Chapter 14: Mendel and the Gene Idea. Genetic Terminology Character – Trait True-breeding...
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Transcript of Chapter 14: Mendel and the Gene Idea. Genetic Terminology Character – Trait True-breeding...
Chapter 14: Mendel and the Gene Idea
Genetic Terminology
• Character– Trait
• True-breeding• Hybridization– P generation– F1 generation
– F2 generation
Mendel’s Ideas• For each trait an organism inherits two alleles• If the alleles are different…– Dominant– Recessive
Mendel’s Laws
• Law of Segregation– Alleles for each character separate during gamete formation
Mendel’s Laws• Law of independent assortment– Pairs of alleles separate individually
Rules of Probability
• Rule of multiplication– Examples• 2 coins land heads up• Parent is YyRr, gamete will carry Y, R• Parents are YyRr, offspring will be YYRR
• Rule of Addition– Event can occur two or more ways– Example• Two ways to produce heterozygote if parents are Pp
Rules of Probability
• PpYyRr x Ppyyrr• What is the probability of offspring having
recessive phenotype for at least two of the three traits– ppyyRr– ppYyrr– Ppyyrr– PPyyrr– ppyyrr
Types of inhertiance
• Incomplete dominance– Snapdragons
• Co-dominance– M,N,MN blood groups
• Multiple alleles– ABO blood groups• Surface carbohydrate• Alleles
ABO Blood Groups
Types of Inheritance
• Pleiotropy– Sickle Cell Anemia
• Epistasis– Coat color in mice
• Polygenic traits– Eye color– Skin color
Pedigrees
Genetic Disorders• Recessive– Tay Sachs– Cystic Fibrosis– Sickle Cell Anemia– Phenylketonuria (PKU)
• Dominant– Achondroplasia– Huntington’s
• Multifactorial– Heart disease, diabetes, cancer, alcoholism,
schizophrenia, manic-depressive disorder
Chapter 15: The Chromosomal Basis of Inheritance
Thomas Morgan’s Experiment• White type restricted to males– Sex-linked• Recessive-
– Father to son
– Linked genes• Passed as unit• Same chromosome
Sex-Linked Disorders
• Duchenne’s– Loss of muscle strength and coordination
• Hemophilia– Failure of blood to clot
• Red-green colorblindness– Primarily males
Chromosomal Complications
• Non-disjunction– Aneuploidy• Trisomy
– Down’s Syndrome– Patau Syndrome– Edward’s Syndrome– Klinefelter’s Syndrome
• Turner’s Syndrome
Chromosomal Complications• Deletion– Cri-du-chat
• Translocation– Chronic myelogenous
leukemia
• Inversions• Duplications
Chi Square Analysis
• Used to determine if there are deviations for the phenotypic ratio of the F2 generation within the limits expected by chance
– Null hypothesis
– Formula X2 = ∑ (o – e)2
e
Chi Square Analysis
• Degrees of freedom• Chi square– Critical value• Reject hypothesis
Probability 1 2 3 4
0.05 3.84 5.99 7.82 9.49
0.01 6.64 9.21 11.30 13.20
0.001 10.8 13.8 16.3 18.5