Copy of Practice - simple genetics - Name: Genetics Practice - Studocu - Free Printable

Let’s go through each problem step by step.

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Problem 1: Heterozygous (He) or Homozygous (Ho)

Remember:
- Homozygous (Ho) = both letters are the same (like AA, ff, GG)
- Heterozygous (He) = letters are different (like Bb, Cc, Dd)

Now check each:

- AA → same → Ho
- Bb → different → He
- Cc → different → He
- Dd → different → He
- Ee → different → He
- ff → same → Ho
- GG → same → Ho
- HH → same → Ho
- Ii → different → He
- Jj → different → He
- kk → same → Ho
- Ll → different → He
- Mm → different → He
- nn → same → Ho
- OO → same → Ho
- Pp → different → He

✔ All correct as written in the image.

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Problem 2: Phenotypes from Genotypes

Rules:
- Dominant trait shows if at least one capital letter is present.
- Recessive trait only shows if both letters are lowercase.

Purple flowers dominant to white:
- PP → Purple (two dominants)
- Pp → Purple (one dominant)
- pp → White (no dominant) ✔

Brown eyes dominant to blue:
- BB → Brown
- Bb → Brown
- bb → Blue ✔

Round seeds dominant to wrinkled:
- RR → Round
- Rr → Round
- rr → Wrinkled ✔

Bobtails recessive (so long tails are dominant):
- TT → long tails
- Tt → long tails
- tt → bobtails ✔

All correct.

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Problem 3: Genotypes from Phenotypes

Use the dominant letter for the trait.

Straight hair dominant to curly:
- Straight → can be SS or Ss
- Curly → must be ss ✔

Tail spikes dominant to plain tails:
- Spikes → SS or Ss
- Plain → ss ✔

All correct.

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Problem 4: Punnett Squares

We’re told purple flowers are dominant to white — but note: the questions ask about “round” offspring? That seems like a mistake — probably meant “purple” since we’re crossing flower color genotypes. But let’s look carefully.

Actually, looking again — the crosses are labeled with R and r, which earlier were used for “round vs wrinkled seeds”. So maybe this section switched traits? Let’s assume that here, R = round (dominant), r = wrinkled (recessive) — even though the intro says “purple flowers”, it might be a typo. We’ll go with seed shape since the alleles are R/r.

So:

Cross 1: Rr x rr

Punnett square:

| | r | r |
|-----|-----|-----|
| R | Rr | Rr |
| r | rr | rr |

Offspring: 2 Rr (round), 2 rr (wrinkled) → 50% round, 50% wrinkled

But the question asks: “What percentage of the offspring will be round?” → 50%

Wait — actually, in the image, the Punnett square is already filled out as:

First cross (Rr x rr):

Top row: Rr, rr
Bottom row: Rr, rr

That’s 2 Rr and 2 rr → so 2 out of 4 are round → 50%

Second cross: Rr x Rr

Punnett square given:

| | R | r |
|-----|-----|-----|
| R | RR | Rr |
| r | Rr | rr |

Offspring: 1 RR, 2 Rr, 1 rr → 3 round (RR + Rr), 1 wrinkled → 75% round

Third cross: RR x Rr

Punnett square:

| | R | R |
|-----|-----|-----|
| R | RR | RR |
| r | Rr | Rr |

All offspring have at least one R → all 4 are round → 100% round

So answers:

- First cross (Rr x rr): 50% round
- Second cross (Rr x Rr): 75% round
- Third cross (RR x Rr): 100% round

But wait — the image has two boxes asking “What percentage... round?” next to the second and third crosses.

So:

→ For Rr x Rr: 75%
→ For RR x Rr: 100%

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Problem 5: TT (tall) x tt (short)

Assume tall is dominant (T), short is recessive (t).

Cross: TT x tt

All offspring get T from first parent and t from second → all Tt

Since T is dominant, all offspring are tall.

Percentage that are tall: 100%

(Though the question doesn’t ask for percentage — it just says “crossed with”, so maybe they want the genotype or phenotype of offspring? But since no specific question is asked beyond setting up, perhaps we just note the result.)

But since the instruction says “Solve the problem accurately”, and Problem 5 is listed without a specific question, we’ll assume they want the offspring genotype and phenotype.

Offspring: all Tt → all tall.

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Now, compiling final answers where needed:

For Problem 4, the two blanks:

- After Rr x Rr: 75%
- After RR x Rr: 100%

For Problem 5, since no blank is shown, but it says “Show all work!”, we can state:

All offspring are Tt (heterozygous tall).

But since the user may expect only the filled-in blanks, we focus on those.

Final Answer:

For Problem 4:
- Rr x Rr cross: 75%
- RR x Rr cross: 100%

For Problem 5: All offspring are Tt (tall).

But to match format — since the image has blanks only in Problem 4’s two boxes, we fill those.

Final Answer:
75%
100%