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AP Biology Exam Review 2003-2004
Heredity and Evolution – 25%
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Heredity and Evolution
Molecular Genetics – 9% Evolutionary Biology – 8%
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Heredity Meiosis and gametogenesis Eukaryotic chromosomes
Inheritance patterns
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Asexual vs. Sexual Reproduction
Asexual reproduction: binary fission, regeneration, vegetative propagation, budding Sexual reproduction: result of gametic fusion, gametes formed from meiosis, promotes genetic recombination (variety) Meiosis: process of gametic nuclear transfer
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Sexual life cycles Remember: Asexual life cycles do not require the fusion (fertilization) of sperm and egg.
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Meiosis overview Each “normal” 2N (diploid) cell has 2 sets of chromosomes, one from each gamete. Gametogenesis: specialized cells (spermatocyte, oocyte) undergoing meiosis to produce gametes with some combination of the 2 chromosome sets
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Important vocabulary Homologous chromosomes: pair of like chromosomes, having similar length, centromere position, gene loci Linkage group: genes that are linked on the same chromosome (linked loci) Locus (pl. loci): site on chromosome where gene is located on the chromosome
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Meiosis
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Meiosis
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Crossing over Genetic variation in meiosis result of crossing over when chromosomes aligned in tetrad formation Breaks linkage groups (genes found on the same chromosome)
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Oogenesis
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Spermatogenesis
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Pine life cycle
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Eukaryotic chromosome
Allele: alternative form of the same genes Chromosome: condensed double helix (DNA)
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Eukaryotic DNA packing
Nucleosomes: “beads on a string” (beads = histones) Chromatin: condensed nucleosomes Looped chromatin on protein scaffolding Chromosomes
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Mendel’s work Law of independent assortment Law of segregation
Dominant vs. recessive phenotype Used peas because of fast generations, easily recognizable characteristics, two alleles
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Inheritance patterns Mendelian inheritance: AA & Aa = dominant phenotype; aa = recessive phenotype Codominance: Aa = shows both A and a equally
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Incomplete dominance Intermediate inheritance AA = dominant
Aa = half way between AA and aa aa = recessive phenotype
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Inheritance patterns Hybrid: mixed genes between two species
Pleiotropy: ability of one gene to affect many different genes
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Epistasis Expression of one gene determines the expression of another gene
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Polygenic inheritance
Many genes affecting a phenotype Leading to many possible phenotypes of a trait
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Multiple alleles
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Test cross If Mendelian inheritance, AA and Aa genotypes are indistinguishable. Crossing dominant phenotype with aa. 100% dominant = PP; 1:1 = Pp
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Sex-linked Sex-linked: gene loci on sex chromosome (X or Y) Ex: hemophilia, color blindness First discovered in 1910 by Thomas Hunt Morgan Autosomal: gene loci on non-sex chromosome
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Sex linkage Look for inheritance patterns that deviate from 3:1 or 1:1. Also look for disorders affecting mostly males.
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Recombination frequencies
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X-inactivation & Barr bodies
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Nondisjunction
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Nondisjunction disorders
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Human pedigrees Square = male Circle = female Colored in = affected
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Molecular Genetics – 9% RNA and DNA structure and function
Gene regulation Mutation Viral structure and replication Nucleic acid technology and application
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DNA structure Nucleotide: nitrogen base, deoxyribose sugar, phosphate group Nitrogen bases: adenine, thymine, cytosine, guanine Joined 5’ – 3’ (phosphodiester bonds) Sugar-phosphate backbone
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RNA structure Nucleotide: nitrogen base, ribose, phosphate group
Nitrogen bases: uracil, adenine, guanine, cytosine Single stranded Joined 5’-3’ In eukaryotes: RNA produced in nucleolus of nucleus. tRNA, rRNA, mRNA
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Griffith experiment Avery did a follow-up experiment and coined “transformation.”
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Phage
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Hershey and Chase
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DNA replication models
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Meselson and Stahl
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Origin of replication
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DNA elongation
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DNA synthesis Leading strand: made continuously
Lagging strand: Okazaki fragments
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DNA priming Necessary for starting DNA synthesis
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Okazaki fragments
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Telomeres Necessary to preserve DNA through successive rounds of DNA replication
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Controlling gene expression
Gene expression = transcription RNA transcript is translated into amino acid polymer. Operons are examples of prokaryotic gene expression control. Methylation is an example of eukaryotic gene expression control.
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One enzyme, one protein (controlling gene expression)
Beadle and Tatum
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Overview Transcription: DNA RNA
Translation: RNA amino acid polymer (peptide)
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Transcription Initiation Elongation Termination
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DNA RNA A U T A C G G C
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RNA processing Removing introns that interrupt the express-able code (exons) Also adding poly-A tail and 5’-CAP
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tRNA tRNA “charged” with amino acid
“assists” ribosomes with protein synthesis
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Translation - initiation
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Translation - elongation
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Translation - termination
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Point mutation Codon can be mutate due to substitution.
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Insertion & deletion Frameshift mutation
Mutation: spontaneously occurs; basis of variation in populations
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Viral reproduction Lytic vs. lysogenic life cycle
Viruses are not cells. Viruses are particles of nucleic material and protein that requires host cells for reproduction. Bacteriophage: viruses that infect bacteria
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Lytic life cycle
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Lysogenic life cycle
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HIV Retrovirus RNA nucleic acid
Requires reverse transcriptase enzyme (RNA DNA)
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Bacterial replication
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Using recombinant bacteria
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Transduction
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Plasmid biotechnology
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Recombinant DNA Restriction enzymes cut host DNA and “gene of interest” Sticky ends complementary (match), enabling recombination
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Genomic library Having multiple copies of DNA or phage
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PCR Polymerase chain reaction: heat, cool, add primer
Forms cDNA (clonal DNA) library
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Gel electrophoresis
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RFLP: cut sites in junk DNA
Restriction fragment length polymorphism
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Southern blotting
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Sanger Method to deduce the DNA sequence that is unknown
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Gene therapy
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Phage as a vector Transduction: using virus as a means to transport eukaryotic gene into bacteria
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