EUKARYOTIC GENE EXPRESSION
ORGANISATION OF EUKARYOTIC GENOME
CONTROL OF GENE EXPRESSION
List of Questions
1. Describe the different levels of condensation of DNA.
2. Describe the structure and function of the telomere.
3. Explain the role of telomerase.
4. Describe the structure and function of the centromere.
5. Compare RNA and DNA.
6. Describe the structure and function of the different types of RNA.
7. Describe the regulation of gene accessibility via chromatin modification.
8. Describe the process of transcription.
9. Describe the regulation of transcription.
10. Describe the post-transcriptional modification of mRNA.
11. Explain the features of the genetic code.
12. Describe the process of translation.
13. Describe the regulation of translation.
14. Describe the action of aminoacyl-tRNA synthetase.
15. Explain the role of ribosomes.
16. Describe the post-translational modification of polypeptides.
Copyright © 2019 tonyndr
, (1) Describe the different levels of condensation of DNA.
First level of condensation
● DNA coiled around an octamer of histone proteins (2 each of histones H2A, H2B, H3 and H4)
to form a nucleosome core
● Formation of ionic bonds between positively-charged residues of histone proteins and
negatively-charged sugar-phosphate backbone of DNA
● Each chromatin subunit consists of nucleosome core, linker DNA and associated non-histone
chromosomal proteins
● Multiple nucleosomes are packed together to produce the 10-nm chromatin fibre
(nucleosome fibre)
Second level of condensation
● Histone H1 and linker DNA are involved in the further folding and coiling of the 10-nm
chromatin fibre to produce the 30-nm chromatin fibre (solenoid)
Third level of condensation
● Scaffold proteins are involved in condensing the 30-nm chromatin fibre to form looped
domains
● Looped domains further coil and fold to produce the metaphase chromosome during mitosis
or meiosis
Significance
● Organise and pack giant DNA molecules of eukaryotic chromosomes into structures that can
fit into the nucleus
● Ensures that DNA molecules of different chromosomes do not entangle and break during
separation at anaphase, allowing proper segregation of chromosomes during cell division
● Facilitates regulation of gene expression by affecting ability of transcription factors/RNA
polymerase to gain access to DNA and activate/initiate transcription; thus the wound DNA is
transcriptionally inactive
Copyright © 2019 tonyndr
ORGANISATION OF EUKARYOTIC GENOME
CONTROL OF GENE EXPRESSION
List of Questions
1. Describe the different levels of condensation of DNA.
2. Describe the structure and function of the telomere.
3. Explain the role of telomerase.
4. Describe the structure and function of the centromere.
5. Compare RNA and DNA.
6. Describe the structure and function of the different types of RNA.
7. Describe the regulation of gene accessibility via chromatin modification.
8. Describe the process of transcription.
9. Describe the regulation of transcription.
10. Describe the post-transcriptional modification of mRNA.
11. Explain the features of the genetic code.
12. Describe the process of translation.
13. Describe the regulation of translation.
14. Describe the action of aminoacyl-tRNA synthetase.
15. Explain the role of ribosomes.
16. Describe the post-translational modification of polypeptides.
Copyright © 2019 tonyndr
, (1) Describe the different levels of condensation of DNA.
First level of condensation
● DNA coiled around an octamer of histone proteins (2 each of histones H2A, H2B, H3 and H4)
to form a nucleosome core
● Formation of ionic bonds between positively-charged residues of histone proteins and
negatively-charged sugar-phosphate backbone of DNA
● Each chromatin subunit consists of nucleosome core, linker DNA and associated non-histone
chromosomal proteins
● Multiple nucleosomes are packed together to produce the 10-nm chromatin fibre
(nucleosome fibre)
Second level of condensation
● Histone H1 and linker DNA are involved in the further folding and coiling of the 10-nm
chromatin fibre to produce the 30-nm chromatin fibre (solenoid)
Third level of condensation
● Scaffold proteins are involved in condensing the 30-nm chromatin fibre to form looped
domains
● Looped domains further coil and fold to produce the metaphase chromosome during mitosis
or meiosis
Significance
● Organise and pack giant DNA molecules of eukaryotic chromosomes into structures that can
fit into the nucleus
● Ensures that DNA molecules of different chromosomes do not entangle and break during
separation at anaphase, allowing proper segregation of chromosomes during cell division
● Facilitates regulation of gene expression by affecting ability of transcription factors/RNA
polymerase to gain access to DNA and activate/initiate transcription; thus the wound DNA is
transcriptionally inactive
Copyright © 2019 tonyndr
