Presentation on theme: "Predicting Inheritance using Punnett Squares"— Presentation transcript:
1Predicting Inheritance using Punnett Squares Unit 5: GeneticsChapter 11-2
2Let’s Review our Vocab! Dominant traits cover up Recessive traits Dominant Allele = capital letter (B)Recessive Allele = lower case letter (b)P = ParentsF1 = first generation offspringF2 = second generation offspring
3Dominant or Recessive? B=Black b=white Bb: Dom or Rec? Color? T=Tall t= shortTT: Dom or Rec? Height?P=Purple p=whitepp?: Dom or Rec? Color?
4Genotype: the actual alleles for a trait Represented by letters: AA, aa, AaHomozygous Dominant: 2 dominant alleles (AA) (purebred)Homozygous Recessive: 2 recessive alleles (aa) (purebred)Heterozygous: 1 dominant allele & 1 recessive allele (Aa) (hybrid)
5Homozygous or Heterozygous? BBKkffHomozygous dominantHeterozygousHomozygous recessivePurebred or Hybrid?rrWwNNpurebredhybridpurbred
6Phenotype: how the trait is seen Ex: Guinae pig fur color: black or whiteP = ParentsF1 = first generation offspringF2 = second generation offspring
7Genotype or Phenotype? Black Bb tt Short KK Pp Tall White Phenotype
8Punnett SquaresUsed to predict the traits of each possible offspring during a crossFive Step Plan1) Legend2) Parents3) Punnett square-set it up4) Punett square-fill it in5) Answers in boxes
95-Step Plan for Punnett Squares Flee Map 1) Legend2) Parents3) Punnett Square:Set it up4) Punnett Square:Fill it in5) AnswersPg 10
10Sample Problem You do NOT have to write this slide! In guinea pigs, Black (B) is dominant to White (b)Black guinea pig (BB) x White guinea pig (bb)What are the chances that the offspring will be black? White?How many offspring will be black? How many will be white?
11Five-Step Plan 1) Legend Always use the first letter of the dominant trait to represent your alleles. (ex: in this case, we use B for black)Set up a table:GenotypePhenotypeBBBbbbBlackBlackWhite
133) Punnett Square - Set it up Draw a square and divide into four sectionsWrite the genotype (letters) from one parent on top (one letter per box)Write the genotype from the other parent along the left sideB Bb
14b B b B b B b B b 4) Punnett Square - Fill it in Fill in the boxes with one letter from the top and one letter from the left (2 letters per box)B BbBbBbBbBb
15b B b B b B b B b 5) Answers 100% Black offspring 0% White offspring Each box = a 25% chance of offspring inheriting that genotypeAlways put a box around your final answer!!!B B100% Black offspring0% White offspringRatio: 4 : 0 OR1 : 0 (Black : White)bBbBbBbBb
16Now you practice on the whiteboard! Now we have COMPLETELY answered the question and we are done!Always double check!Now you practice on the whiteboard!
17Whiteboards Keep your notes & flow map in front of you. Please do not draw on whiteboard unless instructed.For each problem you will do steps 1 & 2 (legend & parents) first.You will then do steps 3-5 (Punnett square and answers).
18Example: Purple Flower (PP) x White Flower (pp) What % of the offspring will be Purple? White?What is the ratio of purple : white?(Hint: how many of each & reduce)100 % Purple0% White1: 0
19Example: Tall (Tt) x short (tt) What % of the offspring will be Tall? Short?What is the ratio of tall : short?(Hint: how many of each & reduce)50 % Tall50% Short1: 1
20Example: Brown eyes (Bb) x Brown eyes (Bb) What % of the offspring will be Brown eyes? Blue eyes?What is the ratio of brown eyes : blue eyes?(Hint: how many of each)75 % Brown25% Blue3: 1
21Example: Dimples (DD) x No Dimples (dd) What % of the offspring will have dimples? No dimples?What is the ratio of dimples : no dimples?(Hint: how many of each & reduce)100 % Dimples0% No dimples1: 0
22Normal thumbs (T) are dominant to hitchiker’s thumbs (t) Normal thumbs (T) are dominant to hitchiker’s thumbs (t). A man with hitchiker’s thumb marries a women that is heterozygous for a normal thumb.t tTtTtTttttt% of Normal thumbs? % Hitchiker’s thumbs?Ratio?50 % Normal50% Hitchiker’s1: 1
23Free earlobes (F) are dominant to attached earlobes (f) Free earlobes (F) are dominant to attached earlobes (f). A man with attached earlobes marries a women that is homozygous for free earlobes.f fFFfFfFfFf% Free Earlobes? % Attached earlobes?Ratio?100 % Free0% Attached1: 0