Biology 240 Test 3 Study Guide
Biology 240 Test 3 Study Guide Bio 240
U of L
Popular in Biology
Popular in Biology
This 17 page Study Guide was uploaded by tpnguy09 on Thursday June 30, 2016. The Study Guide belongs to Bio 240 at University of Louisville taught by Dr. Rabin in Winter 2016. Since its upload, it has received 16 views. For similar materials see Biology in Biology at University of Louisville.
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Date Created: 06/30/16
2/25/16 Dominant vs. Recessive Purple flower color is a dominant trait White flower color is a recessive trait “Heritable factor” Mendel’s Other Crosses Same pattern in six other pea plant characters Mendel developed a model as explanation o Without any genetic knowledge Concept 1: alternative versions of genes account for variations in inherited characters Pea plants have two flower colors (purple and white) =alleles Specific locus Concept 2: An organism inherits one allele for each trait Two alleles at a particular locus o Are the same (Mendel’s P generation) Or o Are different (Mendel’s F1 generation) Remember, he had no knowledge of chromosomes Conept 3: If the two alleles at a locus difffer, then the dominant allele determines appearanace F1 plants o Purple flowers because purple allele is dominant o White allele on homologous plant Concept 4:the two alleles segregate during gamete formation and end up in different gametes Law of segregation Gamete gets only one of two alleles in organism Remember meiosis? These concpets account for the 3:1 ratio dominant/recessive ratio in the F2 generation Punnett square o Uppercase=dominant allele o Lowercase=recessive allele True breeding=both the same letter;homologous pairs o PP, pp Useful Genetic Vocabulary Genotype: genes in plants:PP, pp Phenotype: purple, white Homozygous: same genes; PP,pp Heterozygous: different genes;Pp The Testcross What is the genotype of an individual with the dominant phenotype? o Homozygous dominant or heterozygous Testcross: breed mystery individual with a homozygous recessive individual o Why? Results: All offspring purple Or ½ white, ½ purple Dihybrid cross Heterozygous for two traits seed color yellow green Seed shape round wrinkled P Generation YYRR yyrr Gametes YR yr F1 Generation YrRr What are the gamete possibilities? YR Yr yR yr phenotypic ration=9:3:3:1 Law of independent assortment Mendel’s dihybrid experiments are the basis for this law each pair of alleles segregates independently during gamete formation Caveats: o Genes located in proximity on the same chromosome tend to be inherited together—linkage o Why? The laws of probability Reflect the rules of probability Think about a coin toss o What’s the probability of getting tails? o How about two tails? (multiplication) 3/1/1 6 Chromosomes Mendel ignored until Morgan proved him correct using fruit flies in 1915 o Born in KY o Columbia “fly room” o Problems making mutants The chromosome theory of inheritance (1915) o Genes have specific loci on chromosomes o Chromosomes undergo segregation and independent assortment o Add PDF here The chromosomal basis of sex Two sex chromsomes o A larger x chromosome o A smaller Y chromosome A SRY gene on Y Diagram? Male:50% x ,50% y Female: 100% x Offspring is determined by the male How Linkage Affects Inheritance Morgan mated flies with different body colors and wing sizes o Inherited in specific combinations o Not independent assortment! Why not? They must be on the same chromosome But they don’t always … o Crossing over Sex-Linked Genes Gene located on a sex chromosome Y-linked genes X-linked genes X chromosomes have genes for many characters unrelated to sex X-Linked Genes For a recessive X- linked trait to be expressed o A female: 2 alleles (homozygous o A male: one allele (hemizygous) X-linked recessive disorders more common in males o Color blindness (mostly) o Hemophilia o XLA (no B cells) X Inactivation in Female Mammals One picked at random for inactivation during embryonic development Barr body Mosaic if heterozygous for a gene on X chromosome Mapping the distance between genes Genetic map The farther apparat two genes are, the higher the probability that a crossover will occur o Recombination frequency (0-50%) Genes far apartrecombination frequency near 50% Alterations of chromosome number or structure Large-scale chromosomal alterations o Miscarriage or o Developmental disorders Nondisjunction Chromosome breakage can lead to four types of changes o A.) Deletion o B.) Duplication Why are these structural changes problematic? Homozygous for a large deletion o Generally lethal In inversions, gene expression may change Nondisjunction: anaphase homologous chromosomes don’t separate 3/3/16 Structural Model of DNA James Watson and Francis Crick; Rosalind Franklin Nucleotides Monomers called nucleotides Sugar, phosphate, base Get figure Sugar groups Deoxyribose (in DNA) Ribose (in RNA) Get images 2 bonds for AT 3 bonds for GC antiparallel: one is 5 to 3 and one is 3 to 5 Franklin’s X-ray images showed DNA was helical Double helix The width of the helix The spacing of the bases Semi-Conservative Replication Eukaryotic chromosomes DNA Replication Amazing speed and accuracy >12 enzymes Getting started o Origin of replication o Replication “bubble” o Replication fork Prokaryotes vs. eukaryotes Replication in an E.coli cell Lagging Strand Proofreading and Repairing DNA Proofreading immediately afterwards by polymerase 3’to 5’ 1 mistake for every 10^9 nucleotides ! Find diagrams 3/10/16 The Central Dogma-cell does to transcription and translation o Cell replicates to divide one copies itself o DNARNAProtein o There are 1 strand of RNA o There are 2 strands of DNA o Template: mRNA uses o Codins: hangout o Transcription: makes one strand of RNA o For every 3 codins it makes 1 particular amino acid o Codon: group of 3 nucleotides In mRNA Flow: o DNA template strand o DNA coding strand o Transcription o mRNA o translation o protein Know AUG codon Tells the cell to let the protein go and not to put down anymore amino acids o UAA Stop o UAG Stop o UGA Stop More codons than amino acids Only about 20 amino acids Reading Frame Codons must be read in the correct reading frame Read in a non- overlapping fashion Find diagram Evolution of the Genetic Code Genetic code is nearly universal Genes can be moved from one species to another Transcription RNA polymerase 5’ to 3’ direction Does not need a primer Promoter: right before every gene, tell polymerase where to attach Terminator : where it stops transcribing Initiation of a transcription Promoters and the TATA box TATA box is full of T’s and A’s Multiple RNA can be made at the same time by the same DNA Needs: o Head o Tail o Cut in middle Alteration of mRNA ends Each end of a pre-mRNA molecule is modified o The 5’ end receives a 5’ cap o The 3’ end gets a poly-A tail UTR: untranslated region These modifications share several functions o mRNA export o protection o facilitating translation start (5’ cap) RNA splicing coding (Exons) and noncoding (Introns) regions o intron has to be removed o Exons stays and is translated spliceosome The Structure and Function of Transfer RNA single RNA strand, about 80 nts base-pair to itself amino acids binds at the top the anticodon is located at the bottom o for every anticodon there is an aminoacyl-tRNA syntheses Initiation of Translation Termination of Translation multiple translation can also occur at the same time Completing the protein Translation is not sufficient o Folding o Modification o Transport o Done in the googi Targeting Polypeptides to specific locations Signal sequences Two populations of ribosomes o Free ribosomes—protein in cytosol o Bound ribosomes—protein to organelles or secreted Mutagens Spontaneous mutations can occur during DNA replication, recombination, or repair Mutagens Ames test for mutagenic activity of chemical
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