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

There are many variations of inheritance patterns! Intermediate Inheritance - Inheritance in which heterozygotes have phenotypes between the phenotypes of 2 homozygotes. Example - Red & White = Pink (also called Inbetween or Incomplete Dominance)

Intermediate Inheritance = 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 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

Intermediate Inheritance Chickens C = Trait-Color CB = Black CW = White What do we get if we cross - Black x White CBCB CWCW CBCW CB CW CBCW

Remember, the 1st generation of babies are called the F1 generation. Neither black nor white are dominant. No capital or lower case letters are used Parent Phenotypes can reappear in the F2 generation Now, we’ll cross 2 of the babies… CBCW X CBCW 25% - CBCB BLACK 50% - CB CW BLUE 25 % - CWCW WHITE CB CW CBCB CBCW CWCW

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

Another Example of codominance – Cow color RR WW RW

Codominance 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

Multiple Alleles 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 four Phenotype Genotype A AA or AO B BB or BO AB AB only O OO only three

What is the universal donor? O What is the universal receiver? AB

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

Human examples: skin, eye and hair color When multiple genes affect a character the variation in phenotype is great. Polygenic Inheritance - Combined effect of 2 or more genes on a single characteristic. (not “either-ors”) Example -Skin Color (Yes simplified) A, B, C contributes on unit of color The recessive a, b, c do not contribute any unit of color

Potential combinations of alleles for a character increase with the number of genes that affect one character. Meaning - The more genes there are, the more possible combinations. Think about it like this - the more $$$$ you have, the more possible ways there are to spend it!

Temperature & Sunlight! Importance of environment Sometimes, phenotypes can depend on the environment. Example #1 - Trees & leaves Year to year, the leaves change size, color and shape. What affects this? Temperature & Sunlight!

Siamese cats and Himalayan rabbits Himalayan rabbits normally are white as melanin is not produced at temperatures above 35 C. If one shaves hair from back and places ice pack on the shaven skin, black hair is produced.  The ears, tail, and feet are normally black because they have less hair and are cooler.