Wednesday Feruary 5, 2014 HW: Read pp. 267 269 in THICK OOK and answer questions 1 5 on page 269. W: 1. What is a dominant allele? 2. What is a recessive allele? 3. Could two rown raits have white offspring? 4. If yes, how? 5. What color offspring would two white raits have?
Friday Feruary 7, 2014 HW: Critter Project: Assignment 1 due Monday. IT MUST E TYPED W: 1. How do you indicate whether an allele is dominant? Recessive? 2. Using any letter, give an example of homozygous recessive and heterozygous. 3. What is the difference etween genotype and phenotype? 4. What are the three parts to Mendel s Law of Segregation?
Genetics: the study of heredity Heredity: the passing of traits to offspring
Early Theories of Genetics lended Inheritance: the traits of offspring are a lend of the parents traits. What color(s) would the puppies e if lended inheritance is correct?
The parents had two different forms of the same gene. Alleles for lack coat Alleles for yellow coat Allele: different forms of the same gene
Gregor Mendel Catholic monk in Austria Scholar and worked in the monastery garden Father of Genetics Are there laws aout how traits are passed down from parents to offspring? l Trait: a characteristic that can e passed down from generation to generation Mendel s Methodology Used peas short life cycle, easy to reed, ovious traits Controlled the reeding (not random) Quantified the results (counted LOTS of peas) Estalished and used purereds
Here are some of the traits Mendel looked at in pea plants:
Which one is purered for coat color? = = Purered: can only produce offspring with one form of a trait.
Mendel and his Peas Mendel looked at 7 pea traits, including pod color, height, flower color, and pea color. Pea Color Why was it important for Mendel to use parents with only one type of alleles i.e. purered? If lending were correct, what would you expect to see in the F 1 generation? If lending were correct, what would you expect to see in the F 2 generation?
Mendel s Conclusion What two pod color alleles would e present in the yellow pod Parent of your slate drawing? oth of this parents alleles would e for yellow pods. Particles of Heredity (genes) are passed down! Law of Segregation 1. Each organism has two alleles for a gene, one from the mother and one from the father. We can represent the yellow parent as YY and the green parent as yy.
Mendel s Conclusion Law of Segregation 1. Each organism has two alleles for a gene, one from the mother and one from the father. 2. The alleles separate when eggs or sperm are formed each egg or sperm has one allele. 3. Sperm and eggs comine in predictale proportions. P F 1 YY yy Y Y y y Sperm Eggs Yy What proportion did we see in the F 2 generations for pea color and pod color i.e. how many yellow to how many green? F 2 3 yellow to 1 green or 3:1 The ratio for F 1 is just 1 since they re all the same
Application of Mendel s Work Let s move from pea plants to another model organism, fruit flies P If represents the standard color, what would represent the lack? If a fruit fly has two alleles what color will it e? If a fruit fly has two alleles what color will it e? If a fruit fly has one allele and one allele what color will it e?
Genotype and Phenotype Genotype: an organism s genetic makeup Phenotype: the expression of an organism s genetics In your note-taker, quickly draw the phenotype of a fly (one trait) and then descrie its genotype. See my example elow. The mutant fly has a genotype for two wings, ww. Genotype Phenotype
Zygosity: the similarity or difference etween alleles for a trait. #1 Which flies have different alleles? #2 #3 Which flies have the same two alleles? Homozygous: the alleles for a trait are the same Heterozygous: the alleles for a trait are different
Dominant and Recessive Discuss with your partner: which allele do you think is dominant and which is recessive? Why? Dominant: allele that is expressed even when heterozygous Capital letters represent dominant traits, while lower-case represents recessive traits. Recessive: allele that is only expressed when homozygous
Putting it all together P Now, kinder, fill out the three questions in your notetaker. Which flies are homozygous recessive? F 1 Which flies are homozygous dominant? F 2 Which flies are heterozygous dominant?
Meanwhile, ack at the chromosomes. In your notetakers, draw the chromosomes and alleles for the two homozygous fruit flies. Use this fly as your guide.
P P F 1 = F 1 F 2 F 2
How can we get from this to this without all of that? P F 1 F 2
P Reginald Punnett developed the Punnet square to determine the proaility of an F 1 offspring's having a particular genotype.
P F 1 Now you try! Make the F 2 Punnett Square on your slates. :^) F 2 =
Punnett Squares I was orn without wings sniff and will proaly die a violent death. P F 1 w WW W Ww ww W Ww If W is the allele for wings, what would the allele for vestigial wings e? Which allele is dominant and which is recessive? True. Nom. Nom. Nom. w Ww Ww Are the P generation flies homozygous or heterozygous? F 2 W w W WW Ww w Ww ww Ratio 3:1 In your notetakers, write out Punnett Squares for F 1 and F 2. Just use letters (no fly drawings) Write the recessive allele in cursive. Rememer the phenotype ratio for the F 2.
P P Ww ww F 1 w W Ww w ww F 1 w Ww ww Phenotypic Ratio 1 : 1 Phenotypic Ratio 4 : 0
Eyes were not in my genotype. Good thing I still have my trusty antennae! P EE ee E: eyes e: no eyes 3 seconds later F 1 e E Ee E Ee e Ee Ee E e Phenotypic ratio Eyes:No Eyes = 3 : 1 F 2 E EE Ee Genotypic ratio EE:Ee:ee = _1_:_2_:_1_ e Ee ee
Phenotype Color (wild-type or lack) Wings (present or asent) Eyes (eyes or eyeless) Genotype Color (, ): Eyes (E, e): e e Wings (W, w): WW or Ww