AP Biology Tuesday, March 11 th QUESTION TO PONDER: What is meant by the term map unit? Looking at the chromosome, how many map units are there on this fly chromosome? Today I will: 1.Discuss three sources of genetic variation within a population. 2.Review phenotype vs. genotype. 3.Differentiate between dominance and recessiveness.

AP Biology Random fertilization  Any 2 parents will produce a zygote with over 70 trillion (2 23 x 2 23 ) diploid combinations

AP Biology Sources of genetic variability  Genetic variability in sexual reproduction  independent assortment  homologous chromosomes in Meiosis 1  crossing over  between homologous chromosomes in prophase 1  random fertilization  random ovum fertilized by a random sperm metaphase1

AP Biology Genetic Variation  How do independent assortment and random fertilization contribute to genetic variation?  Orientation of homologous pairs of chromosomes with regard to each-other is random (metaphase I)  There is a 50/50 chance that a particular daughter cell will receive a paternal or maternal chromosome

AP Biology Genetic Variation in all organisms  In asexually reproducing organisms, mutations are the primary source of genetic variation  In sexually reproducing organisms meiosis accounts for most of the variation.

AP Biology Genetics & The Work of Mendel Modified from Kim Foglia

AP Biology Gregor Mendel  Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas  used experimental method  used quantitative analysis  collected data & counted them  excellent example of scientific method

AP Biology Pollen transferred from white flower to stigma of purple flower anthers removed all purple flowers result Mendel’s work F1F1 P F2F2 self-pollinate  Bred pea plants  cross-pollinate true breeding parents (P)  P = parental  raised seed & then observed traits (F 1 )  F = filial  allowed offspring to self-pollinate & observed next generation (F 2 )

AP Biology Mendel collected data for 7 pea traits

AP Biology F 2 generation 3:1 75% purple-flower peas 25% white-flower peas Looking closer at Mendel’s work P 100% F 1 generation (hybrids) 100% purple-flower peas X true-breeding purple-flower peas true-breeding white-flower peas self-pollinate

AP Biology What did Mendel’s findings mean?  Traits come in alternative versions  purple vs. white flower color  alleles  different alleles vary in the sequence of nucleotides at the specific locus of a gene  some difference in sequence of A, T, C, G purple-flower allele & white-flower allele are two DNA variations at flower-color locus different versions of gene at same location on homologous chromosomes

AP Biology Wednesday, March 12 th Please complete the following: A homozygous recessive white pea plant is crossed with a heterozygous purple pea plant. What are the possible genotypic and phenotypic ratios of the offspring (F 1 )? Today I will… 1.Review how to complete a test cross. 2.State the law of segregation. 3.Describe dominance vs. recessiveness.

AP Biology Traits are inherited as discrete units  For each characteristic, an organism inherits 2 alleles, 1 from each parent  diploid organism  inherits 2 sets of chromosomes, 1 from each parent  homologous chromosomes  like having 2 editions of encyclopedia  Encyclopedia Britannica  Encyclopedia Americana

AP Biology What did Mendel’s findings mean?  Some traits mask others  purple & white flower colors are separate traits that do not blend  purple x white ≠ light purple  purple masked white  dominant allele  functional protein  affects characteristic  masks other alleles  recessive allele  no noticeable effect  allele makes a malfunctioning protein homologous chromosomes allele producing functional protein mutant allele malfunctioning protein

AP Biology Genotype vs. phenotype  Difference between how an organism “looks” & its genetics  phenotype  description of an organism’s trait  genotype  description of an organism’s genetic makeup Explain Mendel’s results using …dominant & recessive …phenotype & genotype F1F1 P X purplewhite all purple

AP Biology Making crosses  Can represent alleles as letters  flower color alleles  P or p  true-breeding purple-flower peas  PP  true-breeding white-flower peas  pp PP x pp PpPp F1F1 P X purplewhite all purple

AP Biology F 2 generation 3:1 75% purple-flower peas 25% white-flower peas ???? Looking closer at Mendel’s work P X true-breeding purple-flower peas true-breeding white-flower peas PPpp 100% F 1 generation (hybrids) 100% purple-flower peas PpPpPpPpPpPpPpPp phenotype genotype self-pollinate

AP Biology Punnett squares Pp x Pp Pp male / sperm P p female / eggs PP 75% 25% 3:1 25% 50% 25% 1:2:1 % genotype % phenotype PPPpPp PpPppp PpPp PpPp F 1 generation (hybrids)

AP Biology Genotypes  Homozygous = same alleles = PP, pp  Heterozygous = different alleles = Pp homozygous dominant homozygous recessive heterozygous

AP Biology Phenotype vs. genotype  2 organisms can have the same phenotype but have different genotypes homozygous dominant PPpurplePpPp heterozygous purple How do you determine the genotype of an individual with with a dominant phenotype?

AP Biology Test cross  Breed the dominant phenotype — the unknown genotype — with a homozygous recessive (pp) to determine the identity of the unknown allele pp is it PP or Pp? x

AP Biology PPpp How does a Test cross work? pp P P pp P p PpPppp xx PpPp PpPpPpPp PpPp 100% purple PpPp pp PpPp 50% purple:50% white or 1:1 pp

AP Biology Mendel’s 1 st law of heredity  Law of segregation  during meiosis, alleles segregate  homologous chromosomes separate  each allele for a trait is packaged into a separate gamete PP P P pp p p PpPp P p

AP Biology Thursday, March 13 th Please do the following: Take out your Chapter 14 homework. We will discuss #3 first. So be prepared! Today I will: 1. Complete a LAB QUIZ over the Meiosis lab. Please have your completed labs on your desk. 2. Describe how to apply Chi Square analysis to a real-world situation.

