Practise IB Biology HL D2.2 by tracing gene expression, transcriptional control and epigenetic regulation from DNA activity to cell-specific proteins and phenotype.
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.
What is a consequence of nucleases binding to mRNA?
Transcription stops.
mRNA binds to ribosomes.
More mRNA is synthesized.
mRNA cannot be translated again.
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
Nucleosomes help to regulate transcription in eukaryotes.
State a chemical modification of a nucleosome that could impact gene expression.
Arabidopsis is a small flowering plant in the mustard family (Brassicaceae) that is widely used in basic research. It has a short life cycle, flowers quickly producing a large number of seeds and is easy to cultivate. It forms a circle of leaves known as a rosette that lies close to the soil. Flowers form at the end of short stems.
A study was carried out of differences in development between Arabidopsis plants grown in long days ( 16 hours light, 8 hours dark) or short days ( 8 hours light, 16 hours dark). The sixth leaf (L6) to emerge in the rosette of each plant was used in all investigations.
New leaves are initiated by the meristem and go through four stages as they develop.
- Stage 1 (S1) - rapid cell division
- Stage 2 (S2) - cell division has ceased, cell expansion continues
- Stage 3 (S3) - decreasing cell expansion rate
- Stage 4 (S4) - leaf growth complete
The start of each stage of leaf development for plants grown in long days and short days is shown above the first graph.
Using the data in the bar chart, discuss the evidence for Arabidopsis plants adapting to different daylight regimes by changing the pattern of gene expression.
DNA methylation profiles in zebrafish (Danio rerio) gametes were determined. The methylated areas were divided into three groups according to the amount of methylation: high, medium and low methylation.
Methylation of DNA in sperm and egg is removed immediately after fertilization. What is the reason for this?
Methylation allows RNA polymerase to join the promoter.
It is needed to form homologous pairs of chromosomes.
It allows expression of genes linked to early development.
Transcription of promoters only occurs in methylated genes.
What is the difference between the DNA of adult identical (monozygotic) twins?
Order of genes
Sequence of nucleotides
Methylation pattern
Ratio of complementary base pairs
The diagram shows a nucleosome from the nucleus of a eukaryotic cell.
Explain the role of lactose in the expression of the gene for lactase production.