3T1N , 3SHT , 2WT8 , 3SHV , 3U3Z , 3KTF , 3PA6 , 3SZM
71-535: 79648 244329 ENSG00000147316 ENSG00000285262 ENSMUSG00000039842 Q8NEM0 Q7TT79 NM_001322045 NM_001363979 NM_001363980 NM_173189 NP_078872 NP_001350908 NP_001350909 NP_775281 Microcephalin ( MCPH1 ) is a gene that is expressed during fetal brain development. Certain mutations in MCPH1 , when homozygous , cause primary microcephaly —a severely diminished brain . Hence, it has been assumed that variants have
142-588: A promoter sequence. The promoter is recognized and bound by transcription factors that recruit and help RNA polymerase bind to the region to initiate transcription. The recognition typically occurs as a consensus sequence like the TATA box . A gene can have more than one promoter, resulting in messenger RNAs ( mRNA ) that differ in how far they extend in the 5' end. Highly transcribed genes have "strong" promoter sequences that form strong associations with transcription factors, thereby initiating transcription at
213-486: A " start codon ", and three " stop codons " indicate the beginning and end of the protein coding region . There are 64 possible codons (four possible nucleotides at each of three positions, hence 4 possible codons) and only 20 standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid. The correspondence between codons and amino acids is nearly universal among all known living organisms. Bruce Lahn Bruce Lahn
284-445: A continuous messenger RNA , referred to as a polycistronic mRNA . The term cistron in this context is equivalent to gene. The transcription of an operon's mRNA is often controlled by a repressor that can occur in an active or inactive state depending on the presence of specific metabolites. When active, the repressor binds to a DNA sequence at the beginning of the operon, called the operator region , and represses transcription of
355-498: A double-helix run in opposite directions. Nucleic acid synthesis, including DNA replication and transcription occurs in the 5'→3' direction, because new nucleotides are added via a dehydration reaction that uses the exposed 3' hydroxyl as a nucleophile . The expression of genes encoded in DNA begins by transcribing the gene into RNA , a second type of nucleic acid that is very similar to DNA, but whose monomers contain
426-488: A few genes and are transferable between individuals. For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of different species, via horizontal gene transfer . Whereas the chromosomes of prokaryotes are relatively gene-dense, those of eukaryotes often contain regions of DNA that serve no obvious function. Simple single-celled eukaryotes have relatively small amounts of such DNA, whereas
497-434: A gene - surprisingly, there is no definition that is entirely satisfactory. A gene is a DNA sequence that codes for a diffusible product. This product may be protein (as is the case in the majority of genes) or may be RNA (as is the case of genes that code for tRNA and rRNA). The crucial feature is that the product diffuses away from its site of synthesis to act elsewhere. The important parts of such definitions are: (1) that
568-573: A gene corresponds to a transcription unit; (2) that genes produce both mRNA and noncoding RNAs; and (3) regulatory sequences control gene expression but are not part of the gene itself. However, there's one other important part of the definition and it is emphasized in Kostas Kampourakis' book Making Sense of Genes . Therefore in this book I will consider genes as DNA sequences encoding information for functional products, be it proteins or RNA molecules. With 'encoding information', I mean that
639-410: A gene may be split across chromosomes but those transcripts are concatenated back together into a functional sequence by trans-splicing . It is also possible for overlapping genes to share some of their DNA sequence, either on opposite strands or the same strand (in a different reading frame, or even the same reading frame). In all organisms, two steps are required to read the information encoded in
710-404: A gene's DNA and produce the protein it specifies. First, the gene's DNA is transcribed to messenger RNA ( mRNA ). Second, that mRNA is translated to protein. RNA-coding genes must still go through the first step, but are not translated into protein. The process of producing a biologically functional molecule of either RNA or protein is called gene expression , and the resulting molecule
781-578: A gene: that of bacteriophage MS2 coat protein. The subsequent development of chain-termination DNA sequencing in 1977 by Frederick Sanger improved the efficiency of sequencing and turned it into a routine laboratory tool. An automated version of the Sanger method was used in early phases of the Human Genome Project . The theories developed in the early 20th century to integrate Mendelian genetics with Darwinian evolution are called
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#1732786814912852-439: A gene; however, members of a population may have different alleles at the locus, each with a slightly different gene sequence. The majority of eukaryotic genes are stored on a set of large, linear chromosomes. The chromosomes are packed within the nucleus in complex with storage proteins called histones to form a unit called a nucleosome . DNA packaged and condensed in this way is called chromatin . The manner in which DNA
