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Biology 2- BIOL 1362 Week 4 Notes Heredity

by: Alexis Clowtis

Biology 2- BIOL 1362 Week 4 Notes Heredity BIOL 1362

Marketplace > University of Houston > Biology > BIOL 1362 > Biology 2 BIOL 1362 Week 4 Notes Heredity
Alexis Clowtis
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These notes cover heredity (Mendelian Inheritance). Notation for genetics, independent and dependent assortment, pedigrees, and an introduction to chromosomes are covered in this week's notes.
Biology 2
Class Notes
Biology, Heredity, mendel, Genetics, pedigrees, Chromosomes
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This 8 page Class Notes was uploaded by Alexis Clowtis on Friday February 12, 2016. The Class Notes belongs to BIOL 1362 at University of Houston taught by CHEEK in Spring 2016. Since its upload, it has received 30 views. For similar materials see Biology 2 in Biology at University of Houston.


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Date Created: 02/12/16
Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 2/9/2016 Notation for Dominant/recessive traits by Mendel  Letter represents character (gene)  Use the same letter for both traits (alleles) because this represents 2 versions of the same “character” (gene) Purple: PP White: pp Capital letter: dominant Lowercase letter: recessive *There are many other ways inheritance can occur, this is the simplest form Punnet Square: Method to predict possible combinations of gametes and offspring from a cross Monohybrid cross- “1 mixture” (1 trait) Ex. F1 X F1 Parents are Heterozygous- having 2 different versions of the hereditary “particle” for a character (Pp) –Mendel’s terminology Possible Offspring Genotypes and the ratio at which they will occur: PP, Pp, Pp, pp (3 purple, 1 white) Test Cross- cross individual with genotype you do know (pp) and results tell you genotype of purple flower (PP or Pp) -Method for figuring out genotypes of an individual with the dominant phenotype -Cross dominant phenotype with recessive phenotype -Genotype of dominant phenotype: P_ (some kind of notation to indicate you know 1 of them and are going to figure out the other) -genotype of recessive phenotype: pp -Ratio of offspring phenotypes will indicate whether unknown (_) is P or p Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 2/9/2016 If PP, only can be: If Pp, only can be: Only can get Pp, Purple Half purple, half white so if any are white it’s Pp Law of Independent Assortment 1. Mendel’s experiments with inheritance of 2 characters a. Seed(pea) color (character): yellow or green (traits) b. Seed shape: round or wrinkled c. Notation: Y- yellow R- round y- green r- wrinkled Clicker- Dominant phenotype for both characters: YyRr and YYRR (so both A and B) Crossed round yellow by green wrinkled so knows they are all heterozygous for both traits Dihybrid cross: mating between parents heterozygous for 2 characters Hypothesis of dependent assortment: traits for color and shape stay together when sorted into gametes Hypothesis of independent assortment: traits are sorted into gametes independently of each other Dependent hypothesis: Parent genotypes(F1): YyRr X YyRr from YYRR X yyrr YR and yr determined by P generation because one would have to give yr and the other would have to give YR because they are both homozygous Phenotypes- 3:1 ratio  Predicted F2 genotypes Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 2/9/2016 Independent Hypothesis: Parental genotypesL YyRr X YyRr (F1) Phenotype ratio- 9:3:3:1 Predicted results from Dihybrid cross H1: Dependent Assortment H2: Independent Assortment Predicted Phenotypic ratio: Predicted Phenotypic ratio: 3:1 (round: wrinkled) 9:3:3:1 (round:wrinkled:round:wrinkled) Mendel’s Results: (Use lowest number as base for “1”) 315- Yellow, round 315/32=9.8 108- Green, round 108/32=3.4 101- Yellow, wrinkled 101/32=3.2 32- Green, wrinkled 32/32=1.0 Total: 556 Clicker- this supports H2 (independent assortment) *NOT ALL CHARACTERS WORK THIS WAY* this is the simplest form Law of Independent Assortment -Traits for 1 character are sorted into gametes independently of other character Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 2/9/2016 Probability and Inheritance- Penny flip There are 2 Rr with ¼ chance of occurring so you add them together and there is a ½ chance it will occur RR: ¼ Rr: ½ rr: ¼ -Calculate probability of zygote receiving a particular trait combination for each character: What fraction of offspring will have recessive phenotypes for at least 2 characters? Assume independent assortment. (What is the chance that 2 or 3 get something at the same time- just like the chance that 3 siblings get the same exact thing which involves 3 different fertilizations. She used the example in class that there are 3 people sitting in a row and they all need to get the desired outcome, which decreases the chances, which implies you will be multiplying) PpYyRr X Ppyyrr (probability that the letter combo in the first column will happen) Genotypes that Probability of Probability