaryotes.

What are the components of an operon?

Promoter, operator, genes, and regulatory proteins.

What is the function of the operator in an operon?

It is a regulatory sequence where a repressor protein binds to block transcription.

How does the lac operon function?

It is inducible; when lactose is present, it inactivates the repressor, allowing transcription.

How does the trp operon function?

It is repressible; when tryptophan is present, it activates the repressor to block transcription.

What is the role of transcription factors in eukaryotic gene regulation?

They bind to DNA to increase or decrease transcription of specific genes.

What are enhancers and silencers?

Enhancers increase transcription; silencers decrease transcription.

How does DNA methylation affect gene expression?

It represses transcription by tightly packing DNA, making it less accessible.

How does histone acetylation affect gene expression?

It promotes transcription by loosening chromatin structure.

What are the different types of point mutations?

Silent mutation (no change in protein), Missense mutation (changes one amino acid), Nonsense mutation (creates a stop codon, terminating translation early).

What are frameshift mutations?

Mutations caused by insertions or deletions that shift the reading frame of the genetic code.

What is gel electrophoresis used for?

To separate DNA fragments based on size.

What is the purpose of polymerase chain reaction (PCR)?

To amplify small segments of DNA for analysis.

What is recombinant DNA technology?

Combining DNA from different organisms to create genetically modified organisms (GMOs).

What are restriction enzymes?

Enzymes that cut DNA at specific sequences, used in genetic engineering.

What is CRISPR-Cas9 used for?

Precise genome editing by targeting specific DNA sequences.

What is a bacteriophage?

A virus that infects bacteria.

What are the two types of viral life cycles?

Lytic cycle (virus reproduces rapidly and destroys the host cell) and Lysogenic cycle (viral DNA integrates into the host genome and replicates with it).

What is horizontal gene transfer?

The transfer of genetic material between organisms without reproduction, common in bacteria.

What are the three types of horizontal gene transfer?

Transformation (uptake of foreign DNA), Transduction (gene transfer by viruses), Conjugation (direct transfer of DNA via pili).