923-448: A high rate. Others genes have "weak" promoters that form weak associations with transcription factors and initiate transcription less frequently. Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters. Additionally, genes can have regulatory regions many kilobases upstream or downstream of the gene that alter expression. These act by binding to transcription factors which then cause
994-572: A new expanded definition that includes noncoding genes. However, some modern writers still do not acknowledge noncoding genes although this so-called "new" definition has been recognised for more than half a century. Although some definitions can be more broadly applicable than others, the fundamental complexity of biology means that no definition of a gene can capture all aspects perfectly. Not all genomes are DNA (e.g. RNA viruses ), bacterial operons are multiple protein-coding regions transcribed into single large mRNAs, alternative splicing enables
1065-400: A process known as RNA splicing . Finally, the ends of gene transcripts are defined by cleavage and polyadenylation (CPA) sites , where newly produced pre-mRNA gets cleaved and a string of ~200 adenosine monophosphates is added at the 3' end. The poly(A) tail protects mature mRNA from degradation and has other functions, affecting translation, localization, and transport of the transcript from
1136-419: A protein-coding gene consists of many elements of which the actual protein coding sequence is often only a small part. These include introns and untranslated regions of the mature mRNA. Noncoding genes can also contain introns that are removed during processing to produce the mature functional RNA. All genes are associated with regulatory sequences that are required for their expression. First, genes require
1207-577: A range of SNPs associated with all four MCPH genes, including upstream and downstream regulatory elements , and allowed for separate effects for males and females. In addition to MCPH1, other genes have been designated MCPH genes based on their role in brain size. These include WDR62 ( MCPH2 ), CDK5RAP2 ( MCPH3 ), KNL1 ( MCPH4 ), ASPM ( MCPH5 ), CENPJ ( MCPH6 ), STIL ( MCPH7 ), CEP135 ( MCPH8 ), CEP152 ( MCPH9 ), ZNF335 ( MCPH10 ), PHC1 ( MCPH11 ) and CDK6 ( MCPH12 ). In March 2019, Chinese scientists reported inserting
1278-443: A role in brain development. However, in normal individuals no effect on mental ability or behavior has yet been demonstrated in either this or another similarly studied microcephaly gene, ASPM . However, an association has been established between normal variation in brain structure, as measured with MRI (i.e., primarily cortical surface area and total brain volume) but only in females, and common genetic variants within both
1349-412: A single genomic region to encode multiple district products and trans-splicing concatenates mRNAs from shorter coding sequence across the genome. Since molecular definitions exclude elements such as introns, promotors, and other regulatory regions , these are instead thought of as "associated" with the gene and affect its function. An even broader operational definition is sometimes used to encompass
1420-475: A strict definition of the word "gene" with which nearly every expert can agree. First, in order for a nucleotide sequence to be considered a true gene, an open reading frame (ORF) must be present. The ORF can be thought of as the "gene itself"; it begins with a starting mark common for every gene and ends with one of three possible finish line signals. One of the key enzymes in this process, the RNA polymerase, zips along
1491-409: A true gene, by this definition, one has to prove that the transcript has a biological function. Early speculations on the size of a typical gene were based on high-resolution genetic mapping and on the size of proteins and RNA molecules. A length of 1500 base pairs seemed reasonable at the time (1965). This was based on the idea that the gene was the DNA that was directly responsible for production of
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#17327868149121562-657: Is a Chinese-born American geneticist. Lahn came to the U.S. from China to continue his education in the late 1980s. He is the William B. Graham professor of Human Genetics at the University of Chicago . He is also the founder of the Center for Stem Cell Biology and Tissue Engineering at Sun Yat-sen University in Guangzhou , China . Lahn currently serves as the chief scientist of VectorBuilder, Inc. Lahn's honors include
1633-487: Is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA . There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of RNA or protein from a gene), DNA is first copied into RNA . RNA can be directly functional or be the intermediate template for the synthesis of a protein. The transmission of genes to an organism's offspring ,
1704-456: Is called a gene product . The nucleotide sequence of a gene's DNA specifies the amino acid sequence of a protein through the genetic code . Sets of three nucleotides, known as codons , each correspond to a specific amino acid. The principle that three sequential bases of DNA code for each amino acid was demonstrated in 1961 using frameshift mutations in the rIIB gene of bacteriophage T4 (see Crick, Brenner et al. experiment ). Additionally,
