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Genetics

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Title: Genetics


1
Genetics
2
Section 2 vocabulary
  • 1. Genetics
  • 2. Allele alternate forms of the gene
  • 3. Dominant appears in the F1
  • 4. Recessive not present in the F1
  • 5. Homozygous same alleles
  • 6. Heterozygous different alleles
  • 7. Genotype alleles
  • 8. Phenotype physical
  • 9. Law of segregation
  • 10. Hybrid
  • 11. Law of independent assortment

3
  • Additional Vocabulary

monohybrid cross true-breeding P generation F1
generation F2 generation Punnett square test
cross probability pedigree sex-linked gene
polygenic inheritance incomplete dominance
multiple alleles codominance
4
The Father of Genetics!
  • Genetics the science of heredity.
  • Gregor Mendel

5
Gregor Johann Mendel (1822 - 1884) was a member
of an Augustinian order (Monastic) in Brunn
Austria
6
Mendel began studying plant breading by trying to
find the effects of crossing different strains of
common garden pea
  • He carried out his research with more precision
    than had yet been used. He also used the new
    science of statistics to analyze the results of
    his experiments. This use of mathematics to
    describe biological phenomena was a new concept.

7
  • Gregor Mendel bred varieties of the garden pea in
    an attempt to understand heredity.
  • Mendel observed that contrasting traits appear in
    offspring according to simple ratios.

8
allele
  • Alternate forms of a gene
  • Such as blue, brown or green for the eye color
    gene
  • Or yellow and
  • green for
  • pea color

9
Phenotype
  • The observable or outward expression of the
    allele pair that an organism has what it looks
    like.

10
genotype
  • The organisms allele pairs what genes it has
    to produce the outward appearance it has.

11
Homozygous genotype
  • An organism with two of the same alleles for a
    trail. Both alleles are the same

Dominant
Recessive
12
Heterozygous genotype
  • An organism with 2 different alleles for a trait.

13
Hybrid 279
  • Heterozygous genotypes

14
Monohybrid crosses
  • Two parents differ by only one trait.
  • Height tall or short
  • or
  • smooth/ wrinkled
  • Green/ yellow

15
Monohybrid traits
16
Monohybrid crosses
17
Results of a monohybrid crossfirst generation F1
  • One of the characteristics would kind of take
    over the other and the offspring would all look
    like only one of the parents.
  • Example green and yellow
  • All offspring were yellow!

18
Second generation F2
  • When the parents from the F1 are crossed.
  • Yellow X Yellow
  • ¾ were Yellow but ¼ was green .
  • The green trait reappeared!!!!

19
  • Mendel collected 6022 yellow peas and 2001 green.
  • this was almost a perfect 31 ratio of yellow
    green
  • He studied several traits and each gave this
    ratio!

20
F2 generation
21
What did Mendel learn from this?
  • Each organism has two factors for each of its
    traits.
  • Factors are forms of the Genes on chromosomes.
  • These are the alleles

22
alleles
  • An alternative form of a single gene passed from
    generation to generation.
  • Example the yellow or the green form of the
    color of peas are each alleles of the gene for
    the color of peas.

23
  • In Mendels experiments, only one of the two
    contrasting forms of a character was expressed in
    the F1 generation.
  • The other form reappeared in the F2 generation
    in a 31 ratio

24
  • Factors are Genes on chromosomes
  • Forms are called alleles

25
Rule of Dominance
  • By definition,
  • the trait that shows up in the F1 generation is
    dominant
  • the trait that disappears is recessive

26
What do these mean?
  • P
  • F1
  • F2

27
Out of Mendel's work came two "Laws" of
inheritance
  • 1) Mendel proposed that heredity was controlled
    by paired factors that segregated when gametes
    formed and rejoined at fertilization and,
  • 2) The principle of independent assortment
    indicates that the segregation of one pair of
    factors, or Alleles, has no influence over the
    way any other pair segregates.

28
Gregor Mendel approached problem-solving in new
and different ways.
29
  • 1. He worked with pure strains of garden peas.
  • The flowers have both male (stamen- anther and
    filaments) and female (pistil- stigma, style and
    ovary) reproductive parts.

