Non-Mendelian Genetics - dvusd.org · •XhXh or XhY= hemophilia. •Males CAN’T be carriers of an X-linked gene! Free PowerPoint Backgrounds Environmental genes Phenotype that

Free PowerPoint Backgrounds

Non-Mendelian Genetics

http://www.powerpoint-2010.com/


For all of the inheritance patterns we will be

doing Punnett squares in class. Please leave

room in your notes to add those.



Today, we know that genes often do not

follow Mendel’s Laws all the time! There are

exceptions…..

• Incomplete dominance

• Co-dominance

• Epistasis

• Polygenics

• Sex influenced

• Sex linkage

• Environmental genes

• Pleiotropy



Incomplete dominance

• Characterized by a blending of traits. Phenotype of

offspring falls somewhere between each parent, when

genotype is heterozygotic. These intermediate

offspring are called roans.

• EX: Red horses (RR) crossed with white horses (rr)

produce Rr roans that are “pink” in color.



Co-dominance

• Characterized by the

expression of both

alleles. Even the

recessive allele affects

the organism.



EX: Blood type - A

and B are both

dominant!

• IAIA

or IAi= A type

• IAIB

= AB type

• IBIB

or IBi = B type

• ii = O type



Epistasis

• Characterized where one set of genes (2 alleles) covers

or overrides a totally separate set of genes (2 other

alleles).

Ex: Heterochromia iridum



Epistasis

Ex: Albinism. If an organisms carries the albino gene (a)

no matter what genes that organism has for color, the

organism will be albino.

B=black coat

a= albino

So a mouse with a

genotype of BBaa

will have NO

color!



Polygenic traits

Characterized by many genes are needed to affect a

single trait.

Eye color

Hair color



Sex influenced

Genes that are expressed differently based on hormones

produced by the sex chromosomes X or y.

EX: patterned baldness


http://en.wikipedia.org/wiki/Image:Male_pattern_baldness.jpg

http://en.wikipedia.org/wiki/Image:Male_pattern_baldness.jpg


Sex linkage

• If the genes are on the

y, they are called

holandric. Ex: Ear hair

• Those carried on the X

are more abundant

• EX: Muscular Dystrophy

Characterized by genes carried on the X or Y

chromosomes.



Lets do a

Punnett Square

to show this

• EX: Hemophilia

• XhXh or XhY= hemophilia.

• Males CAN’T be carriers of an X-linked gene!



Environmental genes

Phenotype that changes as genes are exposed

to external stimuli, like temperature.



Pleiotropy

One gene controls multiple expression.

EX: Genes for white coat color in dogs also

controls the ability to hear.


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Non-Mendelian Genetics - dvusd.org · •XhXh or XhY= hemophilia. •Males CAN’T be carriers of an X-linked gene! Free PowerPoint Backgrounds Environmental genes Phenotype that