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Review 4: Heredity & Molecular Genetics AP Biology
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Heredity & Molecular Genetics Meiosis produces haploid gametes. Different versions of same gene are called alleles. Mendelian inheritance Non-Mendelian inheritance Chi-square analysis DNA & RNA Central Dogma Regulation of Genes Mutations Biotechnology
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Meiosis Produces Haploid Gametes Meiosis 1 separates homologous pairs: reduction division Meiosis 2 separates sister chromatids: produces 4 sex cells
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Different Versions of Same Gene are Called Alleles Dominant vs. Recessive Homozygous vs. Heterozygous Phenotype vs. Genotype
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Mendelian Inheritance Monohybrid Crosses -Aa x Az = 3:1 ratio -Law of Segregation Alternative alleles of a character segregate and remain distinct. Dihybrid Crosses -AaBb x AaBb = 9:3:3:1 ratio -Law of Independent Assortment Genes that are located on different chromosomes assort independently during meiosis. Test Cross -Determine genotype of individual showing dominant phenotype. -Unknown (A_) x aa (homozygous recessive)
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Non-Mendelian Inheritance Incomplete Dominance (pink flower color) Co-dominance (blood type) Sex linked (mainly X-linked: color blindness, hemophilia) Epistasis (coat color) Pleiotrophy (dwarfism, giantism) Polygenic (skin color)
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Epistasis The effects of one gene are modified by one or several other genes
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Pleiotropy & Polygenic A single gene influences multiple phenotypic traits Examples: Dwarfism, Gigantism Polygenic
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Chi-square analysis Determining if observed results are significantly different from expected results Know how to use formula when given & how to interpret results -degrees freedom (1 less than number of classes of results) -less than p=.05, then difference can be due to random chance alone & null hypothesis is accepted
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DNA & RNA DNA: ACTG nitrogen bases, double helix - A:T, C:G RNA: ACUG nitrogen bases, single helix
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Central Dogma DNA -> RNA -> protein -> trait Transcription (DNA -> mRNA) Translation (mRNA -> protein)
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Transcription Production of RNA copy of DNA sequence In nucleus RNA polymerase copies coding strand & produces mRNA
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Translation mRNA -> protein In cytoplasm Codons on mRNA read by ribosome Matched to anticodons of tRNA tRNA carries amino acids to mRNA & ribosome assembles polypeptide chain Start codon (Met) & stop codons, redundancy in code Universal code (single common ancestor)
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Regulation of Genes Operons -Prokaryotes -Cluster of genes for enzymes in a pathway -Controlled by repressor protein -Repressible operon (synthesis pathway = tryp operon) vs. inducible operon (digestive pathway = lac operon) Transcription Factors -Proteins which enable bonding of RNA polymerase to gene
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Operons Functioning unit of genomic material containing a cluster of genes under the control of a single regulatory signal or promoter
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Mutations Fuel for evolution = variation, genetic change Gene duplication, point mutation, insertions, deletion
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Biotechnology Scientists can modify an organism’s genome by inserting foreign DNA. Techniques
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Modify Organism’s Genome Bacterial Transformation (human insulin gene in E. coli) Possible because of universal genetic code
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Techniques Restriction digest: Restriction enzymes, sticky ends Transformation: Restriction enzymes, sticky ends, ligase, amp selection, lacZ screening Gel electrophoresis: DNA moves in an electrical field (negative -> positive), small pieces move further PCR: DNA amplification RFLP: DNA fingerprinting Sanger sequencing: Human Genome Project
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