CP Biology Chapter 11 Honors Chapter 10 Introduction to Genetics

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CP Biology Chapter 11 Honors Chapter
10Introduction to Genetics

• Genetics The scientific study of heredity
• Heredity the passing of traits from parents to
  offspring

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Inheritance

• You get your genes from your parents
• In meiosis, half of the chromosomes in a pair
  come from the Dad, half come from the Mom
• What we know today is based on the work of Gregor
  Mendel Austrian monk

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Key terms to know

• Allele each form of a gene for a certain trait
  (R or r)
• Gene sequence of DNA that codes for a protein a
  thus determines a trait
• Genotype combination of alleles for a given
  trait ( RR or Rr or rr)
• Phenotype Appearance of trait ( round seeds or
  wrinkled seeds

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Terms continued

• Homozygous - when you have 2 or the same alleles
  for a given trait (RR or rr)
• Heterozygous when you have 2 different alleles
  for a trait (Rr)
• Incomplete dominance blending of alleles to
  produce a different phenotype (red and white
  produce pink)
• Codominance Both alleles are expressed equally
  ( produces combinations of each)
• Multiple alleles a set of 3 or more different
  alleles controlling a trait ( eye color, skin
  color)

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Figure 14.0 Painting of Mendel
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Gregor Mendel

• Born in 1822 in Czech Republic
• Became a priest and studied math and science at
  the University of Vienna
• Worked for next 14 years in the monastery as head
  of monastery garden and taught at the high school

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Mendel studied seven/eight different pea plant
traits

• Trait a specific characteristic that varies
  from one individual to another
• (ex. Seed color, height, hair color)
• Mendels studied traits had two contrasting
  characters or alleles -- different forms of a
  gene

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Figure 11-3 Mendels Seven F1 Crosses on Pea
Plants
Section 11-1
CP see page 264 in textbook Honors
see page 262
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
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Figure 14.1 A genetic cross
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Figure 14.3 Alleles, alternative versions of a
gene
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Mendels test crosses.

• Testcross experimental cross between an
  individual with the dominant phenotype for a
  given trait (genotype unknown, though) and
  another individual with the recessive phenotype
  (homozygous recessive)
• P1 generation parents that Mendel
  cross-pollinated
• F1 generation offspring of P1 that were allowed
  to self-pollinate
• F2 generation offspring of F1 generation

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Figure 14.2 Mendel tracked heritable characters
for three generations
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Mendels Conclusions.

• Biological inheritance is determined by factors
  that are passed from one generation to a next
  today, called genes
• Law of Dominance where there are two or more
  forms of a gene for a single trait, some alleles
  are dominant and other alleles are recessive
• Law of Segregation alleles segregate (separate)
  from each other during the process of meiosis
  (gamete formation)
• Principle of independent assortment genes for
  different traits can segregate independently
  during the formation of gametes

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Concept Map
Section 11-3
Gregor Mendel
concluded that
experimented with
which is called the
which is called the
Principle of Independent Assortment
This one follows from the law of segregation
all alleles are not permanently associated with
one another.
Go to Section
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Punnet Squares

• Used to predict the possible gene combinations
  for a a cross
• Traits are represented by letters
• Lower case letters recessive traits
• Upper case letters dominate traits

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How to do punnett squares

• 1. determine the genotypes of the parent
  organisms 2. write down your "cross" (mating)
  3. draw a p-square 4. "split" the letters of
  the genotype for each parent put them "outside"
  the p-square 5. determine the possible genotypes
  of the offspring by filling in the p-square 6.
  summarize results (genotypes phenotypes of
  offspring) 7. bask in the glow of your
  accomplishment !

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Links to punnet square practice

• http//www.usoe.k12.ut.us/curr/science/sciber00/7t
  h/genetics/sciber/punnett.htm
• http//www.athro.com/evo/gen/punexam.html
• http//curriculum.calstatela.edu/courses/builders/
  lessons/less/les4/casino/cas1ck.html
• http//biology.clc.uc.edu/courses/bio105/geneprob.
  htm