Biology Chapter 3: DNA The Code of Life
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Questions and Answers

Which structure in the nucleus is responsible for forming ribosomal RNA?

  • Cytoplasm
  • Nucleoplasm
  • Ribosome
  • Nucleolus (correct)

    • What is the role of RNA in protein synthesis?

    RNA is responsible for protein synthesis.

    Match the nitrogenous bases with their complementary base pairing:

    Adenine = Thymine Guanine = Cytosine Thymine = Adenine Cytosine = Guanine

    DNA is a double helix twisted strand.

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

    Identify the organelle (number and name) in Diagram A that is represented by Diagram B.

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

    DNA replication takes place during _____ in the nucleus.

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

    Give the two nucleic acids present in Diagram B.

    <p>DNA (Deoxyribonucleic acid), RNA (Ribonucleic acid)</p> Signup and view all the answers

    Identify label D in Diagram A.

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

    What is the significance of the organelle represented in Diagram B?

    <p>The nucleus controls all of the cell’s activities.</p> Signup and view all the answers

    Complete the table with regard to the location, composition, and function of label D.

    <p>LOCATION: Found along the endoplasmic reticulum, COMPOSITION: Ribosomes are made up of some protein and RNA, FUNCTION OF ORGANELLE: Makes protein for the cell (the site of protein synthesis)</p> Signup and view all the answers

    Identify the organelles labelled 5, 6, and 7, and give the function of each.

    <p>5 - Mitochondria (Make energy through cellular respiration), 6 - Vacuole (Stores water, metabolic waste products, and pigments), 7 - Centrosome (Helps in cell division, assures equal distribution of chromosomes in daughter cells)</p> Signup and view all the answers

    Why is the process of DNA replication important?

    <p>Doubles the genetic material so it can be shared between the resulting daughter cells during cell division. Results in the formation of identical daughter cells during mitosis.</p> Signup and view all the answers

    Give TWO functions of DNA.

    <p>Sections of DNA forming genes carry hereditary information. DNA contains coded information for protein synthesis.</p> Signup and view all the answers

    What is DNA profiling?

    <p>A method to compare DNA patterns for identification purposes, where each individual, except identical twins, has a unique DNA profile.</p> Signup and view all the answers

    What is the role of DNA profiling in determining paternity?

    <p>DNA profiling helps identify biological parents by comparing DNA bands of the mother, child, and possible father.</p> Signup and view all the answers

    Explain the process of protein synthesis.

    <p>Protein synthesis involves transcription (mRNA formation from DNA) and translation (protein formation from mRNA) in cells.</p> Signup and view all the answers

    DNA REPLICATION Template (how many) _____? Product that is formed _____? Bases pairs that are formed ______?

    Signup and view all the answers

    Name the technique that was used to identify the criminal.

    <p>DNA profiling</p> Signup and view all the answers

    Who is the possible criminal?

    <p>The individual whose DNA profile matches the blood sample found at the crime scene.</p> Signup and view all the answers

    State ONE other use of the technique identified in QUESTION (a).

    <p>Paternity testing or determining familial relationships.</p> Signup and view all the answers

    Sometimes the paternity of a son or a daughter is disputed. Describe how DNA profiling is used in paternity testing.

    <p>DNA profiling in paternity testing involves comparing the DNA of the child with that of the alleged father. By analyzing specific genetic markers, paternity can be confirmed.</p> Signup and view all the answers

    Name the part of the protein synthesis indicated by process A.

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

    Name the type of bond that joins two amino acids together.

    <p>Peptide bond</p> Signup and view all the answers

    What is the term for the process of reduction division?

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

    What sugars are present in RNA compared to DNA?

    <p>Ribose in RNA vs Deoxyribose in DNA</p> Signup and view all the answers

    Meiosis causes genetic __________.

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

    Match the nitrogen bases between DNA and RNA:

    <p>Thymine (T) = Uracil (U) Adenine (A) = Adenine (A) Cytosine (C) = Cytosine (C) Guanine (G) = Guanine (G)</p> Signup and view all the answers

    What is the significance of DNA replication for mitosis?

