Information Systems in Biology
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Questions and Answers

What initiates the process of translation in a ribosome?

  • The attachment of the 5′ methylated cap to the small ribosomal subunit
  • The release of amino acids from tRNA
  • The binding of the large ribosomal subunit
  • The formation of the initiation complex (correct)

    • During elongation, what occurs after a tRNA transfers its amino acid to the growing polypeptide?

  • A new tRNA enters with a non-corresponding amino acid
  • The ribosome detaches from the mRNA
  • The tRNA remains bound to the polypeptide
  • The ribosome moves one codon length down the mRNA (correct)

    • What signals the termination of translation?

  • The encounter of a stop codon on the mRNA (correct)
  • The exit of the completed polypeptide chain
  • The release of tRNA from the ribosome
  • The union of the large and small ribosomal subunits

    • Which type of protein binds during termination instead of a tRNA?

    <p>A release factor</p> Signup and view all the answers

    What component is NOT part of the initiation complex formed during translation initiation?

    <p>Release factor</p> Signup and view all the answers

    What is the primary function of telomeres in chromosomes?

    <p>To prevent the fusion of chromosomal segments</p> Signup and view all the answers

    Which component of chromatin is primarily responsible for DNA packing?

    <p>Histones</p> Signup and view all the answers

    What differentiates heterochromatin from euchromatin?

    <p>Heterochromatin contains genetically inactive DNA</p> Signup and view all the answers

    At what stage of cell division is chromatin first visible as distinct chromosomes?

    <p>Prophase</p> Signup and view all the answers

    What are satellite chromosomes characterized by?

    <p>Presence of secondary constriction</p> Signup and view all the answers

    How many base pairs does a typical nucleosome contain?

    <p>200 bp</p> Signup and view all the answers

    Which type of histone protein is NOT present in eukaryotic chromosomes?

    <p>H4A</p> Signup and view all the answers

    What happens to telomeres during cell division?

    <p>They become slightly shorter</p> Signup and view all the answers

    What is the result of the chromatin condensing during cell division?

    <p>Visibility of chromosomes</p> Signup and view all the answers

    Which of the following statements about the nucleolar organizer is true?

    <p>It contains genes required for nucleolus formation</p> Signup and view all the answers

    What primarily determines the complexity of a gene's function?

    <p>The sequence of nucleotides encoding the protein</p> Signup and view all the answers

    What constitutes the sides of the DNA double helix?

    <p>Strands of alternating sugar and phosphate groups</p> Signup and view all the answers

    Which base pair forms 2 hydrogen bonds?

    <p>A - T</p> Signup and view all the answers

    How do nucleotides bond within the DNA double helix?

    <p>They bind with hydrogen bonds between nitrogen bases</p> Signup and view all the answers

    What is the nucleotide's role in the DNA structure?

    <p>Nucleotides are the building blocks that carry genetic information</p> Signup and view all the answers

    What characteristic does the DNA double helix formation allow?

    <p>Fixed distance between the two chains</p> Signup and view all the answers

    Which statement is true about the structure of the DNA backbone?

    <p>It is a polymer of alternating sugar and phosphate sequences.</p> Signup and view all the answers

    What best describes the arrangement of nitrogen bases in the DNA double helix?

    <p>They are on the inside, stacking vertically.</p> Signup and view all the answers

    Why do A - T and G - C base pairs occupy the same space in a DNA double helix?

    <p>To ensure uniformity in structure</p> Signup and view all the answers

    In what direction do the strands of DNA run within the double helix?

    <p>One strand runs backwards to the other.</p> Signup and view all the answers

    What is the primary function of chromosomes in living cells?

    <p>Transmission of genetic material</p> Signup and view all the answers

    Which statement correctly describes the structure of chromosomes in eukaryotes?

    <p>They are thread-like and complex, contained within a nucleus.</p> Signup and view all the answers

    How do alleles contribute to genetic variation within a population?

    <p>They are different versions of the same gene that can affect traits.</p> Signup and view all the answers

    What role do chemical signals play in cellular communication?

    <p>They can influence distant target cells through bloodstream connections.</p> Signup and view all the answers

    What is a key difference between chromosomes in prokaryotes and eukaryotes?

    <p>Prokaryotes typically have a single, circular chromosome.</p> Signup and view all the answers

    During cell division, what is the significance of the centromere?

    <p>It acts as the attachment point for spindle fibers.</p> Signup and view all the answers

    What is chromatin, and how does it relate to chromosomes?

