17.3- Molecular Clocks Flashcards
Model that uses mutations rates to measure evolutionary time
Molecular clocks
DNA found in mitochondria, often used as a molecular clock
Mitochondrial DNA
RNA that is in the ribosomes and also used as a molecular clock and guides the translation of mRNA into a protein.
Ribosomal RNA
Who proposed a new way to measure evolutionary time in the 1960s?
Linus Pauling and Emilie Zuckerkandl
What did Pauling and Zuckerkandl do (experiment)?
They compared amino acid sequences of hemoglobin from a wide range of species.
What did Pauling’s and Zuckerkandl’s findings show?
They showed that the more distantly related 2 species are, the more amino acids differences there were in their hemoglobin.
What did Pauling and Zuckerkandl use their data for?
To calculate a mutation rate for part of the hemoglobin protein.
What do different molecules have?
Different mutation rates
How do scientists choose a molecule to use as a molecular clock?
Based on how closely related the 2 species are.
Why do scientists use mitochondrial DNA to trace mutations?
They’re passed down unshuffled.
Why is mtDNA good for closely related species?
The mutation rate is 10 times faster than nuclear DNA.
When is rRNA best to use as a molecular clock?
When you’re dealing with distantly related species.
What kind of mutation rate does rRNA have?
A slow rate which is best for longer time scales.
What did Pauling and Zuckerkandl find that mutations do for a group of related species?
Add up at a constant rate.m
What can scientists do if they know when species began to diverge?
They can find the mutation rate for the molecule they’re studying.
