Introduction to Medical Biology and Genetics
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What percentage of the average human gene is made up of protein coding sequences?

  • 3% (correct)
  • 10%
  • 20%
  • 50%

    • Which of the following accurately describes introns in human genes?

  • Introns often contain regulatory sequences. (correct)
  • Introns make up less than 50% of each gene.
  • Introns are always shorter than exons.
  • Introns are responsible for protein translation.

    • What is the typical structure of eukaryotic genes?

  • Exons separated by coding sequences.
  • Only coding sequences without any noncoding DNA.
  • Exons separated by noncoding sequences (introns). (correct)
  • A single continuous coding sequence.

    • How much of the average human gene is accounted for by introns?

    <p>Approximately 93%</p> Signup and view all the answers

    In terms of gene expression, what role do regulatory sequences found in introns play?

    <p>They regulate the expression of the gene.</p> Signup and view all the answers

    What is the average number of exons found in a human gene?

    <p>10 exons</p> Signup and view all the answers

    Which part of the mRNA includes sequences that are not translated into protein?

    <p>Both 5′ and 3′ UTRs</p> Signup and view all the answers

    What is the total genomic DNA size for an average human gene including both exons and introns?

    <p>Around 56 kb</p> Signup and view all the answers

    What is the primary function of promoters in gene regulation?

    <p>To initiate transcription of the gene</p> Signup and view all the answers

    What defines the proximal promoter region in relation to the core promoter?

    <p>It is located immediately upstream from the core promoter</p> Signup and view all the answers

    Which of the following statements accurately describes enhancers?

    <p>They are positive control elements that increase transcription levels</p> Signup and view all the answers

    What distinguishes classical silencers from negative regulatory elements?

    <p>Classical silencers are position-independent elements</p> Signup and view all the answers

    In terms of transcriptional control, which element is primarily responsible for actively reducing transcription levels?

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

    How are enhancers and silencers similar in function?

    <p>Both can influence transcription levels from a distance</p> Signup and view all the answers

    What is the role of the core promoter in gene regulation?

    <p>It directs the basal transcription complex to initiate transcription</p> Signup and view all the answers

    Which of the following is NOT a characteristic of enhancers?

    <p>They are always active in simple eukaryotes</p> Signup and view all the answers

    What is a karyotype used for?

    <p>To look for abnormalities in chromosome number or structure</p> Signup and view all the answers

    Which of the following accurately defines an allele?

    <p>A variant form of a gene that can influence characteristics</p> Signup and view all the answers

    How do genotypes and phenotypes differ?

    <p>Genotype includes all genes and alleles, whereas phenotype includes observable characteristics</p> Signup and view all the answers

    What determines the characteristic shape of a chromosome?

    <p>The location of the centromere</p> Signup and view all the answers

    What is the primary focus of the Human Genome Project?

    <p>To determine the sequence of the human genome and identify genes</p> Signup and view all the answers

    Which of the following best describes a dominant trait?

    <p>A trait that requires one or more copies of a dominant allele to be expressed</p> Signup and view all the answers

    What does the term 'genome' encompass?

    <p>All genetic instructions, both coding and noncoding DNA</p> Signup and view all the answers

    What type of DNA is included in the human genome aside from nuclear DNA?

    <p>mtDNA and chloroplast DNA</p> Signup and view all the answers

    What characterizes a homozygous organism?

    <p>It has two identical alleles for a gene.</p> Signup and view all the answers

    Which of the following statements about mutations is true?

    <p>Mutations can be harmless, beneficial, or harmful.</p> Signup and view all the answers

    What is gene expression primarily responsible for?

    <p>Synthesis of a functional gene product.</p> Signup and view all the answers

    How does the genome size of eukaryotes generally compare to that of prokaryotes?

    <p>Eukaryotic genomes are always larger and more complex.</p> Signup and view all the answers

    What structural model do eukaryotic genomes conform to?

    <p>Watson-Crick double helix model.</p> Signup and view all the answers

    Which of the following correctly describes how DNA is organized in eukaryotic cells?

    <p>DNA forms a linear structure with histones.</p> Signup and view all the answers

    What type of alleles does a heterozygous organism possess?

    <p>Two different alleles.</p> Signup and view all the answers

    What are intergenic regions primarily known for?

    <p>Lacking any known function</p> Signup and view all the answers

    Which histones are present in eukaryotic genomes?

    <p>H2A, H2B, H3, and H4.</p> Signup and view all the answers

    Which type of DNA consists of tandemly repeated sequences ranging from 1-10 nucleotides?

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

    What distinguishes Low Copy Number (LCN) DNA profiling from other techniques?

    <p>It is ideal for analyzing degraded DNA samples.</p> Signup and view all the answers

    What is a characteristic of satellite DNA?

    <p>It consists of long arrays of tandem repeats.</p> Signup and view all the answers

    What percentage of microsatellite DNA is found in coding regions?

    <p>A significant percentage</p> Signup and view all the answers

    Which statement about interspersed repeats is true?

    <p>They are scattered throughout the genome.</p> Signup and view all the answers

    Which of the following describes STRs?

