Genomics And Dna Sequencing

Steps of Sanger’s chain termination method of DNA sequencing:
– Reaction Setup: The DNA to be sequenced is used as the template in four different tubes. Each tube also contains a DNA polymerase, a primer, deoxynucleotide triphosphates (dNTPs), and one of the four dideoxynucleotide triphosphates (ddATP, ddGTP, ddCTP, or ddTTP), at a low concentration.
– DNA Synthesis: DNA polymerase starts to extend the primer. If any of the ddNTPs are incorporated into the new strand, it leads to premature chain termination.
– Chain Termination: Synthesis proceeds until a ddNTP is incorporated at random positions of the growing strand. As ddNTPs lack the 3’OH group, extension can no longer proceed. This generates many different chains of varying lengths, with the ddNTP at the terminating position.
– Gel Electrophoresis: The DNA fragments are then separated based on their size using gel electrophoresis. Here, smaller fragments move further down the gel, and larger fragments move slowly.
– Autoradiography/Visualization: The fragments are visualised in the gel using radioactive markers or fluorescent dyes. This produces a ladder-like image with the smallest band appearing at the bottom, and the sequence is read from bottom to top.

• Sampling: Collect environmental samples containing diverse microbial communities.
• DNA Extraction: Isolate total DNA from all microorganisms in the sample.
• Sequencing: Use high-throughput sequencing technologies to sequence the extracted DNA.
• Bioinformatics Analysis: Analyze the sequencing data to identify microbial species, their genes, and functional capabilities.

• Allows study of microorganisms that cannot be cultured in the laboratory.
• Helps understand microbial diversity, ecology, and functions in natural environments.
• Aids in discovering new genes, enzymes, and bioactive compounds.
• Useful in environmental monitoring, agriculture, and human health research.

• Red spots: Genes expressed more in normal cells than in cancerous cells (higher red fluorescence).
• Green spots: Genes expressed more in cancerous cells than in normal cells (higher green fluorescence).
• Yellow spots: Genes expressed equally in both normal and cancerous cells, resulting from the overlap of red and green signals.
• Black or no color: Genes not expressed or below detection level in both cell types.

• Genome Size: The genome size includes both coding (genes) and non-coding DNA (introns, repetitive sequences, regulatory regions, and 'junk DNA'). Some organisms have large amounts of non-coding DNA which increases genome size without increasing the number of genes.
• Number of Chromosomes: The chromosome count indicates how DNA is organized, not how many genes are present. Different organisms can have varying numbers of chromosomes but similar gene counts.

• Option D: Correct. ApoE4 allele increases susceptibility to Alzheimer’s disease.
• Option A, B, C: Incorrect. These conditions are linked to other genes or factors, not the ApoE gene.