Ch 6 Quiz Easy
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Ch 6 Quiz Easy

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Questions and Answers

What is the effect of histone deacetylases (HDACs) on chromatin?

  • They promote condensation of chromatin. (correct)
  • They promote decondensation of chromatin.
  • They enhance transcriptional activity.
  • They interfere with DNA replication.

    • Which type of chromatin is characterized by being highly condensed?

  • Heterochromatin (correct)
  • Active chromatin
  • Facultative chromatin
  • Euchromatin

    • What role does HP1 play in chromatin structure?

  • It prevents chromatin condensation.
  • It binds to trimethylated lysine 9 on histone H3. (correct)
  • It promotes deacetylation of histones.
  • It inhibits histone methylation.

    • What is associated with transcriptionally active chromatin?

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

    What does the term 'histone code' refer to?

    <p>The pattern of histone tail modifications.</p> Signup and view all the answers

    Which kind of DNA modification is not part of epigenetics?

    <p>Alterations to the genetic code</p> Signup and view all the answers

    How does boundary element function in chromatin?

    <p>By blocking histone methylation on one side.</p> Signup and view all the answers

    What modification is characteristic of euchromatin?

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

    What is the function of the left LTR in the retroviral life cycle?

    <p>Serves as a promoter for transcription</p> Signup and view all the answers

    Which enzyme synthesizes the dsDNA in retroviral replication?

    <p>Reverse transcriptase</p> Signup and view all the answers

    What are endogenous retroviruses (ERVs) primarily comprised of?

    <p>Full-length proviral DNA</p> Signup and view all the answers

    What type of DNA comprises approximately 6% of the human genome?

    <p>Simple-sequence DNA</p> Signup and view all the answers

    Which of the following statements about nonviral retrotransposons is true?

    <p>They lack LTRs and are therefore called nonviral retrotransposons.</p> Signup and view all the answers

    In the human genome, what percentage of genomic DNA is transcribed into pre-mRNA precursors?

    <p>50%</p> Signup and view all the answers

    What percentage of the human genome is comprised of LINEs?

    <p>21%</p> Signup and view all the answers

    Which of the following describes the length range of introns in human DNA?

    <p>90 bp to several kilobases</p> Signup and view all the answers

    Which LINE is the most common element found in the human genome?

    <p>L1 LINE</p> Signup and view all the answers

    What is the significance of the A/T rich region in LINEs?

    <p>It is important for retrotransposition.</p> Signup and view all the answers

    What is the typical length range of human exons?

    <p>50 to 200 bp</p> Signup and view all the answers

    What type of DNA consists of short sequences repeated in long tandem arrays and is found at specific chromosome locations?

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

    How many copies of SINEs are typically found in the human genome?

    <p>1.6 million copies</p> Signup and view all the answers

    Which of the following types of DNA is known for its variations in length and includes segments that are often many kilobases long?

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

    What is the primary reason for the lack of a consistent relationship between DNA amount and phylogenetic complexity among eukaryotes?

    <p>The presence of nonfunctional DNA</p> Signup and view all the answers

    What is commonly implicated in neuromuscular diseases due to expanded segments?

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

    In mammals, where do the majority of mitochondria in the embryo come from?

    <p>Virtually all from the egg</p> Signup and view all the answers

    What is the inheritance pattern of mitochondrial DNA in mice?

    <p>99.99% maternal and 0.01% paternal</p> Signup and view all the answers

    What causes the degenerative optic nerve condition in Leber's hereditary optic neuropathy?

    <p>A missense mutation in NADH-CoQ reductase</p> Signup and view all the answers

    What is heteroplasmy in the context of mtDNA?

    <p>A mixture of wild-type and mutant mtDNA in a cell</p> Signup and view all the answers

    Which of the following describes petite mitochondria?

    <p>They result from a deletion in mtDNA affecting oxidative phosphorylation.</p> Signup and view all the answers

    Which statement is true about mitochondrial genetic codes?

    <p>Animal and fungal mtDNA codes differ from that of bacteria.</p> Signup and view all the answers

    What mainly encodes proteins in chloroplasts?

    <p>Circular cpDNA</p> Signup and view all the answers

    What is the typical size range of cpDNA in chloroplasts?

    <p>Approximately 120-160 kb</p> Signup and view all the answers

    What is a gene defined as in terms of nucleic acid sequence?

    <p>The complete sequence needed for synthesis of a functional gene product.</p> Signup and view all the answers

    Which of the following is NOT a component of nuclear eukaryotic DNA?

    <p>Ribosomal RNA</p> Signup and view all the answers

    What does the term 'histone code' refer to?

    <p>The set of epigenetic modifications on histone proteins.</p> Signup and view all the answers

    Which aspect of chromatin structure is primarily affected by histone tail modifications?

    <p>The physical structure and accessibility of chromatin.</p> Signup and view all the answers

    Which of the following best contrasts prokaryotic and eukaryotic gene structure?

    <p>Eukaryotic genes typically contain both exons and introns, while prokaryotic genes rarely do.</p> Signup and view all the answers

    Which classes of DNA are found in eukaryotic nuclei?

    <p>Euchromatin and heterochromatin.</p> Signup and view all the answers

    What role do transposons play in DNA?

    <p>They can move within the genome and affect gene expression.</p> Signup and view all the answers

    Which of these statements regarding organelle DNA is true?

