Genetics

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Genetics

• Principles of Heredity

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Mendels Work

• Gregor Mendel- known as the Father of Genetics
• Studied Pea plants in a Monasterys Garden
• Mendel observed that the pea plants traits were
  often similar to those of their parents.
• However, sometimes the pea plants had different
  traits than their parents.
• The passing of traits (different physical
  characteristics) from parents to offspring is
  called Heredity.
• Mendel spent 10 years experimenting with
  thousands of pea plants.
• Mendels work formed the foundation of genetics,
  the scientific study of heredity.

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Language Arts Connection
Gregor Mendel presented a detailed description
of his observations in a scientific paper in
1866. In the excerpt that follows, notice how
clearly he describes his observations of the two
different seed shapes. These are either round or
roundish, the depressions, if any, occur on the
surface, being always only shallow or they are
irregularly angular and deeply wrinkled. Choose
an everyday object, such as a piece of fruit or a
pen. Make a list of the objects features. Then
write a short paragraph describing the object.
Use clear, precise language in your description.
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Dominant and Recessive Alleles
Allele-different forms of a gene. Dominant
Alleles- is one whose trait always shows up in
the organism when the allele is
present. Recessive Alleles- is masked, or covered
up, whenever the dominant allele is present.
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Mendels Experiments
Lifes Structure Function Page 129 Writing to
Learn- Imagine that you are a student in the
1860s visiting Gregor Mendel in his Garden.
Write a letter to a friend describing Mendels
experiments with pea plants.
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Genetics

• Principles of Heredity

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Inheritance of Traits
Phenotype- The appearance of an
organism. Genotype- the genetic make-up of an
organism, or the traits that it
carries. Dominant alleles (genes) represented by
capital letters (T) Recessive alleles (genes)
represented by lower case (t)
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Punnett Squares
A punnett square is a table that shows all the
possible combinations of traits among the
offspring produced in a cross.
T
t
t
T
T
T
T
t
t
t
t
T
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(No Transcript)
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Problems
Lifes Structure Function p133 Practice
Problems 1-2 Self-Check p. 134 1-5
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Phenotypes Genotypes
Homozygous- is an organism that has two identical
alleles for a trait. Heterozygous- is an organism
that has two different alleles for a trait.
Phenotype Genotype
Tall TT
Tall Tt
Short tt
Homozygous
Heterozygous
Homozygous
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In codominance, the alleles are neither dominant
nor recessive.
In incomplete Dominance, no alleles are
completely dominant.
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Chromosomes
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Activity
Read pages 136-142. Self-Check p. 142 (1-5)
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Genetic Disorders
A genetic disorder is an abnormal condition that
a person inherits through genes or
chromosomes. Genetic disorders are caused by
mutations, or changes in a persons DNA. Cystic
Fibrosis- a genetic disorder in which the body
produces abnormally thick mucus in the lungs and
intestine. -hard to breathe -caused by a
mutation
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Genetic Disorders
Sickle-cell disease- a genetic disease that
affects the blood. -suffer from lack of oxygen
in the blood and experience pain and
weakness. Hemophilia- is a genetic disorder in
which a persons blood clots very slowly or not
at all. -a person with this disease can bleed
to death.
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Writing to Learn

• As the webmaster for a national genetics
  foundation, you must create a web site to inform
  the public about genetic disorders. Choose one
  human genetic disorder discussed in this chapter.
  Write a description of the disorder that you
  will use for the Website.

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Problem Solving
Suppose you are growing purebred green-skinned
watermelons. One day you find a mutant striped
watermelon. You cross the striped watermelon
with a purebred green watermelon. Fifty percent
of the offspring are striped, while fifty percent
are solid green. Is the allele for the striped
trait dominant or recessive? Explain your answer.
In Rabbits, the allele for a spotted coat is
dominant over the allele for a solid-colored
coat. A spotted rabbit was crossed with a
solid-colored rabbit. The offspring all had
spotted coats. What were the genotypes of the
parents? Explain