30
  • He removed (emasculated) the male part (anthers
    and filaments that produce the male sex cells) so
    he could control the way each plant was
    fertilized.
  • This was done artificially by mechanically
    transferring the male sex cells from the desired
    plant to the stamen of the emasculated plant.
  • The offspring using this procedure are referred
    to as "crosses".

31
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32
  • 2. He only worked with traits of the peas that
    could easily be seen.
  • He experimented using only one trait at a time.
  • Traits included a) stem length, b) flower color
    or c) seed shape.

33
  • 3. Mendel kept detailed records of his "crosses".
  • He counted the pea offspring and calculated,
    using mathematics, how often the trait occurred
    in the offspring.

34
  • Mendel believed that traits were determined by
    individual units called factors.
  • He believed that each offspring received a factor
    from each parent.
  • Today these factors are called genes.

35
Punnett Squares
Dad Mom Allele allele
Allele
Allele
  • The square shows how the alleles separate when
    gametes are formed.
  • It shows the possible combinations of the alleles
    when fertilization occurs.

36
Punnett Square
  • G green peas g yellow peas
  • pure breed green

G G
g
g
Pure breed yellow
37
What are the results?
  • 100 are phenotype green
  • 100 are genotype heterozygous

4/4
38
Both parents are heterozygous genotype and
brown hair phenotype



39
What are the results?
Brown hair
blonde hair
40
Chances for Genotypes
1/4
1/4
2/4
41
Chances for Phenotypes
¾ Brown
¼ blonde
42
Flower color
  • R red
  • r white

43
Mendel's First Law Law of Segregation
  • Mendel guessed that the TWO genes for flower
    color separate or segregate, when the sex cells
    form during meiosis.
  • In the case of the hybrid pea flowers (RR), each
    plant would have one gene (allele) for red color
    (R) and one gene (allele) for white color (r).
  • These two genes would separate or segregate from
    each other during the formation of the sex cells.
    About half of the sex cells would receive the
    gene for red color and the other half the gene
    for white color.

44
Meiosis/ sex cell formation
Sperm cells each get one allele
45
Mendel's Law of Segregation states-
  • The two genes that determine a particular trait
    will separate when sex cells form.
  • Half of the cells will receive one gene (allele)
    and half of the cells will receive the other gene
    (allele) of the allelic pair.

46
Law of segregation
47
  • _ The law of segregation states that the two
    alleles for a gene separate when gametes are
    formed.

48
Mendel's Second Law
  • - the law of independent assortment
  • Random distribution of alleles occurs during
    gamete formation. Genes on separate chromosomes
    sort independently during meiosis.
  • during gamete formation the segregation of the
    alleles of one allelic pair is independent of the
    segregation of the alleles of another allelic
    pair

49
  • The law of independent assortment states that two
    or more pairs of alleles separate independently
    of one another during gamete formation.

50
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51
In other words
  • Where the allele for color goes is not connected
    to where the gene for height goes.

Color r
Color R
Height T
Height t
52
R
r
r
R
T
T
t
t
t
53
Mendels Theory
  • _ Different versions of a gene are called
    alleles. An individual usually has two alleles
    for a gene, each inherited from a different
    parent.

54
  • _ Individuals with the same two alleles for a
    gene are homozygous those with two different
    alleles for a gene are heterozygous.

55
Studying Heredity
  • _ The results of genetic crosses can be predicted
    with the use of Punnett squares and
    probabilities.
  • _ A test cross can be used to determine whether
    an individual expressing a dominant trait is
    heterozygous or homozygous.
  • _ A traits pattern of inheritance within a
    family can be determined by analyzing a pedigree.

56
Linked genes
  • Unless. The genes are located on the same
    chromosome and then they are called linked genes
    and they do travel together to the same gamete.

57
Genes on the same chromosome will always travel
together into the same gamete
  • red hair r
  • freckles f

58
2 traits
  • Dihybrid cross
  • When you look at two traits at a time the Punnett
    square gets bigger because the possible
    combinations get bigger!





59
dihybrid
  • A attached ears
  • a unattached ears
  • B brown hair
  • b blonde hair
  • So when we look at the chances of getting two
    traits the possibilities increase

60
Heterozygous hybrid
  • So 2 pure breed parents for both traits would be
  • P generation AABB X aabb
  • All of the kids would be AaBb

61
Dihybrid cross means hybrid for two traits so
  • F1 generation
  • AaBb X AaBb
  • What are the possible combinations of gametes?
  • Remember the law of segregation only one letter
    or allele for a trait.
  • Only A or a but not both!

