Introduction To Genetics- Chapter 11

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Introduction To Genetics- Chapter 11
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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.

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I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel

• 1. Mendel carried out his work with garden peas

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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.

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I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel
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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

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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!!!
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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.

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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

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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.

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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.

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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?

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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)

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Punnett square example
11-2 Probability and Punnett Squares
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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.

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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.

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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.

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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.
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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.
•  

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C. Segregation
11-2 Probability and Punnett Squares

• 4. A recessive trait needs two genes in order
  to be expressed.
•  

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11-2 Probability and Punnett Squares
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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.

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11-2 Probability and Punnett Squares
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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.

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II. Probability and Punnett Squares
11-2 Probability and Punnett Squares
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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.
•  

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11-2 Probability and Punnett Squares
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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.

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11-2 Probability and Punnett Squares
B. Punnett Squares
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B. Punnett Squares
11-2 Probability and Punnett Squares

• 6. Physical characteristics are called the
  phenotype.
•  
• 7. Genetic make up is the genotype.

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11-2 Probability and Punnett Squares
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III. Exploring Mendalian Genetics
11-3 Exploring Mendelian Genetics

• A. Independent assortment
• 1. Genes segregate independently.

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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.

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11-3 Exploring Mendelian Genetics
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The dihybrid cross
11-3 Exploring Mendelian Genetics

• Punnett square on board

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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.

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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.

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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.

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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.

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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.

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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

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11-3 Exploring Mendelian Genetics
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C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics

• 3. Codominance is when both alleles contribute
  to the phenotype.
•  
• Example Feather colors

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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.

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C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics
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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.

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Meiosis

• Division of Sex Cells

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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.
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2 types Spermatogeneis Oogenesis
11-4 Meiosis
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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

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Meiosis
11-4 Meiosis
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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.

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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.

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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.
•  

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11-4 Meiosis
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Meiosis Stages
11-4 Meiosis

• Meiosis usually involves 2 distinct stages
• Meiosis I (animation)
• Meiosis II (animation)

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11-4 Meiosis
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11-4 Meiosis
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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.

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11-4 Meiosis
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Prophase I
11-4 Meiosis
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Metaphase I
11-4 Meiosis

• Spindle fibers attach to the chromosomes

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Metaphase I
11-4 Meiosis
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Anaphase I
11-4 Meiosis

• The fibers pull the homologous chromosomes toward
  opposite ends of the cell.

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Anaphase I
11-4 Meiosis
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Telophase I Cytokinesis
11-4 Meiosis

• Nuclear membranes form.
• The cell separates into 2 cells.

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Telophase I
11-4 Meiosis
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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.

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Prophase II
11-4 Meiosis
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Metaphase II
11-4 Meiosis

• The chromosomes line up similar to metaphase in
  mitosis.

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Metaphase II
11-4 Meiosis
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Anaphase II
11-4 Meiosis

• Sister chromatids separate and move to opposite
  ends of the cell.

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Anaphase II
11-4 Meiosis
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Telophase II
11-4 Meiosis

• Meiosis II results in 4 haploid cells.

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Telophase II
11-4 Meiosis
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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.

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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.

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2 types Spermatogeneis Oogenesis
11-4 Meiosis
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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
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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.

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11-5 Linkage and Gene Maps
V. Linkage and gene maps
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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.

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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.

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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

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11-5 Linkage and Gene Maps
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Alleles, alternative versions of a gene
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Pedigree analysis
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Testing a fetus for genetic disorders