Choose a gene to sequence
-
Geneticists make comparisons between and within
species by using specific genes from specific places
in the genome. How do you choose which gene to
sequence?
Most evolutionary trees are constructed using
data from mitochondrial DNA. Why?
Mitochondrial DNA
- What makes mitochondrial DNA better than nuclear DNA for looking at
evolutionary relationships?
- There are lots of mitochondria in each
cell but only one nucleus. So one cell can provide many copies of mtDNA,
but only one of nuclear DNA.
- Mitochondrial DNA has a higher rate of
substitution (mutations where one nucleotide is replaced with another)
than nuclear DNA, making it easier to find differences between closely
related individuals.
- Mitochondrial DNA is inherited only from the
mother, which allows scientists to trace a direct genetic line through
mothers.
- In nuclear DNA, chromosomes recombine during meiosis,
resulting in a garbled genetic history. Mitochondrial DNA does not
recombine.
Within the mitochondrial DNA, geneticists chose specific
genes to sequence, such as cytochrome b, 12S, 16S, and
d-loop.
Mitochondrial DNA is not the only part of the genome that
gets sequenced. Often scientists use DNA from nuclear genes
in addition to mitochondrial genes.
Once geneticists have the right gene chosen, how do they
sequence the DNA?
