* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Patterns Of Inheritance
Neuronal ceroid lipofuscinosis wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Epigenetics of diabetes Type 2 wikipedia , lookup
Pathogenomics wikipedia , lookup
X-inactivation wikipedia , lookup
Genetic engineering wikipedia , lookup
Public health genomics wikipedia , lookup
Genetic drift wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Gene therapy wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Genome evolution wikipedia , lookup
Gene desert wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Gene nomenclature wikipedia , lookup
Genetically modified crops wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Genome (book) wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Genomic imprinting wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
Gene expression programming wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Gene expression profiling wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
History of genetic engineering wikipedia , lookup
Designer baby wikipedia , lookup
Microevolution wikipedia , lookup
Patterns of Inheritance Chapter 12 Early Ideas of Heredity Before the 20th century, 2 concepts were the basis for ideas about heredity: -heredity occurs within species -traits are transmitted directly from parent to offspring This led to the belief that inheritance is a matter of blending traits from the parents. 2 Early Ideas of Heredity Botanists in the 18th and 19th centuries produced hybrid plants. When the hybrids were crossed with each other, some of the offspring resembled the original strains, rather than the hybrid strains. This evidence contradicted the idea that traits are directly passed from parent to offspring. 3 1 Early Ideas of Heredity Gregor Mendel -chose to study pea plants because: 1. other research showed that pea hybrids could be produced 2. many pea varieties were available 3. peas are small plants and easy to grow 4. peas can self-fertilize or be crossfertilized 4 Early Ideas of Heredity Mendel’s experimental method: 1. produce true-breeding strains for each trait he was studying 2. cross-fertilize true-breeding strains having alternate forms of a trait -perform reciprocal crosses as well 3. allow the hybrid offspring to self-fertilize and count the number of offspring showing each form of the trait 5 6 2 7 Monohybrid Crosses F2 plants exhibited both forms of the trait in a very specific pattern: ¾ plants with the dominant form ¼ plant with the recessive form The dominant to recessive ratio was 3 : 1. Mendel discovered the ratio is actually: 1 true-breeding dominant plant 2 not-true-breeding dominant plants 1 true-breeding recessive plant 8 9 3 Monohybrid Crosses gene: information for a trait passed from parent to offspring alleles: alternate forms of a gene homozygous: having 2 of the same allele heterozygous: having 2 different alleles 10 Monohybrid Crosses genotype: total set of alleles of an individual PP = homozygous dominant Pp = heterozygous pp = homozygous recessive phenotype: outward appearance of an individual 11 Monohybrid Crosses Principle of Segregation Two alleles for a gene segregate during gamete formation and are rejoined at random, one from each parent, during fertilization. 12 4 Monohybrid Crosses Some human traits are controlled by a single gene. -some of these exhibit dominant inheritance -some of these exhibit recessive inheritance Pedigree analysis is used to track inheritance patterns in families. 13 14 15 5 16 Testcross Testcross: a cross used to determine the genotype of an individual with dominant phenotype -cross the individual with unknown genotype (e.g. P_) with a homozygous recessive (pp) -the phenotypic ratios among offspring are different, depending on the genotype of the unknown parent 17 18 6 Extensions to Mendel Mendel’s model of inheritance assumes that: -each trait is controlled by a single gene -each gene has only 2 alleles -there is a clear dominant-recessive relationship between the alleles Most genes do not meet these criteria. 19 Extensions to Mendel Polygenic inheritance occurs when multiple genes are involved in controlling the phenotype of a trait. The phenotype is an accumulation of contributions by multiple genes. These traits show continuous variation and are referred to as quantitative traits. For example – human height 20 21 7 Extensions to Mendel Pleiotropy refers to an allele which has more than one effect on the phenotype. This can be seen in human diseases such as cystic fibrosis or sickle cell anemia. In these diseases, multiple symptoms can be traced back to one defective allele. 22 Extensions to Mendel Incomplete dominance: the heterozygote is intermediate in phenotype between the 2 homozygotes. Codominance: the heterozygote shows some aspect of the phenotypes of both homozygotes. 23 24 8 Extensions to Mendel The human ABO blood group system demonstrates: -multiple alleles: there are 3 alleles of the I gene (IA, IB, and i) -codominance: IA and IB are dominant to i but codominant to each other 25 26 Extensions to Mendel The expression of some genes can be influenced by the environment. for example: coat color in Himalayan rabbits and Siamese cats -an allele produces an enzyme that allows pigment production only at temperatures below 30oC 27 9 Extensions to Mendel 28 Extensions to Mendel The products of some genes interact with each other and influence the phenotype of the individual. Epistasis: one gene can interfere with the expression of another gene 29 30 10