* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Genetics
Medical genetics wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Neocentromere wikipedia , lookup
Human genetic variation wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Frameshift mutation wikipedia , lookup
Y chromosome wikipedia , lookup
Oncogenomics wikipedia , lookup
Genetic drift wikipedia , lookup
Public health genomics wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Minimal genome wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Genome evolution wikipedia , lookup
Gene expression profiling wikipedia , lookup
Gene expression programming wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Population genetics wikipedia , lookup
Genomic imprinting wikipedia , lookup
Genetic engineering wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
X-inactivation wikipedia , lookup
History of genetic engineering wikipedia , lookup
Point mutation wikipedia , lookup
Genome (book) wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Quantitative trait locus wikipedia , lookup
SC Biology Standard B-4.6-4.9- The students will be able to predict inherited traits by using the principles of Mendelian Genetics, summarize the chromosome theory of inheritance and compare the consequences of mutations in body cells. The students will be able to exemplify ways that introduce new genetic characteristics into an organism. Study of patterns of inheritance and variation Genes control each trait of a living thing by controlling the formation of an organism’s proteins All cells are diploid- 2 sets of chromosomes-except gametes. This means each cell contains two genes for each trait- one from mom and one from dad. The two genes may be the same form or they may be different. Different forms of a gene are called alleles The two alleles segregate during Meiosis II Principle of Dominance states that some alleles are dominant whereas others are recessive If a dominant allele is present, that trait will always show An organism with a recessive trait will only show if the dominant allele is not present Since organisms receive one gene for a chromosome pair from each parent, they can be heterozygous or homozygous. When an organism has 2 identical alleles for a particular trait- it is homozygous for that trait This can be two dominant alleles or two recessive alleles When an organism has two different alleles for a trait, it is heterozygous- one is dominant and one is recessive Genotype- genetic makeup of an organism- reveals the type of alleles an organism has inherited for a particular trait. Usually represented by a letter. Capital letter= dominant allele Lower case letter= recessive allele Examples: TT= homozygous dominant Tt= heterozygous dominant tt= homozygous recessive Phenotype- physical characteristics- the way the traits are expressed TT=tall Tt= tall tt= short Explains how alleles are separated during Meiosis. Each gamete receives one of two alleles that the parent carries for each trait During fertilization (sperm + egg) each parent donates one copy of each gene to the offspring States that the segregation of the alleles of one trait does not affect the segregation of the alleles of another trait. Genes on separate chromosomes separate independently during meiosis Holds true for ALL genes unless the genes are linked. If this is the case, the genes are too close on the same chromosome to segregate independently Used to predict inherited traits Punnett squares can be used to predict the probable genetic combinations in the offspring Monohybrid cross looks at one trait Punnett square represents the probable outcome and the ratio Dihybrid cross examines the inheritance of two different traits Continued: Dihybrid crosses: studies inheritance of 2 different alleles. The alleles independently assort resulting in offspring possibilities. KNOW- 1-3, 1-4, 2-3, 2-4 This will help you know how to independently assort and get your possible gametes. Multiple alleles- blood types. 3 alleles exist for blood types- only 2 are inherited. Polygenic traits- traits controlled by 2 or more genes. often result in a variety of phenotypes. Example = skin color More: Mendel’s Principles of Genetics includes segregation, independent assortment, and dominance, but couldn’t explain the more complex theories- polygenic traits, inheritance patterns and genetic variation Chromosome theory of Inheritance states that genes are located on chromosomes and that the behavior of chromosomes during Meiosis accounts for inheritance patterns. Mendel’s theories support this. New since Mendel Gene linkage- simply means that genes that are located on the same chromosome will be inherited together. ( exception to Mendel’s independent assortment because linked genes do not segregate) Crossing over- process in which alleles in close proximity to each other on homologous chromosomes are exchanged= new combination of alleles Incomplete dominance- when one allele is not completely dominant over another. Phenotype is expressed as a blend. Codominance- when both alleles for a gene are expressed completely. Phenotype shows both alleles More New since Mendel: Multiple alleles- can exist for a particular trait even though only 2 are inherited. Example- blood types A, B, O which result in 4 different blood types. Polygenic traits- traits that are controlled by 2 or more gene. Often shows great variety of phenotypes. Example- skin color Sex linked traits- genes that are carried on either the x or y chromosome. Mendel didn’t explain sex linked traits. Females = XX, Males= Xy Y chromosome carries very few genes X chromosome has many genes that affect many traits Sex linked continued: If a gene is linked on the X chromosome- females will inherit the gene as they do all others (dom/rec) Male offspring will inherit the gene on their X chromosome but not on the Y. Since males have only one X, they express their allele whether it is dominant or recessive. There is no second allele to mask the effects of the other allele. Color blindness and Hemophilia are sex linked. In rare cases, the female can be affected Pedigree: Is a chart to show inheritance pattern (trait, disease, disorder) within a family throughout multiple generations. Through the use of a pedigree chart and key, the genotype and phenotype of the family members and the genetic characteristics (dominant/recessive, sexlinked) of the trait can be tracked. Family with a dominant autosomal genetic trait In generation III, the offspring of all of the females from generation II have a 50/50 chance of passing a traitcarrying gene to their children. If the males receive the trait-carrying gene, they will express the trait. If the females receive the trait-carrying gene, they will again be carriers. A mutation is the alteration of an organism’s DNA. Mutations can range from a change in one base pair to the insertion or deletion of large segments of DNA. Mutations can result from a malfunction during the process of meiosis or from exposure to a physical or a chemical agent, a mutagen. Most mutations are automatically repaired by the organism’s enzymes and therefore have no effect. However, when the mutation is not repaired, the resulting altered chromosome or gene structure is then passed to all subsequent daughter cells of the mutant cell, which may have adverse or beneficial effects on the cell, the organism, and future generations. If the mutant cell is a body cell (somatic cell), the daughter cells can be affected by the altered DNA, but the mutation will not be passed to the offspring of the organism. Body cell mutations can contribute to the aging process or the development of many types of cancer. If the mutant cell is a gamete (sex cell), the altered DNA will be transmitted to the embryo and may be passed to subsequent generations. Gamete cell mutations can result in genetic disorders. If the mutation affects a single gene, it is known as a gene mutation. For example, the genetic basis of sickle-cell disease is the mutation of a single base pair in the gene that codes for one of the proteins of hemoglobin. Other examples of genetic disorders are Tay-Sachs disease, Huntington’s disease, cystic fibrosis, or albinism. If the mutation affects a group of genes or an entire chromosome, it is know as a chromosomal mutation. Nondisjunction results in an abnormal number of chromosomes, usually occurring during meiosis. Examples of abnormalities in humans due to nondisjunction of sex chromosomes are Klinefelter’s syndrome (male) and Turner’s syndrome (female). Examples of abnormalities in humans due to nondisjunction of autosomal chromosomes include Down syndrome. In some cases mutations are beneficial to organisms. Beneficial mutations are changes that may be useful to organisms in different or changing environments. These mutations result in phenotypes that are favored by natural selection and increase in a population.