Genetics Rules Rule #1? Rule #2: Incomplete dominancesome

alleles aren’t completely dominant so they BLEND

Rule #3: Codominancesome alleles dominate together so BOTH ARE SEEN

Rule #4: sex-linked genesALL alleles on a male’s X chromosome (X-linked) are expressed.

Complete Dominance

Rule #1—some alleles completely dominate over others: B=brown eyes b=blue eyes Bb= brown eyes, so B is completely

dominant.

Incomplete Dominance Rule #2—some alleles

DON’T COMPLETELY DOMINATE, so they blend: RR= red flowers rr = white flowers Rr = pink flowers

PINK FLOWERS!!!BLENDING!!!

Codominance

Rule #3—some alleles dominate TOGETHER so they BOTH are shown H = brown hair on horses H’ = white hair on horses HH’ = both brown and white hairs, so

the horse is roan color. Blood types are like this, too.

Roan Horse

Antigens-markers on cells

Blood type determined by your carbohydrate markers on your red blood cells

4 blood group phenotypes:Type A has A antigens

Type B has B antigens

Type AB has A and B antigens

Type O has no antigens

Blood Types

Multiple Alleles Multiple alleles- 3 different

forms of the gene code for blood types IA, IB, and i Allele IA makes an “A”

antigen IB makes a “B” antigen i makes none

6 blood group genotypes Complete dominance- IA

and IB dominate over i Codominance- IAIB genotype

shows BOTH A and B carbs

Blood Types Reactivity to blood transfusions and

organs: Antibodies-proteins produced by your

immune system to fight off things that look “foreign.”

Type A (makes anti-B antibodies) Type B (makes anti-A antibodies) Type AB (makes NO antibodies—universal

receiver) Type O (makes anti-A and anti-B antibodies—

universal donor)

Free Write Journal Entry Why? Take time to absorb the

material and think about and process the information.

What should you do? Take a couple of minutes to write

down any thoughts, questions, or ideas at the bottom of your notes.

There are no right or wrong entries, as long as you try.

Sex-Linked Genes

Rule #4: sex-linked genesALL alleles on a male’s X chromosome (X-linked) are expressed. Male sex chromosomes?_________ Female sex chromosomes?_________ We also call sex-linked genes by another

name, X-linked, because the X chromosome has the majority of the genes.

Sex-Linked Genes

In males, EVERY gene on their X chromosome is expressed. The Y doesn’t have the same genes.

In females this is not the case because they have another copy on their other X chromosome to overcome it.

Sex-Linked Genes

Examples of sex-linked disorders: Colorblindness Hemophilia Fragile X Syndrome Duchene Muscular Dystrophy Cleft Palate Vitamin D Resistant Ricketts 3 types of deafness Male Pattern Baldness

Sex-Linked Genes The genes that occur on the sex

chromosomes must be written with X’s and Y’s to show this special situation. For example: red-green colorblindness

is a recessive trait. It is found on the X chromosome, not the Y.

We write the alleles (forms of the gene) this way:

XC = colorblindness XC = normal

Sex-Linked Genes Try to complete

this table:Phenotypes Genotypes

Normal Male

Colorblind Male

Normal Female

Normal “carrier” Female

Colorblind female