Genetics notes week 1
Genetics notes week 1 Bios 206
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This 6 page Class Notes was uploaded by Becca Sehnert on Tuesday January 12, 2016. The Class Notes belongs to Bios 206 at University of Nebraska Lincoln taught by Dr. Christensen in Fall 2016. Since its upload, it has received 18 views. For similar materials see Genetics in Biological Sciences at University of Nebraska Lincoln.
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Date Created: 01/12/16
LECTURE 1 Very quantitative and analytical. Not memorization “Memorization will not get you through the class” Do some problems on your own throughout the course. DON’T GET BEHIND Due every week at recitation Master concepts and be good at practice problems Most questions come from old exams Grading Lowest exam and homework dropped Homework is an exam predictor, don’t buy Mastering Genetics Need to do the homework yourself but working in groups is a good idea. 70 clicker questions worth points. 50 points recorded. If you cheat, you get an F Do the extra credit early SECTION 1.2 Chromosome theory of Inheritance Inherited traits, controlled by genes on chromosomes Genes transmitted through gametes Maintains genetic continuity Alleles –alt form of gene Mutatins produce alleles –source og genetic variation Genetics focuses on this variation and transmission Set of alleles is the genotype –instructions in DNA Physical manifestation of genotype is phenotype MITOSIS Chroms copied and distributed –results in 2 daughter cells and each receives diploid set MEIOSIS Gemetes produces are haploid Fusion of gametes makes diploid DNA Carries genetic info Anti parallel Double stranded A-G C-T RNA –same U-C Single stranded Ribose CENTRAL DOGMA DNA transcribed to RNA\ Genetic code consists of triplet nucleotides in mRNA Biotechnology has been used for GMO –Table 1.1 1.5 Gene therapy 1.6 Genomics –all genes in organism Model organisms –good for experiments Yeast, ecoli, pea plant, arabadopsis, fruit fly BAD –humans 1.8 Genetics helps to understand function and malfunction of biological systems READ and know MEIOSIS LECTURE #2 Meiosis –in eukaryotes, transmission of genetic material from 1 generation to next involving meiosis. Mendal figured this stuff out without knowing about chromosomes If you understand theres only 2, mendelian genetics will be easy Chromosomes 1 m of DNA in all 46 chromosomes (humans) Packaged with proteins to make it fit Only packaged when dividing because genes need to be available for copying Once pinched in half, uncoil again Diploid cells –chrom pairs (from each parents) # chrom pairs constants for each species Homologous chromosomes -2 members of each pair (homologs) Alleles may be different Genes (and function) are the same Not identical Allele –alternative forms of same gene Centromere Can be anywhere on chromosomes Handle for spindle to attach to during mit or meio Telomere –end of chromosome LOOK AT CHART FROM CHAP 2 NOTES o (named before people knew it was genetic material) o Looked at these under a microscope Sister Chromatids IDENTICAL!!’Most of our cells are diploid DNA replication makes EXACT copy of each chrom Before division, each homologue has a sister (G2 phase) G2 –to make sure replication has occurred properly Sister chromatids cohesive –stick together Most in G0 arrest (stop growing, 1 copy of each chrom) Some still active (meiosis to make gametes) If goes through S phase, will go through mitosis KNOW DIFFERENCE BETWEEN HOMOLOGUES AND SISTERS Diploid Haploid Diploid Diploids have 2 sets of crhom Gametes have haploid set 1 S phase (DNA synthesis) followed by 2 divisions (meiosis) LAST point Sex chromosomes Differ between sexes Behave as homologs in meiosis Have a region that is the same Autosome –any chrom other than sex chrom Meiosis I is Reductional Reduces # of chrom to half The funny division (novel) Meiosis converts diploid (2n) to haploid (1n) Occurs during first division AKA Reductional Division This is the key difference between meiosis and mitosis HOW?! o Homologous chrom, with sister chromatids, PAIR during (only) meiosis 1 o Can disjoin to reduce chrom # o Sister chromatids already stuck together, homologues have to find each other PROPHASE I (Don’t have to memorize specific steps within this) Long and complex (more than mitosis) Recombination –exchange of chrom material (Chap 5) Metaphase I Anaphase I Homologues are separated Telophase I *In mitosis, homologues, not sisters, are pulled to opposite sides WHEN DO Centromeres divide # diff chrom reduced by meiosis I Cell looks haploid cell gonna go through mitosis Sisters separate in meiosis II How hold homologous/sister chromosomes together –recombination genes, protein interactions with protein complex Meiosis II is Equational Like mitosis Essentially same cells, except recombination 4 cells, each haploid (Won’t ask “How many chrom in telophase?”) Spermatogenesis –male meiosis Oogenesis –female meiosis Meiosis is the basis for genetic variation Can line up and meiosis I in different ways Don’t care how other chrom line up Gametes get either crhom from each pair Meiosis makes 2n combinations of chrom in gametes Crossing over makes more variation CLICKER QUESTION A cell has 3 pairs of chrom 2n=6 2 are metacentric and 1 is telocentric A. wrong -sister chromatids should have same alleles A. wrong -homologues need to be paired E. wrong –already haploid, no homologs E. wrong –sister chromatids aren’t identical D. wrong –genes are on every chrom B. C. correct! Will have to draw this on the exam End of chapter 2. LECTURE 3 All sections important, look at old exams to see what the emphasis is on Mendel 100 years after found out what DNA was 1953 –know how replicates Sorted material into plants differing with visible phenotypes o 2 different phenotypes/alleles only o Had to make sure he had homozygous for the traits o Simplified and used the scientific method Monohybrid crosses o Has single pair of alleles (round vs wrinkled) o Parents are P1 generation o Offspring are F1 generation o Offspring of F1 gen come from self (fertilizing) = F2 o Offspring of monohybrid cross, all have 2 contrasting traits (no blending) o Didn’t study development of trait Proposed “particulate unit factor” for each trait = now called genes o Basic unit of heredity o Remains unchanged for offspring o Defined “dominant” and “recessive” in F1 gen Reciprocal crosses o Didn’t matter who pollinated who, no difference If a true-breeding all-white cat is crossed with a true-breeding tabby, all kittens white. Which allele is dominant? A. White B. Tabby C. Need to cross them to make an F2 to find out Self crossed F1 o ¾ plants show dominant trait o ¼ show recessive trait that disappeared in F1 generation 3 postulates of inheritance o Genes exist in pairs o Some are dominant, other recessive o Pairs of alleles segregate during gamete formation Genotype –genetic makeup of individual Phenotype is physical expression of genotype Homo vs Heterozygous o When 2 alleles for trait are same o LOOK OVER THIS SLIDE Punnett square o Can see geno and pheno together Testcross to homo recessive o Can determined if individual with dominant phenol is homo or hetero o Crossing with homo recessive for every trait o Can be used with 2 independent traits Dihybrid crosses -4 postulate: Independent assortment o Traits assort independently in gamete formation o All combinations equally possible o Learn how to use double arrows instead of Punnett squares (much faster) How many different types of gametes can be formed by the genotype DdEeFf? a. 3 b. 6 c. 8 d. 9 e. 16 Meiosis 1 –can line up differently, independent assortment KNOW MATERIAL IN CHAP 1 & 2 Make it concrete
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