BIOL 2255 EXAM 3 HIGH-YIELD EVOLUTION, ECOLOGY, AND ORGANISMAL BIOLOGY SUMMARY 2026

BIOL 2255 EXAM 3 HIGH-YIELD EVOLUTION,
ECOLOGY, AND ORGANISMAL BIOLOGY
SUMMARY 2026

◉ Okazaki fragments.
Answer: Short DNA fragments made on the lagging strand


◉ Why does the lagging strand exist?.
Answer: DNA polymerase can only synthesize 5' to 3', so one strand
must be copied in fragments


◉ Silent mutation.
Answer: Mutation that codes for the same amino acid


◉ Missense mutation.
Answer: Mutation that changes one amino acid to another


◉ Nonsense mutation.
Answer: Mutation that creates a stop codon


◉ Frameshift mutation.

,Answer: Mutation that shifts the reading frame


◉ What causes a frameshift mutation?.
Answer: Insertion or deletion not in a multiple of 3


◉ Why are frameshift mutations usually severe?.
Answer: They change every downstream codon after the mutation


◉ UV light as a mutagen.
Answer: Causes thymine dimers


◉ Nitrous acid as a mutagen.
Answer: Causes deamination


◉ X-rays as mutagens.
Answer: Cause DNA strand breaks


◉ Intercalating agents as mutagens.
Answer: Cause frameshift mutations


◉ Photoreactivation.
Answer: Repair mechanism that directly breaks thymine dimers

, ◉ Photolyase.
Answer: Enzyme used in photoreactivation


◉ What does photoreactivation require?.
Answer: Photolyase and visible light


◉ Nucleotide excision repair.
Answer: Removes damaged sections of DNA and replaces them


◉ Mismatch repair.
Answer: Fixes replication errors


◉ SOS repair.
Answer: Error-prone DNA damage bypass system


◉ Operon.
Answer: Multiple genes controlled by one promoter


◉ Promoter.
Answer: DNA region where RNA polymerase binds to begin
transcription