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Basic Genetics and Cell Cycle

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Gene: Today, a gene is recognized as a region of DNA that encodes a specific protein or particular type of RNA. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.14

Alleles: Alternative forms of a single gene. Leland Hartwell. Genetics from genes to genomes. 4th edition. G-1

Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. http://en.wikipedia.org/wiki/Chromatin

Chromosomes: The DNA molecules carrying the genes are assembled into chromosomes: organelles that package and manage the storage, duplication, expression, and evolution of DNA. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.2. Genome: The sum total of genetic information in a particular cell or organism.The human (Homo sapiens) genome is stored on 23 chromosome pairs and in the small mitochondrial DNA.

http://en.wikipedia.org/wiki/Human_genome Leland Hartwell. Genetics from genes to genomes. 4th edition. G-9. RNA: Like DNA, RNA has the capacity to store, replicate, mutate, and express information; like proteins, RNA can fold in three dimensions to produce molecules capable of catalysing the chemistry of life. RNA molecules, however, are intrinsically unstable. Thus it is probable that the more stable DNA took over the linear information storage and replication functions of RNA, while proteins, with their far greater capacity for diversity, pre-empted the functions derived from RNAs three-dimensional folding. With this division of labour, RNA became an intermediary in converting the information in DNA into the sequence of amino acids in protein. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.5 Exons and Introns: The protein-coding region of most genes is subdivided into as many as 10 or more small pieces (called exons), separated by DNA that does not code for protein (called introns). P.6 In eukaryotes, separated exons composing a single gene allow potential rearrangements and rapid diversification. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.7.

DNA duplication: Duplication of genes has allowed divergence of copies and the potential for evolution of new functions. P.7 Leland Hartwell. Genetics from genes to genomes. 4th edition. P.7. Heredity: the ways genes transmit physiological, anatomical, and behavioural traits from parents to offspring. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.13. Pure breeding lines: pure-breeding lines produce offspring carrying specific parental traits that remain constant from generation to generation. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.17.

Antagonistic pairs: Mendel called constant but mutually exclusive traits antagonistic pairs. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.17. [Note: Once Mendel had isolated pure-breeding lines for several sets of characteristics, he carried out a series of matings between individuals that differed in only one trait. P.19]

Mendels proposition: Mendel proposed that each individual possess two copies of each unit of inheritance. Today, we call these units of inheritance genes. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.20 Mendels law of segregation: Mendel proposed that the two copies of each gene in the parent separate (or segregate) so that each gamete receives only one allele for each trait. That is, two alleles for each gene separate (segregate) during gamete formation, and then unites at random, one from each parent, at fertilization. Leland Hartwell. Genetics from genes to genomes. 4th edition P.21 Law of independent assortment: The independent assortment of gene pairs during gamete formation states that the presence of a particular allele of one gene provides no information whatsoever about the allele of the second gene. P.25 That is, during gamete formation, different pairs of alleles segregate independently of each other. Leland Hartwell. Genetics from genes to genomes. 4th edition. P.26

Whether pure-breeding or hybrid? We can observe the appearance of the next generation. P.24 And for species that do not self-fertilize, we have to use testcrosses. Leland Hartwell. Genetics from genes to genomes. 4th edition P.24

Homozygous: Having two identical alleles for a given gene. Reece Campbell, Biology, 9th edition. G-17 Heterozygous: Having two different alleles for a given gene. Reece Campbell, Biology, 9th edition. G-17

Hybrid: Offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species. Reece Campbell, Biology, 9th edition. G-17

Genotype The term genotype may be used in two ways: 1. When the term genotype is used to refer to a gene, it is the particular pair of alleles that the individual happens to possess for that gene. 2. Genotype may also be used to refer to the entire set of all alleles that the individual happens to possess. Human genes and genomes by Leon Rosenberg, Diane Rosenberg.1st edition 2012. P.59 http://biomed.brown.edu/Courses/BIO48/5.Geno.Pheno.HTML http://bio.research.ucsc.edu/~barrylab/classes/animal_behavior/GENETIC.HTM

