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Introduction To Genetics- Chapter 11

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Title: Introduction To Genetics- Chapter 11


1
Introduction To Genetics- Chapter 11
2
I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel
  • A. Gregor Mendel was born in 1822 and after
    becoming a priest Mendel was a math teacher for
    14 years and a monastery. Mendel was also in
    charge of the monastery garden.

3
I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel
  • 1. Mendel carried out his work with garden peas

4
I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel
  • 2. Fertilization is the fusion of an egg and a
    sperm.
  •  
  • 3. True breeding plants are plants that were
    allowed to self-pollinate and the offspring would
    be exactly like the parent.

5
I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel
6
Mendels experiments
11-1 The Work of Gregor Mendel
  • The first thing Mendel did was create a pure
    generation or true-breeding generation.
  • He made sure that certain pea plants were only
    able to self pollinate, eliminating unwanted
    traits.
  • He did this by cutting away the stamen, or male
    part of each flower

7
11-1 The Work of Gregor Mendel
Figure 11-3 Mendels Seven F1 Crosses on Pea
Plants
Section 11-1
Mendels experiments
Seed Shape
Flower Position
Seed Coat Color
Seed Color
Pod Color
Plant Height
Pod Shape
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Wrinkled
Green
White
Constricted
Yellow
Terminal
Short
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Flower color purple (P) vs. white (p)
Seed coat color and flower color are often put in
for one another thus, the EIGHT traits!!!
Go to Section
8
Genes and dominance
11-1 The Work of Gregor Mendel
  • Trait a characteristic
  • Mendel studied seven of these traits
  • After Mendel ensured that his true-breeding
    generation was pure, he then crossed plants
    showing contrasting traits.
  • He called the offspring the F1 generation or
    first filial.

9
What will happen when pure yellow peas are
crossed with pure green peas?
11-1 The Work of Gregor Mendel
  • All of the offspring were yellow.
  • Hybrids the offspring of crosses between
    parents with contrasting traits

10
What did Mendel conclude?
11-1 The Work of Gregor Mendel
  • Inheritance is determined by factors passed on
    from one generation to another.
  • Mendel knew nothing about chromosomes, genes, or
    DNA. Why?
  • These terms hadnt yet been defined.

11
What were Mendels factors
11-1 The Work of Gregor Mendel
  • The factors that Mendel mentioned were the
    genes.
  • Each gene has different forms called alleles
  • Mendels second principle stated that some
    alleles are dominant and some are recessive.

12
Mendels second cross
11-1 The Work of Gregor Mendel
  • He allowed the F1 generation to self-pollinate
    thus producing the F2 generation.
  • Did the recessive allele completely disappear?
  • What happened when he crossed two yellow pea
    hybrid (F1) plants?

13
Results
11-1 The Work of Gregor Mendel
  • ¾ of the peas were yellow, ¼ of the peas were
    green.
  • During the formation of the sex cells or gametes,
    the alleles separated or segregated to different
    gametes. (pollen and egg)

14
Punnett square example
11-2 Probability and Punnett Squares
15
Reading Punnett squares
11-2 Probability and Punnett Squares
  • Gametes are placed above and to the left of the
    square
  • Offspring are placed in the square.
  • Capital letters (Y) represent dominant alleles.
  • Lower case letters (y) represent recessive
    alleles.

16
Phenotype vs genotype
11-2 Probability and Punnett Squares
  • Genotype
  • The genetic makeup
  • Symbolized with letters
  • Tt or TT
  • Phenotype
  • Physical appearance of the organism
  • Expression of the trait
  • Short, tall, yellow, smooth, etc.

17
Genes and Dominance
11-2 Probability and Punnett Squares
  • 1. The different forms of a gene is called and
    an alleles.
  •  
  • 2. The principal of dominance states that some
    alleles are dominant and others are recessive.

18
11-2 Probability and Punnett Squares
  1. Genes and Dominance

Pinky Finger Traits
At Paris Gibson Ed Center we tested dominant and
recessive traits in our school population. We
tested pinky finger traits, whereby, the bent
finger is dominant and the straight finger is
recessive.
19
C. Segregation
11-2 Probability and Punnett Squares
  • 1. Each trait has two genes, one from the
    mother and one from the father.
  •  
  • 2. Traits can be either dominant or recessive.
  •  
  • 3. A dominant trait only needs one gene in
    order to be expressed.
  •  

20
C. Segregation
11-2 Probability and Punnett Squares
  • 4. A recessive trait needs two genes in order
    to be expressed.
  •  

21
11-2 Probability and Punnett Squares
22
C. Segregation
11-2 Probability and Punnett Squares
  • 5. Egg and sperm are sex cells called gametes.
  •  
  • 6. Segregation is the separation of alleles
    during gamete formation.

