67 Questions
Which structure in the nucleus is responsible for forming ribosomal RNA?
Nucleolus
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.
True
Identify the organelle (number and name) in Diagram A that is represented by Diagram B.
nucleus
DNA replication takes place during _____ in the nucleus.
interphase
Give the two nucleic acids present in Diagram B.
DNA (Deoxyribonucleic acid), RNA (Ribonucleic acid)
Identify label D in Diagram A.
Ribosome
What is the significance of the organelle represented in Diagram B?
The nucleus controls all of the cell’s activities.
Complete the table with regard to the location, composition, and function of label D.
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)
Identify the organelles labelled 5, 6, and 7, and give the function of each.
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)
Why is the process of DNA replication important?
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.
Give TWO functions of DNA.
Sections of DNA forming genes carry hereditary information. DNA contains coded information for protein synthesis.
What is DNA profiling?
A method to compare DNA patterns for identification purposes, where each individual, except identical twins, has a unique DNA profile.
What is the role of DNA profiling in determining paternity?
DNA profiling helps identify biological parents by comparing DNA bands of the mother, child, and possible father.
Explain the process of protein synthesis.
Protein synthesis involves transcription (mRNA formation from DNA) and translation (protein formation from mRNA) in cells.
DNA REPLICATION Template (how many) _____? Product that is formed _____? Bases pairs that are formed ______?
Name the technique that was used to identify the criminal.
DNA profiling
Who is the possible criminal?
The individual whose DNA profile matches the blood sample found at the crime scene.
State ONE other use of the technique identified in QUESTION (a).
Paternity testing or determining familial relationships.
Sometimes the paternity of a son or a daughter is disputed. Describe how DNA profiling is used in paternity testing.
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.
Name the part of the protein synthesis indicated by process A.
Transcription
Name the type of bond that joins two amino acids together.
Peptide bond
What is the term for the process of reduction division?
Meiosis
What sugars are present in RNA compared to DNA?
Ribose in RNA vs Deoxyribose in DNA
Meiosis causes genetic __________.
variation
Match the nitrogen bases between DNA and RNA:
Thymine (T) = Uracil (U) Adenine (A) = Adenine (A) Cytosine (C) = Cytosine (C) Guanine (G) = Guanine (G)
What is the significance of DNA replication for mitosis?
To double the genetic material, each daughter cell receives the same amount of DNA, to ensure genetically identical daughter cells.
What is the function of the centromere during cell division?
To hold the chromatids of a replicated chromosome together
Match the following terms with their definitions:
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
What is the term for chromosomes that are identical in shape, size, and gene content?
Homologous chromosomes
Mitosis results in the formation of four sex cells.
False
State the gender of individual P in the provided karyotype diagram.
Male
Why does the provided karyotype diagram represent human chromosomes?
Because the Gonosomes (chromosome pair 23) are of different size and shape (XY).
State what happens to structure D in the next phase of meiosis.
The chromatids separate / centromere splits
Name the process during which genetic material was exchanged, as shown in the diagrams.
Crossing over
State the consequence if the process named in the previous question does not occur.
Reduces genetic variation
Give the number of chromosomes present in the original parent cell in this organism.
23
Give the number of chromosomes present in a human cell in the same phase as that shown in Diagram 2.
23
Explain why the gametes represented by diagrams C and D do not have any chromosomes.
Due to non-disjunction
If gamete A is involved in fertilisation, describe how this may result in down syndrome.
Due to the presence of an extra copy of chromosome 21
Identify the phase of meiosis during which crossing over occurs.
Prophase I
Describe the events during crossing over.
Genetic material exchanges between homologous chromosomes
How many chromosomes are found in a human sperm cell?
23
How many chromosomes are found in a muscle cell?
46
How many chromosomes are found in the somatic cells of a normal mother who has a son with Down syndrome?
46
What is the expected number of chromosomes in each cell when a chemical prevents spindle fibers from forming in cells undergoing meiosis?
24 replicated chromosomes
Match the meiosis phase with the correct event:
Prophase I = Unique to a particular phase Anaphase I = Shows separation of replicated chromosomes Metaphase II = Single chromosomes are at the equator
Identify part A in the diagram: centriole
centriole
What causes chromosomes to have a combination of genes as shown in the diagrams?
Crossing over
Explain why structure B and structure C are structurally different.
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.
What mutation type occurred in the cell where non-disjunction happened?
Chromosomal mutation
Why is the process of DNA replication important?
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.
Give TWO functions of DNA.
Sections of DNA forming genes carry hereditary information. DNA contains coded information for protein synthesis.
What is DNA Profiling?
A process used to create a unique pattern of DNA bands/bars specific to an individual, except identical twins.
What is the purpose of DNA profiling in paternity testing?
To determine the biological relationship between a child and a possible father by comparing their DNA profiles.
Describe the process of Protein Synthesis.
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.
What is Genetic Coding?
Genetic coding is the process where the sequence of DNA or mRNA nucleotides instructs the cell on how to produce specific proteins.
Describe the mutation that occurred based on the given information.
C was replaced by U on the 4th codon/AGC
Explain how the mutation will affect the resulting protein.
The amino acid sequence will not change, therefore, the same protein will be formed.
Identify the molecules labelled Y and Z in the provided diagram.
Y - tRNA, Z - mRNA
Name the phase of protein synthesis represented in the diagram.
Translation
Give the name of the group of three bases indicated by number 4 on the diagram.
Codon
Write down the base codes (from left to right) that would be found at point 3 on the diagram.
GAA
Which diagram shows traditional DNA replication?
Diagram D
The first THREE nitrogenous bases on the DNA strand that led to the formation of molecule Z are ____.
AGT
State the anticodon in molecule Q based on the provided data.
CCG
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
Differentiate between Related Terminologies
- 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:
- The DNA double helix unwinds
- The weak hydrogen bonds between nitrogenous bases are broken
- Each original DNA strand serves as a template for the synthesis of a new complementary strand
- 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
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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