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Chapter: Heredity

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Genetically Engineered Plants Genetic engineering can produce improvements in crop plants, such as corn, wheat, and rice. 3 One type of genetic engineering involves ... – PowerPoint PPT presentation

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Title: Chapter: Heredity


1
(No Transcript)
2
Table of Contents
Chapter Heredity
Section 1 Genetics
Section 2 Genetics Since Mendel
Section 3 Biotechnology
3
Genetics
1
Inheriting Traits
  • Eye color, nose shape, and many other physical
    features are some of the traits that are
    inherited from parents.
  • An organism is a collection of traits, all
    inherited from its parents.

4
Genetics
1
Inheriting Traits
  • Heredity (huh REH duh tee) is the passing of
    traits from parent to offspring.

5
Genetics
1
What is genetics?
  • Generally, genes on chromosomes control an
    organisms form and function.
  • The different forms of a trait that a gene may
    have are called alleles (uh LEELZ).
  • When a pair of chromosomes separates during
    meiosis (mi OH sus), alleles for each trait also
    separate into different sex cells.

6
Genetics
1
What is genetics?
  • Every sex cell has one allele for each trait.
  • The study of how traits are inherited through the
    interactions of alleles is the science of
    genetics (juh NE tihks).

7
Genetics
1
MendelThe Father of Genetics
  • Gregor Mendel began experimenting with garden
    peas in 1856.
  • Mendel made careful use of scientific methods,
    which resulted in the first recorded study of how
    traits pass from one generation to the next.

8
Genetics
1
MendelThe Father of Genetics
  • Mendel was the first to trace one trait through
    several generations.
  • He was also the first to use the mathematics of
    probability to explain heredity.

9
Genetics
1
Genetics in a Garden
  • Each time Mendel studied a trait, he crossed two
    plants with different expressions of the trait
    and found that the new plants all looked like one
    of the two parents.
  • He called these new plants hybrids (HI brudz)
    because they received different genetic
    information, or different alleles, for a trait
    from each parent.

10
Genetics
1
Genetics in a Garden
  • An organism that always produces the same traits
    generation after generation is called a purebred.

11
Genetics
1
Genetics in a Garden
  • Tall plants that always produce seeds that
    produce tall plants are purebred for the trait of
    tall height.

12
Genetics
1
Dominant and Recessive Factors
  • In his experiments, Mendel used pollen from the
    flowers of purebred tall plants to pollinate by
    hand the flowers of purebred short plants.
  • This process is called cross-pollination.

13
Genetics
1
Dominant and Recessive Factors
  • He found that tall plants crossed with short
    plants produced seed that produced all tall
    plants.

14
Genetics
1
Dominant and Recessive Factors
  • Mendel called the tall form the dominant (DAH muh
    nunt) factor because it dominated, or covered up,
    the short form.
  • He called the form that seemed to disappear the
    recessive (rih SE sihv) factor.

Click image to view movie.
15
Genetics
1
Using Probability to Make Predictions
  • Probability is a branch of mathematics that helps
    you predict the chance that something will happen.

16
Genetics
1
Using Probability to Make Predictions
  • Mendel also dealt with probabilities.
  • One of the things that made his predictions
    accurate was that he worked with large numbers of
    plants.
  • He studied almost 30,000 pea plants over a period
    of eight years.
  • By doing so, Mendel increased his chances of
    seeing a repeatable pattern.

17
Genetics
1
Punnett Squares
  • How could you predict what the offspring would
    look like without making the cross?
  • A handy tool used to predict results in Mendelian
    genetics is the Punnett (PUH nut) square.

Click image to view movie.
18
Genetics
1
Punnett Squares
  • In a Punnett square, letters represent dominant
    and recessive alleles.

19
Genetics
1
Punnett Squares
  • An uppercase letter stands for a dominant allele.
  • A lowercase letter stands for a recessive allele.

20
Genetics
1
Punnett Squares
  • They show the genotype (JEE nuh tipe), or genetic
    makeup, of an organism.
  • The way an organism looks and behaves as a result
    of its genotype is its phenotype (FEE nuh tipe).

21
Genetics
1
Alleles Determine Traits
  • Most cells in your body have two alleles for
    every trait.
  • These alleles are located on chromosomes within
    the nucleus of cells.

22
Genetics
1
Alleles Determine Traits
  • An organism with two alleles that are the same is
    called homozygous (hoh muh ZI gus).
  • An organism that has two different alleles for a
    trait is called heterozygous (he tuh roh ZI gus).