23
11-2 Probability and Punnett Squares
24
II. Probability and Punnett Squares
11-2 Probability and Punnett Squares
  • A. Genetics and Probability
  •  1. The likelihood that a particular event will
    occur is called probability.
  •  
  • 2. The principals of probability can be used to
    predict the outcome of genetic crosses.

25
II. Probability and Punnett Squares
11-2 Probability and Punnett Squares
26
B. Punnett Squares
11-2 Probability and Punnett Squares
  • 1. The gene combination that might result from
    a genetic cross can be determined by drawing a
    diagram known as a Punnett square.
  •  
  • 2. Punnett squares can be used to predict and
    compare the genetic variations that will result
    from a cross.
  •  

27
11-2 Probability and Punnett Squares
28
B. Punnett Squares
11-2 Probability and Punnett Squares
  • 3. Each trait has two genes- one from the
    mother and one from the father.
  •  
  • 4. Alleles can be homozygous having the same
    traits.
  •  
  • 5. Alleles can be heterozygous- having
    different traits.

29
11-2 Probability and Punnett Squares
B. Punnett Squares
30
B. Punnett Squares
11-2 Probability and Punnett Squares
  • 6. Physical characteristics are called the
    phenotype.
  •  
  • 7. Genetic make up is the genotype.

31
11-2 Probability and Punnett Squares
32
III. Exploring Mendalian Genetics
11-3 Exploring Mendelian Genetics
  • A. Independent assortment
  • 1. Genes segregate independently.

33
III. Exploring Mendalian Genetics
11-3 Exploring Mendelian Genetics
  • 2. The principle of independent assortment
    states that genes for different traits can
    segregate independently during the formation of
    gametes.
  •  
  • 3. Independent assortment helps account for the
    many genetic variations observed in plants,
    animals and other organisms.

34
11-3 Exploring Mendelian Genetics
35
The dihybrid cross
11-3 Exploring Mendelian Genetics
  • Punnett square on board

36
B. A summary of Mendels Principals
11-3 Exploring Mendelian Genetics
  • 1. Genes are passed from parent to offspring.
  •  
  • 2. Some forms of a gene may be dominant and
    others recessive.

37
B. A summary of Mendels Principals
11-3 Exploring Mendelian Genetics
  • 3. In most sexually producing organisms, each
    adult has two copies of each gene- one from each
    parent. These genes are segregated from each
    other when gametes are formed.
  •  
  • 4. The alleles for different genes usually
    segregate independently of one another.

38
C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics
  • 1. Some alleles are neither dominant nor
    recessive, and many traits are controlled by
    multiple alleles or multiple genes.
  •  
  • 2. Cases in which one allele is not completely
    dominant over another are called incomplete
    dominance.

39
Incomplete dominance
11-3 Exploring Mendelian Genetics
  • A situation in which neither allele is dominant.
  • When both alleles are present a new phenotype
    appears that is a blend of each allele.
  • Alleles will be represented by capital letters
    only.

40
Incomplete dominance
11-3 Exploring Mendelian Genetics
  • Example White (W) and Red (R) is both dominate.
    If WW X RR the F1 generation would be WR
    pink.

41
What happens when a red flower is crossed with a
white flower?
11-3 Exploring Mendelian Genetics
  • According to Mendel either some white and some
    red or all offspring either red or white.
  • All are pink

42
11-3 Exploring Mendelian Genetics
43
C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics
  • 3. Codominance is when both alleles contribute
    to the phenotype.
  •  
  • Example Feather colors

44
C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics
  • 4. Many genes have more than two alleles and
    are referred to have multiple alleles.
  •  
  • a. This means that more than two possible
    alleles exist in a population. Example colors
    of rabbits see page 273.

45
C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics
46
C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics
  •   5. Traits that are controlled by two or more
    genes are said to be polygenic traits, which
    means, having many genes.
  • a. Example eye color has many different
    genes.

47
Meiosis
  • Division of Sex Cells

48
The Point of Meiosis
11-4 Meiosis
  • Meiosis is a process of reduction division in
    which the number of chromosomes per cell is cut
    in half through the separation of homologous
    chromosomes in a diploid cell.
  •  

49
2 types Spermatogeneis Oogenesis
11-4 Meiosis
50
Meiosis
11-4 Meiosis
  • Diploid 2 sets of chromosomes
  • Haploid 1 set of chromosomes
  • Homologous chromosomes that each have a
    corresponding chromosome from the opposite sex
    parent

51
Meiosis
11-4 Meiosis
52
Meiosis
11-4 Meiosis
  • A. Chromosome number
  •  
  • 1. Every individual has two sets of
    chromosomes. One from the mother one from the
    father. When the chromosomes pair up for the
    same trait they are called homologous
    chromosomes.

