IB Biology D2.2 HL Gene Expression

Practise connecting transcriptional regulation and epigenetic change to protein production, cell specialization and phenotype.

Exam points

trace gene expression from transcription and translation to a functional RNA or protein affecting phenotype
explain how activators, repressors, promoters and enhancers alter the probability of transcription
interpret methylation or expression data without assuming every epigenetic mark has the same effect
distinguish genome, transcriptome and proteome and interpret tissue-specific or treatment-linked expression data

Covered syllabus points

D2.2.1 (HL)—Gene expression mechanism D2.2.2 (HL)—Regulation of transcription D2.2.3 (HL)—Control of mRNA degradation D2.2.4 (HL)—Epigenesis D2.2.5 (HL)—Genome, transcriptome, proteome D2.2.6 (HL)—Epigenetic tags D2.2.7 (HL)—Epigenetic inheritance D2.2.8 (HL)—Environmental effects on expression D2.2.9 (HL)—Epigenetic tag removal D2.2.10 (HL)—Monozygotic twin studies D2.2.11 (HL)—External factors

[Maximum number: 1]

Stem cells in the bone marrow can be forced into blood vessels in a process called mobilization. Mobilization of stem cells from the bone marrow into the blood vessels represents the basis for modern bone marrow transplantation procedures.

To test the effect of light on the mobilization of stem cells, mice were subjected to a simulated "jet lag" by advancing the light-dark cycle by 12 hours. This was done by subjecting mice to a 24 -hour light period before the results shown in the graph were recorded. The results were compared to the stem cells in control mice under normal conditions of 12 hours of light ( □ ) and 12 hours of darkness ( dark box) and 12 hours of darkness ( dark box ).

Figure for Question D2.2 Gene expression [HL only] question 1 — IB Biology HL

One important chemical in the mobilization of stem cells is a protein, CXCL12, which maintains the stem cells inside the bone marrow. The breakdown of CXCL12 causes the mobilization of stem cells to the blood vessels.

The graph below shows the mobilization of stem cells and the production of mRNA for CXCL12 when the bone marrow is treated with two different chemicals (isoprenaline and clenbuterol).

Explain how the amount of mRNA for CXCL12 gives an indication of the amount of protein CXCL12 produced.

[Maximum number: 7]

The genome is the total of all the DNA in an organism, containing all the genetic information required for development and growth.

Explain how gene expression can be regulated during transcription to determine an organism's phenotype.

[Maximum number: 1]

What is the proteome of an individual?

The amino acids unique to an individual making up the proteins in cells

The way in which an individual's polypeptides are folded into a three-dimensional structure

The proteins synthesized as an expression of an individual's genes

All possible combinations of amino acids an individual contains

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Covered syllabus points

D2.2 Gene expression [HL only] question 1

D2.2 Gene expression [HL only] question 2

D2.2 Gene expression [HL only] question 3