62
A
a
B
b
  • The gene alleles for attached or unattached ears
    must segregate from each other during meiosis.
  • In other words. You will only have one or the
    other in the gametes.

63
a
B
b
A
  • The same is true for the alleles for hair color.
  • gametes

64
Possible gametes
  • AB
  • Ab
  • aB
  • ab

A
a
B
b
65
Place the possible gametes on the sides of the
square
AB
Ab
aB
ab




AB
Ab
Which becomes AABB
aB
ab
66
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67
What are the phenotypic results?
  • ___/16 attached ears and brown hair
  • ___/16 attached ears and blonde hair
  • ___/16 unattached ears and brown hair
  • ___/16 unattached ears and blonde hair

68
You always get
  • 9331

69
The genotypic results?
  • Homozygous dominant for both traits ___/16
  • Heterozygous for both traits
    ___/16
  • Homo recessive for both traits ___/16
  • Homo dominant for first hetero for 2nd ___/16
  • Homo recessive for 1st hetero for 2nd ___/16
  • Homo recessive for 1st homo dom 2nd ___/16
  • Hetero for 1st homo/dom for 2nd ___/16
  • Hetero for 1st homo rec for 2nd ___/16
  • Complete the list

70
Reflections
  • The genetics questions will be part of your
    reflections for benchmark 16.1
  • After completing them and checking your answers
    tomorrow, write a statement about your level of
    understanding . Can you do them? Which types do
    you still have trouble with? Have you studied the
    vocabulary? Do you understand the question, how
    to set up the question? Be specific so I know how
    to help you! These will be due after we go over
    the answers to the problems!

71
Corn Questions
  • Write the answers on your own paper.
  • Draw the punnett squares.

72
Now that you have determined the predicted
percentages of phenotypes and genotypes, you will
examine an ear of corn resulting from two
heterozygous parents and compare the observed
percentage to the predicted percentage.
  • Procedure Count the number of red and yellow
    kernels on the ear of corn pictured below. Count
    FIVE rows of kernels. Record the numbers of red
    kernels, yellow kernels, and total kernels.

73
Analysis
  • Calculate the percentage of red and yellow
    kernels from your data.
  • Compare your observed percentages with the
    theoretical percentage you predicted from the
    Punnett Square you completed in Part A, 4.
  • Hypothesize Would you have calculated the same
    ratio if you had counted only half the kernels on
    the ear of corn above? Explain.
  • Apply How could you determine whether a
    particular red kernel is homozygous dominant or
    heterozygous? Hint Look at the Punnett squares
    in Part A.
  • This is due today!

74
Do the Worksheet 1 Monohybrid cross questions.
  • Write the answers on your own paper.
  • Draw punnett squares for each question to show
    your work.
  • Use the following letters for each question.
  • 1. Cc
  • 2. Gg
  • 3. Bb
  • 4. Bb
  • 5. Aa
  • 6. Ff
  • 7. Ll
  • 8. Y yellow y grey
  • 9. P p
  • 10. B b
  • These are due tomorrow!

75
Reflections
  • The genetics questions will be part of your
    reflections for benchmark 16.1
  • After completing them and checking your answers
    tomorrow, write a statement about your level of
    understanding . Can you do them? Which types do
    you still have trouble with? Have you studied the
    vocabulary? Do you understand the question, how
    to set up the question? Be specific so I know how
    to help you!

76
Section 3
  • Section 3 vocabulary
  • Genetic recombination
  • Polyploidy

77
Genetic recombination
  • New combinations of genes produced by crossing
    over and independent assortment.
  • Add variations
  • 2n n is the number of chromosome pairs

78
Gene linkage
  • Genes close together on the same chromosome are
    said to be linked and travel together!
  • These are exceptions to the independent
    assortment law!

79
  • Crossing over happens more when genes are far
    apart than those that are close together.
  • Chromosome maps show the location of genes on
    chromosomes.