53
Meiosis
11-4 Meiosis
  • 2. A cell that contains homologous chromosomes
    (2 genes) is said to be diploid/ 2n.
  •  
  • 3. Gametes (egg /sperm) have only one
    chromosome and are said to be haploid/ n.

54
Meiosis
11-4 Meiosis
  • Meiosis I- The homologous chromosomes line up BUT
    then they CROSS OVER, exchanging genetic
    information.
  • Meiosis II- The two cells produced by meiosis I
    now enter a second meiotic division. The final
    product start with 1 cell with 46 chromosomes
    and get 4 DIFFERENT cells each with 23
    chromosomes.
  •  

55
11-4 Meiosis
56
Meiosis Stages
11-4 Meiosis
  • Meiosis usually involves 2 distinct stages
  • Meiosis I (animation)
  • Meiosis II (animation)

57
11-4 Meiosis
58
11-4 Meiosis
59
Prophase I
11-4 Meiosis
  • Each chromosome pairs with its corresponding
    homologous chromosome to form a tetrad.
  • There are 4 chromosomes in a tetrad.
  • The pairing of homologous chromosomes is the key
    to understanding meiosis.
  • Crossing-over may occur here
  • Crossing-over is when chromosomes overlap and
    exchange portions of their chromatids.

60
11-4 Meiosis
61
Prophase I
11-4 Meiosis
62
Metaphase I
11-4 Meiosis
  • Spindle fibers attach to the chromosomes

63
Metaphase I
11-4 Meiosis
64
Anaphase I
11-4 Meiosis
  • The fibers pull the homologous chromosomes toward
    opposite ends of the cell.

65
Anaphase I
11-4 Meiosis
66
Telophase I Cytokinesis
11-4 Meiosis
  • Nuclear membranes form.
  • The cell separates into 2 cells.

67
Telophase I
11-4 Meiosis
68
Prophase II
11-4 Meiosis
  • Meiosis I results in two haploid (N) cells.
  • Each cell has half the number of chromosomes as
    the original cell.

69
Prophase II
11-4 Meiosis
70
Metaphase II
11-4 Meiosis
  • The chromosomes line up similar to metaphase in
    mitosis.

71
Metaphase II
11-4 Meiosis
72
Anaphase II
11-4 Meiosis
  • Sister chromatids separate and move to opposite
    ends of the cell.

73
Anaphase II
11-4 Meiosis
74
Telophase II
11-4 Meiosis
  • Meiosis II results in 4 haploid cells.

75
Telophase II
11-4 Meiosis
76
Gamete Formation
11-4 Meiosis
  • In males, meiosis results in 4 sperm cells
  • In females, meiosis results in 1 egg cell and
    three polar bodies, which are not used in
    reproduction.

77
Net result
11-4 Meiosis
  • Spermatogensis
  • 4 mature sperm
  • Each sperm has exactly half the number of
    chromosomes as the father.
  • Oogensis
  • 1 mature ova or egg.
  • Each egg has exactly half the number of
    chromosomes as the mother.

78
2 types Spermatogeneis Oogenesis
11-4 Meiosis
79
Mitosis vs Meiosis
11-4 Meiosis
Mitosis Meiosis
Results in 2 Diploid Cells (2N) 4 Haploid Cells (N)
Cells are Genetically Identical Genetically Different
Occurs in Somatic (Body) Cells Sex Cells
80
V. Linkage and gene maps
11-5 Linkage and Gene Maps
  • A. Gene linkage
  •  
  • 1. Thomas Hunt Morgan research on fruit flies
    led him to the principal of linkage.
  •  
  • 2. Morgan discovered that many genes appeared
    linked together.

81
11-5 Linkage and Gene Maps
V. Linkage and gene maps
82
V. Linkage and gene maps
11-5 Linkage and Gene Maps
  • 3. It is the chromosomes, however, that assort
    independently not individual genes.
  •  
  • 4. Mendel DID miss gene linkage.

83
V. Linkage and gene maps
11-5 Linkage and Gene Maps
  • 5. Even though if two genes are found on the
    same chromosome this does not mean they are
    linked forever. Crossing over can occur.
  •  
  • 6. Crossing over creates genetic diversity.

84
V. Linkage and gene maps
11-5 Linkage and Gene Maps
  • 7. A gene map shows the relative location of
    each gene. See page 280 figure 11.9

85
11-5 Linkage and Gene Maps
86
Alleles, alternative versions of a gene
87
(No Transcript)
88
Pedigree analysis
89
Testing a fetus for genetic disorders
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