Biology 3 Homework Assignment: Genetic Diseases and Epigenetic Studies

This assignment addresses the impact of dysregulated genes and epigenetic factors in various diseases, including cancer. It explores specific examples of RNA interference (RNAi), DNA methylation, and histone modifications, providing insights into their mechanisms. The assignment also challenges traditional beliefs by examining how epigenetics influences phenotype, the limitations of cancer cell lines as models for normal gene regulation, and the essential functions of non-coding DNA. The solution uses examples from the course to illustrate these concepts, offering a comprehensive overview of gene regulation and its role in disease.

Running head: BIOLOGY
BIOLOGY
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BIOLOGY
Question 1
a) RNA interference (RNAi) can be considered as a biologic response to RNA that causes
silencing of the target gene expression that is sequence specific. RNAi technique is the
helpful in investigating diseases related to chromosomal abnormalities like myeloid
malignancies. The silencing of the gene is done by a shirt 22-mer double stranded RNA,
that is used for silencing the Bcr-Abl fusion protein, used in the treatment Bcr-Abl–
positive leukemia.
b) DNA methylation
DNA methylation can be referred to as an epigenetic approach that is caused due the
addition of Methyl group to the DNA, modifying the gene function and its expression.
DNA methylation of the promoter and the first exon can mimic mutations in various
tumour suppressor genes and the proto-oncogenes. Again hyper-methylation and hypo-
methylation caused in the initial exon and promoter of the tumour suppression genes can
cease their translational process. Again, hypo-methylation occurring in the regulatory
DNA sequence can initiate the transcription of the proto-oncogenes and also activates the
genes to express proteins that are involved in the genomic instability and metastasis of
the malignant cells, thus increasing the chance of cancer.
c) Histone modification or chromatin proteins
Histone modification can include phosphorylation, methylation, acetylation, sumoylation
and ubquitylation. Histone modification can cause chromosome deregulation that results
s neurodevelopmental disorder. Research studies have found that in Alzheimer’s disease,
deregulation in histone occurs by the acetylation of the lysine residues by histone
acetyltransferases (HAT), which is related to active translation in the genes.

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BIOLOGY
Question 2
a) Phenotype is controlled by genotypes
Epigenetics is involved in many normal cellular processes. In the organs there are several
genes that can be turned on and off, which can cause differential genetic expressions.
Gene silencing can be the reason by why genetic twins are not equal. Difference in skin
colour, hair colour can be due to epigenetics like DNA methylation.
b) Cancer cell lines are useful models for studying normal gene regulation
Cancer cell lines are not perfect models to study regulation of cells. After the first development
of the cancer cell lines. Several cell lines of cancer have been recognised, but none of the cell
lines actually similar to the tumours from which they had been derived. It has been revealed from
the cytogentic studies that the cell lines that are used for modelling the various types of cancers
were obtained from HeLa cervical cell line and not from other types of cancers. One such
specific example that can be given is about the KB cell line in the MDR field, which was used
for the anticancer drug screening was previously thought to be obtained from a mouth
carcinoma, but it was actually derived from the HeLa cells. Hence, across contamination of the
cell lines.
c) 99% of our DNA that is never translated to protein is “garbage”
The saying that 99 % of out DNA is never translated is “garbage” is a myth, but they have
essential biological functions. Some of the non-coding region of the DNA undergoes
transcription to produce non-coding RNAs like ribosomal RNA, regulatory RNA and tRNA. The
non-coding regions are often termed as the genetic switches. The non-coding region also shows
positive selection throughout the evolution. Mutations in the non-coding region of DNA has been

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BIOLOGY
associated with Austism spectrum disorder