Introduction to Basic Genetics
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Questions and Answers

What is defined as a variation of a gene located on a specific section of a chromosome?

  • Allele (correct)
  • Genotype
  • Homozygote
  • Phenotype

    • What describes an organism that has two identical alleles of a gene?

  • Dominant allele
  • Homozygote (correct)
  • Recessive allele
  • Heterozygote

    • What is true about a recessive allele?

  • It expresses in pairs only. (correct)
  • It is always dominant over other alleles.
  • It requires only one copy to be expressed.
  • It can be expressed alone.

    • Which of the following best describes the term 'phenotype'?

    <p>The observable traits of an organism</p> Signup and view all the answers

    Which organelles in plant cells contain hereditary material?

    <p>Mitochondria and nucleus</p> Signup and view all the answers

    What characterizes the plastid genome (cpDNA)?

    <p>It contains an inverted repetitive region separated by gene segments.</p> Signup and view all the answers

    Which of the following statements about the mitochondrial genome (mtDNA) is true?

    <p>It exhibits greater diversity in size compared to the plastid genome.</p> Signup and view all the answers

    What types of genes are present in the plastid genome?

    <p>Genes for rRNA, tRNA, and some involved in photosynthesis.</p> Signup and view all the answers

    Which characteristic is common to both plastid and mitochondrial genomes?

    <p>Both have circular DNA structures.</p> Signup and view all the answers

    What is the primary function of the genes coded in the mitochondrial genome?

    <p>They largely contribute to mitochondrial function and energy production.</p> Signup and view all the answers

    Which of the following components are found in the basis of DNA?

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

    What is the role of histone proteins in DNA unwinding?

    <p>To provide structural support and control DNA packaging</p> Signup and view all the answers

    What structural element plays a critical role in chromosome pairing during cell division?

    <p>Centromere region</p> Signup and view all the answers

    Which sequence is not encoded in the coding region of a gene?

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

    What percentage of the total DNA content in a cell can the plastid genome represent?

    <p>5% to 10%</p> Signup and view all the answers

    What role do telomeres serve at the ends of chromosomes?

    <p>They stabilize chromosome ends and prevent loss of sequence</p> Signup and view all the answers

    What is the primary role of the promoter region in a gene?

    <p>To regulate the transcription process</p> Signup and view all the answers

    What components are included in the plastid genome (cpDNA)?

    <p>Protein-coding genes and tRNA genes</p> Signup and view all the answers

    What is the primary phase of the cell cycle where DNA duplication occurs?

    <p>S Phase</p> Signup and view all the answers

    In which stage of the cell cycle do cells enter a state of unchanged readiness, waiting for signals?

    <p>G0 Phase</p> Signup and view all the answers

    Which proteins play a crucial role in regulating the cell cycle?

    <p>Cyclins and cyclin-dependent kinases (CDK)</p> Signup and view all the answers

    During which phase of mitosis does chromatin condense into organized chromosomes?

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

    In the context of DNA replication, which direction does the synthesis occur?

    <p>5'-3' direction</p> Signup and view all the answers

    What characterizes the M Phase of the cell cycle?

    <p>Cell division through mitosis and cytokinesis</p> Signup and view all the answers

    What is the correct order of the phases in the cell cycle?

    <p>G1, S, G2, M</p> Signup and view all the answers

    What is the role of telomere sections in DNA replication?

    <p>They ensure the preservation of chromosomal integrity.</p> Signup and view all the answers

    What occurs during metaphase of cell division?

    <p>Chromosomes align along the equatorial line.</p> Signup and view all the answers

    Which event is characteristic of anaphase?

    <p>Separation of sister chromatids.</p> Signup and view all the answers

    During which phase is the physical division of the cell most evident?

    <p>Telophase.</p> Signup and view all the answers

    What is the primary function of crossing over during meiosis?

    <p>To create genetic diversity through allele substitution.</p> Signup and view all the answers

    Which statement describes the contractile ring system during cytokinesis?

    <p>It starts to develop during anaphase.</p> Signup and view all the answers

    Which of the following best describes the role of nucleosomes?

    <p>They condense DNA into a compact form.</p> Signup and view all the answers

    What happens to the microtubules after cytokinesis is completed?

    <p>They re-establish typical interphase characteristics.</p> Signup and view all the answers

    Which process occurs during the presynapsis stage of meiosis I?

    <p>Homologous chromosomes may undergo crossing over.</p> Signup and view all the answers

    Study Notes

    Basic Genetics

    • Genetics is the study of inherited traits and how they are passed from one generation to the next.
    • Genes are the functional units of heredity. They are distinct sections of DNA, providing instructions for specific traits.
    • These instructions are encoded within the DNA base sequences.
    • Genes encode RNA and proteins; specifically, they contain the instructions for building RNA molecules and protein molecules.
    • Alleles are variations of a gene located on a specific section of a chromosome.
    • Homozygotes have identical alleles for a particular gene (e.g., AA or aa).
    • Heterozygotes have different alleles for a particular gene (e.g., Aa).
    • Dominant alleles are expressed even if only one copy is present.
    • Recessive alleles are only expressed when two copies are present.
    • Genotype is the genetic makeup of an organism, specifying the combination of alleles for a trait.
    • Phenotype is the observable physical characteristic or trait. It's the result of the genetic material (genotype).

    Useful Terms

    • The genetic structure that encodes a trait or the material basis for trait inheritance.
    • Visible physical characteristic of an organism.