    <p>To double the genetic material, each daughter cell receives the same amount of DNA, to ensure genetically identical daughter cells.</p> Signup and view all the answers

    What is the function of the centromere during cell division?

    <p>To hold the chromatids of a replicated chromosome together</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Nuclear membrane = Surrounds the nucleus, enclosing genetic material Cell membrane = Separates the interior of cells from the outside environment Centrosome = Organelle containing centrioles responsible for spindle fiber formation Centriole = Structures formed when centrosome divides, moving to opposite cell poles Centromere = Site where two chromatids are held together in a replicated chromosome</p> Signup and view all the answers

    What is the term for chromosomes that are identical in shape, size, and gene content?

    <p>Homologous chromosomes</p> Signup and view all the answers

    Mitosis results in the formation of four sex cells.

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

    State the gender of individual P in the provided karyotype diagram.

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

    Why does the provided karyotype diagram represent human chromosomes?

    <p>Because the Gonosomes (chromosome pair 23) are of different size and shape (XY).</p> Signup and view all the answers

    State what happens to structure D in the next phase of meiosis.

    <p>The chromatids separate / centromere splits</p> Signup and view all the answers

    Name the process during which genetic material was exchanged, as shown in the diagrams.

    <p>Crossing over</p> Signup and view all the answers

    State the consequence if the process named in the previous question does not occur.

    <p>Reduces genetic variation</p> Signup and view all the answers

    Give the number of chromosomes present in the original parent cell in this organism.

    <p>23</p> Signup and view all the answers

    Give the number of chromosomes present in a human cell in the same phase as that shown in Diagram 2.

    <p>23</p> Signup and view all the answers

    Explain why the gametes represented by diagrams C and D do not have any chromosomes.

    <p>Due to non-disjunction</p> Signup and view all the answers

    If gamete A is involved in fertilisation, describe how this may result in down syndrome.

    <p>Due to the presence of an extra copy of chromosome 21</p> Signup and view all the answers

    Identify the phase of meiosis during which crossing over occurs.

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

    Describe the events during crossing over.

    <p>Genetic material exchanges between homologous chromosomes</p> Signup and view all the answers

    How many chromosomes are found in a human sperm cell?

    <p>23</p> Signup and view all the answers

    How many chromosomes are found in a muscle cell?

    <p>46</p> Signup and view all the answers

    How many chromosomes are found in the somatic cells of a normal mother who has a son with Down syndrome?

    <p>46</p> Signup and view all the answers

    What is the expected number of chromosomes in each cell when a chemical prevents spindle fibers from forming in cells undergoing meiosis?

    <p>24 replicated chromosomes</p> Signup and view all the answers

    Match the meiosis phase with the correct event:

    <p>Prophase I = Unique to a particular phase Anaphase I = Shows separation of replicated chromosomes Metaphase II = Single chromosomes are at the equator</p> Signup and view all the answers

    Identify part A in the diagram: centriole

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

    What causes chromosomes to have a combination of genes as shown in the diagrams?

    <p>Crossing over</p> Signup and view all the answers

    Explain why structure B and structure C are structurally different.

    <p>Structure B has two DNA molecules and is replicated, while structure C has one DNA molecule and is unreplicated. Structure B is made up of two chromatids, while structure C has one chromatid.</p> Signup and view all the answers

    What mutation type occurred in the cell where non-disjunction happened?

    <p>Chromosomal mutation</p> Signup and view all the answers

    Why is the process of DNA replication important?

    <p>Doubles the genetic material so it can be shared between the resulting daughter cells during cell division. Results in the formation of identical daughter cells during mitosis.</p> Signup and view all the answers

    Give TWO functions of DNA.

    <p>Sections of DNA forming genes carry hereditary information. DNA contains coded information for protein synthesis.</p> Signup and view all the answers

    What is DNA Profiling?

    <p>A process used to create a unique pattern of DNA bands/bars specific to an individual, except identical twins.</p> Signup and view all the answers

    What is the purpose of DNA profiling in paternity testing?

