7.2 Transcription are gene expression – Sciences for IGCSE & IB

Some regions of DNA do not code for the production of proteins. What are these regions of DNA used as?

They have no known function and are recycled to provide nucleotides
Gene regulation and coding for production of enzymes used in translation
Telomeres and coding for production of tRNA
Introns and coding for production of structural proteins

2. Which structure found in eukaryotes has a single membrane?

Nucleus
Lysosome
Chloroplast
. Mitochondrion

3. In which process(es) do nucleosomes play a role in eukaryotes? I. tRNA activation II. Transcription regulation III. DNA supercoiling

I only
II only
II and III only
I, II and III

4. Very soon after fertilization, parental epigenetic methylation is reversed in the DNA. Later, tissue-specific epigenetic modifications are made to the embryonic DNA. The graph follows the degree of methylation from different sources during embryonic development.

According to the graph, what are the changes in DNA methylation during embryonic development?

Only the paternal DNA becomes demethylated.
The maternal DNA becomes demethylated first.
The methylation patterns of the parents’ DNA are erased before fertilization.
The methylation patterns of both parents are erased after fertilization.

5. What happens during transcription in eukaryotes?

Polysomes move
Nucleosomes are phosphorylated
RNA polymerase separates DNA strands
Okazaki fragments are produced

6. What is a feature of transcription?

Both strands of a DNA molecule act as a template for mRNA
Nucleoside triphosphates become nucleotides by losing three phosphates
RNA polymerase binds to the promoter region
The sense strand acts as a template for mRNA

7. What makes up eukaryotic RNA immediately after transcription?

Exons, introns and primers
Exons and introns
Introns only
Exons only

8. What are introns?

Sequences of nucleotides that are removed to form mature RNA in eukaryotes
Sequences of nucleotides that are removed to form mature RNA in prokaryotes
Sequences that remain in mature RNA after exons have been removed
Small pieces of circular DNA that are found in prokaryotes

9. The antisense strand of a DNA molecule has the sequence TACCCGATC. What would be the resulting mRNA strand sequence?

TACCCGATC
ATGGGCTAG
UACCCGAUC
AUGGGCUAG

10. Which statement applies to transcription in eukaryotic cells but not to prokaryotic cells?

RNA polymerase transcribes the antisense strand of DNA to produce a strand of RNA
During transcription, uracil replaces thymine in RNA
Transcription takes place in the cell nucleus
Initiation of transcription requires a promoter sequence of DNA

11. The sequence of nucleotides in a section of RNA is: GCCAUACGAUCG What is the base sequence of the DNA sense strand?

CGGUAUGCUAGC
GCCATACGATCG
CGGTATGCTAGC
GCCAUACGAUCG

12. What is removed during the formation of mature RNA in eukaryotes?

Exons
Introns
Codons
Nucleosomes

13. The antisense strand on the DNA molecule coding for three codons of a gene is TATCGCACG What are the anticodons of the three tRNA molecules that correspond to this sequence?

UAU, CGC and ACG
ATA, GCG and TGC
AUA, GCG and UGC
TAT, CGC and ACG

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