生物专业英语 第十一章
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2013-5-30 10
Transvection
• Transvection is an epigenetic phenomenon that results from an interaction between an allele on one chromosome and the corresponding allele on the homologous chromosome. Transvection can lead to either gene activation or repression. Formally, it can also occur between nonallelic regions of the genome as well as regions of the genome that are not transcribed.
2013-5-30 6
• In biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name -genetics. • It refers to functionally relevant modifications to the genome that do not involve a change in the nucleotide sequence. • Examples of such changes are DNA methylation and histone modification, both of which serve to regulate gene expression without altering the underlying DNA sequence.
2013-5-30 7
• These changes may remain through cell divisions for the remainder of the cell's life and may also last for multiple generations. However, there is no change in the underlying DNA sequence of the organism; instead, non-genetic factors cause the organism's genes to behave differently. There are however objections to the use of term epigenetic to describe chemical modification of histone since there is little evidence that these modifications are heritable.
2013-5-30 4
• These studies normally compare the DNA of two groups of participants: people with the disease (cases) and similar people without (controls). Each person gives a sample of DNA, from which millions of genetic variants are read using SNP arrays. • If one type of the variant (one allele) is more frequent in people with the disease, the SNP is said to be "associated" with the disease. • The associated SNPs are then considered to mark a region of the human genome which influences the risk of disease.
2013-5-30 5
Epigenetics
• The study of the processes involved in the unfolding development of an organism. This includes phenomena such as X chromosome inactivation in mammalian females, and gene silencing within an organism. • The study of heritable changes in gene function that occur without a change in the sequence of nuclear DNA. This includes the study of how environmental factors affecting a parent can result in changes in the way genes are expressed in the offspring.
2013-5-30
3
Genome-Wide Association Studies
• In genetic epidemiology, a genome-wide association study (GWA study, or GWAS), also known as whole genome association study (WGA study, or WGAS), is an examination of many common genetic variants in different individuals to see if any variant is associated with a trait. • GWAS typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major diseases.
2013-5-30 9
Bookmarking
• In genetics and epigenetics, bookmarking is a biological phenomenon believed to function as an epigenetic mechanism for transmitting cellular memory of the pattern of gene expression in a cell, throughout mitosis, to its daughter cells. This is vital for maintaining the phenotype in a lineage of cells so that, for example, liver cells divide into liver cells and not some other cell type.
2013-5-30 2
Biblioteka Baidu
• Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viruses and bacteria, through plants and domestic animals, to humans (as in medical genetics).
2013-5-30
8
• Specific epigenetic processes include paramutation, bookmarking, imprinting, gene silencing, X chromosome inactivation, position effect, reprogramming, transvection, maternal effects, the progress of carcinogenesis, many effects of teratogens, regulation of histone modifications and heterochromatin, and technical limitations affecting parthenogenesis and cloning.
2013-5-30 12
2013-5-30
13
Glossary
• Allele [ə‘li:l] n 等位基因; 基因等位
• dihybrid cross 双因子杂种杂交；双因子杂 合子杂交 • Dominant [‘dɔminənt] a. 占优势的；n. 显性
• Gene [dʒi:n] n. 基因
Lesson Four
Foundations of Genetics
2013-5-30
1
• Genetics (from Ancient Greek , "genitive" and that from , "origin"), a discipline of biology, is the science of genes, heredity, and variation in living organisms. • Genetics deals with the molecular structure and function of genes, gene behavior in context of a cell or organism (e.g. dominance and epigenetics), patterns of inheritance from parent to offspring, and gene distribution, variation and change in populations, such as through Genome-Wide Association Studies.
2013-5-30 11
• Epigenetic research uses a wide range of molecular biologic techniques to further our understanding of epigenetic phenomena, including chromatin immunoprecipitation (together with its large-scale variants ChIP-on-chip and ChIP-Seq), fluorescent in situ hybridization, methylationsensitive restriction enzymes, DNA adenine methyltransferase identification (DamID) and bisulfite sequencing. Furthermore, the use of bioinformatic methods is playing an increasing role (computational epigenetics).
