GENETICS Practice Ms. Golphin Science

What is a Punnett Square? Punnett square: a diagram that is used to predict the genotypes and phenotypes of an offspring. Each box is worth 25%, the total of a punnett square is 100%

How to complete a Punnett square Step 1: The genes on the top are brought down to the boxes below it. TtTt TTTT T t T t TtTt

How to complete a Punnett square Step 2: The genes are pushed into the boxes to the right of them. TTTT TtTt T T T T

Try These Punnett Squares on your worksheet 1 2 3

HOMOZYGOUS Definition: 2 genes that are the same. It could be 2 dominant genes or 2 recessive genes Example. ff or FF Example. 2 blue eyed genes Example. 2 brown genes

HETEROZYGOUS Definition: 2 genes that are different. There is 1 dominant gene and 1 recessive gene. Example. Rr or tT Example. 1 blue gene and 1 brown gene

1. The parents in this cross are _____________? Homozygous OR Heterozygous 2. If G is dominant for green pods and g is recessive for yellow pods, what percentage of the offspring will have green pods? _______% GGGgGg GgGggg G g G g

GENOTYPE Definition: The 2 letters that stand for a gene. You get ONE from each parent. Example. eE, QQ, Ll, rr

Bb B b 3. The genotype of the offspring in the blue box is _______? 4. The offspring in the blue box is homozygous OR heterozygous

PHENOTYPE Definition: what the gene actually looks like. Example. Red hair, Dark Skin, Tongue roll

Label the following as genotype or phenotype. A- Small nose B- Long toes C- HH D- 5 feet tall E- gG F- Pp G- Green eyes H- Qq

Bb B b 5. In guinea pigs black fur (B) is dominant over brown fur (b). The Punnett square for a cross between a HETEROZYGOUS black guinea pig and a HOMOZYGOUS brown guinea pig would look like BB b b Bb b b Bb B B Answer_______?__________ ABD C

6. What are the possible phenotypes of their offspring? (% and color) Red throats (R) are dominant over white (r) throats in Goonie birds. Make a cross between a PURE RECESSIVE and a HETEROZYGOUS Goonie bird. Rr rr R r r

7. What are the possible phenotypes of their offspring? (% and color) Black eyes (B) are dominant over red eyes (b) in rats. Make a cross between two HETEROZYGOUS rats. B b B b BB Bb Bb bb

8. The parents in this cross are _____________ Homozygous Heterozygous 9. If W is dominant for long wings and w is recessive for short wings, what percentage of these offspring will have short wings? _______%

10. What kind of cross is this? -Pure dominant X pure recessive? -Heterozygous X heterozygous? -Heterozygous X homozygous? -Hybrid recessive X hybrid pure? Another name for heterozygous is __Hybrid_____________

Aa A a 11. The genotype of the offspring in the blue box is _______ homozygous heterozygous How many of the offspring from this cross will show the dominant characteristic? ¾ (75%) – AA and Aa

Gg G GGGg g gg G is dominant for green pods. g is recessive for yellow pods. What is the genotype of the offspring in the shaded box? Gg What is the phenotype of the offspring in the shaded box? Green pods

What will the offspring be like? (% and color) 12. Purple (P)is the dominant color for monsters. Yellow is recessive (p). Make a cross between a HOMOZYGOUS purple and a yellow monster. P P p

What genotype would a PURPLE dad have to be to make a yellow monster baby with a Purple (Pp) mom monster? Pp ? ? pp Pp Dad needs to have: a little p to give one to the baby a big P to be purple himself