DNA and Molecular Biology Quiz

DNA and Molecular Biology

• DNA and RNA are nucleic acids.
• Nucleotides are the structural units of nucleic acids.
• Nucleotides are composed of a nitrogenous base, a pentose sugar, and a phosphate group.
• Nucleosides are composed of a nitrogenous base and a pentose sugar.
• Purines include adenine and guanine.
• Pyrimidines include cytosine, uracil, and thymine.
• Ribose is found in RNA
• Deoxyribose is found in DNA
• Uracil is found in RNA
• Thymine is found in DNA
• Cytosine is found in both DNA and RNA

Chemistry of Nucleotides

• A nucleotide is formed from a nitrogenous base, a pentose sugar, and a phosphate group.
• A nucleoside is formed from a nitrogenous base and a pentose sugar.
• The carbons of the pentose are named 1', 2', 3', 4', and 5'.

Nitrogenous Bases

• Major pyrimidines are uracil (RNA), thymine (DNA), and cytosine (both DNA and RNA).
• Minor pyrimidines include dihydro uracil and methyl cytosine.
• Major purines are adenine (DNA and RNA) and guanine (DNA and RNA).

Oxy Purines

• Hypoxanthine is not found in DNA or RNA
• Xanthine is formed during the synthesis or catabolism of major purines.
• Uric acid is the end-product of purine catabolism.
• Normal blood level is 3-7mg/dl. Elevated levels relate to gout (hyperuricemia).
• Methylated purines (Caffeine, Theophylline, Theobromine) are found in coffee, tea, and cocoa.

Nucleosides and Nucleotides

• Nucleosides are formed when a nitrogenous base is connected to a pentose sugar by an N-glycosidic bond.
• Nucleotides are formed when a phosphate group is attached to the 5' carbon of the pentose sugar.
• The naming of nucleosides and nucleotides is dependent on the nitrogenous base.

Free Nucleosides and Nucleotides

• Nucleotides and nucleosides are the building blocks of DNA and RNA.
• ATP, ADP, and AMP are examples of adenosine monophosphate, diphosphate and triphosphate.
• GMP, GDP, and GTP are examples of guanosine monophosphate, diphosphate and triphosphate,
• ATP is the body's energy currency.
• High-energy bonds link phosphate groups in ATP.
• ATP is used in mechanical, electrical, and chemical processes.
• Cyclic AMP (cAMP) and cyclic GMP (cGMP) are examples of secondary messengers.

Structure of Chromatin and Chromosomes

• Chromatin is DNA in non-dividing cells, not visible with light microscopes.
• Chromatin is visible in electron microscopes as a network of fibers.
• A chromosome is condensed DNA, formed before cell division, consisting of two identical chromatids.
• Chromosomes consist of one single DNA molecule and histone proteins.
• Histone proteins are basic and positively charged, attracting DNA (which has a negative charge).
• 5 types of histones are (H1, H2A, H2B, H3, H4).
• Nucleosomes are the basic repeating units of chromatin, consisting of a core of histone proteins with DNA wrapped around them.
• Linker DNA connects nucleosomes.

DNA Tertiary Structure

• Circular DNA occurs in mitochondria, chloroplasts and bacteria.
• DNA is mainly linear in eukaryotes.
• Supercoiling occurs in DNA which can be right handed or left handed.
• DNA can be in a toroidal, or interwound coil conformation.

Mitochondrial DNA (mtDNA)

• mtDNA is circular, double-stranded DNA.
• mtDNA is maternally inherited.
• mtDNA codes for some tRNA, rRNA and proteins involved in oxidative phosphorylation.

RNAs Structure

• RNA is a single-stranded nucleic acid.
• RNA is formed of ribonucleoside monophosphate.
• RNA is responsible for protein synthesis.
• Types of RNA include mRNA, tRNA, and rRNA.

Other forms of RNA

• Small nuclear RNA (snRNA) is involved in RNA processing.
• Micro RNA (miRNA) is involved in gene expression.
• Small interfering RNA (siRNA) inhibits gene expression.

Comparing DNA and RNA

• DNA is located in the nucleus and mitochondria (mostly), while RNA is located mainly in the cytoplasm.
• DNA is a double helix, while RNA is usually single-stranded.
• DNA has deoxyribose, while RNA has ribose.
• DNA has thymine while RNA has uracil.