Transvection
• Transvection is an epigenetic phenomenon that results from an interaction between an allele on one chromosome and the corresponding allele on the homologous chromosome. Transvection can lead to either gene activation or repression. Formally, it can also occur between nonallelic regions of the genome as well as regions of the genome that are not transcribed.
2013-5-30 6
• In biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name -genetics. • It refers to functionally relevant modifications to the genome that do not involve a change in the nucleotide sequence. • Examples of such changes are DNA methylation and histone modification, both of which serve to regulate gene expression without altering the underlying DNA sequence.
2013-5-30 7
• These changes may remain through cell divisions for the remainder of the cell's life and may also last for multiple generations. However, there is no change in the underlying DNA sequence of the organism; instead, non-genetic factors cause the organism's genes to behave differently. There are however objections to the use of term epigenetic to describe chemical modification of histone since there is little evidence that these modifications are heritable.
2013-5-30 4
• These studies normally compare the DNA of two groups of participants: people with the disease (cases) and similar people without (controls). Each person gives a sample of DNA, from which millions of genetic variants are read using SNP arrays. • If one type of the variant (one allele) is more frequent in people with the disease, the SNP is said to be "associated" with the disease. • The associated SNPs are then considered to mark a region of the human genome which influences the risk of disease.
2013-5-30 5
Epigenetics
• The study of the processes involved in the unfolding development of an organism. This includes phenomena such as X chromosome inactivation in mammalian females, and gene silencing within an organism. • The study of heritable changes in gene function that occur without a change in the sequence of nuclear DNA. This includes the study of how environmental factors affecting a parent can result in changes in the way genes are expressed in the offspring.
2013-5-30
3
Genome-Wide Association Studies
• In genetic epidemiology, a genome-wide association study (GWA study, or GWAS), also known as whole genome association study (WGA study, or WGAS), is an examination of many common genetic variants in different individuals to see if any variant is associated with a trait. • GWAS typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major diseases.
2013-5-30 9
Bookmarking
• In genetics and epigenetics, bookmarking is a biological phenomenon believed to function as an epigenetic mechanism for transmitting cellular memory of the pattern of gene expression in a cell, throughout mitosis, to its daughter cells. This is vital for maintaining the phenotype in a lineage of cells so that, for example, liver cells divide into liver cells and not some other cell type.
2013-5-30 2
Biblioteka Baidu
• Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viruses and bacteria, through plants and domestic animals, to humans (as in medical genetics).
2013-5-30
8
• Specific epigenetic processes include paramutation, bookmarking, imprinting, gene silencing, X chromosome inactivation, position effect, reprogramming, transvection, maternal effects, the progress of carcinogenesis, many effects of teratogens, regulation of histone modifications and heterochromatin, and technical limitations affecting parthenogenesis and cloning.
2013-5-30 12
2013-5-30
13
Glossary
• Allele [ə‘li:l] n 等位基因; 基因等位
• dihybrid cross 双因子杂种杂交；双因子杂 合子杂交 • Dominant [‘dɔminənt] a. 占优势的；n. 显性
• Gene [dʒi:n] n. 基因
Lesson Four
Foundations of Genetics
2013-5-30
1
• Genetics (from Ancient Greek , "genitive" and that from , "origin"), a discipline of biology, is the science of genes, heredity, and variation in living organisms. • Genetics deals with the molecular structure and function of genes, gene behavior in context of a cell or organism (e.g. dominance and epigenetics), patterns of inheritance from parent to offspring, and gene distribution, variation and change in populations, such as through Genome-Wide Association Studies.
2013-5-30 11
• Epigenetic research uses a wide range of molecular biologic techniques to further our understanding of epigenetic phenomena, including chromatin immunoprecipitation (together with its large-scale variants ChIP-on-chip and ChIP-Seq), fluorescent in situ hybridization, methylationsensitive restriction enzymes, DNA adenine methyltransferase identification (DamID) and bisulfite sequencing. Furthermore, the use of bioinformatic methods is playing an increasing role (computational epigenetics).