1775-400: Is nearly the same for all known organisms. The total complement of genes in an organism or cell is known as its genome , which may be stored on one or more chromosomes . A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded. The region of the chromosome at which a particular gene is located is called its locus . Each locus contains one allele of
1846-403: Is still part of the definition of a gene in most textbooks. For example, The primary function of the genome is to produce RNA molecules. Selected portions of the DNA nucleotide sequence are copied into a corresponding RNA nucleotide sequence, which either encodes a protein (if it is an mRNA) or forms a 'structural' RNA, such as a transfer RNA (tRNA) or ribosomal RNA (rRNA) molecule. Each region of
1917-399: Is stored on the histones, as well as chemical modifications of the histone itself, regulate whether a particular region of DNA is accessible for gene expression . In addition to genes, eukaryotic chromosomes contain sequences involved in ensuring that the DNA is copied without degradation of end regions and sorted into daughter cells during cell division: replication origins , telomeres , and
1988-431: Is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype , that is specific to every given individual, within the gene pool of the population of a given species . The genotype, along with environmental and developmental factors, ultimately determines the phenotype of the individual. Most biological traits occur under
2059-454: Is the founder and Chief Scientist of VectorBuilder, a global leader in gene delivery solutions. In the past he has studied human genetics and evolutionary genetics. His main objective with previous studies was to study the evolution of human sex chromosomes and the underlying basis for the growth of the human brain. Lahn is currently doing a wide spread of stem cell research as well as working with epigenetics. Lahn's previous research has led to
2130-811: The Merrill Lynch Forum Global Innovation Award, the TR100 Award from Technology Review , the Burroughs Wellcome Career Award, and a Searle Scholarship . He was also named to the 40-Under-40 list by Crains Chicago Business. Lahn received his B.A. in General Biology from Harvard University and his Ph.D. from the Massachusetts Institute of Technology in the lab of David C. Page . From 2000 to 2012, Lahn
2201-511: The aging process. The centromere is required for binding spindle fibres to separate sister chromatids into daughter cells during cell division . Prokaryotes ( bacteria and archaea ) typically store their genomes on a single, large, circular chromosome . Similarly, some eukaryotic organelles contain a remnant circular chromosome with a small number of genes. Prokaryotes sometimes supplement their chromosome with additional small circles of DNA called plasmids , which usually encode only
Microcephalin - Misplaced Pages Continue
2272-401: The central dogma of molecular biology , which states that proteins are translated from RNA , which is transcribed from DNA . This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses . The modern study of genetics at the level of DNA is known as molecular genetics . In 1972, Walter Fiers and his team were the first to determine the sequence of
2343-419: The centromere . Replication origins are the sequence regions where DNA replication is initiated to make two copies of the chromosome. Telomeres are long stretches of repetitive sequences that cap the ends of the linear chromosomes and prevent degradation of coding and regulatory regions during DNA replication . The length of the telomeres decreases each time the genome is replicated and has been implicated in
2414-554: The modern synthesis , a term introduced by Julian Huxley . This view of evolution was emphasized by George C. Williams ' gene-centric view of evolution . He proposed that the Mendelian gene is a unit of natural selection with the definition: "that which segregates and recombines with appreciable frequency." Related ideas emphasizing the centrality of Mendelian genes and the importance of natural selection in evolution were popularized by Richard Dawkins . The development of
2485-475: The neutral theory of evolution in the late 1960s led to the recognition that random genetic drift is a major player in evolution and that neutral theory should be the null hypothesis of molecular evolution. This led to the construction of phylogenetic trees and the development of the molecular clock , which is the basis of all dating techniques using DNA sequences. These techniques are not confined to molecular gene sequences but can be used on all DNA segments in
2556-750: The operon ; when the repressor is inactive transcription of the operon can occur (see e.g. Lac operon ). The products of operon genes typically have related functions and are involved in the same regulatory network . Though many genes have simple structures, as with much of biology, others can be quite complex or represent unusual edge-cases. Eukaryotic genes often have introns that are much larger than their exons, and those introns can even have other genes nested inside them . Associated enhancers may be many kilobase away, or even on entirely different chromosomes operating via physical contact between two chromosomes. A single gene can encode multiple different functional products by alternative splicing , and conversely