Trait = an observable characteristic Phenotype = trait value (the measured value of the trait)

[Note: The word phenotype and trait are used interexchangebly by some authors.] http://babcock.wisc.edu/sites/default/files/de/en/de_14.en.pdf http://www.mesacc.edu/~grens94401/MCC%20Website/BIO240/Course%20Notes/Mendel %20notes%20Chap%2011.pdf Adaptive Genetic Variation in the Wild By Timothy A. Mousseau. P.96 Genetics of Diabetes Mellitus p.8 Genetics: A conceptual approach. 2nd edition. Benjamin A. Pierce. G-14 Cross: The deliberate mating of two parental types of organisms in genetic analysis. http://www.ncbi.nlm.nih.gov/books/NBK21878/ Leland Hartwell. Genetics from genes to genomes. 4th edition. G-5

Monohyrbid Cross: A cross between two individuals that differ in one trait of particular interest. Leland Hartwell. Genetics from genes to genomes. 4th edition. G-14 Dihybrid Cross: A cross between two individuals that differ in two traits of particular interest. http://en.wikipedia.org/wiki/Dihybrid_cross Genetics: A conceptual approach. 2nd edition. Benjamin A. Pierce. G-5 first filial (F 1 ) generation progeny of the parental generation in a controlled series of crosses. single gene trait (Mendelian trait)- Trait controlled by a single gene. Polygenic trait: a trait controlled by multiple genes. Multifactorial: Both Mendelian and polygenic traits can also be multifactorial, which means they are influenced by the environment (multifactorial traits are also called complex traits). Pure polygenic traitsthose not influenced by the environmentare very rare. Testcrosses: Testcross can be used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait. It is a mating in which an individual with genotype Y- mates with an individual with genotype yy. If the dominant phenotype in question derives from a homozygous YY genotype, all the offspring of the testcross will show the dominant phenotype. But if the dominant phenotype in question derives from a heterozygous Yy genotype, then of the progency is expected to show a different phenotype (recessive). Leland Hartwell. Genetics from genes to genomes. 4th edition P.24

Single-Gene Traits: Although many human traits clearly run in families, most do not show a simple Mendelian pattern of inheritance. This is because a lot of human traits are influenced by more than one gene. In contrast, single-gene traits in people usually involve an abnormality that is disabling or life threatening. Examples are the progressive mental retardation and other neurological damage of Huntington disease and the clogged lungs and potential respiratory failure of cystic fribrosis. P.30 Traits produced by complex interactions between genes and between genes and the environment, extended rather than contradicted Mendels laws of inheritance. p.35 If the traits under analysis behaved as predicted by Mendels laws (i.e. Mendels 3:1 phenotypic ratio), then they were assumed to be determined by a single gene with alternative dominant and recessive alleles. Many traits, however, did not behave in this way. For some, no definitive dominance and recessiveness could be observed. Other traits turned out to be multifactorial, that is, determined by two or more genes, or by the interaction of genes with the environment. Leland Hartwell. Genetics from genes to genomes. 4th edition P.43

Pedigree: A family history, known as pedigree, is an orderly diagram of a familys relevant genetic features. P.31 Mode of inheritance from pedigree: To reach a conclusion about the mode of inheritance of a family trait (dominant/recessive), geneticists must use a pedigree that supplies sufficient information. Several kinds of additional information could help resolve this uncertainty. Human geneticists would particularly want to know the frequency at which the trait in question is found in the population from which the family came. If the trait is rare in the population, then the allele giving rise to the trait should also be rare, and the most likely hypothesis would require that the fewest genetically unrelated people carry the allele. p.31

Vertical pattern of inheritance: Vertical pattern of inheritance in where everyone who develops the disease has at least one parent who shows the trait. If you trace back through the ancestors of any affected individual, you would see at least one affected person in each generation, giving a continuous line of family members with the disease. When a disease is rare in the population as a whole, a vertical pattern is strong evidence that a dominant allele causes the trait. The alternative would require that many unrelated people carry a rare recessive allele. p.32 [Note: In

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