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.

Test your knowledge on DNA, RNA, and the chemistry of nucleotides. This quiz covers essential concepts, including the structures and differences between nucleic acids, as well as the major nitrogenous bases. Perfect for students studying molecular biology.