Chapter 14 and 15
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This 5 page Class Notes was uploaded by Kendall Mansfield on Friday October 30, 2015. The Class Notes belongs to BIOL 1020 at Auburn University taught by Min Zhong in Fall 2015. Since its upload, it has received 14 views.
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Date Created: 10/30/15
Chapters 14 and 15 process by which the characteristics traits of individuals are passed to their offspring unit of heredity encodes the characteristics that determine the phenotype alternate versions of the same gene at the same locus in homologous pairs gene forms the location of a particular gene on a chromosome appearance or characteristics of an organism physical traits 0 Ex Yellow seeds genetic makeup of an organism Determines Phenotype genetic makeup 0 Ex Yy allele that dominates over others in determining phenotype capitalized letter allele whose phenotype expression is hidden when a dominant allele is present lowercase letter Both homologous chromosomes carry the same allele at a given gene locus YY or yy two homologous chromosomes carry different alleles at a given locus Yy offspring from a cross breeding evaluate the inheritance pattern of 1 trait evaluate 2 traits parental generation first generation offspring second generation offspring offspring of F1 generation Track the traits for several generations Count the numbers of offspring phenotype Analyze gene alternative versions of genes 0 Each trait is determined by a gene with two alleles 0 One allele is present on each homologous chromosome two alleles separate to each other during meiosis randomly 0 Parents are either homozygous or heterozygous for the trait Punnett Square Seed color yellow vs green and seed shape smooth vs wrinkled yellow dominant green recessive smooth dominant wrinkled recessive O Traits are inherited independently of each other Easy way to determine this is to draw 2 Punnett square instead of 1 one for the seed color and one for the seed shape independent assortment does not always occur Genes on the same chromosome tend to be inherited together genetic linkage linked genes breaks the linkage But crossing over in prophase I of meiosis break the linked genes and creates new allele combinations Recombination frequency is related to the distance between linked genes placement of a gene into a position in a linkage group Distances between genes 0 One map unit 1 recombination between genes on the same chromosome are measured in map units all genes on a particular chromosome tend to be linked together combined phenotypes Homozygous dominant red Homozygous recessive white Heterozygous intermediate pink snapdragon ower color In incomplete dominance the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties occurs when phenotypes of the heterozygote and dominant homozygote are identical 0 pea color seed shape two dominant alleles affect the phenotype in separate distinguishable ways 0 human ABO blood type MN blood group OOOOO o A species may have more than two alleles for a given trait 0 Each individual still carries two alleles for this trait o I Human ABO blood types 0 IA IB i o Codominance Alleles at a single locus may have effects on two or more traits o Albinism One gene in uences the phenotype that a second gene usually controls masking any effects of alleles at the second gene 0 mice coat color traits affected by interaction of two or more genes result in population variation human skin color When plotted out for a population polygenic traits produce a normal distribution curve is mating is random with respect to the trait Phenotypes are a combination of genetics and environment Himalayan rabbit Hydrangea owers the phenotypic range of a genotype in uenced by the environment have two X chromosomes genotype XX have an X chromosome and a Y chromosome genotype XY nonsex chromosomes human sex ratio is approximately 11 two types of sex chromosomes only one type of sex chromosome sex determined by female no sex chromosome Carried on one sex chromosome Ex eye color of fruit ies XAXa or XAY hemizygous o Recessive XLinked alleles are expressed more often in males than in females normal phenotype heterozygous genotype Redgreen colorblindness Hemophilia Some disorders caused by recessive alleles on the X chromosomes in humans Colorblindness mostly Xlinked Duchene muscular dystrophy Hemophilia a family tree that describes the interrelationships of parents and children across generations 0 Reveal inheritance pattern of a trait Albinism defective or absent chloride transport channels in plasma membranes o Abnormal hemoglobin synthesis 0 Heterozygotes are less susceptible to the malaria parasite Achondroplasia o Nervous system disease 0 No obvious phenotypic effects until the individual is about 35 40 years of age Marfan Syndrome Polydactyly Progeria Hemophilia Redgreen color blindness Many diseases such as heart disease diabetes alcoholism mental illness and cancer have both genetic and environmental components Little is understood about the genetic contribution to most multifactorial diseases T animals complete extra sets 3n etc fatal in humans and most missing one copy or have an extra copy of a single chromosome three copies of a chromosome one copy of a chromosome Incorrect separation of chromosomes or chromatids in meiosis Mistake in meiotic anaphases Down Syndrome three copies of chromosome 21 o Sterile woman with only one X chromosome X0 0 A fertile quotnormalquot woman with an extra X chromosome XXX 0 An infertile man with an extra X chromosome XXY a tall man with an extra Y low IQ Translocations Inversions Deletions Duplications OOOO
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