    <p>To determine the biological relationship between a child and a possible father by comparing their DNA profiles.</p> Signup and view all the answers

    Describe the process of Protein Synthesis.

    <p>Protein synthesis involves two main stages - Transcription and Translation. Transcription occurs in the nucleus where mRNA is formed from DNA. Translation takes place in the cytoplasm on ribosomes, where mRNA is decoded to produce proteins.</p> Signup and view all the answers

    What is Genetic Coding?

    <p>Genetic coding is the process where the sequence of DNA or mRNA nucleotides instructs the cell on how to produce specific proteins.</p> Signup and view all the answers

    Describe the mutation that occurred based on the given information.

    <p>C was replaced by U on the 4th codon/AGC</p> Signup and view all the answers

    Explain how the mutation will affect the resulting protein.

    <p>The amino acid sequence will not change, therefore, the same protein will be formed.</p> Signup and view all the answers

    Identify the molecules labelled Y and Z in the provided diagram.

    <p>Y - tRNA, Z - mRNA</p> Signup and view all the answers

    Name the phase of protein synthesis represented in the diagram.

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

    Give the name of the group of three bases indicated by number 4 on the diagram.

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

    Write down the base codes (from left to right) that would be found at point 3 on the diagram.

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

    Which diagram shows traditional DNA replication?

    <p>Diagram D</p> Signup and view all the answers

    The first THREE nitrogenous bases on the DNA strand that led to the formation of molecule Z are ____.

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

    State the anticodon in molecule Q based on the provided data.

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

    Study Notes

    Introduction

    • The Department of Basic Education (DBE) developed this Self-Study Guide to mitigate the impact of COVID-19 on Grade 12 learners in South Africa
    • The guide aims to close pre-existing content gaps and strengthen mastery of subject knowledge in Grade 12

    How to use this Self-Study Guide

    • This guide is part of a series of five booklets covering all Grade 12 topics
    • Use this guide together with the Life Sciences Mind the Gap Study Guide
    • Ensure you understand all relevant concepts and content, and focus on skills needed to answer examination questions

    DNA - Code of Life

    Prior-Knowledge/Background Knowledge

    • Grade 10: Plant and Animal cells, proteins, nucleic acids, location of DNA and chromosome
    • Resources: Textbooks, Study Guides, MTG, Past NSC, SC & Provincial Question Papers

    Mind Map on DNA - Code of Life

    • Structure of a cell:
      • Nucleoplasm/Nuclear sap
      • Cytoplasm
      • Nuclear membrane/Nuclear envelope
      • Chromatin network
      • Ribosome
      • Nucleolus
    • Functions:
      • Controls what goes in and out of nucleus
      • Makes protein for the cell
      • Forms the chromosomes
      • Regulates exchange of materials between nucleus and cytoplasm

    Practice Questions on Prior-Knowledge

    • Identify organelles and their functions
    • Describe the structure and function of the nucleus
    • Explain the significance of the nucleus and its components
    • Nucleolus vs. Nucleoplasm vs. Cytoplasm vs. Ribosome
    • Chromatin vs. Chromatid vs. Centromere vs. Chromosome
    • DNA vs. RNA
    • Monomer vs. Polymer
    • Nucleotide
    • Enzyme
    • Amino Acid
    • Uracil vs. Thymine

    DNA Replication

    • Process involving the formation of two new identical DNA molecules from an original DNA
    • Steps:
      1. The DNA double helix unwinds
      2. The weak hydrogen bonds between nitrogenous bases are broken
      3. Each original DNA strand serves as a template for the synthesis of a new complementary strand
      4. The process is repeated to form two new identical DNA molecules### DNA Replication
    • DNA replication occurs during interphase of the cell cycle in the nucleus
    • It results in the formation of two identical DNA molecules
    • Each molecule consists of one original strand and one new strand
    • The process involves:
      • Unwinding of the double helix
      • Weak hydrogen bonds breaking and two DNA strands unzipping
      • Free nucleotides building a DNA strand onto each original strand by attaching to complementary nitrogenous bases
      • Formation of two identical DNA molecules