2627-449: The population . These alleles encode slightly different versions of a gene, which may cause different phenotypical traits. Genes evolve due to natural selection or survival of the fittest and genetic drift of the alleles. There are many different ways to use the term "gene" based on different aspects of their inheritance, selection, biological function, or molecular structure but most of these definitions fall into two categories,
2698-404: The DNA helix that produces a functional RNA molecule constitutes a gene. We define a gene as a DNA sequence that is transcribed. This definition includes genes that do not encode proteins (not all transcripts are messenger RNA). The definition normally excludes regions of the genome that control transcription but are not themselves transcribed. We will encounter some exceptions to our definition of
2769-450: The DNA sequence is used as a template for the production of an RNA molecule or a protein that performs some function. The emphasis on function is essential because there are stretches of DNA that produce non-functional transcripts and they do not qualify as genes. These include obvious examples such as transcribed pseudogenes as well as less obvious examples such as junk RNA produced as noise due to transcription errors. In order to qualify as
2840-766: The DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site. For example, enhancers increase transcription by binding an activator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase. The mature messenger RNA produced from protein-coding genes contains untranslated regions at both ends which contain binding sites for ribosomes , RNA-binding proteins , miRNA , as well as terminator , and start and stop codons . In addition, most eukaryotic open reading frames contain untranslated introns , which are removed and exons , which are connected together in
2911-547: The MCPH1 gene and another similarly studied microcephaly gene, CDK5RAP2 . Microcephalin proteins contain the following three domains: MCPH1 is expressed in the fetal brain, in the developing forebrain , and on the walls of the lateral ventricles . Cells of this area divide, producing neurons that migrate to eventually form the cerebral cortex . A derived form of MCPH1 appeared about 37,000 years ago (any time between 14,000 and 60,000 years ago) and has spread to become
Microcephalin - Misplaced Pages Continue
2982-514: The Mendelian gene or the molecular gene. The Mendelian gene is the classical gene of genetics and it refers to any heritable trait. This is the gene described in The Selfish Gene . More thorough discussions of this version of a gene can be found in the articles Genetics and Gene-centered view of evolution . The molecular gene definition is more commonly used across biochemistry, molecular biology, and most of genetics —
3053-433: The adenines of one strand are paired with the thymines of the other strand, and so on. Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose ; this is known as the 3' end of the molecule. The other end contains an exposed phosphate group; this is the 5' end . The two strands of
3124-425: The ancestral forms of MCPH1 and ASPM showed neither microcephalin or ASPM had any significant effect on IQ . The derived form of MCPH1 may have originated from a lineage separated from modern humans approximately 1.1 million years ago and later introgressed into humans. This finding supports the possibility of admixture between modern humans and extinct Homo spp . While Neanderthals have been suggested as
3195-436: The combined influence of polygenes (a set of different genes) and gene–environment interactions . Some genetic traits are instantly visible, such as eye color or the number of limbs, others are not, such as blood type , the risk for specific diseases, or the thousands of basic biochemical processes that constitute life . A gene can acquire mutations in its sequence , leading to different variants, known as alleles , in
3266-402: The complexity of these diverse phenomena, where a gene is defined as a union of genomic sequences encoding a coherent set of potentially overlapping functional products. This definition categorizes genes by their functional products (proteins or RNA) rather than their specific DNA loci, with regulatory elements classified as gene-associated regions. The existence of discrete inheritable units
3337-524: The distinction between a heterozygote and homozygote , and the phenomenon of discontinuous inheritance. Prior to Mendel's work, the dominant theory of heredity was one of blending inheritance , which suggested that each parent contributed fluids to the fertilization process and that the traits of the parents blended and mixed to produce the offspring. Charles Darwin developed a theory of inheritance he termed pangenesis , from Greek pan ("all, whole") and genesis ("birth") / genos ("origin"). Darwin used
3408-410: The early 1950s the prevailing view was that the genes in a chromosome acted like discrete entities arranged like beads on a string. The experiments of Benzer using mutants defective in the rII region of bacteriophage T4 (1955–1959) showed that individual genes have a simple linear structure and are likely to be equivalent to a linear section of DNA. Collectively, this body of research established
