Non-Mendelian Inheritance_bea784ebae8b049ca48eadf8073ca9e7.pdf

Non-Mendelian Inheritance FISH 147 (FISH GENETICS) https://wallpaperaccess.com/full/1195227.jpg Introduction Introduction Tancho Koi Introduction Between 1856-1863, Mendel chose pea plants as his subject for the hybridization experiment After conducting a monoh...

Non-Mendelian Inheritance FISH 147 (FISH GENETICS) https://wallpaperaccess.com/full/1195227.jpg Introduction Introduction Tancho Koi Introduction Between 1856-1863, Mendel chose pea plants as his subject for the hybridization experiment After conducting a monohybrid cross and dihybrid cross experiment in a pea plant, he found out about some of the factors which were being transferred to the offspring with utmost stability The two experiments later led to the formation of Mendel's Laws widely known as the Laws of Inheritance, which are: Law of Dominance Law of Segregation Law of Independent Assortment Non-Mendelian Inheritance Mendel’s work on inheritance became widely known, and biologists set out to verify his conclusions by using other organisms to conduct crosses Lucien Cuénot experimented with coat colors in mice and was among the first to show that Mendel’s principles applied to animals Pure-breeding gray mice crossed with pure-breeding white mice followed Mendelian inheritance His crosses of yellow mice suggested that yellow coat color was dominant over gray, but he was never able to obtain true-breeding yellow mice Crossed of two yellow mice resulted in yellow and gray mice in approximately a 3 : 1 ratio, suggesting that the yellow mice were heterozygous Non-Mendelian Inheritance In 1910, William Ernest Castle and his student Clarence Little solved the mystery of Cuénot’s unusual results Carried out a large series of crosses between two yellow mice and showed that the progeny appeared, not in the 3 : 1 ratio, but actually in a 2 : 1 ratio of yellow and nonyellow Recognized that the allele for yellow was lethal when homozygous, and thus all the yellow mice were heterozygous A cross between two yellow heterozygous mice produces an initial genotypic ratio of 1/4 YY, 1/2 Yy, and 1/4 yy, but the homozygous YY mice die early in development and do not appear among the progeny, resulting in a 2 : 1 ratio of Yy (yellow) to yy (nonyellow) in offspring Non-Mendelian Inheritance Non-Mendelian Inheritance does not follow the iconic Mendel's Laws and can be defined as any inheritance pattern that fails to follow one or more laws of Mendelian genetics Non-Mendelian traits are not determined by dominant or recessive alleles Can involve more than one gene leading to a complex pattern of inheritance Some traits exhibited blending where the organisms’ offspring had two separate traits from the parent, meaning that certain alleles were not dominant Can also be a result of issues in reproduction Types of Non-Mendelian Inheritance Incomplete Dominance As the name indicates, in this type of inheritance, a single trait isn’t fully dominant, so you’ll see resulting progeny with a mixed phenotype of a recessive and a dominant trait When the heterozygote has a phenotype intermediate between the phenotypes of the two homozygotes, the trait is said to display incomplete dominance Occurs when the phenotype of a heterozygote offspring is somewhere in between the phenotypes of both homozygous parents; a completely dominant allele does not occur The genotype of an organism with incomplete dominance can be determined from its phenotype Types of Non-Mendelian Inheritance Types of Non-Mendelian Inheritance Codominance Occurs when both alleles are expressed equally in the phenotype of the heterozygote Phenotype of the heterozygote is not intermediate between the phenotypes of the homozygotes; rather, the heterozygote simultaneously expresses the phenotypes of both homozygotes It’s almost like the dominant traits compete to be represented on the offspring’s phenotype, and they then reach a compromise - both the traits show up on the offspring Types of Non-Mendelian Inheritance Concept Checkpoint Which is an example of incomplete dominance and codominance? Types of Non-Mendelian Inheritance Multiple Allele Traits A trait which has more than just two types of alleles that can be inherited Traits controlled by a single gene with more than two alleles are called multiple allele traits An example is ABO blood type Our blood type refers to which of certain proteins called antigens (isoagglutinogens) are found on your red blood cells There are six possible ABO genotypes, because the three alleles, taken two at a time, result in six possible combinations Presence of antibodies against foreign ABO antigens means that successful bloodtransfusions are possible only between persons with certain compatible blood types Types of Non-Mendelian Inheritance Polygenic Traits A trait which is the result of many genes being expressed at one time Many traits in animals are controlled by more than one gene The alleles of each gene have a minor additive effect on the phenotype There are many possible combinations of alleles, especially if each gene has multiple alleles Types of Non-Mendelian Inheritance Sex-Linked Traits Some traits are carried on the sex chromosomes Women have XX and men have XY Usually X-linked If a trait is carried on the X chromosome, then the female have two of them and male would only have one Since the Y chromosome is much smaller than the X chromosome and carries fewer genes, Y-linked traits are relatively rare Examples of sex-linked traits in humans include color blindness, baldness and hemophilia Types of Non-Mendelian Inheritance Epigenetics Epigenetics refers to genetic factors that change an organism’s appearance or biological functions without changing the actual DNA sequence Gene expression changes, but the genes themselves don’t Environmental effects on phenotype At the molecular level, this refers to the addition or deletion of a methyl group to a DNA base, turning the gene on or off, or to packaging of the chromatin structure by silencing or opening regions of the genome by winding or unwinding the DNA around histones Types of Non-Mendelian Inheritance Epigenetics DNA Methylation Types of Non-Mendelian Inheritance Epigenetics Histone Modification Types of Non-Mendelian Inheritance Pleiotropy This refers to genes that affect more than one phenotypic trait Mutations in one gene results in problems not only in tissue or organ, which is how the gene’s pleiotropic effects were discovered The number of functions a gene has, which isn't only defined as the number of measured traits affected by a knockout, but also biochemically, for example, by the number of protein– protein interactors a gene has or the number of reactions it catalyzes Types of Non-Mendelian Inheritance Types of Non-Mendelian Inheritance Epistasis This refers to genes that affect the expression of other genes A modifier gene controls another gene Epistasis is like dominance, except that it occurs between different genes, rather than between different alleles for the same gene Not considered dominant, because it is not on the same gene, but will still override whatever gene it is modifying, whether it be underexpression, overexpression, or no expression at all