Mendelian Exceptions Chapter 12 Section 4 Mendels Principles

Mendelian Exceptions Chapter 12 Section 4

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

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

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

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

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

Incomplete Dominance l l RRand blue In another flower, if red ____ BB flowers are crossed, they produce a ____ 3 rd purple ____ flower RB What would be the genotype ratio and phenotype ratio if you crossed two purple flowers?

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

Codominance l l These cattle or horses actually have both red and white hairs intermixed, or are spotted. phenotype Roan is a third ______. If you cross a roan with a white… W W R RW roan W WW white RW roan WW white

Codominance l l 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

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

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

Multiple Alleles l Examples of Blood type crosses

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

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

4. Polygenic Traits l l l Traits controlled by two or more genes Show a wide range of phenotypes The phenotype is produced by the interaction of more than 1 pair ____ of genes.

Polygenic Traits l l l polygenic traits, which These are called ______ means “having _______ many genes”. eye In humans, _____ color, skin _____ color,

Polygenic Traits l l polygenic traits, which These are called ______ means “having _______many genes”. eye In humans, _____ color, skin _____ color, hair and _____ color

Polygenic Traits l l l polygenic traits, which These are called ______ means “having _______ many genes”. eye color, In humans, _____ skin color, _____ hair color and _____ are just a few of the many traits controlled _____ by many genes.