Mendelian+Genetics

=__Mendelian Genetics__= //by Ashley Collman//

//My scientific studies have afforded me great gratification; and I am convinced that it will not be long before the whole world acknowledges the results of my work.// - Gregor Mendel

Related activities

 * Lab 7
 * Ch 14 outline
 * Book Problems: Page 259
 * I am going to go crazy and do all of the objectives as we were not assigned any for this chapter.

Objectives

 * Mendel brought an experimental and quantitative approach to genetics: //science as a process//
 * By the law of segregation, the two alleles for a character are packaged in seperate gametes
 * By the law of independent assortment, each pair of alleles segregates into gametes independently
 * Mendelian inheritance reflects the rules of probability
 * Mendel discovered the particulate behavior of genes: //a review//
 * The relationship between genotype and phenotype is rarely simple
 * Pedigree analysis reveals Mendelian patterns in human inheritance
 * Many human disorders follow Mendelian patterns of inheritance
 * Technology is providing new tools for genetics testing and counsling

Vocabulary

 * [|character]
 * [|trait]
 * true-breeding - breeding a plant that is not a hybrid.
 * [|hybridization]
 * [|monohybrid cross]
 * [|P generation]
 * [|F1 generartion]
 * [|F2 generation]
 * [|alleles]
 * [|dominant allele]
 * [|recessive allele]
 * [|law of segregation]
 * [|homozygous]
 * [|heterozygous]
 * [|phenotype]
 * [|genotype]
 * [|dihybrid cross]
 * [|incomplete dominance]
 * [|complete dominance]
 * [|codominance]
 * [|pleitropy]
 * [|polygenic inheritance/quantitative characters]
 * norm of reaction -The range of phenotypic possiblities over which there may be a variation due to environment
 * [|pedigree]
 * carriers
 * Tay-Sachs disease - recessively aquired disease
 * Sickle Cell disease - recessively acquired disease
 * [|Huntington's disease]
 * [|amniocentesis]
 * chronic villus sampling (CVS)- Alternate technique to fetal testing in which the physician suctions off a small amount of feta tissue from the placenta.

Important Content
Obj 1: __Mendel brough an experimental and quantitative approach to genetics: //science as a process//__ Obj 2:__By the Law of segregation, the two alleles for a character are packaged in seperate gametes__ Obj 3__:By the law of independent assortment, each pair of alleles segregates into gametes independently__
 * Mendel chose to breed peas because they had a characters (such as flower color) that produced a variety of traits ( purple or white flower color) and therefore could be observed through heredity.
 * Mendel himself fertilized the eggs of the pea plants and therefore had control over heredity.
 * He tracked only characters that could be one or the other not a mix. (ex: purple of white: not more purple or less white)
 * Followed traits for two to three generations which led him to deiscover the basic patterns of inheritance.
 * For flower color there were three different arragenments of alleles possible. Either a pea plant could have one purple allele and one white allele, or two of either purple or white.
 * In genetics there is a dominant allele and a recessive allele. In a hybrid cross (purple x white) the F1 generation will have all purple flowers, but since they are now hybrids (have one allele for purple and one for white), when they mate again they produce the recessive trait 1/4 times because there is a one and four chance that the F2 generation will receive 2 white alleles from their parents.
 * This not just happened in color but in various other characters such as pea smoothness (smooth or wrinkled).
 * Law of segregation: 1. Alternative versions of genes (different alleles) account for variations in inherited characters. 2. For each character, an organism inherits two alleles from each parent. 3. If the two alles differ, then one, the dominant allele, is fully expressed in the organisms appearance; the other, the recessive allele, has no noticeable effect on the organisms appearance. 4. The two alleles for each character segragate during gamete production.
 * Testcrosses determine the possible genotypes a generation will have by crossing the parents in a test like problem.
 * A di-hybrid cross can determine whether two traits are independent of each other.
 * By doing a di-hybrid cross on pea plants with two characters, pea smoothness and pea color, found that the two traits are not dependent of each other and are inherited the same as all other traits. No two alleles are grouped together.

Obj 4__:Mendelian inheritance reflects the rules of probability__
 * The Rule of Multiplication determines whether the chance of two or more in dependent events will occur together in a specific combination.
 * The Rule of Addition: the probability of an event that can occur in two or more different ways is the sum of the seperate probabilities of those two ways.

Obj 5__:Mendel discovered the particulate behavior of genes: //a review//__
 * The larger the sample size the closer the results will be to the expected.

Obj 6__:The relationship between genotype and phenotype is rarely simple__
 * The combination of alleles does not always render a black and white answer for the phenotype. In the case of pea flower color, they could be either purple or white, but in other cases domincance can be incomplete, complete, or co dominant. In some other cases there can be multiple alleles.
 * Incomplete Dominance: When neither allele is dominant. The hybrids have a mix while purebreeds have one distinct feature. (ex: Snap dragons)
 * Codominance: When both alleles are dominant. In this case hybrids have both alleles present while purebreeds have one single allele appear.
 * Multiple alleles: When there are multiple alleles available. This occurs in blood where humans can have either O, A, B, or AB. A persons blood may have the one carbohydrate substance ( A or B), both (AB), or none.
 * Pleitropy is the ability for a gene to have multiple phenotypic effects. (Ex: Sickle-cell can effect the body in many ways and cause multiple symptoms.)
 * Epistasis: A gene at one locus determines the expression of a gene at another locus. ( ex: mice fur coloring )
 * Polygenic Inheritance: You will have to read the book for this one because I can not explain it. I do remember distinctly that Miss Beauchemin said the example was bad. This is on page 250.
 * Phenotype depends on environemnt as well as on genes. ( Ex: identical twins develop phenotypic differences as a result of their unique experiences like nutrition, sun tanning, etc.)

Obj 7__:Pedigree analysis reveals Mendelian patterns in human inheritance__
 * Pedigrees trace genetic inheritance on a family tree
 * Pedigrees can be used to determine the exact allelic combinations for each member of the tree.

Obj 8__:Many human disorders follow Mendelian patterns of inheritance__
 * Recessively Inherited Disorders: Ex: Cystic Fibrosis, Tay- Sachs disease, and Sickle-Cell disease.
 * Dominantly Inherited Disorders: Huntington's Disease and dwarfism.
 * Multifactorial Disorders: Heart Disease, alcoholism, and certain mental illnesses. It's a combination of lifestyle and genes.

Obj 9__:Technology is providing new tools for genetics testing and counsling__
 * Genetic disorders can be detected at birth by simple tests that are now routine.
 * Fetal Testing can test to see if the baby can have a disease.