of Probability of Probability of produce at specified allele specified allele specified allele specified P-Y- least 2 combination for combination for combination for R combination recessive traits P gene Y gene R gene (total of column 2,3, and 4) ppYyrr pp: ½*1/2=1/4 Yy: ½*1=1/2 rr: ½*1=1/2 ¼*1/2*1/2=1/16 ppyyRr pp: ½*1/2=1/4 yy: ½*1=1/2 Rr: ½*1=1/2 ¼*1/2*1/2=1/16 PPyyrr PP: ½*1/2=1/4 yy: ½*1=1/2 rr: ½*1=1/2 ¼*1/2*1/2=1/16 Ppyyrr ** Pp: ½*1/2 + yy: ½*1=1/2 rr: ½*1=1/2 ½*1/2*1/2=1/8 ½*1/2= 1/2 ppyyrr pp: ½*1/2=1/4 yy: ½*1=1/2 rr: ½*1=1/2 ¼*1/2*1/2=1/16 ** have to add 2 Pp possibilities because both parents have a P and a p so 2 ways to get Pp are added like in the punnet square with the R’s above -Calculate probability of a zygote receiving a particular genotype d. Multiple probabilities for character 1 genotype X character 2 X character 3 X character y Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 2/9/2016 Check yourself with a punnet square for each character (P) PpYyRr X Ppyyrr (F1) PpyyRr PP: ¼ Yy: ½ Rr: ½ Pp: ½ yy: ½ rr: ½ pp: ¼ Youtube: Bozeman Science- Mr. Anderson Calculating Probability  Rule of addition o If there is more than 1 combination that results in particular outcome o ADD the probability of each combination occurring o Probability of two or more mutually exclusive events  Rule of multiplication o If several events must happen simultaneously to achieve a particular outcome o Multiply the probability of each combination occurring o Ex. What is the probability that I will flip a coin and have it land on heads at the same time the person next to me flips a coin and have it ALSO land on heads at the same time? That’s multiplication because there are two separate events having to happen at the same time, which is related to siblings getting the same trait because there were different instances of fertilization *Never should get above 1* (if you do, cry) Pedigree Analysis  Analyzing human genetics through history of traits Male Female or Shading- this person has the trait Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 2/9/2016 Roman numerals indicate generation All on the same bar= same generation Chronological order from LR (first child is son on the left) Recessive trait: Both parents are homozygous recessive so 100% of offspring will have trait; only possible genotype is aa Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek-2/9/2016 Teamwork activity at the beginning of class- Notes:  DD is homozygous dominant  Dd is heterozygous  dd is homozygous recessive  For the offspring to be different from one another, AT LEAST one parent has to be HETEROZYGOUS because if they are both homozygous, then the only allele (D or d) they can give they will give to all offspring, so all of the possibilities will be the same  Pay attention to graph details and read axes to make sure you are getting the right information. The graph in this exercise had to do with hearing/frequency, which means at a certain frequency, how loud does the sound have to be for a person to hear it? Chromosomal Basis of Mendel’s Laws  Characters are expressed as different traits (what he would see- example: flower color) Modern Terminology  Character is programmed by a gene- unique sequence of DNA nucleotides that codes for a protein  Traits result from an allele- version (“flavor”) of a gene- codes for specific version of its respective character o An allele is a gene but a more specific identification Clicker- identify picture of a chromosome Pair of Homologous (same length with same genes on them) chromosomes- allele may not be the same locus- location of gene on chromosome, used interchangeably with gene; An individual inherits 2 alleles for each gene (1 from mom, 1 from dad) (From Dr. Cheek’s slides, also on page 209 of textbook) Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek-2/9/2016 Chromosome: A DNA molecule associated with histone proteins  Bacteria and Archea: chromosome=DNA double helix, circular structure  Eukaryotes: DNA double helix associated with histone proteins o Nucleosome: 8 histone proteins organized into a spool shape (threat is helix); double stranded (ds) DNA is wound around nucleosomes o 3 picture is Coiled chromatin fiber 30nm wide (like mardi gras beads wound tighter together) o Each nucleus in our body has 2 meters of DNA o Eukaryotes have multiple chromosomes (bacteria have 1 circular chromosome)  Each contains unique portion of organism’s genes  Each is different length  1 can have 100s of genes, up to 1000s o Eukaryotes have 2+ sets of chromosomes  Plants can have more than 2 full sets Karyotype: picture of stained chromosomes; picture of all eukaryote’s chromosomes arranged in matched pairs from longest to shortest- one of each pair from mom, the other from dad (Image from Dr. Cheek’s lecture) Extra notes: Recessive= weak allele, it needs 2 to show; Heterozygous is a “carrier” of recessive trait Dominant= strong allele, doesn’t care about what it’s paired with, it will show (in independent assortment as we have been learning


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