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Questions and Answers
All genes in the genome can be actively expressed in every cell at all times.
All genes in the genome can be actively expressed in every cell at all times.
False
How many estimated protein-coding genes are in the human genome?
How many estimated protein-coding genes are in the human genome?
approximately 20,000
What are pseudogenes?
What are pseudogenes?
What does the Central Dogma of Molecular Biology state?
What does the Central Dogma of Molecular Biology state?
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What are the two types of pseudogenes?
What are the two types of pseudogenes?
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Epigenetics focuses on reversible changes of _____ landscape as determinants of gene function.
Epigenetics focuses on reversible changes of _____ landscape as determinants of gene function.
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Which of the following modifications occur at the N-terminal tails of histones?
Which of the following modifications occur at the N-terminal tails of histones?
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What are topologically associating domains (TADs)?
What are topologically associating domains (TADs)?
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Chromosomes are spatially segregated into A- and B-type genomic compartments.
Chromosomes are spatially segregated into A- and B-type genomic compartments.
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How many protein-coding genes are estimated to be in the human genome?
How many protein-coding genes are estimated to be in the human genome?
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Many genes are capable of generating multiple different products.
Many genes are capable of generating multiple different products.
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What is the average density of genes in the human genome?
What is the average density of genes in the human genome?
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What does the Central Dogma of Molecular Biology describe?
What does the Central Dogma of Molecular Biology describe?
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Which type of pseudogenes were once functional but are now vestigial?
Which type of pseudogenes were once functional but are now vestigial?
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Epigenetic changes are irreversible.
Epigenetic changes are irreversible.
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What is the role of histone modifications?
What is the role of histone modifications?
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What do topologically associating domains (TADs) in chromosomes facilitate?
What do topologically associating domains (TADs) in chromosomes facilitate?
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______ are involved in cell cycle processes and DNA repair.
______ are involved in cell cycle processes and DNA repair.
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Study Notes
Gene Structure and Function
- The human genome contains approximately 20,000 protein-coding genes.
- Many genes can produce multiple protein products.
- Proteins function in complex networks, leading to a broad range of cellular functions.
- Chromosomes can be gene rich or gene poor.
- Abnormalities in gene-rich regions tend to be more severe clinically than abnormalities in gene-poor regions.
Central Dogma of Molecular Biology
- DNA is transcribed into RNA, which is translated into protein - DNA --> RNA --> Protein
Gene Structure
- Genes are composed of exons and introns.
- Exons contain protein-coding sequences.
- Introns are non-coding sequences that are removed during RNA processing.
- Genes can have varying numbers of exons; for example, the gene for hemoglobin has three exons, while the gene for inherited breast cancer has 24 exons.
Pseudogenes
- Pseudogenes are DNA sequences that resemble functional genes but are non-functional.
- Nonprocessed pseudogenes were once functional genes but have become inactivated by mutations.
- Processed pseudogenes are formed by retrotransposition, which involves the transcription of a gene into mRNA, followed by reverse transcription of the mRNA into cDNA, which is integrated into the genome at a different location.
Genetic Code
- The genetic code is degenerate, meaning that multiple codons can code for the same amino acid.
Gene Regulation
- Not all genes are expressed in all cells at all times.
- Gene expression is regulated by epigenetic mechanisms, which are reversible changes to chromatin structure, the complex of DNA and proteins that makes up chromosomes.
- Epigenetic changes can be transient or long-lasting.
Epigenetics
- Epigenetics focuses on changes to chromatin structure as determinants of gene function, rather than changes to the DNA sequence itself.
- Chromatin structure is influenced by modifications to histones, the proteins around which DNA is wrapped.
- Histone modifications include methylation, acetylation, and phosphorylation.
- Histone variants, which have different amino acid sequences from canonical histones, are also involved in chromatin structure.
- CENP-A is a variant histone related to histone H3, found in centromeres.
Chromatin Architecture
- Chromosomes are organized in the 3D space of the nucleus to regulate gene expression.
- Chromosomes are spatially segregated into A- and B-type genomic compartments, which represent active (euchromatin) and inactive (heterochromatin) domains, respectively.
Genomic Compartmentalization
- Genomic compartmentalization can comprise multiple subcompartments.
- The nucleolus forms at the site of ribosomal genes on acrocentric chromosomes for the assembly of ribosomal subunits.
- Splicing speckles are nuclear domains enriched for splicing machinery.
- Promyelocytic leukemia (PML) bodies are involved in cell cycle processes and DNA repair.
Human Genome
- Estimated to have approximately 20,000 protein-coding genes.
- Genes can produce multiple products through alternative splicing.
- Proteins work together in networks to provide a diverse range of cellular functions.
Chromosome Structure
- Chromosomes can be categorized as gene-rich or gene-poor regions.
- Gene-rich chromosomes or regions are clinically more susceptible to abnormalities, compared to gene-poor regions.
Central Dogma of Molecular Biology
- The flow of genetic information from DNA to RNA to protein.
Gene Structure
- A typical human gene can have numerous exons, ranging from 3 exons in disorders of hemoglobin to 40 exons in inherited hypertrophic cardiomyopathy.
Pseudogenes
- Nonfunctional DNA sequences resembling functional genes.
- Nonprocessed pseudogenes are inactivated due to mutations in coding or regulatory sequences.
- Processed pseudogenes are formed through retrotransposition: transcription, reverse transcription of mRNA into cDNA, and integration into the genome.
Genetic Code
- Genetic code is degenerate, meaning multiple codons can code for the same amino acid.
Gene Expression
- Gene expression is regulated and not all genes are active in all cells at all times.
Epigenetics
- Focuses on reversible changes in chromatin landscape, determining gene function without altering DNA sequences.
Epigenetic Modifications
- Epigenetic changes can be temporary or long-lasting.
DNA Methylation
- Extensive demethylation occurs during germ cell and early embryonic development.
- Reprogramming involves conversion of 5-mC to 5-hmC as an intermediate step in demethylation.
Histone Modifications
- Histone modifications include methylation, acetylation, and phosphorylation of histone tails.
- Histone variants differ in amino acid sequences and play specific roles.
- CENP-A, a variant related to histone H3, is found in centromeres.
Chromatin Organization
- The genome adopts a highly ordered and dynamic 3D structure.
Topologically Associating Domains (TADs)
- Chromosomes are spatially organized in the nucleus for gene regulation.
- Chromosomes are segregated into A and B-type compartments representing active (euchromatin) and inactive (heterochromatin) domains, respectively.
Genomic Compartmentalization
- Multi-compartmental organization exists within the nucleus.
- Nucleolus is the site of ribosomal gene synthesis and ribosome subunit assembly.
- Splicing speckles are domains enriched in splicing machinery.
- PML bodies are implicated in cell cycle processes and DNA repair.
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Description
Test your knowledge on the human genome and gene structure with this quiz. Explore concepts such as the Central Dogma of Molecular Biology, the role of exons and introns, and the significance of pseudogenes. Understand how genes influence protein production and cellular functions.
