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Gene classification based on purpose of study can be categorized in various ways. What are some of the common ways genes are classified?
Gene classification based on purpose of study can be categorized in various ways. What are some of the common ways genes are classified?
What are the two primary types of gene evolution?
What are the two primary types of gene evolution?
Some genes evolve rapidly while others are highly conserved.
New genes are completely created from scratch.
New genes are completely created from scratch.
False
Gene duplication is a primary mechanism by which new gene families arise.
Gene duplication is a primary mechanism by which new gene families arise.
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What are the four modes of genetic innovation?
What are the four modes of genetic innovation?
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Evolutionary conservation is a significant factor in understanding gene functions.
Evolutionary conservation is a significant factor in understanding gene functions.
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Gene duplication is a significant factor in understanding gene functions.
Gene duplication is a significant factor in understanding gene functions.
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What is the function of orthologs?
What is the function of orthologs?
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What is the function of paralogs?
What is the function of paralogs?
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What is the function of homologs?
What is the function of homologs?
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Gene duplication is the primary mechanism by which new gene families arise.
Gene duplication is the primary mechanism by which new gene families arise.
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New gene families are always identified through gene duplication.
New gene families are always identified through gene duplication.
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The function of a gene can be deduced from its sequence.
The function of a gene can be deduced from its sequence.
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What is the significance of family relationships among genes?
What is the significance of family relationships among genes?
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Gene families are essential for understanding the historical context of genes.
Gene families are essential for understanding the historical context of genes.
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What are the three domains of life?
What are the three domains of life?
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What is the primary component used in the classification of the three domains of life?
What is the primary component used in the classification of the three domains of life?
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The 16S rRNA is approximately 1500 nucleotides long.
The 16S rRNA is approximately 1500 nucleotides long.
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The process of translation is fundamental to all living cells.
The process of translation is fundamental to all living cells.
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Genes evolve at a constant rate.
Genes evolve at a constant rate.
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Gene evolution can be traced through family relationships.
Gene evolution can be traced through family relationships.
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What is the significance of highly conserved genes in tracing family relationships?
What is the significance of highly conserved genes in tracing family relationships?
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Gene evolution is a purely random process.
Gene evolution is a purely random process.
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Genes that are highly conserved play a crucial role in tracing family relationships.
Genes that are highly conserved play a crucial role in tracing family relationships.
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What is the role of comparative genomics in understanding the biology of organisms?
What is the role of comparative genomics in understanding the biology of organisms?
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The biological history of an organism can be deciphered through the analysis of its DNA sequence.
The biological history of an organism can be deciphered through the analysis of its DNA sequence.
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The entire genome needs to be sequenced to study the biology of an organism.
The entire genome needs to be sequenced to study the biology of an organism.
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The development of new genes is always a result of random mutations.
The development of new genes is always a result of random mutations.
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The function of an unknown gene can be predicted by identifying homologous genes with known functions.
The function of an unknown gene can be predicted by identifying homologous genes with known functions.
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Study Notes
Gene Classification
- Genes can be classified based on purpose of study
- Some genes evolve rapidly, others are highly conserved
- New genes are generated from preexisting genes
- Gene duplication gives rise to related gene families within a single cell
- Gene function can often be deduced from its sequence.
- More than 200 gene families are common to all three primary branches of the tree of life
Classification Criteria
- Function: Genes are grouped based on their function (e.g., structural genes coding for proteins, regulatory genes controlling expression, non-coding regulatory genes, pseudogenes).
- Inheritance: Genes are categorized based on inheritance patterns (e.g., autosomal, sex-linked).
- Expression: Genes are classified based on their expression patterns (e.g., housekeeping genes expressed constantly, tissue-specific genes expressed in specific tissues, inducible genes expressed in response to stimuli).
- Evolutionary Conservation: Genes grouped by evolutionary conservation across species (e.g., orthologs, paralogs).
- Location: Genes are categorized by their genomic location (e.g., genes on different chromosomes, clustered gene families).
- Role in Disease: Genes can be classified based on their role in diseases (e.g., oncogenes).
Gene Evolution
- Some genes evolve rapidly, others are highly conserved.
- Random accidents and errors during the storage and copying of genetic information create mutations.
- Mutations may be neutral, beneficial, or detrimental affecting daughter cells.
- Changes due to mistakes of the first type are perpetuated because the altered cell have an increased likelihood of reproducing itself.
- Changes due to mistakes of the second type-selectively neutral changes - may be perpetuated or not in the competition for limited resources.
- Changes that cause serious damage lead to cell death, leaving no progeny.
- Through endless repetition of the cycle of error and trial of mutation and natural selection, organisms evolve: their genetic specifications change giving them new ways to exploit the environment and reproduce successfully.
- Some parts of the genome change more easily than others during evolution.
- A segment of DNA that does not code for protein and has no significant regulatory role is readily subject to change.
- Genes that code for highly optimized proteins or RNA molecules are not easily altered, so they remain highly conserved.
- Highly conserved genes remain easily recognizable over billions of years.
- Gene analysis is necessary to trace family relationships between distantly related organisms.
- Analysis of ribosomal RNA (16S RNA) is used to classify the living world into bacteria, archaea, and eukaryotes.
New Genes from Preexisting Genes
- The raw material of evolution is the existing DNA sequence, there is no natural mechanism for creating entirely new DNA sequences.
- New genes can arise in multiple ways, including intragenic mutation, gene duplication, segment shuffling, and horizontal gene transfer.
- Intragenic mutation: A pre-existing gene is modified by mutations in its DNA sequence
- Gene duplication: An existing gene is duplicated to create two closely related genes in a single cell.
- Segment shuffling (exon shuffling): Two or more existing genes can be broken and rejoined to form a hybrid gene, combining DNA segments from separate genes.
- Horizontal gene transfer: A piece of DNA can transfer from the genome of one cell to another, including another species. This differentiates from typical vertical transfer from parent to progeny.
Gene Duplication
- Duplication of genes leads to families of related genes within a single cell.
- Repeated rounds of gene duplication and divergence, over millions of years, enable one gene to give rise to a whole family of genes within a single genome
- Analysis of genomes, particularly in prokaryotes, shows many examples of gene families with obvious related genes.
Gene Function Deduction
- Family relationships among genes are critical for deciphering gene functions.
- If a gene's sequence is known, the database can be searched for homologous genes with known functions.
- The function of a new gene is likely similar to those of its homologs.
Gene Function in Organisms
- The sequence of the genome of Mycobacterium tuberculosis, an organism that causes tuberculosis, has been determined.
- 40% of the genes in M. tuberculosis are homologs with known genes in other organisms.
- 44% of genes have some similarity to others.
- 16% were not similar to other known genes.
- A large number of genes coding for enzymes involved in lipid metabolism suggests unusual outer coat which can aid in the organism's escape from the immune system.
Universal Gene Families
- Complete genome sequences allows for systematic analysis of homologies across various domains.
- Only a small percentage of ancestral gene families are universally retained.
- Most universal gene families are related to translation and transcription.
- Genes in many kingdoms can be analyzed to understand shared functions.
- A better and less crude view can be obtained by analyzing gene families across several domains to understand universal domains.
- Many ancient conserved families can be attributed to functions, and are commonly involved in translation, ribosome production or amino acid metabolism and transport.
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Description
This quiz covers the classification of genes based on their functions, inheritance patterns, expression levels, and evolutionary conservation. Understanding these categories is essential for studying genetics and the evolution of genes across different life forms.
