BIO_SC 1010 1st Edition Lecture 13Outline of Last Lecture I. Heredity II. Trait inheritanceIII. Punnett square Outline of Current Lecture I. Pedigrees II. Independent AssortmentIII. Environmental FactorsIV. Polygenic Current LecturePedigrees • Goals of Pedigree Analysis1. Determine the mode of inheritance; dominant, recessive, partial dominance, sex-linked, autosomal, mitochondrial, maternal effect2. Determine the probability of an affected offspring for a given cross • Basic symbols • Autosomes- 22 paired chromosomes present in both males and females• Sex chromosomes- paired chromosomes that differ between males and females• XX- female, XY- male• Y chromosome- triggers males developmental pathway during fetal development • Women have 2 X chromosomes, so women have 2 copies of each gene on the X chromosome These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Therefore, in women, the patterns of gene expression for genes on the X chromosome are the same as for gees on other chromosomes • Problem: since men have only one X chromosome, if a gene on the X chromosome is defective, they have no ‘back-up’ to produce the protein• Diseases associated with genes on the X chromosome are much more common in men than in women-women need to inherit 2 defective alleles, men need only one • A person’s sex is only relevant when the defective gene is located on a sex chromosome -baldness-color blindness -hemophilia Independent Assortment• The law of independent assortment states that the inheritance of one character has no effect on the inheritance of another• Independent assortment can be observed during a dihybrid cross-a dihybrid cross is one in which two separate characters are studied• Incomplete dominance: heterozygotes have a phenotype that is intermediate between homozygous dominant and homozygous recessive • Codominance is a form of inheritance in which both alleles contribute equally to the phenotype • There are three basic blood group alleles: A B, and O. We inherit one allele from each parent-the possible combinations: OO, AO, BO, AB, AA, BB• Blood type alleles A and B are co-dominant, while O is recessive to both A and B• Co-dominance and blood typing -the positive Rh factor allele (Rh+) is dominant over the recessive Rh factor allele (Rh-)• Blood transfusions-the ability to donate or receive blood is based on immune rejectionEnvironmental Factors• Environmental factors can also influence some phenotypes-interaction between genes and the environment contributes to a phenotype or trait, the trait ismultifactorial • The environment also shapes phenotypes Polygenic• Polygenic trait is a ingle trait whose phenotype is determined by the interaction betweenalleles of more than one
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