IB Biology Topic A3.2.5 Gradual Accumulation of Sequence Differences Revision Notes (HL)

IB Biology Topic A3.2.5 Gradual Accumulation of Sequence Differences Revision Notes (HL) | RevisionDojo

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Sequence Differences Act as a Molecular Clock

Definition

Molecular Clock

The use of the gradual accumulation of mutations to infer when species diverged from a common ancestor.

Scientists estimate evolutionary timelines by measuring changes in DNA sequences.
This technique is called the molecular clock.

Analogy

It is like estimating the years between two old family photos from the visible signs of ageing.

Why Sequence Differences Matter

DNA encodes proteins, so changes in DNA often change amino acid sequences.
The more differences between two species' homologous sequences, the longer since they diverged.
These differences arise through mutations: base substitutions, insertions, or deletions.

Tip

In exams, state that differences accumulate gradually at a relatively constant rate.

The Basis of the Molecular Clock

Mutations change the nucleotide base sequences of DNA.
Some change amino acid sequences, while others are silent.
Over time, differences accumulate between lineages that no longer interbreed.

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Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Sequence Differences Act as a Molecular Clock

Definition

Molecular Clock

The use of the gradual accumulation of mutations to infer when species diverged from a common ancestor.

Scientists estimate evolutionary timelines by measuring changes in DNA sequences.
This technique is called the molecular clock.

Analogy

It is like estimating the years between two old family photos from the visible signs of ageing.

Why Sequence Differences Matter

DNA encodes proteins, so changes in DNA often change amino acid sequences.
The more differences between two species' homologous sequences, the longer since they diverged.
These differences arise through mutations: base substitutions, insertions, or deletions.

Tip

In exams, state that differences accumulate gradually at a relatively constant rate.

The Basis of the Molecular Clock

Mutations change the nucleotide base sequences of DNA.
Some change amino acid sequences, while others are silent.
Over time, differences accumulate between lineages that no longer interbreed.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

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

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic A3.2.5: Gradual Accumulation of Sequence Differences Notes

Sequence Differences Act as a Molecular Clock

Why Sequence Differences Matter

The Basis of the Molecular Clock

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Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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Sequence Differences Act as a Molecular Clock

Why Sequence Differences Matter

The Basis of the Molecular Clock

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