Mendelian Exceptions

Mendel’s Principles Revisited Inheritance of biological _____________ is determined by individual units known as ______. During sexual reproduction, genes are passed from parents to _________. Two or more forms of the gene for a single _____ exist, some forms of the gene may be _________ and others may be recessive. characteristics genes offspring trait dominant

Mendel’s Principles Revisited Organisms typically have ____copies of each gene, (one from each _______) An organism’s _____ of genes (2 alleles) are segregated from each other when ________ are formed. Alleles for different ______ usually segregate _____________ of one another. (through meiosis) (Law of Independent Assortment) two parent pair gametes genes independently

Independent Assortment in Peas __ Round yellow __ Round green __ Wrinkled yellow __ Wrinkled green 9 3 3 1

Incomplete Dominance dominant traits heterozygous red pink white In incomplete dominance, neither allele is __________ so there is a blending of ______ when two different alleles for the same trait occur together. Colors blend together (______________ individuals = 3rd phenotype) dominant traits heterozygous red pink white

Incomplete Dominance RR WW RW In Four O’ Clocks, if you cross a red _____ (which is always pure) with a white _____ (that is also always pure) , you get a pink _____ (which is always hybrid / heterozygous RR WW RW RW RW RW RW

Incomplete Dominance RR BB RB In another flower, if red ____ and blue ____ flowers are crossed, they produce a 3rd purple ____ flower What would be the genotype ratio and phenotype ratio if you crossed two purple flowers? BB RB http://www.gwu.edu/~darwin/BiSc150/One/rose.GIF

Incomplete Dominance Cross of two purple flowers ____ X ____ What are gamete possibilities? genotype ratio 1RR : 2RB : 1BB phenotype ratio 1red : 2 purple : 1 blue Can you have a heterozygous red or hybrid blue flower? ___ RB RB R B RR RB R red purple http://www.gwu.edu/~darwin/BiSc150/One/rose.GIF BB RB B purple blue no

Familial Hypercholesterolemia FF = cholesterol about 200 mg/dL Ff = cholesterol about 400 mg/dL ff = cholesterol about 800 mg/dL Ff have heart attacks in 20’s ff have heart attacks as children What type of inheritance is this?

Familial Hypercholesterolemia F is allele for receptors in the liver that remove excess cholesterol from the blood FF makes enough receptors removes the right amount of cholesterol Ff only makes half the needed receptors ff makes no receptors This trait represents incomplete dominance

Problem Tom is a 21 year old college student. His father died of a heart attack at age 25. Tom is a vegetarian and eats no junk food. He has a fasting cholesterol of 435. Tom’s wife, Mary, has a fasting cholesterol of 177. They are contemplating having children What is the chance they will have a child with abnormal cholesterol?

FF = 200 Ff = 400 ff = 800 F F F FF Ff f 50% chance for abnormal cholesterol

California Court Case 1946 the California supreme court ruled that Charlie Chaplin was the biological father of child he claimed was not his. His defense was that the baby had type B blood. He had type A and the woman who sued him had type O (These may not be the actual blood types, but it illustrates the point) Was the court correct?

O A AO OO AA, AO = Type A BB, BO = Type B AB = Type AB OO = Type O O O The judge should take a course in genetics!

Codominance alleles Both _______ contribute to the phenotype of the organism by showing up simultaneously (at the same time) in heterozygous individuals. In cattle and horses, if you cross a pure ____ (RR) with a pure ______ (WW), you get (RW) which produces the color _____. red white roan

Codominance phenotype These cattle or horses actually have both red and white hairs intermixed, or are spotted. Roan is a third ___________. If you cross a roan with a white… phenotype R W http://www.ccs.k12.in.us/chsteachers/Amayhew/Biology%20Notes/beyond%20dominance%20notes_files/image004.jpg RW WW W roan white RW WW W roan white

Codominance Andalusian chickens also show this pattern of inheritance. If you cross a black (BB) chicken With a white (WW) chicken You get black+white speckled (BW) chicken

Multiple Alleles two two two trait In this pattern of inheritance, the genes have more than _____ alleles controlling them and are therefore said to have multiple alleles. No individual has more than _____ alleles, but there are more than _____ possible alleles in a population, so a ______ will be expressed in more than two forms. two two two trait

