Presentation on theme: "Predicting Inheritance using Punnett Squares"— Presentation transcript:
1 Predicting Inheritance using Punnett Squares Unit 5: GeneticsChapter 11-2
2 Let’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
3 Dominant 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?
4 Genotype: 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)
5 Homozygous or Heterozygous? BBKkffHomozygous dominantHeterozygousHomozygous recessivePurebred or Hybrid?rrWwNNpurebredhybridpurbred
6 Phenotype: how the trait is seen Ex: Guinae pig fur color: black or whiteP = ParentsF1 = first generation offspringF2 = second generation offspring
7 Genotype or Phenotype? Black Bb tt Short KK Pp Tall White Phenotype
8 Punnett 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
9 5-Step Plan for Punnett Squares Flee Map 1) Legend2) Parents3) Punnett Square:Set it up4) Punnett Square:Fill it in5) AnswersPg 10
10 Sample 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?
11 Five-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
13 3) 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
14 b 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
15 b 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
16 Now 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!
17 Whiteboards 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).
18 Example: 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
19 Example: 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
20 Example: 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
21 Example: 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
22 Normal 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
23 Free 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