23
Genetics
1
Making a Punnett Square
24
Section Check
1
Question 1
How did Gregor Mendel use his knowledge of
mathematics in his study of heredity in pea
plants?
25
Section Check
1
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.
26
Section Check
1
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?
27
Section Check
1
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.
28
Section Check
1
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?
29
Section Check
1
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.
30
Genetics Since Mendel
2
Incomplete Dominance
  • When the offspring of two homozygous parents show
    an intermediate phenotype, this inheritance is
    called incomplete dominance.
  • Examples of incomplete dominance include the
    flower color of some plant breeds and the coat
    color of some horse breeds.

31
Genetics Since Mendel
2
Multiple Alleles
  • Many traits are controlled by more than two
    alleles.
  • A trait that is controlled by more than two
    alleles is said to be controlled by multiple
    alleles.

32
Genetics Since Mendel
2
Multiple Alleles
  • Traits controlled by multiple alleles produce
    more than three phenotypes of that trait.
  • Blood type in humans is an example of multiple
    alleles that produce only four phenotypes.
  • The alleles for blood types are called A, B, and
    O.

33
Genetics Since Mendel
2
Multiple Alleles
  • When a person inherits one A allele and one B
    allele for blood type, both are
    expressed?phenotype AB.
  • A person with phenotype A blood has the genetic
    makeup, or genotype?AA or AO.

34
Genetics Since Mendel
2
Multiple Alleles
  • Someone with phenotype B blood has the genotype
    BB or BO.
  • Finally, a person with phenotype O blood has the
    genotype OO.

35
Genetics Since Mendel
2
Polygenic Inheritance
  • Polygenic (pah lih JEH nihk) inheritance occurs
    when a group of gene pairs acts together to
    produce a trait.
  • The effects of many alleles produces a wide
    variety of phenotypes.

Click image to view movie.
36
Genetics Since Mendel
2
Polygenic Inheritance
  • Your height and the color of your eyes and skin
    are just some of the many human traits controlled
    by polygenic inheritance.
  • It is estimated that three to six gene pairs
    control your skin color.
  • The environment also plays an important role in
    the expression of traits controlled by polygenic
    inheritance.

37
Genetics Since Mendel
2
Impact of the Environment
  • Your environment plays a role in how some of your
    genes are expressed or whether they are expressed
    at all.
  • Environmental influences can be internal or
    external.

38
Genetics Since Mendel
2
Impact of the Environment
  • Although genes determine many of your traits, you
    might be able to influence their expression by
    the decisions you make.
  • For instance, if some people at risk for skin
    cancer limit their exposure to the Sun and take
    care of their skin, they might never develop
    cancer.

39
Genetics Since Mendel
2
Human Genes and Mutations
  • Occasionally errors occur in the DNA when it is
    copied inside of a cell.
  • Such changes and errors are called mutations.
  • Not all mutations are harmful. They might be
    helpful or have no effect on an organism.

40
Genetics Since Mendel
2
Chromosome Disorders
  • Every organism has a specific number of
    chromosomes.
  • However, mistakes in the process of meiosis can
    result in a new organism with more or fewer
    chromosomes than normal.

41
Genetics Since Mendel
2
Chromosome Disorders
  • If three copies of chromosome 21 are produced in
    the fertilized human egg, Downs syndrome
    results.
  • Individuals with Downs syndrome can be short,
    exhibit learning disabilities, and have heart
    problems.

42
Genetics Since Mendel
2
Recessive Genetic Disorders
  • Many human genetic disorders, such as cystic
    fibrosis, are caused by recessive genes.
  • Some recessive genes are the result of a mutation
    within the gene.
  • Many of these alleles are rare.

43
Genetics Since Mendel
2
Recessive Genetic Disorders
  • Such genetic disorders occur when both parents
    have a recessive allele responsible for this
    disorder.
  • Because the parents are heterozygous, they dont
    show any symptoms.

44
Genetics Since Mendel
2
Recessive Genetic Disorders
  • If each parent passes the recessive allele to the
    child, the child inherits both recessive alleles
    and will have a recessive genetic disorder.

45
Genetics Since Mendel
2
Recessive Genetic Disorders
  • Cystic fibrosis is the most common genetic
    disorder that can lead to death among Caucasian
    Americans.
  • In most people, a thin fluid is produced that
    lubricates the lungs and intestinal tract.
  • People with cystic fibrosis produce thick mucus
    instead of this thin fluid.

