Genomes and Chromosomes
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Questions and Answers

What is the term for the entirety of genetic material found within a cell or organism?

  • Genotype
  • Chromatin
  • Karyotype
  • Genome (correct)

    • What is the term for the set of chromosomes found in a particular species?

  • Genotype
  • Karyotype (correct)
  • Genome
  • Phenotype

    • What is the term for chromosomes that are diploid in all individuals of a species, regardless of sex?

  • Homologous chromosomes
  • Autosomes (correct)
  • Allosomes
  • Sex chromosomes

    • What is the term for the site of spindle attachment during mitosis and the site of constriction between the two sister chromatids in G2 cells?

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

    What percentage of the genome is non-coding?

    <p>98%</p> Signup and view all the answers

    Approximately how many genes are there in the mammalian genome?

    <p>20,000</p> Signup and view all the answers

    What is the term for a completely sequenced genome isolate that is used as a reference for genetic studies?

    <p>Reference genome</p> Signup and view all the answers

    Which arm of the chromosome is longer?

    <p>q-arm</p> Signup and view all the answers

    What are small insertions and deletions usually defined as?

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

    What type of genetic variation do indels represent?

    <p>Small insertions and deletions</p> Signup and view all the answers

    What is the characteristic of indels in terms of size?

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

    What is the primary feature of indels?

    <p>Insertions and deletions</p> Signup and view all the answers

    What is the term used to describe small insertions and deletions?

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

    What is the primary characteristic of small insertions and deletions?

    <p>They are small in size</p> Signup and view all the answers

    What type of genetic variation do small insertions and deletions represent?

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

    What is the term used to describe small insertions and deletions?

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

    What is the characteristic of small insertions and deletions in terms of size?

    <p>They are typically small</p> Signup and view all the answers

    What is the definition of small insertions and deletions?

    <p>Small insertions and deletions</p> Signup and view all the answers

    What is the primary function of the reverse transcriptase encoded by autonomous transposable elements?

    <p>To synthesize DNA from an RNA template</p> Signup and view all the answers

    How do non-autonomous transposable elements, such as SINE elements, achieve transposition?

    <p>By using proteins encoded by autonomous elements</p> Signup and view all the answers

    Which of the following is an example of the phenotypic effect caused by transposable element insertions?

    <p>Merle pattern in dogs</p> Signup and view all the answers

    Which of the following correctly describes how transposable elements can contribute to disease?

    <p>By altering the coding sequences of essential genes</p> Signup and view all the answers

    What type of sequences do autonomous transposable elements, such as LINE elements, usually encode?

    <p>Proteins required for their own transposition</p> Signup and view all the answers

    What is the primary purpose of using computational algorithms during the genome sequencing process?

    <p>To map short sequence reads to the reference genome</p> Signup and view all the answers

    Which technology currently facilitates the identification of genome variation?

    <p>Whole genome sequencing</p> Signup and view all the answers

    What is the approximate current cost of sequencing a mammalian genome?

    <p>$1,000</p> Signup and view all the answers

    What type of genomic variation can be identified by analyzing the number of reads mapping to the reference genome?

    <p>Copy number variants (CNVs)</p> Signup and view all the answers

    What role do computer clusters play in the genome sequencing process?

    <p>Mapping short sequence reads back to the reference genome</p> Signup and view all the answers

    Study Notes

    Genome and Chromosomes

    • A genome is the entirety of genetic material (DNA) found within a cell or organism.
    • DNA is made up of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), and thymine (T).
    • Chromosomes are linear elements that package DNA.

    Karyotype

    • A karyotype is the set of chromosomes found in a particular species.
    • Mammals have a diploid karyotype, meaning they have two copies of each chromosome.
    • Genome size and karyotype vary among mammals and do not relate to organism complexity.

    Types of Chromosomes

    • Autosomes are chromosomes that are diploid in all individuals of a species, regardless of sex.
    • Sex chromosomes confer sexual traits and are different between males and females.
    • In mammals, sex chromosomes are known as X and Y, and males are the heterogametic sex.

    Chromosomal Structure

    • Chromosomes have centromeres, which are the site of spindle attachment during mitosis.
    • Chromosomes have telomeres, which are DNA sequences at the ends of chromosomes characterized by a conserved repeat structure.
    • A chromosomal arm is the region from the centromere to the end of the telomere.
    • The p-arm refers to the shorter of the two chromosome arms, and the q-arm to the longer arm.

    Genome Composition

    • The majority of the genome (~98%) is non-coding, meaning it does not encode protein-coding gene exons.
    • The number of genes (~20,000) is fairly constant among mammals.

    Reference Genome

    • A reference genome is a completely sequenced genome isolate used as a reference for genetic studies.
    • The human reference genome is the best assembled and annotated mammalian reference genome.
    • Reference genomes exist for dozens of mammals, including dog, cat, and livestock species.
    • Each base in the reference genome has its own unique genome coordinates, e.g., chr18:28,000,000, designating the 28,000,000th base on chromosome 18.

    Indels

    • Small insertions and deletions in DNA, usually defined as
    • Involves insertion or deletion of a small number of nucleotides in a DNA sequence

    Indels

    • Small insertions and deletions in DNA, usually defined as
    • Involves insertion or deletion of a small number of nucleotides in a DNA sequence

    Transposable Elements

    • Transposable elements are virus-like sequences that copy themselves and move around the genome.
    • There are two types of transposable elements: autonomous and non-autonomous.
    • Autonomous transposable elements, such as LINE elements, encode genes necessary for transposition, including reverse transcriptase.
    • Non-autonomous transposable elements, such as SINE elements, rely on transposition proteins encoded by autonomous elements to support transposition.
    • Transposable element insertions can disrupt genes and cause disease.
    • An example of a disease caused by transposable element insertions is the merle phenotype observed in dogs.

    Genome Variation Detection

    • Genome variation is detected through whole genome sequencing.
    • The process involves extracting DNA from cells and breaking it down into small, evenly-sized fragments.
    • These fragments are then loaded onto a sequencing machine, which produces hundreds of millions of short sequences.
    • Computer clusters (many computers working in parallel) are used to map these short sequence 'reads' back to the reference genome.
    • Computational algorithms are used to identify variants, which are positions that differ between the sequenced genome and the reference genome.
    • Whole genome sequencing can also identify copy number variants by detecting differences in the number of reads mapping to the reference genome.
    • The current cost of sequencing a mammalian genome is approximately £1,000.

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    Description

    Test your knowledge of genomes, chromosomes, and their composition in cells and organisms. Learn about the nitrogenous bases, karyotype, and their variations among mammals.

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