    Where Can Be DNA Found in Plant Cells?

    • Every cell in a plant contains the same genetic information.
    • Cellular organelles such as the nucleus, chloroplasts, and mitochondria contain hereditary material.
    • Gene transfer between different organelles in cells is typical.

    Organisation of Cellular DNA

    • DNA is a nucleic acid that stores genetic information.
    • It was discovered by Friedrich Meischer in 1869.
    • DNA has three main components: bases (adenine, cytosine, guanine, thymine), pentose (2-deoxy-β-d-ribose), and phosphorus acid.
    • The two strands of DNA are antiparallel.
    • Opposite bases are connected by hydrogen bonds.

    Organisation of Cellular DNA - Basic Proteins Involved in DNA Unwinding

    • Histone proteins are basic proteins involved in DNA unwinding.
    • There are five types of histone proteins: H2A, H2B, H3, H4, and H1.
    • These histone proteins form a core structure (nucleosome), around which DNA is wrapped.
    • A nucleosome is a structural unit consisting of DNA wrapped around histone proteins.
    • The length of DNA in a human cell is approximately 2 meters.
    • DNA folding is essential in packaging and preventing tangling, breakage, or clumping.

    Organisation of Cellular DNA - Chromosome

    • Centromere regions play a role in chromosome pairing and displacement in cell division.
    • The centromere acts as a binding site for microtubules.
    • Cohesin proteins link homologous chromosomes.
    • Telomere regions are located at the ends of chromosomes.
    • Telomeres assist in stabilizing chromosome ends and prevent the loss of sequence ends.
    • Tandem repeats form the telomere region.

    Organisation of Cellular DNA - Structure of a Gene

    • Promoter region is a transcriptional regulatory stage for RNA polymerase recognition.
    • Coding region is the segment of the gene that codes for proteins.
    • Exons are gene segments that code for proteins.
    • Introns are gene segments that do not code for proteins.
    • Termination sequence is a regulatory region that signals the end of transcription.

    Organellar DNA Organization - Plastid Genome (ptDNA)

    • Plant cells have chloroplasts, whose number ranges from 10-100 per cell, and their size is approximately 5-10 µm.
    • Plastid genome, cpDNA, typically contains approximately 120-130 genes, including around 80 protein-coding genes and different rRNA and tRNA genes.
    • The genome is comparatively small (0.1-0.001%), but it can sometimes take up 5-10% of the total DNA in a cell.
    • Various plastid types have the same genetic composition.

    Plastid Genome - cpDNA

    • Circular DNA typically contains repetitive inverted regions (IRA and IRB).

    Organellar DNA Organization - Plastid Genome (ptDNA)

    Organisation of Mitochondrial Genome

    • Mitochondria are cellular organelles for energy production and ATP synthesis.
    • They have a double membrane system (internal and external membranes).
    • Usually they have a bacterial shape (sphere or cylinder).

    Mitochondrial Genome (mtDNS)

    • Mitochondrial genome is more diverse than the plastid genome.
    • Its size varies from 100-3000 kb, which is significantly more diverse than the size range for plastid DNA.
    • It is usually circular and double-stranded.
    • Coded genes are separated into "housekeeping" genes (for rRNA, tRNA, and proteins) and other genes required for mitochondrial function, including ATP synthase, NADPH dehydrogenase, etc.

    Cell Cycle (in Plants ~29 Hours)

    • The cell cycle is the series of events that occur in eukaryotic cells between two divisions.
    • It comprises interphase, mitosis, and cell division.
    • Interphase stages include G1 (first growing stage), G0 (waiting stage), S (DNA duplication), G2 (second growing stage), and the M (mitosis and cytokinesis) stage.
    • Cyclin and cyclin-dependent kinase (CDK) proteins are key regulators of the cell cycle.

    Cell Cycle – S Phase – DNA Replication

    • DNA replication (in the S phase) is a semi-conservative process, using both strands as templates.
    • Replication involves three phases: initiation (formation of the replication fork), elongation (DNA synthesis in the 5'-3'), and termination (at telomere sections).
    • Essential enzymes involved include DNA polymerase, DNA primase, helicase and topoisomerase.

    Cell Cycle – M Phase – Division

    • Mitosis is cell division in somatic cells that involves duplication and separation of chromatin to form two daughter cells with an identical number of chromosomes as the parental cell.
    • The stages include interphase, prophase, metaphase, anaphase, telophase, and cytokinesis.

    Cell Division - Cytokinesis

    • Cytokinesis marks the physical division of the cytoplasm, starting during anaphase.
    • It involves the formation of a cell wall or other structure to separate the two daughter cells.

    Cell Division – Meiosis

    • Meiosis is a cell division process for gametes (sex cells) and involves two stages each comprising several phases (e.g., prophase, metaphase, anaphase, telophase).
    • The first stage involves pairing homologous chromosomes and crossing over.
    • The second stage involves pulling homologous chromosomes to opposite poles of the cell, followed by a mitotic-like division.

    Meiosis – Crossing Over

    • During meiosis I, homologous chromosomes exchange segments of DNA through crossing over (allele substitution)
    • This leads to genetic variation.

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    Basic Genetics Lecture PDF

    Description

    Explore the fundamental concepts of genetics including the roles of genes, alleles, and genetic makeup. This quiz covers essential terms such as homozygous, heterozygous, genotype, and phenotype. Understand how traits are inherited and expressed in organisms.

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