    <p>Organelle DNA is exclusively circular.</p> Signup and view all the answers

    What is the primary function of the coding region of a gene?

    <p>To code for the amino acid or RNA sequence.</p> Signup and view all the answers

    In prokaryotes, what characterizes an operon?

    <p>It produces polycistronic mRNAs for related functions.</p> Signup and view all the answers

    What is a key characteristic of eukaryotic genes compared to prokaryotic genes?

    <p>Eukaryotic genes contain lengthy introns and noncoding regions.</p> Signup and view all the answers

    What role do splice sites play in complex transcriptional units in eukaryotic genes?

    <p>They allow for the production of different mRNAs from the same gene.</p> Signup and view all the answers

    What is one major difference between monocistronic and polycistronic mRNAs?

    <p>Monocistronic mRNAs are more common in eukaryotes.</p> Signup and view all the answers

    Which of the following regions in eukaryotic genes often requires processing to create multiple mRNA variants?

    <p>Polyadenylation site.</p> Signup and view all the answers

    Which of the following components are commonly found in eukaryotic genes but absent in prokaryotic genes?

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

    What is the transcriptional-control region primarily responsible for?

    <p>Regulating the expression of a gene.</p> Signup and view all the answers

    Study Notes

    Genes, Chromatin, and Chromosomes

    • A gene is the complete nucleic acid sequence needed for a functional gene product (polypeptide or RNA).
    • Eukaryotic genes contain coding regions (for amino acids/RNA) and transcriptional control regions (promoters).
    • Prokaryotic genes often occur in operons, which are single transcriptional units for related functions.
    • Eukaryotic genes are typically monocistronic, meaning one mRNA codes for one protein. They also frequently contain introns.
    • The human genome is approximately 96% similar to the genomes of the greater apes.

    Eukaryotic Gene Structure

    • Genes are DNA containing regions coding for RNA molecules (e.g., tRNA, rRNA).
    • Eukaryotic genes have coding regions interspersed with non-coding DNA; genes may contain many non-coding DNA regions.
    • Eukaryotic genes contain exons (coding regions) and introns (non-coding regions).
    • Introns are removed during mRNA processing.
    • Different forms of Transcriptional units yield various mRNAs from a single gene.

    Prokaryotic Genes

    • Prokaryotic genes often produce polycistronic mRNAs, meaning one mRNA can code for multiple proteins.
    • Prokaryotic mRNAs lack introns.
    • Operons control gene expression in prokaryotes.

    Gene Families

    • Gene families are sets of duplicated genes with similar sequences.
    • Paralogs are genes within the same species that arose from duplication events.
    • Orthologs are genes in different species that arose from a common ancestor.
    • Duplicated genes arose via gene duplication.

    Noncoding DNA

    • Much of eukaryotic genomes consists of non-coding DNA.
    • Intergenic regions are stretches of DNA between genes.
    • Simple-sequence DNA is composed of repeated short sequences.
    • Repetitive DNA is a significant portion of eukaryotic genomes.

    Transposable Elements

    • Transposable elements, or transposons, are DNA sequences that can change position within a genome.
    • Two types of transposons: DNA transposons and retrotransposons.
    • DNA transposons move directly as DNA.
    • Retrotransposons are transcribed into RNA, then reverse transcribed to DNA before moving.
    • Transposons sometimes cause mutations.
    • LINEs and SINEs are types of retrotransposons.

    Chromosomal Organization of Genes

    • Density of genes varies across a chromosome.
    • Human exon sequences comprise about 2% of the genome.
    • Gene copying events produce similar genes.
    • Intergenic regions often contain regulatory elements.

    Variation Between Individuals

    • Single nucleotide polymorphisms (SNPs) account for ~1-2% of genomic differences between diverse human individuals.
    • These variations frequently occur in non-coding regions.
    • Deletion and duplication events alter gene copy numbers.

    Eukaryotic Chromosomes

    • Chromosomes are composed of chromatin, which is a complex of DNA and proteins (histones).
    • Nucleosomes are DNA-protein complexes with a characteristic “beads-on-a-string” structure.
    • Histone tails are subject to modifications (e.g., methylation, acetylation).
    • Euchromatin is less condensed, while heterochromatin is more compact.
    • Interphase chromosomes are less tightly compacted.
    • Metaphase chromosomes are most tightly compacted (typically observed in microscopic cells).
    • Nonhistone proteins constitute up to half of the chromosomal mass.
    • Chromosome structures are organized by banding (e.g., Giemsa staining).

    Genomics

    • Genomics is the study of complete genomes.
    • Genomic analyses include comparative genome sequencing and analysis, and identifying and characterizing genes.
    • Databases, such as GenBank for sequence information, are important resources in genomics.

    Organelle DNAs

    • Mitochondrial DNA and chloroplast DNA have different characteristics.
    • Mitochondrial DNA (mtDNA) has non-coding regions.
    • mtDNA is involved in energy production
    • mtDNA is inherited primarily from the mother.
    • Chloroplast DNAs are often circular.

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    2024 Cell#6 Genes & Chromosomes Notes PDF

    Description

    Explore the fundamentals of genes, chromatin, and chromosomes in this quiz. Learn about the differences between eukaryotic and prokaryotic genes, their structures, and the significance of introns and exons. Test your understanding of genomic similarities across species and gene transcription.

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