Mendelian Mendelian ExceptionsExceptions

Chapter 12Chapter 12

Section 4Section 4

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.

characteristicscharacteristics

offspringoffspring

genesgenes

traittraitdominantdominant

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)(Law of Independent Assortment)

independentlindependentlyy

parentparenttwotwo

gametesgametesgenesgenes

pairpair

Independent Assortment in Peas

__ Round yellow__ Round green__ Wrinkled yellow__ Wrinkled green

99333311

1.Incomplete Dominance

In incomplete dominance, neither allele is __________ so there is a blending of ______ when two different alleles for the same trait occur together.

Colors blendblend together (______________

individuals = 3rd phenotype)

dominantdominanttraitstraits

heterozygousheterozygous

red whitepink

Incomplete Dominance

In Four O’ Clocks, if you cross a red _____(which is always pure) with a white _____ (that is also always pure) , you get apink _____ (whichis always hybrid /heterozygous

RRRRWWWW

RWRW

RWRW

RW RW

Incomplete Dominance

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?

RRRRBBBB

RBRB

2.Codominance 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 _____.

allelesalleles

redredwhitewhite

roanroan

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…

W

W

R W

WWRW

RW WW

phenotypephenotype

roan

roan

white

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

3.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.

twotwo

twotwotwotwo

traittrait

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

fourfour

threethree

Phenotype Genotype

A AA or AO

B BB or BO

AB AB only

O OO only

Multiple Alleles Examples of Blood type crosses

Phenotype(Blood Type

Multiple Alleles

Genotype

Blood Groups

Antigen on Red Blood Cell

Safe Transfusions

To From

Multiple Alleles

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

rabbitrabbit

4. 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.1 pair1 pair

Polygenic Traits These are called ___________ traits,

which means “having _______ genes”. In humans, _____ color, _____ color,

polygenicpolygenicmanymany

skinskineyeeye

Polygenic Traits These are called ___________ traits,

which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color

polygenicpolygenicmanymany

skinskineyeeye

hairhair

Polygenic Traits 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.

polygenicpolygenicmanymany

skinskin

controlledcontrolled

eyeeye

hairhair