Blended and both-showing traits
Grade 9 Science Worksheet
Circle the best answer.
Ari crosses two pink snapdragons. What is the ratio of red to pink to white flowers in the offspring?
- 1 red : 2 pink : 1 white
- 3 red : 0 pink : 1 white
- 0 red : 4 pink : 0 white
- 2 red : 1 pink : 1 white
Bo crosses a pink snapdragon with a white one. What is the ratio of pink to white flowers in the offspring?
- 4 pink : 0 white
- 3 pink : 1 white
- 1 pink : 1 white
- 1 red : 1 white
Esme crosses a roan parent with a red parent in a model cross. What is the ratio of red to roan calves?
- 1 red : 1 roan
- 4 red : 0 roan
- 3 red : 1 roan
- 2 red : 1 roan
Read this first
Table
Cross results for model cattle (model data), 3 rows. Columns: generation, what the calves showed. Row 1: parents, one red line and one white line. Row 2: F1, roan, with red hairs and white hairs. Row 3: F2, 26 red, 49 roan and 25 white.
Kira reads the cross results for model cattle. Which pattern fits?
- Codominance: roan calves show both hair colors
- Blending: mixed coats cannot split into red and white again
- Incomplete dominance: roan is one in-between color
- Complete dominance: red hides white in the F1
Table
Four traits and their heterozygote looks (model), 4 rows. Columns: trait, what the heterozygote shows. Row 1: pea seed shape, round seeds, as one allele hides the other. Row 2: snapdragon flower color, pink flowers, in between red and white. Row 3: roan cattle coat, red hairs and white hairs together. Row 4: ABO blood type AB, both the A form and the B form.
Luz reads a card of four traits. Which row shows incomplete dominance?
- Row 1: the pea seed shape
- Row 4: ABO blood type AB
- Row 2: snapdragon flowers
- Row 3: the roan cattle coat
Milo plans 200 seedlings from the cross in the square (model data). About how many should have red flowers?
- About 50, one quarter of 200
- About 150, three quarters of 200
- About 0, since the red allele is blended away
- About 100, the two pink boxes together
Pia expects about 90 pink seedlings from the cross in the square (model data). About how many seedlings is that in all?
Use the picture in question 6.
- About 180, since pink is half
- About 120, since pink is three quarters
- About 270, since 90 is multiplied by 3
- About 360, since pink is one quarter
Table
Two crosses of heterozygous parents (model), 2 rows. Columns: cross, the four boxes, the four looks. Row 1: pea Vv × Vv, VV, Vv, Vv and vv, violet, violet, violet and white. Row 2: snapdragon RW × RW, RR, RW, RW and WW, red, pink, pink and white.
Ren compares two crosses of heterozygous parents. How do the ratios of looks compare?
- Pea 3 : 1; snapdragon 3 : 1, since both crosses use two heterozygous parents
- Pea 1 : 2 : 1; snapdragon 1 : 2 : 1, since both have the same boxes
- Pea 3 violet : 1 white; snapdragon 1 red : 2 pink : 1 white
- Pea 1 violet : 2 mixed : 1 white; snapdragon 3 : 1
Genotype ratio and ratio of looks (model)
cross genotype ratio ratio of looks pea Vv × Vv 1 : 2 : 1 3 : 1 snapdragon RW × RW 1 : 2 : 1 1 : 2 : 1 Tala reads a table of two crosses. Why does the snapdragon ratio of looks match its ratio of genotypes?
- Each genotype has its own look, so 3 genotypes give 3 looks
- Snapdragons have three alleles, one for each look
- Red is dominant, so RR and RW look the same
- The alleles blend into one pink allele that is passed on
Three patterns of dominance (model)
pattern heterozygote example heterozygote look complete dominance pea Vv violet incomplete dominance snapdragon RW pink codominance roan cattle RW red hairs and white hairs Zee crosses two heterozygous parents in each pattern. What is true for all three patterns?
- The ratio of looks is 3 : 1
- The heterozygote shows one mixed color
- The heterozygote hides one of its alleles
- The genotypes come out 1 : 2 : 1