Mendel's laws of segregation and independent assortment
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Bo crosses a round plant with a wrinkled plant (rr). If the round plant is Rr, what is the chance that three offspring in a row are all round?
- 1 in 8
- 1 in 4
- 3 in 4
- 1 in 2
Read this first
Two genes on different chromosomes (model)
gene each parent's alleles where the gene sits flower position Aa one chromosome pod color Gg a different chromosome Esme crosses two AaGg plants (A for axial flowers, a for terminal; G for green pods, g for yellow). What is the chance one offspring has terminal flowers and yellow pods?
- 1 in 4
- 9 in 16
- 1 in 16
- 1 in 2, since 1/4 + 1/4
Mendel's real counts, flower position (real data: Mendel)
generation what the plants showed F1 100 percent axial F2 651 axial and 207 terminal The F2 plants came from F1 plants crossed with themselves (A for axial flowers, a for terminal). Jun works backward. What were the letters of the F1 plants?
- aa (two terminal alleles), since terminal flowers appeared
- Aa (one axial, one terminal allele), since the F2 is near 3 : 1
- AA (two axial alleles), since the terminal allele disappeared in the F1
- Half Aa and half AA, since the F2 is not exactly 3 : 1
Cross card
A cross of two tall plants (model data), 1 row. Columns: parents, offspring. Row 1: two tall plants, letters unknown, 30 tall and 10 dwarf.
Kira reads a cross card for two tall pea plants. What are the parents' letters, most likely?
- Tt × tt (one parent has two dwarf alleles)
- Tt × Tt (each parent has one tall, one dwarf allele)
- TT × Tt (one parent has two tall alleles)
- TT × TT (both parents have two tall alleles)
Cross card
A surprise dwarf plant (model data), 1 row. Columns: parents, one offspring. Row 1: two tall plants, letters unknown, a dwarf plant.
Two tall pea plants have one dwarf offspring. Luz asks what must be true of both parents.
- Neither has a dwarf allele; the heights blended into a small plant
- Both are TT, since a tall plant has lost its dwarf allele
- Both carry a dwarf allele, so both are Tt
- One needs a dwarf allele, so TT × Tt could do it
Notebook
Notes on two Vv plants (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Each Vv parent passes on one of its two alleles, chosen at random. Line 2: So the four boxes are VV, Vv, Vv and vv. Line 3: The three kinds of genotype are in the ratio 3 : 1. Line 4: The phenotypes are 3 violet to 1 white.
Milo reads a classmate's notebook about two Vv pea plants. Which line has the mistake?
- Line 2: the two Vv boxes should be counted as one
- Line 4: the phenotypes are in the ratio 1 : 2 : 1
- Line 3: the genotypes are in the ratio 1 : 2 : 1
- Line 1: a parent should pass on both of its alleles
Notebook
Notes on a class seed count (classmate's notebook), 4 lines. Columns: line, entry. Line 1: A class crossed Rr × Rr and planted 400 seeds (model data). Line 2: A 3 : 1 ratio predicts 300 round and 100 wrinkled. Line 3: The class counted 293 round and 107 wrinkled. Line 4: These are not exactly 300 and 100, so the 3 : 1 idea is wrong.
Pia reads a classmate's notebook about a class seed count. Which line has the mistake?
- Line 1: Rr × Rr cannot give wrinkled seeds
- Line 2: a 3 : 1 ratio predicts 100 round and 300 wrinkled
- Line 3: the class should have counted exactly 300 round
- Line 4: counts near 300 and 100 still fit 3 : 1
Ren says: two Vv parents with four offspring will have exactly 3 violet and 1 white. Do you agree?
- Yes, because a 3 : 1 ratio fixes the numbers in a family of four
- No, because the ratio of looks is 1 : 2 : 1, not 3 : 1
- No, because each offspring has a 3 in 4 chance of violet, so four can differ
- Yes, because the square has 3 violet boxes and 1 white box
Mendel's real counts, flower color (real data: Mendel)
generation what the plants showed F1 100 percent violet F2 705 violet and 224 white Tala claims that the F1 plants lost the white allele. Do you agree?
- No, because the F1 flowers were pale violet, a blend
- Yes, because 705 : 224 is not exactly 3 : 1
- Yes, because 100 percent of the F1 plants had violet flowers
- No, because 224 white F2 plants show the allele was still there
Two Vv parents have three violet offspring so far. Zee says the next one must be white to make 3 : 1. Do you agree?
- Yes, because the square has one white box left
- No, because the next offspring is violet with chance 3 in 4, as before
- Yes, because a family has to match the 3 : 1 ratio
- No, because the next offspring is Vv, which blends violet and white