    <p>Chromatin is loosely packed DNA that condenses to form chromosomes.</p> Signup and view all the answers

    What determines the compatibility of target cells to respond to hormones?

    <p>The presence of compatible receptors on the target cells</p> Signup and view all the answers

    What is the primary role of nucleosomes in cellular biology?

    <p>To prevent DNA from becoming tangled</p> Signup and view all the answers

    Which type of chromosome has arms that are equal in length?

    <p>Metacentric</p> Signup and view all the answers

    What forms the 30 nm compact chromatin fiber?

    <p>Nucleosomes and linker DNA</p> Signup and view all the answers

    What is a characteristic of sub-metacentric chromosomes?

    <p>Their centromere is situated near, but not at the center.</p> Signup and view all the answers

    What component of DNA determines the biological instructions it encodes?

    <p>The sequence of nitrogenous bases</p> Signup and view all the answers

    Which of the following types of nucleotides is classified as a purine?

    <p>Adenine</p> Signup and view all the answers

    What role do scaffolding proteins play in chromatin structure?

    <p>They provide structural support to DNA loops.</p> Signup and view all the answers

    Which of the following accurately describes telocentric chromosomes?

    <p>They possess one arm located at one end.</p> Signup and view all the answers

    How are nucleotides linked together to form a DNA strand?

    <p>By alternating phosphate and sugar groups</p> Signup and view all the answers

    What is the main purpose of DNA in organisms?

    <p>To store and transmit genetic information</p> Signup and view all the answers

    Study Notes

    Information System

    • Information is transmitted within and between individuals through various methods.
    • DNA transmits information from one generation to the next using chemical substances.

    Chemical and Electrical Signals

    • Chemical signals (ligands/signaling molecules) are a common form of cellular communication.
    • These signals are secreted by cells and travel through extracellular fluid to target cells.
    • Examples include neurotransmitters and hormones.

    Hormones

    • Hormones are chemical signaling molecules produced by endocrine glands.
    • They are secreted directly into the bloodstream and travel to distant tissues/organs.
    • Only target cells with compatible receptors can respond.

    Neurotransmitters

    • Many animals use electrical signals for information transmission.
    • The nervous system transmits information via neurotransmitters and electrical impulses.

    Chromosomes

    • Chromosomes are thread-like bodies present in the nucleoplasm of living cells, crucial for inheriting genetic information (genes) from one generation to the next.
    • This genetic material is deoxyribonucleic acid (DNA).
    • In prokaryotes (cells without a nucleus), the chromosome is a circular DNA structure.
    • In eukaryotes (cells with a nucleus), chromosomes are more complex in structure.
    • Eukaryotic genomes comprise multiple chromosomes.
    • Diploid organisms (like humans) have two copies of each chromosome.
    • Chromosome pairs share identical genes arranged in the same order, but often have different versions of the genes (alleles).
    • Chromosomes vary in number across different organisms, but the number is specific for each organism.
    • Chromosomes are essential for cell division, needing replication, division, and successful transmission to daughter cells.
    • Chromosomes control organism growth and development.
    • Chromosome structure and chromatin vary throughout the cell cycle.

    Chromosome Structure

    • Chromosomes are composed of chromatin, which contains DNA and associated proteins (histone proteins).
    • Chromosomes are made up of many genes that code for various proteins in the cell.
    • Chromosome structure can be best examined during cell division.

    Main parts of Chromosomes

    • Each chromosome has two symmetrical chromatids.
    • Each chromatid contains a single DNA molecule.
    • During anaphase of mitotic cell division, sister chromatids separate and migrate to opposite poles.

    Centromere and Kinetochore

    • Sister chromatids are connected by the centromere.
    • Spindle fibers attach to the centromere during cell division.
    • Centromere is the primary constriction point.
    • Centromere divides a chromosome into two parts—p arm (shorter) and q arm (longer).
    • The kinetochore is a protein complex assembled on the centromere before cell division.
    • Each chromosome has two kinetochores on either side of the centromere during metaphase.
    • The kinetochore acts as an interface between chromosomes and spindle microtubules.
    • Kinetochores pull chromosomes apart during anaphase and ensure equal distribution of sister chromatids in daughter cells.

    Secondary Constriction and Nucleolar Organisers

    • Chromosomes have secondary constrictions besides the centromere (primary constriction).
    • Secondary constrictions, called nucleolar organizers, contain genes that form nucleoli.

