DNA/RNA structure, composition and manipulation

• After DNA amplification, copies are available for study and comparison against other DNA samples.

DNA Structure

• Adenine bonds to thymine, while cytosine bonds to guanine
• DNA is a polymer comprised of nucleotides
• Nucleotides consist of a sugar, a phosphate, and a nitrogenous base
• DNA contains deoxyribose
• DNA's two strands connect through hydrogen bonding

DNA Composition

• If guanine constitutes 28% of a DNA sample, cytosine also makes up 28%
• This leaves 44% for adenine and thymine combined
• Consequently, thymine makes up 22% of the nucleotides in the DNA sample

RNA Types and Composition

• mRNA, rRNA, and tRNA are all types of RNA
• RNA is single-stranded and consists of the sugar ribose
• RNA contains the nitrogen bases C, G, A, and U (uracil), instead of thymine

DNA Manipulation

• DNA can be fragmented using restriction enzymes at specific restriction sites, which is essential for genetic engineering

RNA Transcription

• When DNA creates RNA, adenine binds to uracil, and cytosine binds to guanine
• Uracil replaces thymine in RNA

RNA Processing

• RNA processing is a standard part of protein synthesis.
• It occurs post-transcription but before mRNA exits the nucleus to reach the ribosome.
• Introns are removed during RNA processing
• The final transcript is shorter than the initial one

Central Dogma

• Transcription synthesizes RNA using DNA as a template and requires RNA polymerase; this happens in the nucleus
• Replication is the creation of a new DNA molecule from a template DNA molecule
• DNA polymerase are required for replication
• It occurs during the S phase of interphase
• Translation converts the mRNA sequence into an amino acid sequence within the ribosome

RNA Editing

• Before a newly synthesized RNA strand exits the nucleus for the ribosome, it undergoes editing or processing where introns, which are noncoding regions, are removed

Polyploidy

• Polyploidy is characterized by extra sets of chromosomes (3n, 4n, etc.) within a cell, resulting from nondisjunction
• Nondisjunction occurs during meiosis I when homologous chromosome pairs fail to separate properly
• Aneuploidy and Down syndrome also stem from nondisjunction and infections do not cause polyploidy

Restriction Enzymes

• Restriction enzymes, derived from bacteria, serve as biotechnology tools, cutting DNA at specific sites like GAATTCC

Gel Electrophoresis

• Gel electrophoresis separates DNA molecules based on their movement rate through an agarose gel in an electric field
• First, the DNA sample must be cut into pieces by restriction enzymes

Recombinant DNA

• Recombinant DNA technology is biotechnology or genetic engineering

Cystic Fibrosis

• A cure for cystic fibrosis could be achieved by replacing the nonfunctioning gene with a proper gene

PCR

• PCR can produce millions of DNA copies in hours, requiring heat-stable enzymes, which will then be used in biotechnology

Human Genome

• The human genome has 30,000 genes and 3 billion base pairs
• Most of the human genome is non-coding DNA, known as junk, including introns, but most DNA resides in the nucleus
• A small amount of DNA (16,000 base pairs) exists in mitochondria