ch.9 how are purebreeds different from mixed breeds? purebreeds are from parents who share the...
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Ch.9
How are purebreeds different from mixed breeds?
Purebreeds are from parents who share the same genes while mixed breeds are not
Gregor Mendel is known as the father of modern genetics
What process is illustrated on the right?
The purple flower is being fertilized by the pollen of the white flower (cross-fertilization).
What do we call the parental generation?
The P generation What do we call the
offspring? F1
Mendel looked at several traits. Which is dominant yellow pea seed or green pea seed?
Yellow
When you make a cross for one trait like flower color it is called a _______ cross
Monohybrid - mono for one hybrid for different
Why are all the F1 purple?
Because purple is dominant to white each F1 flower has a P allele and a p allele.
Why is the F2 different from the F1?
Because in the F2 generation two pp can occur in the offspring
Purple flower crossed to White Flower
Possible Gametes
Purple
P
Flower
P
White
p
Pp
Purple heterozygote
Pp
Purple heterozygote
Flower
p
Pp
Purple heterozygote
Pp
Purple heterozygote
F1 crossed to F1
Gametes Purple
P
Heterozygote
p
Purple
P
PP
Purple homozygote
Pp
Purple heterozygote
Heterozygote
p
Pp
Purple heterozygote
pp
White homozgote
What does loci mean?
Location of a gene Define homozygous
and heterozygous Homozygous - same
alleles PP or pp Heterozygous -
different alleles Pp
When two traits are crossed it is called a _________ cross
Dihybrid Why doesn’t a dihybrid cross
produce the same outcome as a monohybrid cross?
Independent assortment- where the alleles for pea shape go, have nothing to do with the alleles for pea color.
What is the ratio of phenotypes, coat color and vision?
9 both dominant 3 One dominant, one
recessive 3 One recessive, one
dominant 1 both recessive
Gametes BN Bn bN bn
BN BBNN BBNn BbNn BbNn
Bn BBNn BBnn BbNn Bbnn
bN BbNN BbNn bbNN bbNn
bn BbNn Bbnn bbNn bbnn
What do you think is the purpose of a testcross?
To determine the genotype of a dominant individual
Why cross the unknown individual to a homozygous recessive?
If any recessives show up in the offspring we know the unknown carries the recessive trait.
What is the chance of getting two Bb in a row?
2/4 x 2/4 = 4/16 = 1/4
Does dominant mean more common?
No freckles are not necessarily more common.
What is this diagram called?
Pedigree chart Why can’t we predict
Abigail Lambert’s genotype?
We don’t know about her offspring and she possesses the dominant trait so she could be Dd or DD
Why do you think we call Dd a carrier?
They carry the trait, but since it is recessive you can’t see it.
What type of disorder is this?
A recessive disorder like Cystic Fibrosis
Achondroplasia, a type of dwarfism, is a __________ trait.
Dominant Huntington’s is also
dominant but doesn’t usually take effect until after the age of 30. What is the potential problem with that?
They have already had children and passed it on.
What are two ways to test for inherited disorders in a fetus?
Amniocentesis and Chronic villus sampling.
When red and white make pink offspring it is called _______ dominance?
Incomplete What is the ratio of
the F2 generation? 1red:2pink:1white
In blood type A is dominant to O and B is dominant to O but A and B arre equally dominant. What do we call this type of inheritance?
Codominance
If Maria is type O and her sister is type AB blood and they know there mother’s grandparents are type A. What are the genotypes of their parents?
Mother is Iai and dad is IBi
Normal red blood cells and sickle cells
This picture illustrates pleiotropy, what do you think that means?
One gene can have an affect on many different things in the body - sickle cell shaped cells can cause heart failure, kidney failure etc.
How many different genes are involved in skin color?
3 When many genes
cause a trait like skin color it is called _______
Polygenic inheritance
What does this picture illustrate?
Independent assortment - shape and color line up separately.
When two genes are on the same chromosome like purple flower and long pollen or red hair and freckles, it is called _________.
Linked - they tend to travel together because the are close together and are rarely separated by crossing over.
What would you expect to be the outcome of the cross GgLl and ggll
1GgLl:1Ggll:1ggLl:1ggll = equal numbers of each type.
Is that what was observed? No - most were like either
parent What is the chance that
crossing over will happen? 17%
The crossing over frequency can be used to calculate the distance between genes on the chromosome. What is the distance between body color and wing shape in fruit flies?
17
Many organisms have chromosomes that determine sex, humans have ___ and ____
X and Y In chickens it is ___
and ____ Z and W
Where is the eye color gene located?
X What is the only way
to get a female that has white eyes?
The dad must have an X with white eyes
When a gene is on the sex chromosome it is called sex linked. Red/green colorblindness is sex linked.
How would this test for colorblindeness?
A colorblind person would not see the seven in the middle
Queen Victoria passed on a sex linked trait to her family, what was it?
Hemophilia Duchenne muscular
dysytrophy is also sex linked