AP Biology Lab Quiz: Meiosis 1. Define crossing over. (+2 pt) 2. Describe homologous chromosomes. (+1 pt) 3. Please list the stages of meiosis, including interphase. (+ 5 pt) 4. What is the purpose or function of the ascus of the fungus, Sordaria fimicola? (+ 2 pt) 5. Reproduce your data table (Table 3) from the lab. (+ 4 pt) 6. What is meant by map units? (+ 1 pt) 7. Suppose your are counting ascospores on a slide. You find that out of 100 asci, 25 show crossing over and 75 do not. What is the distance from the gene for spore color to the centromere (map units)? (+ 5 pt) Set up a table like Table 3 to show your results.

AP Biology Law of Segregation  Which stage of meiosis creates the law of segregation? Metaphase 1

AP Biology Chi Square Analysis Monday, 3/24  The chi square analysis allows you to use statistics to determine if your data is “good” or not.  In our M & M Activity we are using laws of probability to determine possible outcomes for genetic crosses.  How will we know if our M & M data is “good”?

AP Biology  The following formula is used If your hypothesis is true, then the squared deviations between the observed and expected values will most likely be small and so will the test statistic. If your hypothesis is false, then the squared deviations between the observed and expected values will most likely be large and so will the test statistic.

AP Biology  The test statistic is compared to a theoretical probability distribution  In order to use this distribution properly you need to determine the degrees of freedom  Degrees of freedom is the number of phenotypic possibilities in your cross minus one.  If the level of significance read from the table is greater than.05 or 5% then your hypothesis is accepted and the data is useful

AP Biology  The hypothesis is termed the null hypothesis which states that there is no substantial statistical deviation between observed and expected data.  Your null hypothesis:

AP Biology Monohybrid cross  Some of Mendel’s experiments followed the inheritance of single characters  flower color  seed color  monohybrid crosses

AP Biology Dihybrid cross  Other of Mendel’s experiments followed the inheritance of 2 different characters  seed color and seed shape  dihybrid crosses

AP Biology Dihybrid cross true-breeding yellow, round peas true-breeding green, wrinkled peas x YYRRyyrr P 100% F 1 generation (hybrids) yellow, round peas Y = yellow R = round y = green r = wrinkled self-pollinate 9:3:3:1 9/16 yellow round peas 3/16 green round peas 3/16 yellow wrinkled peas 1/16 green wrinkled peas F 2 generation YyRr

AP Biology Dihybrid cross YyRr YRYryR yr YR Yr yR yr YYRR x YYRrYyRRYyRr YYRrYYrrYyRrYyrr YyRRYyRryyRRyyRr YyRrYyrryyRryyrr 9/16 yellow round 3/16 green round 3/16 yellow wrinkled 1/16 green wrinkled YyRr YryRYR yr

AP Biology Andrea Grace Nate Mandi Alex Taylor W. Devin Connor Melanie Skyler Brooke Cierre Kylee Sarah Britynn Taylor H. Zach Blake Lauren Dallas Becca Breana

AP Biology Tuesday, March 25 th QUESTION TO PONDER Suppose you cross a heterozygous purple flowered/pure-breeding yellow pea plant with a white flowered/heterozygous yellow pea plant. List the phenotypic ratios of the possible F 1 generation. Today I will: 1. Perform a dihybrid cross. 2. Use Chi Squared analysis on Indian corn.

AP Biology Wednesday, March 26 th Please continue working on your Indian Corn activity. You need to complete your counting and be ready to start your Chi Square Analysis. When finished, you need to pick up the article off of the front counter. The Science and Ethics of Cloning (USA Today) Please read this over the course of the next two days.

AP Biology Thursday, March 27 th Today I will: Define cloning. Differentiate between various types of stem cells, embryonic vs. adult. Please watch The Island. Be sure to follow the plotline and pay attention to the details.

AP Biology Friday, March 28 th Please be prepared to continue with The Island. You will need to pick up the ESSAY requirement off of the front counter today. You must write a one page essay to answer the prompt at the top of your paper. This WILL be taken for a grade, and the due date is MONDAY, March 31 st.

AP Biology Mendel’s 2 nd law of heredity  Law of independent assortment  different loci (genes) separate into gametes independently  non-homologous chromosomes align independently  classes of gametes produced in equal amounts  YR = Yr = yR = yr  only true for genes on separate chromosomes or on same chromosome but so far apart that crossing over happens frequently YyRr

AP Biology Law of Independent Assortment  Which stage of meiosis creates the law of independent assortment? Metaphase 1 EXCEPTION  If genes are on same chromosome & close together  will usually be inherited together  rarely crossover separately  “linked”

AP Biology The chromosomal basis of Mendel’s laws… Trace the genetic events through meiosis, gamete formation & fertilization to offspring

AP Biology Review: Mendel’s laws of heredity  Law of segregation  monohybrid cross  single trait  each allele segregates into separate gametes  established by Metaphase 1  Law of independent assortment  dihybrid (or more) cross  2 or more traits  genes on separate chromosomes assort into gametes independently  established by Metaphase 1 metaphase1 EXCEPTION  linked genes

AP Biology Mendel chose peas wisely  Pea plants are good for genetic research  available in many varieties with distinct heritable features with different variations  flower color, seed color, seed shape, etc.  Mendel had strict control over which plants mated with which  each pea plant has male & female structures  pea plants can self-fertilize  Mendel could also cross-pollinate plants: moving pollen from one plant to another

AP Biology Mendel chose peas luckily  Pea plants are good for genetic research  relatively simple genetically  most characters are controlled by a single gene with each gene having only 2 alleles,  one completely dominant over the other