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Probability of Traits in a Population Name _________________ Date _________ Background Vocabulary Purebred Hybrid or Homozygous : - the same genes for a trait - ex; BB, bb or Heterozygous : - Genotype - differnet genes for a trait - ex: Bb, Ww What the allele or gene is; ex.. BB or Bb. Phenotype - What the traits “physically” looks like. Brown Eyes , Tall Frequency : Number of individuals with a certain trait in a population. Dominant Trait : A trait that masks another trait. Recessive Trait : A trait that is suppressed by a dominant trait. Problem: What are some observable inherited traits in humans? What is the relationship between frequency of a trait in a population and whether the trait is dominant or recessive? Make a hypothesis; Make a hypothesis on the frequency of traits. Choose one of the hypotheses below.(you can never really prove something true, but you can prove it false) 1- There are more dominant traits expressed in SMS students. or 2- There are more recessive traits expressed in SMS students. Hypothesis:____________________________________________________ _____________________________________________________________ Procedure In this investigation you will conduct a survey of observable traits in humans (the population tested will be your class). 1- Conduct the survey and record results. 2- Graph your results and calculate the frequency of each trait in a population. Mr. Mullany 1 Probability of Traits in a Population Observable Human Traits Hair Line Widow’s peak (W) or Straight across (w ) Earlobe attached ( e ) or unattached ( E ) Eyes Brown/Hazel ( B ) Mr. Mullany or Blue/Green ( b ) Tongue Roller ( R ) or Non - roller ( r ) Thumb Straight Thumb ( t ) or Hitchhiker’s Thumb ( T ) Folded Hands Left ( H ) or right ( h ) 2 Probability of Traits in a Population Observations Record all results from the class survey. Trait Hairline Dominant Total Recessive Window’s Peak (W) Tongue Earlobe Thumb Eyes Folded Hands Total Straight Across Hairline Roller (R) Unattached (E) (w) Non-roller (r) Attached (e) Hitchhiker’s Thumb Straight Thumb (T) Brown/ Hazel (B) Left thumb over right (H) (t) Blue/Green (b) Right thumb over left (h) Total Number of Students in Survey _________ 1- Graph your observations on a piece of graph paper (attach graph paper to the lab and use the format below). This is just an example. You have to graph your data as a double bar graph on graph paper. Graph Dominant and Recessive Traits in SMS Number of Students 20 15 10 5 0 Tongue Rolling Dimples Ear Lobes eye Color Traits Dominant Mr. Mullany Recessive 3 Probability of Traits in a Population Thought Questions 1- How many dominant traits tested in this lab do you have? 2- According to your chart, do most students in SMS have dominant or recessive traits? (use the data from your class survey) 3-Which recessive traits are more common than dominant traits? 4- If you have brown eyes how many genotypes could you write for that dominant trait? Explain? 5- If you have blue eyes, how many genotypes could you write for that recessive trait? Explain? Mr. Mullany 4 Probability of Traits in a Population Conclusions 1- Generalize: According to your results are the dominant traits the most common in a population or are recessive traits more common? You are supporting or rejecting your hypothesis. Explain your answer using the data to support it. 2- Infer: Write a possible genotype for yourself using all your traits. (Remember if you have brown eyes your genotype for eyes can be BB or Bb. But if you have blue eyes it can only be bb. ) My Genotype Trait Hairline (W) Tongue Roller (R) Ear Lobe (E) Thumb (T) Eyes (B) Folded Hands (H) Mr. Mullany Genotype 5