    DNA Profiling

    • DNA profiling is used to:
      • Prove paternity and maternity
      • Determine the probability or causes of genetic defects
      • Establish the compatibility of tissue types for organ transplants
      • Identify relatives
      • Identify crime suspects in forensic investigations
    • A DNA profile is a pattern produced on X-ray film, consisting of lines of different lengths and thicknesses and in different positions
    • Each individual, except identical twins, has a unique DNA profile
    • Comparison of DNA profiles involves comparing the bands of an unknown or evidence sample with a known or reference sample

    Protein Synthesis

    • Protein synthesis is the process by which proteins are made in each cell of an organism
    • It involves two main processes:
      • Transcription of mRNA from DNA
      • Translation of mRNA to form proteins
    • Transcription occurs in the nucleus, where a section of the DNA double helix unwinds and an mRNA strand is formed
    • Translation occurs in the cytoplasm, where the mRNA attaches to a ribosome and tRNA brings amino acids to the ribosome to form a protein

    Genetic Coding

    • The genetic code is the instructions in a gene that tell the cell how to make a specific protein
    • It involves the sequence of DNA or mRNA nucleotides that code for a specific amino acid sequence
    • The sequence of nucleotides determines the sequence of amino acids in a protein molecule
    • A mutation in the DNA sequence can affect the type or arrangement of nitrogen bases, leading to a change in the amino acid sequence in the protein

    The Effect of Mutation on Protein Structure

    • A mutation is a change in the DNA sequence that affects the type or arrangement of nitrogen bases
    • Mutations can occur during DNA replication and can lead to changes in the amino acid sequence of a protein
    • The effect of a mutation on protein structure depends on the specific change in the DNA sequence and can result in either no change, a change in the amino acid sequence, or a different protein being formed.### Mutation and Protein Structure
    • A mutation in the DNA triplet of bases can lead to a change in the amino acid coded for
    • If the codon AGC (serine) mutates to AGU, it still codes for serine, so the amino acid sequence will not change
    • If the codon UCC (phenylalanine) mutates to AUC, it will code for isoleucine, changing the amino acid sequence and potentially leading to a different protein

    DNA Replication and Protein Synthesis

    • DNA replication takes place during interphase
    • During DNA replication, complementary nucleotides bind to each of the two strands, sugar phosphate bonds form between the nucleotides, and the newly formed DNA molecules are identical to each other
    • Protein synthesis involves the translation of mRNA codons into amino acids
    • tRNA molecules bring amino acids to the ribosome during protein synthesis
    • The sequence of amino acids in a protein is determined by the sequence of codons in the mRNA

    Practice Questions on Mutation and Protein Structure

    • Identify the molecules and processes involved in protein synthesis
    • Determine the amino acid sequence of a protein from the mRNA codons
    • Describe the effects of mutations on protein synthesis and structure

    DNA Replication

    • DNA replication takes place during interphase
    • The process involves the unwinding of the double helix, the binding of complementary nucleotides, and the formation of sugar phosphate bonds
    • The correct order of events in DNA replication is: unwinding, binding of complementary nucleotides, sugar phosphate bonds, and the formation of two identical DNA molecules

    Protein Synthesis and Mutation

    • A mutation in the DNA sequence can lead to a change in the amino acid sequence of a protein
    • Describe how a mutation in the DNA sequence can lead to a change in the structure of a protein
    • Identify the DNA triplets and mRNA codons that code for specific amino acids

    DNA Profiling

    • DNA profiling is a technique used to identify an individual based on their DNA sequence
    • The technique is used in forensic science to solve crimes and in paternity testing
    • DNA profiling can be used to identify a person's ancestry and determine the likelihood of a DNA sample coming from an individual

    Protein Synthesis

    • Describe the process of protein synthesis, including transcription and translation
    • Identify the molecules and organelles involved in protein synthesis
    • Describe the role of tRNA and mRNA in protein synthesis

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    Learn about DNA, the code of life, and practice with questions to strengthen your understanding. This self-study guide covers DNA's structure, function, and prior knowledge.

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