Molecular Biology: Nucleic Acids Quiz

Nucleic Acids

• Nucleic acids are unbranched polymers containing monomer units called nucleotides.
• Two types of nucleic acids exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
• DNA is primarily found within the cell nucleus, its function is storing and transferring genetic information, passed from existing cells to new cells during cell division.
• RNA occurs in all parts of a cell and functions primarily in protein synthesis.

Types of Nucleic Acids

• Deoxyribonucleic acid (DNA)
  • Found primarily in the nucleus
  • Stores genetic information
  • Passed from existing cells to new cells during cell division.
• Ribonucleic acid (RNA)
  • Occurs in all parts of a cell
  • Functions in protein synthesis

Chemical Composition of DNA and RNA

• Components:
  • Five-carbon (pentose) sugar
  • Phosphate
  • Nitrogenous bases (four types)

Nucleotides: Structural Building Blocks

• A nucleotide is a three-subunit molecule.
• A sugar (ribose or deoxyribose) is bonded to both a phosphate group and a nitrogenous base.
• Nucleosides are formed by combining a sugar (ribose or deoxyribose) with a purine or pyrimidine base.
• Nucleotides are produced from nucleosides by adding a phosphate group.

Nucleotides: Pentose Sugar

• The sugar unit of a nucleotide is either ribose or 2'-deoxyribose.
• The only structural difference between these sugars is at carbon 2'.
• Ribose has an -OH group at carbon 2', while deoxyribose has an -H atom.

Nucleotides: Nitrogen-Containing Heterocyclic Bases

• Two types of nitrogenous bases: Purines (Adenine, Guanine) and Pyrimidines (Cytosine, Thymine, Uracil).
• Purines have two rings, while pyrimidines have one.
• DNA contains Adenine, Guanine, Cytosine, and Thymine.
• RNA contains Adenine, Guanine, Cytosine, and Uracil.

Nucleotides: Phosphate

• Phosphate is derived from phosphoric acid (H3PO4).
• Under cellular pH conditions, phosphoric acid loses two hydrogen atoms to form a hydrogen phosphate ion (HPO42-).

Nucleotides: Structural Building Blocks

• Nucleosides consist of a sugar and a base
• Nucleotides consist of a nucleoside and a phosphate group

Nucleotide Formation

• Nucleotide formation occurs in two steps.
• First, a pentose sugar and a nitrogenous base react to form a nucleoside.
• Second, the nucleoside reacts with a phosphate group to form a nucleotide.

Nucleoside Formation & Important Characteristics

• The nitrogenous base is always attached to carbon 1' of the sugar.
• For purines, the attachment is through N-9; for pyrimidines, the attachment is through N-1.
• The bond connecting the sugar and base is a β-N-glycosidic linkage.
• A molecule of water is formed

Naming of Nucleosides

• Pyrimidine bases are named with the suffix -idine (cytidine, thymidine, uridine).
• Purine bases are named with the suffix -osine (adenosine, guanosine).
• The prefix deoxy- is used for deoxyribonucleosides.

Nucleotide Formation: (c) Phosphate

• Phosphate, the third component of nucleotide, is derived from phosphoric acid (H3PO4).
• Under cellular pH conditions, the phosphoric acid loses two hydrogen atoms to form a hydrogen phosphate ion (HPO42-).

Nucleotides: Structural Building Blocks

• Nucleotides are the building blocks for nucleic acids, composed of a sugar, a nitrogenous base, and a phosphate group.
• DNA contains deoxyribose sugar, while RNA contains ribose.
• DNA has A, T, G, C, and RNA has A, U, G, C.

Primary Structure of Nucleic Acids

• The primary structure of nucleic acids (DNA and RNA) is linear sequences of nucleotides.
• Nucleotides are linked together by phosphodiester bonds.
• The sequence of bases determines the unique properties of each nucleic acid.

DNA Structure: Double Helix

• DNA's double helix is made of two polynucleotide chains wound around each other.
• The sugar-phosphate backbone forms the outer edges of the helix.
• Nitrogen bases pair in the interior, forming hydrogen bonds (A-T, G-C).

DNA Structure: Base Pairing

• A-T base pairs form two hydrogen bonds.
• G-C base pairs form three hydrogen bonds.
• Base pairing ensures complementary strands.

DNA Structure: Chromosomes

• Chromosomes are organized structures of DNA.
• They contain the genetic information encoded for a particular organism.
• Chromosomes contain a combination of DNA and proteins called chromatin.

DNA Replication

• DNA replication is the process through which DNA molecules produce exact duplicates of themselves.
• Crucial for genetic information to be passed on to daughter cells accurately.
• Mistakes during DNA replication can lead to mutations.

DNA Replication: Overview

• Chromatin disassembly (eukaryotes).
• DNA double helix unwinding.
• Primer binding.
• Elongation.
• Termination.

Telomeres

• Telomeres protect the ends of linear chromosomes, preventing deletion of important genes.
• Telomeres consist of repetitive sequences (TTAGGG in humans).
• They act as protective caps.

Karyotype

• Karyotype is a laboratory-produced image of an individual's complete set of chromosomes.
• Used to look for chromosomal abnormalities.

Human Genetic Disorders

• Some human genetic disorders are characterized by unusual chromosome numbers.
• Examples include Down syndrome, Edward syndrome, and Klinefelter syndrome.

Anti-metabolites (Anticancer Drugs)

• These drugs inhibit DNA synthesis by mimicking the chemical structure of normal molecules needed for DNA replication.
• They are used in cancer treatment to inhibit the rapid cell division in tumors.

Information Flow in Biological Systems

• The central dogma of molecular biology describes the flow of genetic information in cells.
• It illustrates how genetic information flows from DNA to RNA to protein.
• Transcription converts a DNA sequence into an hnRNA/mRNA sequence.
• Translation converts an mRNA sequence into a polypeptide (protein) sequence.

Types of RNA

• Types of RNA include hnRNA, mRNA, snRNA, rRNA, and tRNA.
• Each type has a specific role in the process of protein synthesis and gene expression.

RNA Synthesis (Transcription)

• Transcription is the process of copying a DNA sequence into a complementary RNA sequence.
• It involves three major steps: initiation, elongation, and termination.
• RNA polymerase is the main enzyme involved in the transcription process.

RNA Splicing

• RNA splicing is the process of removing introns (non-coding regions) and joining exons (coding regions) in a hnRNA molecule.
• It converts the hnRNA into a mature mRNA molecule.

The Genetic Code

• The genetic code is a set of rules that translates a sequence of nucleotides in mRNA into a amino acid sequence in a polypeptide (protein).
• It consists of three-nucleotide codons.
• The genetic code is universal (nearly identical) in most organisms.

Translation: Protein Synthesis

• Translation is the process of converting the mRNA sequence into a protein sequence.
• Ribosomes, composed of rRNA and proteins, are the sites of translation.
• tRNA molecules bring amino acids to the ribosome, guided by the mRNA. This process involves initiation, elongation, and termination steps.

Post-Translation Processing

• Post-translation processes modify the newly synthesized protein into its functional form.
• This often involves the removal of initial amino acids, disulfide bridge formation, and protein folding.

Efficiency of mRNA Utilization

• mRNA molecules can be translated by multiple ribosomes simultaneously.
• This process is called polyribosome or polysome formation, ensuring that many proteins are generated from one mRNA molecule.

Test your knowledge on nucleic acids' structure and function with this quiz. Explore key concepts such as DNA and RNA characteristics, transcription processes, and the discoveries that shaped our understanding of molecular biology. Perfect for students studying molecular genetics or biology.