80
Polyploidy
  • One or more sets of chromosomes.
  • Triploid organisms 3n have 3 sets
  • this is rare in animals but more common in
    plants.
  • In humans this is lethal deadly!
  • 1/3 plants are polyploids.
  • Wheat, oats, sugar are all polyploids, this
    increases their vigor and size.

81
polyploid
82
Kleinfelder Karyotype
83
  • Question 1
  • Let's say that in seals, the gene for the length
    of the whiskers has two alleles.  The dominant
    allele (W) codes long whiskers the recessive
    allele (w) codes for short whiskers.
  • a)  What percentage of offspring would be
    expected to have short whiskers from the cross of
    two long-whiskered seals, one that is homozygous
    dominant and one that is heterozygous? b) If one
    parent seal is pure long-whiskered and the other
    is short-whiskered, what percent of offspring
    would have short whiskers?

84
  • P-sqARE PraCTice qUesTiON 2
  • 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. Summarize the genotypes
    phenotypes of the possible offspring.

85
  • Question 3
  • A green-leafed luboplant (I made this plant up)
    is crossed with a luboplant with yellow-striped
    leaves.  The cross produces 185 green-leafed
    luboplants. Summarize the genotypes phenotypes
    of the offspring that would be produced by
    crossing two of the green-leafed luboplants
    obtained from the initial parent plants.

86
P-squARE PRacTice qUeStION 4
  • Mendel found that crossing wrinkle-seeded plants
    with pure round-seeded plants produced only
    round-seeded plants.  What genotypic phenotypic
    ratios can be expected from a cross of a
    wrinkle-seeded plant a plant heterozygous for
    this trait (seed appearance)?

87
Gene Linkage
  • Genes on the same chromosome are linked.
  • Linked genes are inherited together.
  • Linked genes do not undergo independent
    assortment.
  • THEREFORE, MENDELS LAW OF INDEPENDENT ASSORTMENT
    ONLY IS TRUE IF THE GENES ARE ON DIFFERENT
    CHROMOSOMES.
  • Studies have shown that linked genes on the same
    chromosome sometimes can separate. This occurs by
    a process called "crossing over".
  •  

88
Crossing Over
  • Occurs at prophase during the first part of
    meiosis (Anaphase I)
  • Chromosomes pair before they divide
  • Chromosome pairs wind around each other
  • Each pair of chromosomes duplicates itself
  • Chromosomes break and exchange equal amounts of
    chromosome material. The newly exchanged pieces
    are enzymatically "glued" together.
  • Chromosomes separate (to individual chromatids).
    Each chromatid now has different traits or
    genes/alleles.

89
Purpose of crossing over
  • provides new combinations of genes/alleles
    (traits) in male and female sex cells (gametes)
    so that when fertilization occurs the offspring
    demonstrate increased genotypic and phenotypic
    variability.

90
Sex-linked genes
  • Genes located on one of the sex chromosomes.
    Usually the X
  • Most often expressed in males because they only
    have one X chromosome

91
  • The inheritance of abnormal genes found on the 22
    pairs of human chromosomes (autosomes) obey the
    principles of Mendelian genetics.

92
  • The inheritance of abnormal genes on the
    X-chromosomes also are based on Mendel's
    principles.

93
Gender issues
  • complicate this process only in regard to the Y
    chromosome.
  • Males have only one X chromosome whereas females
    have a pair of X-chromosomes. The expression of
    genetic abnormalities in the offspring of
    affected people takes on a new dimension when the
    Y-chromosome is included in the "equation".  

94
  •  

95
  • Traits which are determined by one or more genes
    show
  • dominance,
  • recessiveness,
  • sex linkage,
  • phenotypes,
  • genotypes
  • and incomplete dominance

96
Complex Patterns of Heredity
  • _ Characters usually display complex patterns of
    heredity, such as incomplete dominance,
    codominance, and multiple alleles.
  • _

97
  • Mutations can cause genetic disorders, such as
    sickle cell anemia, hemophilia, and Huntingtons
    disease.
  • _ Genetic counseling can help patients concerned
    about a genetic disorder.

98
Section 3 vocabulary
  • 1. Genetic recombination 2. Polyploidy

99
Summary of genetics video
  • http//www.bing.com/videos/search?qgeneticvideos
    viewdetailmidE7AEA272F3FDDB885163E7AEA272F3FDD
    B885163first0FORMLKVR19
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