Predicting Inheritance using Punnett Squares Unit 5 Genetics

Let’s Review our Vocab! • Dominant traits cover up Recessive traits – Dominant Allele

Dominant or Recessive? • B=Black b=white – Bb: Dom or Rec? Color? • T=Tall

• Genotype: Genotype the actual alleles for a trait • Represented by letters:

Homozygous or Heterozygous? • BB • Kk • ff • Homozygous dominant • Heterozygous

• Phenotype: Phenotype how the trait is seen – Ex: Guinae pig fur

Genotype or Phenotype? • • Black Bb tt Short KK Pp Tall White •

Punnett Squares • Used to predict the traits of each possible offspring during a

5 -Step Plan for Punnett Squares Flee Map 5 -Step Plan 1) Legend 2)

Sample Problem You do NOT have to write this slide! • In guinea pigs,

Five-Step Plan • 1) Legend – Always use the first letter of the dominant

• 2) Parents - Write this as a “cross” – BB x bb

• 3) Punnett Square - Set it up – Draw a square and

• 4) Punnett Square - Fill it in – Fill in the boxes

• 5) Answers – Each box = a 25% chance of offspring inheriting

• Now we have COMPLETELY answered the question and we are done! –

Whiteboards • Keep your notes & flow map in front of you. • Please

Example: Purple Flower (PP) x White Flower (pp) P p p P Pp Pp

Example: Tall (Tt) x short (tt) t Tt tt What % of the offspring

Example: Brown eyes (Bb) x Brown eyes (Bb) B B b BB Bb bb

Example: Dimples (DD) x No Dimples (dd) D d d Dd Dd Dd What

Normal thumbs (T) are dominant to hitchiker’s thumbs (t). A man with hitchiker’s thumb

Free earlobes (F) are dominant to attached earlobes (f). A man with attached earlobes

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Predicting Inheritance using Punnett Squares Unit 5: Genetics Chapter 11 -2

Let’s Review our Vocab! • Dominant traits cover up Recessive traits – Dominant Allele = capital letter (B) – Recessive Allele = lower case letter (b) P = Parents F 1 = first generation offspring F 2 = second generation offspring

Dominant or Recessive? • B=Black b=white – Bb: Dom or Rec? Color? • T=Tall t= short – TT: Dom or Rec? Height? • P=Purple p=white – pp? : Dom or Rec? Color?

• Genotype: Genotype the actual alleles for a trait • Represented by letters: AA, aa, Aa – Homozygous Dominant: 2 dominant alleles (AA) (purebred) – Homozygous Recessive: 2 recessive alleles (aa) (purebred) – Heterozygous: 1 dominant allele & 1 recessive allele (Aa) (hybrid)

Homozygous or Heterozygous? • BB • Kk • ff • Homozygous dominant • Heterozygous • Homozygous recessive Purebred or Hybrid? • rr • Ww • NN • purebred • hybrid • purbred

• Phenotype: Phenotype how the trait is seen – Ex: Guinae pig fur color: black or white P = Parents F 1 = first generation offspring F 2 = second generation offspring

Genotype or Phenotype? • • Black Bb tt Short KK Pp Tall White • • Phenotype Genotype Phenotype

Punnett Squares • Used to predict the traits of each possible offspring during a cross • Five Step Plan – 1) Legend – 2) Parents – 3) Punnett square-set it up – 4) Punett square-fill it in – 5) Answers in boxes

5 -Step Plan for Punnett Squares Flee Map 5 -Step Plan 1) Legend 2) Parents 3) Punnett Square: Set it up 4) Punnett Square: Fill it in 5) Answers Pg 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?

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: Genotype Phenotype BB Black Bb Black bb White

• 2) Parents - Write this as a “cross” – BB x bb

• 3) Punnett Square - Set it up – Draw a square and divide into four sections – Write the genotype (letters) from one parent on top (one letter per box) – Write the genotype from the other parent along the left side 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 B b B b

• 5) Answers – Each box = a 25% chance of offspring inheriting that genotype – Always put a box around your final answer!!! B B b B b 100% Black offspring 0% White offspring Ratio: 4 : 0 OR 1 : 0 (Black : White)

• Now we have COMPLETELY answered the question and we are done! – Always double check! Now you practice on the whiteboard!

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).

Example: Purple Flower (PP) x White Flower (pp) P p p P Pp Pp What % of the offspring will be Purple? White? 100 % Purple 0% White What is the ratio of purple : white? 1: 0 (Hint: how many of each & reduce)

Example: Tall (Tt) x short (tt) t Tt tt What % of the offspring will be Tall? Short? 50 % Tall 50% Short What is the ratio of tall : short? 1: 1 (Hint: how many of each & reduce)

Example: Brown eyes (Bb) x Brown eyes (Bb) B B b BB Bb bb What % of the offspring will be Brown eyes? 75 % Brown 25% Blue eyes? What is the ratio of brown eyes : blue eyes? 3: 1 (Hint: how many of each)

Example: Dimples (DD) x No Dimples (dd) D d d Dd Dd Dd What % of the offspring will have dimples? 100 % Dimples 0% No dimples? What is the ratio of dimples : no dimples? 1: 0 (Hint: how many of each & reduce)

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 Tt T tt t t Tt tt % of Normal thumbs? % Hitchiker’s thumbs? 50 % Normal 50% Hitchiker’s Ratio? 1: 1

Free earlobes (F) are dominant to attached earlobes (f). A man with attached earlobes marries a women that is homozygous for free earlobes. f Ff Ff % Free Earlobes? % Attached earlobes? 100 % Free 0% Attached Ratio? 1: 0