Podcast
Questions and Answers
What is the term for the entirety of genetic material found within a cell or organism?
What is the term for the entirety of genetic material found within a cell or organism?
What is the term for the set of chromosomes found in a particular species?
What is the term for the set of chromosomes found in a particular species?
What is the term for chromosomes that are diploid in all individuals of a species, regardless of sex?
What is the term for chromosomes that are diploid in all individuals of a species, regardless of sex?
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?
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?
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What percentage of the genome is non-coding?
What percentage of the genome is non-coding?
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Approximately how many genes are there in the mammalian genome?
Approximately how many genes are there in the mammalian genome?
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What is the term for a completely sequenced genome isolate that is used as a reference for genetic studies?
What is the term for a completely sequenced genome isolate that is used as a reference for genetic studies?
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Which arm of the chromosome is longer?
Which arm of the chromosome is longer?
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What are small insertions and deletions usually defined as?
What are small insertions and deletions usually defined as?
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What type of genetic variation do indels represent?
What type of genetic variation do indels represent?
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What is the characteristic of indels in terms of size?
What is the characteristic of indels in terms of size?
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What is the primary feature of indels?
What is the primary feature of indels?
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What is the term used to describe small insertions and deletions?
What is the term used to describe small insertions and deletions?
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What is the primary characteristic of small insertions and deletions?
What is the primary characteristic of small insertions and deletions?
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What type of genetic variation do small insertions and deletions represent?
What type of genetic variation do small insertions and deletions represent?
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What is the term used to describe small insertions and deletions?
What is the term used to describe small insertions and deletions?
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What is the characteristic of small insertions and deletions in terms of size?
What is the characteristic of small insertions and deletions in terms of size?
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What is the definition of small insertions and deletions?
What is the definition of small insertions and deletions?
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What is the primary function of the reverse transcriptase encoded by autonomous transposable elements?
What is the primary function of the reverse transcriptase encoded by autonomous transposable elements?
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How do non-autonomous transposable elements, such as SINE elements, achieve transposition?
How do non-autonomous transposable elements, such as SINE elements, achieve transposition?
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Which of the following is an example of the phenotypic effect caused by transposable element insertions?
Which of the following is an example of the phenotypic effect caused by transposable element insertions?
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Which of the following correctly describes how transposable elements can contribute to disease?
Which of the following correctly describes how transposable elements can contribute to disease?
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What type of sequences do autonomous transposable elements, such as LINE elements, usually encode?
What type of sequences do autonomous transposable elements, such as LINE elements, usually encode?
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What is the primary purpose of using computational algorithms during the genome sequencing process?
What is the primary purpose of using computational algorithms during the genome sequencing process?
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Which technology currently facilitates the identification of genome variation?
Which technology currently facilitates the identification of genome variation?
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What is the approximate current cost of sequencing a mammalian genome?
What is the approximate current cost of sequencing a mammalian genome?
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What type of genomic variation can be identified by analyzing the number of reads mapping to the reference genome?
What type of genomic variation can be identified by analyzing the number of reads mapping to the reference genome?
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What role do computer clusters play in the genome sequencing process?
What role do computer clusters play in the genome sequencing process?
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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.