    Telomere

    • The terminal part of a chromosome is called the telomere.
    • Telomeres are polar, preventing fusion of chromosomal segments.
    • Telomeres shorten each time a cell divides, eventually leading to cell division cessation.

    Satellite

    • Sometimes, chromosomes have an elongated segment called the satellite located at the secondary constriction.
    • Chromosomes with satellites are known as sat-chromosomes.

    Chromatin

    • Chromosomes are composed of chromatin, which is made up of DNA, RNA, and proteins.
    • During the interphase, chromosomes are visible as thin chromatin fibers in the nucleoplasm.
    • During cell division, chromatin fibers condense, making chromosomes visible with distinct features.
    • Heterochromatin (darkly stained): condensed regions, contain tightly packed DNA, genetically inactive, and commonly found in constitutive heterochromatin.
    • Euchromatin (light stained, diffused regions): contain loosely packed DNA, genetically active, and common in active genes.
    • Chromatin material appears as thin filaments (chromonemata) during prophase.

    Structural Organisation of Chromatin

    • Chromatin is made of DNA and associated proteins.
    • DNA is organized into nucleosomes, the basic units of chromatin.
    • DNA coils around histone proteins to form nucleosomes.
    • Five types of histone proteins exist in eukaryotic chromosomes.
    • Histones are positively charged due to amino acids, enabling association with negatively charged DNA (due to phosphate groups).
    • Histones play a role in gene regulation.
    • Nucleosomes consist of 200 base pairs of coiled DNA around a core of eight histone molecules. Linked by linker DNA.
    • Nucleosomes prevent DNA tangling.

    Linker DNA

    • Linker DNA and the fifth histone protein assemble adjacent nucleosomes into a compact chromatin fibre (30nm).
    • These fibres coil to form extended chromatin (300nm), held together by non-histone proteins like actin, alpha/beta tubulin, and myosin (scaffolding proteins)

    Nucleotide Binding and Bonding

    • Nucleotides covalently bond through sugar-phosphate backbone (5' carbon of sugar to 3' carbon).
    • Nucleotides form hydrogen bonds with opposing strand bases.
    • Complementary base pairings: A-T (2 H-bonds) and G-C (3 H-bonds).
    • Consistent base pairings maintain a uniform DNA diameter.

    Base Pairs

    • A-T pairings and G-C pairings maintain a consistent DNA diameter.

    DNA Backbone

    • DNA backbone is a polymer with an alternating sugar-phosphate sequence.
    • Deoxyribose sugars in the backbone are connected through ester links to phosphate groups in a 3'-5' direction.

    Features of the DNA Double Helix

    • DNA consists of two intertwined strands running in opposite directions (antiparallel).
    • The strands are arranged in a spiral (double helix).
    • Nitrogenous bases are inside the helix, stacked atop each other.

    A final structure for DNA

    • DNA consists of two antiparallel strands.
    • The right-hand chain is essentially upside-down.

    RNA

    • RNA consists of ribose, phosphate, and nitrogenous bases (purines, pyrimidines).

    • RNA typically forms a single-stranded biopolymer.

    • Nucleotides are linked by 5'-3' phosphodiester bonds between ribose sugars in the RNA backbone.

    • RNA differs from DNA: uracil replaces thymine, and RNA contains a 2' hydroxyl group.

    • Self-complementary RNA sequences can fold into complex structures.

    How is RNA Made

    • RNA polymerases synthesize RNA from DNA through transcription.
    • RNA polymerase binds to the promoter region of DNA, unwinding it to expose the template strand.
    • RNA polymerase uses the template DNA strand to synthesize a complementary RNA strand.
    • The newly synthesized RNA strand is almost identical to the non-coding strand of the DNA, barring uracil replacing thymine.

    Types of RNA

    • mRNA serves as a template and carries genetic information out of the nucleus for protein synthesis.
    • tRNA binds both mRNA & amino acids, bringing the correct amino acids to ribosomes during protein formation.
    • rRNA constitutes 50% of a ribosome, a molecular assembly essential for protein synthesis.

    Protein Synthesis

    • The mechanism of RNA translation into protein consists of initiation, elongation, and termination steps.
    • Initiation involves mRNA joining with tRNA and ribosomes.
    • Elongation involves tRNA bringing amino acids according to codon sequences.
    • During termination, ribosome encounters a stop codon, triggering polypeptide chain release and complex disassembly.

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    Description

    Explore the fascinating methods of information transmission in biology, including chemical and electrical signals. This quiz covers the roles of hormones, neurotransmitters, and chromosomes in cellular communication and genetic information transfer.

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