Biology - Review 11 Flashcards
What evidence do proteins & DNA give on ancestory?
If two species have a similar set of proteins or DNA sequences, it is evidence that they shared a recent common ancestor.
How do mutations occur?
- Changes in nucleotide sequences are caused by mutations.
- Mutations accumulate throughout the genome over time.
What is the impact of mutation of the DNA sequence?
A mutation to a DNA sequence may not necessarily cause a change to the amino acid sequence because the genetic code is degenerate. However, as more differences in the nucleotide sequence of DNA occur due to mutations, more differences in the amino acid sequence occur.
What is conservative mutation?
Even when a point mutation leads to a change in amino acid, the mutation may not lead to a change in phenotype. This is called a conservative mutation and involves a change from one amino acid to a different amino acid with biochemically similar properties.
What is non-conservative mutation?
A non-conservative mutation results in a change to a very different amino acid, which often leads to biochemical changes.
How do genes accumulate?
- Some genes accumulate mutations faster than others.
- Conserved genes accumulate mutations slowly.
What is the molecular clock?
The more mutations accumulated in the DNA sequences of two species, the more time has passed since they shared a common ancestor. This is the principle of a molecular clock.
What is unique about mitochondrial DNA?
Mitochondrial DNA (mtDNA) is passed through the maternal line.
Why is mtDNA useful?
MtDNA does not have the same repair mechanisms as nuclear DNA. This means mutations can accumulate at a faster rate than in nuclear DNA. making mtDNA a useful molecular clock for species that diverged recently in evolutionary time.
Why is mtDNA analysis easier?
Most cells contain many mitochondria and therefore copies of mtDNA are easier to obtain for analysis than nuclear DNA.
What is DNA hybridisation?
DNA hybridisation involves the heating of DNA from two organisms so that they become single stranded, and mixing them to allow the complementary strands of the two organisms to bond when cooled.
What does DNA hybridisation tell us?
- The more similar the individual strands of DNA of the two species, the more hydrogen bonds will form between their complementary nitrogen bases, and the greater the amount of heat required to separate them.
- The formation of many hydrogen bonds means the DNA strands of the two organisms are very similar and share a recent common ancestor; a relatively high temperature will be required to separate the hybridised DNA strands.
What do the branches and nodes indicate?
The branches and nodes of phylogenetic trees indicate common ancestry between organisms.
What is a clade?
A clade is a group of organisms that includes an ancestor and all the descendants of that ancestor.
What are the types of groups in phylogenetic trees?
3 Types
Groups in phylogenetic trees can be described as
- Monophyletic
- Paraphyletic
- Polyphyletic
depending on their evolutionary relationships.