3479-522: The fact that both protein-coding genes and noncoding genes have been known for more than 50 years, there are still a number of textbooks, websites, and scientific publications that define a gene as a DNA sequence that specifies a protein. In other words, the definition is restricted to protein-coding genes. Here is an example from a recent article in American Scientist. ... to truly assess the potential significance of de novo genes, we relied on
3550-413: The functional product. The discovery of introns in the 1970s meant that many eukaryotic genes were much larger than the size of the functional product would imply. Typical mammalian protein-coding genes, for example, are about 62,000 base pairs in length (transcribed region) and since there are about 20,000 of them they occupy about 35–40% of the mammalian genome (including the human genome). In spite of
3621-630: The gene that is described in terms of DNA sequence. There are many different definitions of this gene — some of which are misleading or incorrect. Very early work in the field that became molecular genetics suggested the concept that one gene makes one protein (originally 'one gene - one enzyme'). However, genes that produce repressor RNAs were proposed in the 1950s and by the 1960s, textbooks were using molecular gene definitions that included those that specified functional RNA molecules such as ribosomal RNA and tRNA (noncoding genes) as well as protein-coding genes. This idea of two kinds of genes
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#17327868149123692-421: The genome. The vast majority of organisms encode their genes in long strands of DNA (deoxyribonucleic acid). DNA consists of a chain made from four types of nucleotide subunits, each composed of: a five-carbon sugar ( 2-deoxyribose ), a phosphate group, and one of the four bases adenine , cytosine , guanine , and thymine . Two chains of DNA twist around each other to form a DNA double helix with
3763-421: The genomes of complex multicellular organisms , including humans, contain an absolute majority of DNA without an identified function. This DNA has often been referred to as " junk DNA ". However, more recent analyses suggest that, although protein-coding DNA makes up barely 2% of the human genome , about 80% of the bases in the genome may be expressed, so the term "junk DNA" may be a misnomer. The structure of
3834-558: The genotype for MCPH1 was under positive selection. An analysis by Timpson et al. , found "no meaningful associations with brain size and various cognitive measures". A later 2010 study by Rimol et al. demonstrated a link between brain size and structure and two microcephaly genes, MCPH1 (only in females) and CDK5RAP2 (only in males). In contrast to previous studies, which only considered small numbers of exonic single nucleotide polymorphisms (SNPs) and did not investigate sex-specific effects, this study used microarray technology to genotype
3905-421: The human brain-related MCPH1 gene into laboratory rhesus monkeys , resulting in the transgenic monkeys performing better and answering faster on "short-term memory tests involving matching colors and shapes", compared to control non-transgenic monkeys, according to the researchers. Gene In biology , the word gene has two meanings. The Mendelian gene is a basic unit of heredity . The molecular gene
3976-508: The human brain. His research also suggested that newly arisen variants of two brain size genes, ASPM and MCPH1, might have been favored by positive natural selection in recent human history. This research provoked controversy due to the finding that the positively selected variants of these genes had spread to higher frequencies in some parts of the world than in others (for ASPM, it is higher in Europe and surrounding regions than other parts of
4047-534: The hypothesis that the Neanderthals contributed to evolution of the human brain's size. Lahn is currently working to contribute a better understanding of the widespread use of stem cells to the science world. His research on the microcephaly-associated gene, MCPH1 , led to the hypothesis that an archaic Homo sapiens lineage such as the Neanderthals might have contributed to the recent development of
4118-446: The most common form of microcephalin throughout the world except Sub-Saharan Africa ; this rapid spread suggests a selective sweep . However, scientists have not identified the evolutionary pressures that may have caused the spread of these mutations. This variant of the gene is thought to contribute to increased brain volume and may correlate with the incidence of tonal languages , though modern distributions of chromosomes bearing
4189-413: The nucleus. Splicing, followed by CPA, generate the final mature mRNA , which encodes the protein or RNA product. Many noncoding genes in eukaryotes have different transcription termination mechanisms and they do not have poly(A) tails. Many prokaryotic genes are organized into operons , with multiple protein-coding sequences that are transcribed as a unit. The genes in an operon are transcribed as