46
Genetics Since Mendel
2
Recessive Genetic Disorders
  • The thick mucus builds up in the lungs and makes
    it hard to breathe.
  • This buildup often results in repeated bacterial
    respiratory infections.

47
Genetics Since Mendel
2
Sex Determination
  • Each egg produced by a female normally contains
    one X chromosome.
  • Males produce sperm that normally have either an
    X or a Y chromosome.

48
Genetics Since Mendel
2
Sex Determination
  • When a sperm with an X chromosome fertilizes an
    egg, the offspring is a female, XX.
  • A male offspring, XY is the result of a
    Y-containing sperm fertilizing an egg.

49
Genetics Since Mendel
2
Sex-Linked Disorders
  • An allele inherited on a sex chromosome is called
    a sex-linked gene.
  • Color blindness is a sex-linked disorder in which
    people cannot distinguish between certain colors,
    particularly red and green.

50
Genetics Since Mendel
2
Sex-Linked Disorders
  • This trait is a recessive allele on the X
    chromosome.
  • Because males have only one X chromosome, a male
    with this allele on his X chromosome is
    color-blind.
  • A color-blind female occurs only when both of her
    X chromosomes have the allele for this trait.

51
Genetics Since Mendel
2
Pedigrees Trace Traits
  • A pedigree is a visual tool for following a trait
    through generations of a family.
  • Males are represented by squares and females by
    circles.

52
Genetics Since Mendel
2
Pedigrees Trace Traits
  • A completely filled circle or square shows that
    the trait is seen in that person.
  • Half-colored circles or squares indicate
    carriers.
  • People represented by empty circles or squares do
    not have the trait and are not carriers.

53
Genetics Since Mendel
2
Using Pedigrees
  • A pedigree is a useful tool for a geneticist.
  • When geneticists understand how a trait is
    inherited, they can predict the probability that
    a baby will be born with a specific trait.

54
Genetics Since Mendel
2
Using Pedigrees
  • Pedigrees also are important in breeding animals
    or plants.

55
Section Check
2
Question 1
Why is color blindness a sex-linked trait?
56
Section Check
2
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.
57
Section Check
2
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
58
Section Check
2
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.
59
Section Check
2
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
60
Section Check
2
Answer
The correct answer is C. Downs syndrome occurs
when there are three copies of chromosome 21
instead of the usual two.
61
Biotechnology
3
Genetic Engineering
  • Through genetic engineering, scientists are
    experimenting with biological and chemical
    methods to change the arrangement of DNA that
    makes up a gene.
  • Genetic engineering already is used to help
    produce large volumes of medicine.

62
Biotechnology
3
Recombinant DNA
  • Recombinant DNA is made by inserting a useful
    segment of DNA from one organism into a
    bacterium.
  • This method is used to produce human insulin,
    human growth hormone, and other chemicals by
    bacteria.

63
Biotechnology
3
Gene Therapy
  • In gene therapy, a normal allele is placed in a
    virus.
  • The virus then delivers the normal allele when it
    infects its target cell.
  • The normal allele replaces the defective one.

64
Biotechnology
3
Gene Therapy
  • Scientists are conducting experiments that use
    this method to test ways of controlling cystic
    fibrosis and some kinds of cancer.
  • Gene therapy might be a method of curing several
    other genetic disorders in the future.

65
Biotechnology
3
Genetically Engineered Plants
  • Selecting plants with the most desired traits to
    breed for the next generation is called selective
    breeding.
  • Recent advances in genetics have not replaced
    selective breeding.

66
Biotechnology
3
Genetically Engineered Plants
  • Genetic engineering can produce improvements in
    crop plants, such as corn, wheat, and rice.
  • One type of genetic engineering involves finding
    the genes that produce desired traits in one
    plant and then inserting those genes into a
    different plant.

67
Section Check
3
Question 1
What is it called when scientists use biological
and chemical methods to change the arrangement of
DNA in a gene?
68
Section Check
3
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.
69
Section Check
3
Question 2
What does this diagram illustrate?
70
Section Check
3
A. Bacteria cells can produce human insulin. B.
Bacteria genes are put in human cells.
71
Section Check
3
C. People with diabetes are given the gene for
insulin. D. The insulin gene is inserted in
people with diabetes.
72
Section Check
3
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.
73
Section Check
3
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
74
Section Check
3
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.
75
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