Transcript Biology 1 Intro. To Genetics

Biology 1
Intro. To Genetics
We went over how to do a monohybrid punnett square.
Hopefully you are okay with that – if not we can go over it when I get back
For now, please copy the rest of these notes, so we can go over them a
little faster when I get back
Gene Interactions
Gene – section of DNA that codes for a trait
Allele – form of a gene
either dominant (B) or recessive (b)
There are a few exceptions to the Dominant / recessive alleles:
1. Incomplete dominance
2. Codominance
3. Polygenic inheritance
4. Sex linked traits
1. Incomplete Dominance
• 1760’s German scientist : Josef Kolreuter
crossed a pure recessive bred white carnation with a
pure bred dominant red carnation and got a pink carnation
appeared like “blended” parent traits.
When crossed pink f2 generation, he got 1/4 red, 1/4, white, 1/2 pink
With Incomplete dominance the dominant allele doesn’t mask the recessuve
allele and heterozygous is a “blending” between the 2 homologous parents.
Co-dominance
• Both alleles are expressed ( or are active)
• Ex. cattle : cross red hair co-dominant with white hair and get a roan
• (white-brown mix ) both colors are expressed.
Another example is out blood type:
Blood Type
• Receive one allele from mom and one from dad.
• There are 3 possible alleles that contribute to a person’s blood type
• A – which has a particular carbohydrate attached to the surface of the RBC
• B – which has a particular carbohydrate attached to the surface of the RBC
• i – which has neither carbohydrate attached to the RBC
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AA or AO = A blood type
AB = AB blood type
BO or BB = B blood type
io or OO = O blood type
2. Polygenic Inheritance
• Many traits are result of interaction of many genes
Ex. different combination of enzymes produce different color eyes.
• When the product of a gene (a specific protein) is being actively produced by
a cell we say the gene is being expressed . Within an organism, some genes
are rarely expressed, some are constantly expressed, and some are expressed
for a time and they turn off.
Ex. Height, weight, eye color, skin color, hair color
3. Sex Linked Traits
• Any trait that is on the X or Y chromosome is sex linked is considered
to be sex linked
Pedigrees
A pedigree is a tool used to trace a trait through a family.
To make a pedigree you need to know specific symbols and how they
are linked together
The next slide is an example of symbols scientists use to make
pedigrees.
Copy all the symbols (and their meaning) down into your notes so we
will be ready to make these when I get back