LH. Biology Heredity Benchmark 1

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LH. Biology Heredity Benchmark 1
Explain how characteristics of living things
are passed on from generation to generation.
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Being Able to Curl up both sides of the Tongue
is under the control of a dominant allele at one
gene locus.
Homozygous Dominant
RR Rr
rr
Homozygous recessive
Heterozygous
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Inheritance for Tongue Rolling and Non-tongue
Rolling
Susans mom is a tongue roller. Her father is a
non-tongue roller. Susan has three
older brothers and one younger sister. Her
three brothers are all tongue rollers. Her sister
is a non-roller. What are the genotypes of
each member of Susans family?
R allele for ability to roll the tongue
r allele for non-roller
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What are Susans Family Tongue Rolling Genotypes?
Dad rr (non-roller, recessive trait expressed)
Sister rr (non-roller, recessive expressed)
Mom Rr (heterozygous, mom had to donate the r
allele to Susans sister and since mom is a
roller she must have the R allele)
Susan and her brothers Rr (heterozygous,
each child inherits an r allele from dad and
because they can roll they each inherited an R
allele from mom)
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Mark marries Susan. . .
Marks mom is a non-roller and his dad is
a roller. Marks two brothers are rollers.
What is Marks genotype for ability to roll the
tongue?
Rr
Mark and Susan are planning a family. What is the
probability that Susan will deliver a roller, a
non-roller?
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Punnett Square
Mark
R
r
S u s a n
R
R
R
R
r
Roller
Roller
r
r
R
r
Roller
Non Roller
r
Genotypic Ratio 121
Phenotypic Ratio 31
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After fourteen years of marriage...
are all happy ROLLERS !!!
Susan
Mark
Ashley
Jessica
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Baby Peas Dont Go
Gregor Mendel Father of Heredity
Baby Peas Dont Go
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Look, the Structure of DNA!
Crick
DNA Model 1953
Watson
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Family Tree
r r
r r
R r
Rr
If Mary and Peter are both Rollers, what are the
chances for Anne to be roller, a non-roller ?
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Key Concepts
Traits Dominant Recessive Genetic material gene
pair gene combination gene sorting
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Real-world contexts
Common contexts Inheritance of a human genetic
disease/disorder, such as sickle cell anemia A
family tree focused on certain traits Examining
animal or plant pedigrees.
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Sickle Cell Anemia
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http//www.bio.miami.edu/dana/250/25002_4print.htm
l
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A particular species of bird can be brown or
white. The white color is a recessive trait,
while the brown color is a dominant trait.
When two brown birds mate, is it possible for
them to have white offspring?

• no because both parents have
• only genes for being brown
• yes, because offspring color
• does not depend on the genes of the parents
• yes, because both parents
• have and pass on the gene for being white
• no, because the parents can only
• pass on the dominant gene to their offspring.

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a. no because both parents have only genes for
being brown Incorrect You dont know for sure
if both parents have two genes for being brown
(BB). They could have a Brown gene and a white
gene (Bb) and still have the phenotype (what
they look like) of white color
Return to the question
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b. yes, because offspring color does not depend
on the genes of the parents Incorrect The
color does depend on their genes. This is an
inherited trait.
Return to the question
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You Pass with Flying Colors
c. yes, because both parents have and pass on
the gene for being white Correct You dont
know for sure if both parents have two genes for
being brown (BB). They could have a Brown gene
and a white gene (Bb) and still have the
phenotype (what they look like) of white color
Return to the question
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• no, because the parents can only pass on the
  dominant gene to their offspring.
• Incorrect They have an equal chance of passing
  on the dominant and recessive gene if the contain
  both. The term dominant means that when an
  individual has two different genes for a trait
  the dominant is the one that shows up in the
  phenotype (appearance)

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