    <p>They consist of two to thirteen nucleotides repeated.</p> Signup and view all the answers

    Which of the following is NOT typically true about highly repetitive DNA sequences?

    <p>They are generally transcriptionally active</p> Signup and view all the answers

    What is a key feature of LINEs compared to SINEs?

    <p>They can encode the proteins necessary for transposition.</p> Signup and view all the answers

    How do SINEs achieve transposition?

    <p>Through the action of LINE-encoded proteins.</p> Signup and view all the answers

    What is the primary mechanism of movement for DNA transposons?

    <p>Simple 'cut-and-paste' mechanism.</p> Signup and view all the answers

    Which of the following statements is true regarding LTR elements?

    <p>They include proteins for integrase and reverse transcriptase.</p> Signup and view all the answers

    How are SINEs classified among transposable elements?

    <p>As non-autonomous retrotransposons.</p> Signup and view all the answers

    Which characteristic differentiates DNA transposons from retrotransposons?

    <p>DNA transposons move by a 'cut-and-paste' mechanism.</p> Signup and view all the answers

    What proportion of the human genome is constituted by DNA transposons?

    <p>Approximately 3%</p> Signup and view all the answers

    What is the function of terminal inverted repeats in DNA transposons?

    <p>They facilitate recognition and regulation of transposition.</p> Signup and view all the answers

    Study Notes

    Introduction to Medical Biology and Genetics

    • Lecture slides are for reference.
    • Lecture books are for study.
    • Lecture book PDFs are downloadable from Ubis.

    Eukaryotic Genome Organization

    • A genome is an organism's complete set of genetic instructions for development, growth, and function.
    • It is made up of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in RNA viruses.
    • The human genome contains both the genes that encode proteins and non-coding DNA, including mitochondrial DNA and chloroplast DNA.
    • The study of the genome is called genomics.
    • The Human Genome Project, an international effort, determined the human genome's sequence and identified 20,000 to 25,000 genes.

    Basic Genetic Terms

    • A gene is the basic physical and functional unit of heredity, made up of DNA.
    • Genes are passed from parents to offspring, and they determine many traits.
    • Some genes code for proteins; many do not.

    What is a gene?

    • A gene is the basic physical and functional unit of heredity.
    • It is made of DNA.
    • Genes are passed from the parents to their offspring.
    • Genes determine many traits.
    • Some genes code for proteins while many do not.

    What is a DNA?

    • DNA is the hereditary material in humans and most other organisms.
    • Nearly every cell in a person's body contains the same DNA.
    • Most DNA is found in the nucleus.
    • A small amount of DNA is found in mitochondria (mitochondrial DNA or mtDNA).
    • DNA stores information as a code of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
    • Human DNA contains approximately 3 billion bases, with over 99% being the same in all people.

    What is a chromosome?

    • DNA in each cell's nucleus is packaged into thread-like structures called chromosomes.
    • Chromosomes consist of DNA tightly coiled around proteins called histones.
    • Histones support the structure of chromosomes.
    • Chromosomes are not visible under a microscope when the cell is not dividing.
    • Chromosomes are more tightly packed during cell division and then are visible under a microscope.
    • Each chromosome has a constriction point named the centromere, which divides the chromosome into two sections, or arms ("p arm" and "q arm").
    • The location of the centromere gives the chromosome a characteristic shape.
    • A karyotype is an individual's complete set of chromosomes.
    • It is used to identify abnormalities in chromosome number or structure.

    From Chromosomes to Genes

    • Genes are segments of DNA that code for specific proteins.
    • Chromosomes are structures within cells that contain the genes.
    • Genes are contained within chromosomes, which are in the cell nucleus.

    What is an allele?

    • An allele is a variant form of a gene.
    • Different alleles can produce variations in inherited characteristics of an organism.
    • For example, different alleles of a gene might lead to different hair colors.

    What is Genotype and Phenotype?

    • Genotype is the genetic makeup of an organisms, including all its genes and alleles.
    • Genotype is the set of instructions encoded in DNA that contribute to an organism's traits.
    • Phenotype is the observable physical or biochemical characteristics of an organism.
    • Phenotype is the result of interactions between genotype and the environment.
    • Examples of phenotype include height, eye color, and blood type.

    What are Dominant and Recessive Traits?

    • A dominant trait is expressed when at least one dominant allele is present, masking the expression of a recessive trait.
    • A recessive trait is expressed only when two recessive alleles are present, as there is no dominant allele to mask it.

    What is Homozygous and Heterozygous?

    • Homozygous: An organism is homozygous for a trait if it has two identical alleles for a gene (e.g. AA or aa).
    • Heterozygous: An organism is heterozygous for a trait if it has two different alleles for a gene (e.g. Aa).

    What is a Mutation?

    • A mutation is a change in the DNA sequence of a gene.
    • Mutations can be harmless, beneficial, or harmful.
    • Mutations can result in new traits or diseases.
    • Examples of diseases caused by mutations are cystic fibrosis, Huntington's disease, and sickle cell anemia.

    What is Gene Expression?

