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Focus 10-1: Genetics
Transcript of Focus 10-1: Genetics
Brainstorm: What is the purpose of DNA?
write a least TWO things!
What is the difference between a genotype and a phenotype?
Think - Pair - Share
What are some
that you and your parents have in common?
What are some
that you and your extended family have in common?
Do you own a purebred dog or cat?
What makes them purebred?
How do you know they are purebred?
Responsible for the Laws of Inheritance
Father of genetics
He was a friar (kind of like a monk).
More about... MENDEL
Studied the inheritance of traits in pea plants
Mendel's work was not recognized until the turn of the 20th century
Mendel cultivated and tested some 28,000 pea plants
He found that the plants' offspring retained traits of the parents
Mendel focused on...
Pod shape and color
Seed shape and color
Flower position and color
Site of Gregor Mendel’s Experimental Garden
Mendel stated that physical traits are inherited as “particles”
Did not know that the “particles” were actually Chromosomes & DNA
Heredity / Inheritance
- passing of traits from parent to offspring
- any characteristic that can be passed from parent to offspring
- study of heredity
- two forms of a gene (dominant & recessive)
- stronger of two genes expressed; represented by a capital letter
- gene that shows up less often; represented by a lowercase letter
A couple more terms...
- gene combination for a trait
(e.g. RR, rr) -
- the physical feature resulting from a genotype (e.g. red, white) -
Describe the genotype for the boy's hair.
Describe the phenotype for the boy's hair.
Genotype of alleles:
= red flower
= yellow flower
All genes occur in pairs, so
affect a characteristic
Possible combinations are:
Genotype vs. Phenotype
The girl has blonde hair.
The girl's hair is bb.
The girl has blue eyes.
The girl's eyes are tt.
= the parents
= the first-generation offspring
= the second-generation offspring
What about this example?
1. Monohybrid: Examines ONE trait.
2. Dihybrid: Examines TWO traits.
Show possible outcomes of genes that the new generation will have.
We will use...
Mating between two individuals
Focuses on two alleles for only one trait
Cross between short plant and tall plant.
Cross between a blonde woman and a man with brown hair.
A grid for organizing genetic information.
Named after Reginald C. Punnett, who devised the approach.
, not actual results.
Steps to Complete a Punnett Square
1. Make a
2. Determine parent’s
“Split” the letters
of the genotype for each parent and put them “outside” the P-Square
4. Determine the genotypes of the offspring by
filling in the P-Square
Step 1 – Make a Key
IMPORTANT -> do this EVERY time!
Trait: Eye color
Dominant: Brown (B)
Recessive: blue (b)
Without this I will mark it WRONG!
Step 2: Parent’s Genotypes
Sometimes the parents genotype is given in the genetic problem
Other times you will have to use your understanding of the vocab
to determine the genotypes
Example: Cross a short pea plant with one that is heterozygous for tallness. Short is recessive.
Both alleles are the same.
ie: BB or bb
Alleles are different.
: BB - 2 dominant alleles
: bb - 2 recessive alleles
Remember... the DOMINANT allele is ALWAYS expressed!!!
*Brown eyes (B) is dominant to blue eyes(b).
tt x Tt
Step 3: "Split" the Parents
First parent: left side
Step 4: Fill in the P-Square
1. top left
2. bottom left
3. top right
4. bottom right
*write dominant alleles 1st!
Step 5: Summarize Results
50% homozygous recessive
Practice Problem #1 - Left Side
In silkworms, a yellow cocoon is
to a white cocoon. Figure out the genotype and phenotypes of the offspring if a heterozygous yellow is crossed with a heterozygous yellow.
Practice Problem #2 - Left Side
In pea plants, spherical seeds (S) are
to dented seeds (s). In a genetic cross of
for the seed shape trait, what would the genotypes and phenotypes of the offspring be?
Remember to do
if you need help!
when you are done!
Green feathers are dominant to blue feathers. In a cross between a heterozygous bird and a blue bird, what percentage of the offspring would be blue?
If a homozygous dominant individual mates with a homozygous individual the genotypic and phenotypic percentage is ALWAYS...
How can I use a dihybrid cross to determine TWO traits in offspring?
A cross between two individuals that differ in
of particular interest.
Both parents will be heterozygous or homozygous (dominant/recessive) for
two traits at the same time
crosses put together
Let's practice TOGETHER
Norway Rats are usually brown (B), but a few are white (b). They usually have long tails (T), but some have short tails (t).
A rat that is homozygous dominant for both traits mates with a white rat with a short tail.
Think about all combos
Parent 1: BBTT
You need to "FOIL"!!!
Parent 2: bbtt
F - First
L - Last
I - Inner
O - Outer
Genotype - 100% heterozygous color
100% heterozygous tail
Phenotype - 100% brown, long tail
Let's make it harder...
Two rats are heterozygous for both color and tail length.
What will their offspring's genotype and phenotype be?
Wall problems & carousel walk.
1. Tape your problem to the butcher paper.
2. As a team, solve the problem.
3. Hang it up and go back to your seat.
What does F.O.I.L. stand for?
What is its purpose?
If red is dominant to yellow in flowers, what will the phenotype of a heterozygous flower be?
How do incomplete and co-dominance differ from previous mono-hybrid crosses?
Mendel didn't think of this!
A cross between organisms with two different phenotypes produces offspring with a third phenotype that is a
of the parental traits.
Left Side - Incomplete #1
A female black hair mouse is crossed with a male white hair mouse.
What could the offspring look like
State the genotype of the parents
State the phenotype of the parents
Left Side - Incomplete #2
A red daisy and yellow daisy cross.
What would the offspring look like?
Would they all be the same?
Everything we have learned so far.
The dominant allele
blocks out the recessive allele in heterozygous individuals.
Bb = brown eyes
Only homozygous recessive bb can cause a recessive phenotype.
Two different phenotypes produces offspring with a third phenotype in which
of the parental traits appear
Left Side - Codominance #1
A brown cow mates with a white cow. What does the offspring look like?
Brown and white spotted!
States the difference between incomplete and co-dominance.
Use capital and lower case of same letter!
Use different capital letters!