IB Biology Topic D2.2.1 Gene Expression Revision Notes (HL)

IB Biology Topic D2.2.1 Gene Expression Revision Notes (HL) | RevisionDojo

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Gene Expression: The Bridge From Genotype to Phenotype

Definition

Phenotype

The phenotype of an organism refers to its observable traits or characteristics, which result from the interaction between its genetic makeup (genotype) and the environment.

Imagine two siblings with the same genes: one spends all day outdoors in the sun, while the other stays inside.
Over time, one develops a tan while the other does not.
Their DNA is identical, so the difference comes from gene expression: how genetic instructions are switched on or off in response to the environment, shaping the traits we see.

Tip

Remember the relationship: phenotype = genotype + environment.

Phenotypic Plasticity: One Genotype, Many Outcomes

The same genotype can produce different phenotypes depending on the conditions the organism experiences.

Gene Expression Runs in Three Stages: Transcription, Translation, and Protein Function

Gene expression is the process that turns a genotype (the genetic code) into a phenotype (observable traits).
It happens in three stages: transcription, translation, and protein function.

Transcription: DNA to RNA

In transcription, a gene is read and copied into messenger RNA (mRNA).
This happens in the nucleus and runs through three sub-stages.
Initiation
1. The enzyme RNA polymerase binds to a region of DNA called the promoter.
2. The promoter acts as a start signal, marking where transcription should begin.

Elongation
1. RNA polymerase unwinds the DNA and builds a complementary RNA strand using one strand of DNA as a template.
2. The RNA strand grows in the 5' to 3' direction, pairing each DNA base with the correct RNA base.
  1. DNA adenine (A) pairs with RNA uracil (U).
  2. DNA thymine (T) pairs with RNA adenine (A).
  3. DNA cytosine (C) pairs with RNA guanine (G).
  4. DNA guanine (G) pairs with RNA cytosine (C).

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Note

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Tip

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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.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Gene Expression: The Bridge From Genotype to Phenotype

Definition

Phenotype

The phenotype of an organism refers to its observable traits or characteristics, which result from the interaction between its genetic makeup (genotype) and the environment.

Imagine two siblings with the same genes: one spends all day outdoors in the sun, while the other stays inside.
Over time, one develops a tan while the other does not.
Their DNA is identical, so the difference comes from gene expression: how genetic instructions are switched on or off in response to the environment, shaping the traits we see.

Tip

Remember the relationship: phenotype = genotype + environment.

Phenotypic Plasticity: One Genotype, Many Outcomes

The same genotype can produce different phenotypes depending on the conditions the organism experiences.

Gene Expression Runs in Three Stages: Transcription, Translation, and Protein Function

Gene expression is the process that turns a genotype (the genetic code) into a phenotype (observable traits).
It happens in three stages: transcription, translation, and protein function.

Transcription: DNA to RNA

In transcription, a gene is read and copied into messenger RNA (mRNA).
This happens in the nucleus and runs through three sub-stages.
Initiation
1. The enzyme RNA polymerase binds to a region of DNA called the promoter.
2. The promoter acts as a start signal, marking where transcription should begin.

Elongation
1. RNA polymerase unwinds the DNA and builds a complementary RNA strand using one strand of DNA as a template.
2. The RNA strand grows in the 5' to 3' direction, pairing each DNA base with the correct RNA base.
  1. DNA adenine (A) pairs with RNA uracil (U).
  2. DNA thymine (T) pairs with RNA adenine (A).
  3. DNA cytosine (C) pairs with RNA guanine (G).
  4. DNA guanine (G) pairs with RNA cytosine (C).

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 D2.2.1: Gene Expression Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Gene Expression: The Bridge From Genotype to Phenotype

Phenotypic Plasticity: One Genotype, Many Outcomes

Gene Expression Runs in Three Stages: Transcription, Translation, and Protein Function

Transcription: DNA to RNA

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

Gene Expression: The Bridge From Genotype to Phenotype

Phenotypic Plasticity: One Genotype, Many Outcomes

Gene Expression Runs in Three Stages: Transcription, Translation, and Protein Function

Transcription: DNA to RNA

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