    • Gene expression is the process by which the information in a gene is used to create a functional gene product, typically a protein.
    • Gene expression can be regulated at several levels, including transcription, RNA processing, and translation.

    Prokaryotic and Eukaryotic Genome

    • Prokaryotic: single circular chromosome, located in the cytoplasm.
    • Eukaryotic: multiple linear chromosomes, located inside the nucleus.

    Prokaryotic vs Eukaryotic Genome

    • Definitions: Prokaryotic genome is a single circular chromosome with the genetic information, Eukaryotic genome contains multiple linear chromosomes with the genetic information.
    • Number of chromosomes: Prokaryotic cells contain a single chromosome, Eukaryotic cells contain multiple chromosomes, e.g. human is 23 pairs.
    • Location: Prokaryotic cells are found in cytoplasm, Eukaryotic cells are found inside the nucleus.
    • Compactness: Prokaryotic genomes are more compact, Eukaryotic genomes are compact.
    • Coding sequence: Prokaryotic genomes have up to 90% coding sequence, Eukaryotic genomes have up to 3% coding sequence.
    • Structure: Prokaryotic genomes are circular, Eukaryotic genomes are linear.
    • Telomeres: Prokaryotic genomes do not have telomeres, Eukaryotic genomes have telomeres.
    • Introns: Prokaryotic genomes do not have introns, Eukaryotic genomes have introns.
    • Repetitive DNA: Prokaryotic genomes do not have repetitive DNA, Eukaryotic genomes have multiple repetitive DNA.

    Eukaryotic Genome

    • Species, Genome Size, Common Name: Different species have varying genome sizes.
    • Larger size of eukaryotic genomes is not inherently surprising, as more genes are expected in more complex organisms.
    • Genome size does not correlate to genetic complexity.

    Chromatin

    • Chromatin is the complex of DNA and protein that makes up chromosomes, consisting of linear unbroken double-stranded DNA
    • Euchromatin is genetically active, stains lightly, consists of functional genes.
    • Heterochromatin is genetically inactive, stains darkly, consists of repetitive DNA sequences.

    DNA Content of Human Chromosomes

    • Each number chromosome has variable DNA content and heterochromatin content.

    Configuration of Eukaryotic Genome

    • A genome is an organism's complete set of DNA, comprising nuclear and mitochondrial DNA.
    • A human haploid cell contains 23 pairs of nuclear chromosomes and one mitochondrial chromosome; it includes more than 3.2 billion DNA base pairs.
    • The human genome consists of nuclear and mitochondrial genomes.
    • Nuclear genome comprises 30% genes and gene-related sequences, 70% extragenic DNA, 10% coding DNA, and 90% non-coding DNA.
    • Mitochondrial genome contains 37 genes, mainly encoding rRNA (ribosomal RNA) and tRNA, small mitochondrial proteins.
    • Protein-coding region (Exons): These regions encode the protein sequence of a gene.
    • Gene-regulating sequences (Promoters, Enhancers, Silencers, Response elements): Sequences that control gene expression.
    • Non-coding RNA: RNA molecules that are not translated into proteins, including housekeeping RNAs (tRNAs, rRNAs), and regulatory RNAs (miRNAs, siRNAs, IncRNAs).
    • Gene Fragments: Parts of a gene containing only exons (which encode the protein sequence).
    • Pseudogenes: Functional relatives of genes that have lost their ability to code protein.
    • Long Non-coding RNA (lncRNA): A type of non-coding RNA molecule longer than 200 nucleotides.
    • Introns and untranslated regions (UTRs): Introns are non-coding sequences within genes, while UTRs precede and succeed protein-coding exons and may be non-coding or code for regulatory elements.

    MicroRNAs (miRNAs)

    • MicroRNAs are small non-coding RNAs that regulate gene expression.
    • Pre-miRNAs are processed into miRNA in the cell nucleus by enzymes (Drosha and Dicer).
    • miRNAs are integrated into the RNA-induced silencing complex (RISC).
    • The complex targets complementary mRNAs, inhibits translation, and stimulates mRNA degradation.

    siRNAs (short interfering RNAs)

    • siRNAs are short interfering RNAs used for interfering with gene expression.
    • siRNA's are introduced into the cells, interfering with mRNA sequences.
    • siRNAs are effective in affecting gene expression.
    • Boundary elements (insulators): DNA regions that block the spread of heterochromatin and regulate gene expression.
    • Response elements: DNA sequences that respond to specific external stimuli (hormones).

    Key Differences Between LINES and SINES

    • LINES are autonomous transposons, while SINEs are non-autonomous.
    • LINES encode reverse transcriptase; SINEs do not.
    • SINEs depend on LINE-encoded proteins for transposition.
    • Both SINEs & LINEs are retrotransposons (move via reverse transcription).

    Which sequences is primarily responsible for increasing the basal level of transcription?

    • Enhancers.

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    Description

    This quiz covers essential concepts in medical biology and genetics, including genome organization and basic genetic terms. Learn about the human genome, the role of genes, and key projects like the Human Genome Project that shaped our understanding of genetics.

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