Multiple Alleles Blood type in humans is an example of this inheritance pattern. The ______ different blood groups: A, B, O, and AB Are produced by ______ different alleles: A, B, and O Phenotype Genotype A AA or AO B BB or BO AB AB only O OO only four three

Multiple Alleles Examples of Blood type crosses

Multiple Alleles Blood Groups Antigen on Red Blood Cell Safe Transfusions Phenotype (Blood Type Genotype To From

Multiple Alleles rabbit The example of _______ hair color, which has at least four different alleles, is seen in these different Rex rabbits. rabbit

Polygenic Traits Traits controlled by two or more genes Show a wide range of phenotypes The phenotype is produced by the interaction of more than ________ of genes. http://anthro.palomar.edu/adapt/images/skin_color_range.jpg http://www.sciam.com/media/inline/0002E7CA-F27B-13A1-AFAA83414B7FFE9F_1.gif 1 pair

Polygenic Traits polygenic many eye skin These are called ___________ traits, which means “having _______ genes”. In humans, _____ color, _____ color, many eye skin http://anthro.palomar.edu/adapt/images/skin_color_range.jpg http://www.sciam.com/media/inline/0002E7CA-F27B-13A1-AFAA83414B7FFE9F_1.gif

Polygenic Traits polygenic many eye skin hair These are called ___________ traits, which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color many eye skin hair http://anthro.palomar.edu/adapt/images/skin_color_range.jpg http://www.sciam.com/media/inline/0002E7CA-F27B-13A1-AFAA83414B7FFE9F_1.gif

Polygenic Traits polygenic many eye skin hair controlled These are called ___________ traits, which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color are just a few of the many traits __________ by many genes. many eye skin hair http://anthro.palomar.edu/adapt/images/skin_color_range.jpg http://www.sciam.com/media/inline/0002E7CA-F27B-13A1-AFAA83414B7FFE9F_1.gif controlled

James Bond Height Chart Polygenic Traits Sometimes the combination of the different genes results in continuous __________ of these traits. The combined size of all the ______ parts from head to foot, determines the _______ of the person. variation body http://anthro.palomar.edu/adapt/images/skin_color_range.jpg http://www.sciam.com/media/inline/0002E7CA-F27B-13A1-AFAA83414B7FFE9F_1.gif height

Epistasis One gene affects the expression of another H allele h allele Produces protein for A and B antigens to attach to red blood cells h allele Protein has wrong shape and cannot attach to A and B antigens A and or B antigens will fall off. hh genotype + genotype for A,B or AB blood will have type O blood Recessive epistasis in Labrador Retrievers

Penetrance 100% Less than 100% Everyone with the allele for a trait will have the trait Less than 100% Some individuals with the allele will not express the trait Due to interactions of other genes

Incomplete Penetrance for Polydactylism Adam Polydactyle Normal Ben Joe Bill Don Bill did not express polydactylism Frank Mark John Tony

Expressivity Symptoms vary in intensity in different people Due to gene interaction Number of extra digits varies in people with polydactylism

Phenocopy Trait caused by the environment that is similar to an inherited trait Thalidomide causes symptoms of inherited phocomelia

Deafness May be caused by 132 different recessive genes Man has aa for deafness on chromosome 1 & BB for normal hearing on chromosome 5 Woman has bb for deafness on chromosome 5 & AA for normal hearing on chromosome 1 What is the chance their children will inherit deafness?

a b Bb A Aa B AA = Normal BB = Normal Aa = normal Bb = normal aa = deaf BB = Normal Bb = normal bb = deaf a a b b Bb A Aa B A B 0% chance for deafness

Mitochondria Release energy from food Have their own DNA Mitochondrial DNA Many copies in each motochondrion Mutate faster than nuclear DNA Exposed to oxygen free radicals No DNA repair enzymes

Mitochondria Similar to DNA of prokaryotic cells Prokaryotic cells Engulfed into eukaryotic cells in ancient times Have enzymes to release much more energy from food

Only nucleus of sperm enters oocyte Only nucleus of sperm enters oocyte. The baby will get all mitochondia from his mother. Mitochonria Oocyte

Only inherited from mother Mitochondrial Traits Only inherited from mother

Mitochondrial DNA 37 genes Used for metabolic reactions that release energy from food Mitochondrial myopathies Weak muscles Cannot produce enough energy