genetics rules rule #1? rule #2: incomplete dominance some alleles aren’t completely dominant so...
TRANSCRIPT
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