Download Genetics Notes

Genetics
Vocabulary Review
• What is a trait???
-A physical characteristic.
• What is heredity???
-The passing of traits from
parents to offspring.
• What is genetics???
- The scientific study of
heredity.
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Question #1
Which of the following is an example
of a trait?
A. Bb
B. Talking loud
C. Brown eyes
D. Bleach blonde hair
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Alleles
• Genes are the factors that control
Traits.
• Alleles are the different forms of
Genes. Example: pea plants
• Individual Alleles control the
inheritance of Traits.
• An offspring receives one allele
from each parent.
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Question #2
What is the term for factors that
control traits?
A. Genes
B. Purebreds
C. Recessives
D. Parents
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Question #3
Which term refers to physical
characteristics that are studied in
genetics?
A. Traits
B. Offspring
C. Generations
D. Hybrids
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DOMINANT and recessive
Alleles
• A dominant allele is one whose trait
always shows up in an organism when
the allele is present.
- represented by a capital letter.
• A recessive allele is covered up when
the dominant allele is present.
- represented by a lower case letter.
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Practice
• R is the dominant allele for a one
eyed monster.
• r is the recessive allele for a
monster with two eyes.
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Monster Genetics
• Rr
• How many eyes will our monster
have?????
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Monster Genetics
• RR
• How many eyes will our monster
have??
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Monster Genetics
• rr
• How many eyes will our monster
have??
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#4
What does the notation TT mean to
geneticists?
A. Two dominant alleles
B. Two recessive alleles
C. No dominant alleles
D. One dominant and on recessive
allele
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Codominance
• In Mendel’s studies he found
some alleles to be neither
dominant or recessive.
• Codominance is when alleles are
neither dominant or recessive and
as a result both alleles are
expressed in the offspring.
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What will Happen?
• You have two flowers, a white and
a red, that are crossed.
• The flowers are codominant.
• What color will their offspring be.
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End Day 1
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Phenotype
• Phenotype and genotype are
words that scientist use to
describe organisms.
• Phenotype is an organisms
physical appearance or its visible
traits.
• Example: a pea plant can have
one of two phenotypes for stem
height-short or tall.
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Genotype
• Phenotype and genotype are
words that scientist use to
describe organisms.
• Genotype is an organisms genetic
makeup, or allele combination.
• Genotype TT=tall (Phenotype)
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Describing genotypes
• Scientist use the words heterozygous
and homozygous to describe
genotypes.
• Homozygous is used to describe an
organism that has two identical alleles
for a trait.
• Example: PP and pp
• Heterozygous is used to describe an
organism with two different alleles.
-Also called hybrid.
• Example: Tt
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#9
Green seed color (G) is dominant to
yellow seed color (g). If two
heterozygous parents are crossed,
what will be the resulting genotypes
of the offspring?
A. GG, Gg, gg
B. Gg, gg
C. GG, Gg
D. gg, GG
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#5
Pick the answer that best describes
“AA”.
A. Homozygous
B. Heterozygous
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#8
According to Mendel, red flower color (R)
is dominant over white flower color
(r). If a heterozygous parent is
crossed with a homozygous
recessive parent, which of the
following would be true?
A. All four “rr”
B. All four “Rr”
C. Two “rr” and two “Rr”
D. Two “rr” and two “RR”
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#6
Pick the answer that best describes
“Aa”.
A. Homozygous
B. heterozygous
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Probability
• Probability is the likelihood that a
particular event will occur.
• Probability predicts what will
occur, and is not always
necessarily what will occur.
• Example: if you toss a coin there
is a fifty percent chance the coin
will land on heads, and fifty
percent the coin will land on tails.
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Mendel and Probability
• Mendel was the first scientist to
recognize that the principles of
probability can be used to predict
the results of genetic crosses.
• Mendel could predict the
probability of producing a tall or
short pea plant.
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Punnett Squares
• A punnett square is a chart that
shows all possible combinations of
alleles that can result from a
genetic cross.
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Punnett Example
• Yellow is dominant over Green.
• What is the probability that the
offspring will be yellow?
100%
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Punnett Problems
• In purple people eaters, one-horn
is dominant and no horns is
recessive.
• Draw a Punnet Square showing
the cross of a purple people eater
that is hybrid for horns, with a
purple people eater that does not
have horns.
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Answer
• Hybrids have two different alleles
for one trait.
• Hh is the hybrid in the example.
• No horns would have to be hh
because it is a recessive allele.
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Punnett Problems
• In Bears the recessive allele for
brown fur is R, black fur is
recessive.
• The female bear is Rr and the
male bear is rr.
• What are the four possible
phenotypes for the cubs.
• What is the probability that the cub
will have black fur?
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Answer
• The four possible phenotypes
would be 2(black) and 2(brown).
• There would be a fifty percent
chance the cub would be brown
and fifty percent chance the cub
would be black.
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