4260-431: The phosphate–sugar backbone spiralling around the outside, and the bases pointing inward with adenine base pairing to thymine and guanine to cytosine. The specificity of base pairing occurs because adenine and thymine align to form two hydrogen bonds , whereas cytosine and guanine form three hydrogen bonds. The two strands in a double helix must, therefore, be complementary , with their sequence of bases matching such that
4331-479: The possible source of this haplotype, the haplotype was not found in the individuals used to prepare the first draft of the Neanderthal genome. The research results began to attract considerable controversy in the science world. John Derbyshire wrote that as a result of the findings, "our cherished national dream of a well-mixed and harmonious meritocracy [...] may be unattainable." Richard Lewontin considers
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#17327868149124402-467: The strand of DNA like a train on a monorail, transcribing it into its messenger RNA form. This point brings us to our second important criterion: A true gene is one that is both transcribed and translated. That is, a true gene is first used as a template to make transient messenger RNA, which is then translated into a protein. This restricted definition is so common that it has spawned many recent articles that criticize this "standard definition" and call for
4473-461: The sugar ribose rather than deoxyribose . RNA also contains the base uracil in place of thymine . RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three- nucleotide sequences called codons , which serve as the "words" in the genetic "language". The genetic code specifies the correspondence during protein translation between codons and amino acids . The genetic code
4544-809: The term gemmule to describe hypothetical particles that would mix during reproduction. Mendel's work went largely unnoticed after its first publication in 1866, but was rediscovered in the late 19th century by Hugo de Vries , Carl Correns , and Erich von Tschermak , who (claimed to have) reached similar conclusions in their own research. Specifically, in 1889, Hugo de Vries published his book Intracellular Pangenesis , in which he postulated that different characters have individual hereditary carriers and that inheritance of specific traits in organisms comes in particles. De Vries called these units "pangenes" ( Pangens in German), after Darwin's 1868 pangenesis theory. Twenty years later, in 1909, Wilhelm Johannsen introduced
4615-436: The term gene , he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. This description prefigured Wilhelm Johannsen 's distinction between genotype (the genetic material of an organism) and phenotype (the observable traits of that organism). Mendel was also the first to demonstrate independent assortment , the distinction between dominant and recessive traits,
4686-412: The term "gene" (inspired by the ancient Greek : γόνος, gonos , meaning offspring and procreation) and, in 1906, William Bateson , that of " genetics " while Eduard Strasburger , among others, still used the term "pangene" for the fundamental physical and functional unit of heredity. Advances in understanding genes and inheritance continued throughout the 20th century. Deoxyribonucleic acid (DNA)
4757-560: The two published papers as "egregious examples of going well beyond the data to try to make a splash." Bruce Lahn maintains that the science of the studies is sound, and freely admits that a direct link between these particular genes and either cognition or intelligence has not been clearly established. Lahn is now engaging himself with other areas of study. Later studies have not found those gene variants to be associated with mental ability or cognition. Later genetic association studies by Mekel-Bobrov et al. and Evans et al. also reported that
4828-452: The world; for MCPH1, it is higher outside sub-Saharan Africa than inside). He has advocated the moral position that human genetic diversity should be embraced and celebrated as among humanity's great assets. Later studies did not find the ASPM and MCPH1 gene variants identified by Lahn to be associated with mental ability or cognition in modern populations, and the haplotype was not found in
4899-414: Was a Howard Hughes Medical Institute sponsored Investigator. His previous research specialized in human genetics and evolutionary genetics , especially human sex chromosome evolution and the genetic basis that underlies the evolutionary expansion of the human brain . Lahn's current research interests include stem cell biology and epigenetics . Bruce Lahn is a Chinese-born American scientist. He
4970-450: Was first suggested by Gregor Mendel (1822–1884). From 1857 to 1864, in Brno , Austrian Empire (today's Czech Republic), he studied inheritance patterns in 8000 common edible pea plants , tracking distinct traits from parent to offspring. He described these mathematically as 2 combinations where n is the number of differing characteristics in the original peas. Although he did not use
5041-430: Was shown to be the molecular repository of genetic information by experiments in the 1940s to 1950s. The structure of DNA was studied by Rosalind Franklin and Maurice Wilkins using X-ray crystallography , which led James D. Watson and Francis Crick to publish a model of the double-stranded DNA molecule whose paired nucleotide bases indicated a compelling hypothesis for the mechanism of genetic replication. In
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