Chapter: Heredity

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(No Transcript)
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Table of Contents
Chapter Heredity
Section 1 Genetics
Section 2 Genetics Since Mendel
Section 3 Biotechnology
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Genetics
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Inheriting Traits

• Traits are inherited from parents

• Heredity - the passing of traits from parent to
  offspring.

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Genetics
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What is genetics?

• Alleles - different forms of a trait that a gene
  may have

• Alleles for each trait separate into different
  sex cells during meiosis

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Genetics
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What is genetics?

• Genetics - study of how traits are inherited

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Genetics
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MendelThe Father of Genetics

• Mendel (1856) studied genes of pea plants

• First to
• trace one trait through several generations
• use probability to explain heredity

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Genetics
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• Purebred - always produces the same traits
  generation after generation

• Hybrids receive different alleles for a trait
  from each parent

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Genetics
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Dominant and Recessive Factors

• Cross-pollination - using pollen from one flower
  to pollinate others

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Genetics
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Dominant and Recessive Factors

• Dominant - factor expressed if there is only one
  allele for the trait

• Recessive factor expressed only when there are
  2 alleles for the trait

Click image to view movie.
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Genetics
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Punnett Squares

• Studied gt 30,000 pea plants over 8 yrs

• Punnett square -tool used to predict results

Click image to view movie.
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Genetics
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Punnett Squares

• Uppercase - dominant allele

• Lowercase - recessive allele

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Genetics
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• Genotype - genetic makeup

• Phenotype - way an organism looks and behaves

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Genetics
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• Homozygous - two alleles that are the same

• Heterozygous - two different alleles for a trait

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Genetics
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Making a Punnett Square
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Section Check
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Question 1
How did Gregor Mendel use his knowledge of
mathematics in his study of heredity in pea
plants?
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Section Check
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Answer
Mendel was the first person to use the
mathematics of probability to explain heredity.
Probability is the branch of mathematics that
helps you predict the chance that something will
happen.
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Section Check
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Question 2
According to this diagram, if meiosis proceeds
correctly, how many alleles of a particular gene
can a female pass on to her offspring?
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Section Check
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Answer
Although she has two alleles of each gene, a
mother can pass only one allele to her offspring.
Meiosis separates alleles so that eggs have only
one allele for each gene. The new individual then
gets one allele from the mother and the other
from the father.
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Section Check
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Question 3
Mendel crossed pea plants that were pure-bred for
yellow seeds with plants that were pure-bred for
green seeds. All the offspring of this cross had
yellow seeds. Based on these results, which form
of color was recessive and which was dominant?
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Section Check
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Answer
Green seed color was recessive and yellow seed
color was dominant. Mendel called the form that
seemed to disappear (green in this case)
recessive and the form that covered up (yellow in
this case) dominant.
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Genetics Since Mendel
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Incomplete Dominance

• Incomplete dominance results in an intermediate
  phenotype

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Genetics Since Mendel
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• Multiple alleles - trait that is controlled by
  more than two alleles

• Produce more than three phenotypes

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Genetics Since Mendel
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Multiple Alleles

• Alleles for blood types
• A, B, and O.

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Genetics Since Mendel
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Polygenic Inheritance

• Polygenic inheritance - a group of gene pairs
  acts together to produce a trait.

• Produces a wide variety of phenotypes.

Click image to view movie.
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Genetics Since Mendel
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Polygenic Inheritance

• Examples
• Height
• Eye color
• Skin color

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Genetics Since Mendel
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Impact of the Environment

• Environment plays a role in how some genes are
  expressed

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Genetics Since Mendel
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Human Genes and Mutations

• Mutations errors when DNA copies
• Can be harmful or helpful

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Genetics Since Mendel
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• Chromosome Disorders - error in the number of
  chromosomes

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Genetics Since Mendel
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Recessive Genetic Disorders - caused by
recessive genes.
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Genetics Since Mendel
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Sex Determination

• Egg - 1 X chromosome

• Sperm - 1 X or 1 Y chromosome

• Male XY
• Female XX

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Genetics Since Mendel
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Sex-Linked Disorders

• Sex-linked gene - allele inherited on a sex
  chromosome

• Color blindness is sex-linked

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Genetics Since Mendel
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Pedigrees Trace Traits

• Pedigree - visual tool for following a trait
  through generations

• Males squares
• Females circles

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Genetics Since Mendel
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Pedigrees Trace Traits

• Filled circle or square - shows trait

• Half-colored - carriers

• Empty - do not have the trait and are not
  carriers.

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Section Check
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Question 1
Why is color blindness a sex-linked trait?
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Section Check
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Answer
This trait is sex-linked because the alleles for
this trait are carried on the X-chromosome, one
of the sex chromosomes. Color-blindness is caused
by a recessive allele and because males get only
one X-chromosome, they are more likely to be
color-blind than females.
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Section Check
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Question 2
In Himalayan rabbits, dark-colored fur is only
found on cooler parts of the rabbits bodies.
This is an example of _______.
A. how sex-linked conditions change coat color B.
the risk of cancer in rabbits with light fur C.
the impact of internal environment on gene
expression D. what hybrid rabbits look like
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Section Check
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Answer
The correct answer is C. The alleles for dark fur
color are controlled by the internal temperature
of the rabbits. These alleles are expressed only
at lower temperatures.
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Section Check
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Question 3
If an individual has three copies of chromosome
21, what condition will result?
A. color blindness B. cystic fibrosis C. Downs
syndrome D. Hemophilia
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Section Check
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Answer
The correct answer is C. Downs syndrome occurs
when there are three copies of chromosome 21
instead of the usual two.
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Biotechnology
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• Genetic engineering - scientists are
  experimenting to change the arrangement of DNA
  that makes up a gene.

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Biotechnology
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• Recombinant DNA - made by inserting a useful
  segment of DNA from one organism into a
  bacterium.

• Used to produce
• human insulin,
• human growth hormone

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Biotechnology
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Gene Therapy

• Normal allele is placed in a virus.

• The virus then delivers the normal allele and
  replaces the defective one

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Biotechnology
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Genetically Engineered Plants

• Selective breeding - selecting plants with the
  most desired traits to breed

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Biotechnology
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Genetically Engineered Plants

• Find genes that produce desired traits in one
  plant and then insert them into a different plant

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Section Check
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Question 1
What is it called when scientists use biological
and chemical methods to change the arrangement of
DNA in a gene?
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Section Check
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Answer
This is called genetic engineering. This process
has been used to make large volumes of medicines
and research is being conducted to find many
other ways to use these techniques.
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Section Check
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Question 2
What does this diagram illustrate?
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Section Check
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A. Bacteria cells can produce human insulin. B.
Bacteria genes are put in human cells.
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Section Check
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C. People with diabetes are given the gene for
insulin. D. The insulin gene is inserted in
people with diabetes.
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Section Check
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Answer
The correct answer is A. Genetic engineering can
be used to insert the human gene for insulin into
bacterial cells. The bacterial cells then produce
human insulin. This insulin can be used to treat
people who have diabetes.
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Section Check
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Question 3
Using genetic engineering to replace defective
alleles in people with genetic diseases is called
_______.
A. gene therapy B. Mendelian genetics C.
pedigree analysis D. recombinant DNA
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Section Check
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Answer
The correct answer is A. Often a virus is used
to deliver the normal allele to the patient.
Scientists have been conducting experiments to
cure many different genetic diseases, including
cystic fibrosis, in this way.
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