IB Biology Topic A4.1.2 Evidence for Evolution from Base Sequences in DNA or RNA and Amino Acid Sequences Revision Notes (SL/HL)

IB Biology Topic A4.1.2 Evidence for Evolution from Base Sequences in DNA or RNA and Amino Acid Sequences Revision Notes (SL/HL) | RevisionDojo

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DNA, RNA, and Protein Sequences Record Evolutionary History

Heritable change arises from mutations in DNA, which accumulate in a lineage over time.
Because DNA is copied to RNA and used to build proteins, this history is recorded in three kinds of sequence.
1. Base sequences of DNA.
2. Base sequences of RNA.
3. Amino acid sequences of proteins.
Comparing these sequences between species measures how closely related they are and supports common descent.

Note

Molecular evidence is one strand of the wider evidence for evolution.
Anatomical evidence such as homologous structures is covered separately in A4.1.4.

More Sequence Similarity Means More Recent Common Ancestry

Sequence differences accumulate as mutations build up after two lineages split from a common ancestor.
More differences therefore mean an older divergence and a more distant relationship.
1. Humans and chimpanzees share about 98 to 99 percent of their DNA, reflecting a recent common ancestor.
2. Humans and fruit flies share far less, indicating a much older common ancestor.
The molecular clock uses this steady build-up of mutations to estimate how long ago two lineages diverged.
1. It assumes that mutations in a given gene accumulate at a roughly constant rate over time.

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IB Biology Topic A4.1.2: Evidence for Evolution from Base Sequences in DNA or RNA and Amino Acid Sequences Notes

DNA, RNA, and Protein Sequences Record Evolutionary History

More Sequence Similarity Means More Recent Common Ancestry

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

DNA, RNA, and Protein Sequences Record Evolutionary History

More Sequence Similarity Means More Recent Common Ancestry

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic A4.1.2: Evidence for Evolution from Base Sequences in DNA or RNA and Amino Acid Sequences Notes

DNA, RNA, and Protein Sequences Record Evolutionary History

More Sequence Similarity Means More Recent Common Ancestry

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

DNA, RNA, and Protein Sequences Record Evolutionary History

More Sequence Similarity Means More Recent Common Ancestry

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics