Intro to Genetics
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Transcript of Intro to Genetics
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Intro to Genetics
Mendel
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Mendel (Father of Genetics)Studied the inheritance of traits in pea plantsDeveloped the laws of inheritanceMendel's work was not recognized until the turn of the 20th century
Gregor Gregor MendelMendel
(1822-1884)(1822-1884)
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InheritanceInheritance
Mendel stated that physical traits are inherited as “particles”Mendel did not know that the “particles” were actually Chromosomes & DNA
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Vocabulary Trait:- any characteristic that can
be passed from parent to offspring Heredity: - passing of traits from
parent to offspring Genetics: - study of heredity Purebred: one that always
produces offspring with the same form of a trait as the parent. (homozygous)
• Hybrid: has both forms of a trait (heterozygous)
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More Vocabulary
Alleles - two forms of a gene (dominant & recessive)
Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R)
• Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r)
• Homozygous and purebred = BB• Heterozygous and hybrid= Bb
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Eight Pea Plant Traits
• Seed shape --- Round (R) or Wrinkled (r)
• Seed Color ---- Yellow (Y) or Green (y)• Pod Shape --- Smooth (S) or wrinkled
(s)• Pod Color --- Green (G) or Yellow (g)• Seed Coat Color ---Gray (G) or White
(g)• Flower position---Axial (A) or Terminal
(a)• Plant Height --- Tall (T) or Short (t)• Flower color --- Purple (P) or white (p)
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Generations
P-Generation (Parents)
F1 Generation (1st Generation of Offspring)
F2 Generation (2nd Generation of Offspring)
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Punnett Squares
• The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as the punnett square.
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Pare
nt
2
Parent 1
Try these: Tt x TT, Bb x bb, TT x tt , and Bb x Bb
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Genotype and Phenotype• Genotype is an organisms genetic
makeup. For example Bb or BB or bb
• Phenotype is the physical characteristics or what they look like. For example if we were talking about eye color, the phenotype would be blue or brown eyes.
• If B =brown eyes and b= blue eyes– Bb=would have brown eyes– BB= brown eyes– bb = blue eyes
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Let’s PracticeGenotype or phenotype
• BB• Brown• Blonde• Bb• bb
• Blue• Tt• Tall• Tt• Short
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Beyond Dominant and Recessive Alleles
• Some alleles are neither dominant or recessive, and many traits are controlled by multiple alleles or multiple genes.
• Incomplete dominance: one allele is not completely dominant over another. A red flower crossed with a white flower, produce pink flowers. (blending)
• Codominance: Both alleles contribute to the phenotype of the organism. Black chicken crossed to a white chicken produce a black and white chicken
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Incomplete Dominance
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Codominance
• Two alleles are expressed (multiple alleles) in heterozygous individuals.
• Example: blood type
• 1. type A = IAIA or IAi• 2. type B = IBIB or IBi• 3. type AB= IAIB
• 4. type O = ii