Chapter 18: Mutations
A mutation occurs but does NOT change amino acid sequence. What term best describes this?
Silent mutation
Why must PCR use heat-resistant DNA polymerase?
Because high heat is required to denature DNA each cycle
What is a microarray used for?
To determine which genes are being expressed
What are the two key traits of epigenetic modifications?
1. Do not alter DNA sequence
2. Reversible
What is a SNP?
A single nucleotide polymorphisms difference between individuals
Why are insertions/deletions more disruptive than substitutions?
They often cause frameshifts that alter all downstream codons.
What is the key functional difference between blunt and sticky ends in cloning?
Sticky ends can base pair and ligate more easily due to overhangs
What is genetic (linkage) mapping based on? What is physical mapping based on?
Rates of recombination between genes; Direct DNA sequence distance (bp, kbp, mbp)
What are three main mechanisms of epigenetic regulation?
DNA methylation, histone modification, RNA-based regulation
How can a single mutation become "hidden" in a cell but still present in the genome?
A suppressor mutation restores the wild-type phenotype even though the original mutaiton is still present
How does mismatch repair distinguish the newly synthesized strand from the template strand?
Methylation pattern (unmethylated new strand vs methylated old strand)
Why is a plasmid considered a good cloning vector?
It has an origin of replication and can be independently replicated in bacteria
What is the Human Genome Project?
It was a large-scale computational analysis to assemble and interpret genome data
How does DNA methylation typically affect gene expression?
It represses transcription
Why are transposable elements sometimes considered important in genome evolution?
They create mutations, genome rearrangements, and contribute to genetic diversity
A DNA lesion distorts the helix but does NOT break both strands. Which repair pathway is most appropriate?
Nucleotide-excision repair
What determines fragment separation in gel electrophoresis?
DNA size (and charge through the gel matrix)
What is the transcriptome and what is the proteome?
All RNA molecules transcribed from a genome; all proteins encoded by the genome
What is the role of Xist RNA in X-inactivation?
Bonus: What is an example of an organism whose phenotype is determined by X-inactivation?
It coats the inactive X chromosome and silences gene expression
-Calico cat or tortoise shell
Why can insertions and deletions from strand slippage or unequal crossing over have large effects on protein function?
They can change reading frame or gene copy number, altering many downstream codons or gene dosage
Explain why radiation-induced mutations can persist if not repaired before replication.
Damage is copied into a permanent mutation during DNA replication
Why does ddNTP incorporation terminate DNA synthesis in Sanger sequencing?
It lacks a 3’ OH group needed for phosphodiester bond formation
Why is the proteome different from the transcriptome?
Not all RNA is translated, and protein levels are regulated after transcription
Why can environmental factors influence phenotype without changing DNA sequence?
They can alter epigenetic marks that regulate gene expression
Explain how royal jelly influences whether a bee develops into a queen or worker.
It suppresses & inhibits Dnmt3 gene, reducing DNA methylation and allowing queen genes to be expressed.