Molecular Biology Worksheet: Comparing Cytochrome C Amino Acid Sequences Across Species

Absolutely! Let’s solve this step by step.

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🧬 Objective:

Compare the cytochrome c amino acid sequence of each non-human animal to the human sequence and count how many positions differ. The human sequence is your reference.

We are given two tables with positions 42–57 and 58–104. We’ll go row by row, comparing each animal to human.

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## 🔍 Step-by-Step Comparison:

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✔ Human Sequence (Reference):

Positions 42–57:
Q A P Y S T A K N K G I

Positions 58–104:
I G E D T L M E K A T N E

*(Note: Position 104 is included, but position 103 is also shown — we'll include all listed positions from 42 to 104.)*

Total positions compared: 63 positions (from 42 to 104 inclusive: 104 - 42 + 1 = 63)

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## 🐔 Chicken:

42–57: Q A E F S T D K N K G I
→ Compare to Human: Q A P Y S T A K N K G I
Differences at:
- 44: P vs E → ✘
- 46: Y vs F → ✘
- 50: A vs D → ✘
→ 3 differences

58–104: T G E D T L M E D A T S K
→ Compare to Human: I G E D T L M E K A T N E
Differences at:
- 58: I vs T → ✘
- 60: G vs G → ✔️
- 61: E vs E → ✔️
- 62: D vs D → ✔️
- 63: T vs T → ✔️
- 64: L vs L → ✔️
- 65: M vs M → ✔️
- 66: E vs E → ✔️
- 100: K vs D → ✘
- 101: A vs A → ✔️
- 102: T vs T → ✔️
- 103: N vs S → ✘
- 104: E vs K → ✘
→ 4 differences

✔ Total for Chicken: 3 + 4 = 7

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## 🐎 Horse:

42–57: Q A P F S T D K N K G I
→ Differences:
- 46: Y vs F → ✘
- 50: A vs D → ✘
→ 2 differences

58–104: T K E E T L M E K A T N E
→ Differences:
- 58: I vs T → ✘
- 60: G vs K → ✘
- 62: D vs E → ✘
- 65: M vs M → ✔️
- 66: E vs E → ✔️
- 100: K vs K → ✔️
- 101: A vs A → ✔️
- 102: T vs T → ✔️
- 103: N vs N → ✔️
- 104: E vs E → ✔️
→ Wait — let's recheck:

Actually:
- 58: I vs T → ✘
- 60: G vs K → ✘
- 62: D vs E → ✘
- 63: T vs T → ✔️
- 64: L vs L → ✔️
- 65: M vs M → ✔️
- 66: E vs E → ✔️
- 100: K vs K → ✔️
- 101: A vs A → ✔️
- 102: T vs T → ✔️
- 103: N vs N → ✔️
- 104: E vs E → ✔️
→ Only 3 differences here? Wait — position 62 is D vs E → that’s one. But position 60 is G vs K → another. 58 is I vs T → third. That’s it?

Wait — position 62: Human has D, Horse has E → difference.
Also, position 60: Human G, Horse K → difference.
Position 58: Human I, Horse T → difference.

But what about position 63? Both T → same. 64 both L → same. 65 both M → same. 66 both E → same. 100 both K → same. So yes, only 3 in second half.

✔ Total for Horse: 2 + 3 = 5

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## 🐟 Tuna:

42–57: Q A E F S T D K S K G I
→ Differences:
- 44: P vs E → ✘
- 46: Y vs F → ✘
- 50: A vs D → ✘
- 54: N vs S → ✘
→ 4 differences

58–104: V N N E T L R E K A T S -
→ Differences:
- 58: I vs V → ✘
- 60: G vs N → ✘
- 61: E vs N → ✘
- 62: D vs E → ✘
- 63: T vs T → ✔️
- 64: L vs L → ✔️
- 65: M vs R → ✘
- 66: E vs E → ✔️
- 100: K vs K → ✔️
- 101: A vs A → ✔️
- 102: T vs T → ✔️
- 103: N vs S → ✘
- 104: E vs - → ✘ (missing or different)
→ 8 differences

✔ Total for Tuna: 4 + 8 = 12

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## 🐸 Frog:

42–57: Q A A F S T D K N K G I
→ Differences:
- 44: P vs A → ✘
- 46: Y vs F → ✘
- 50: A vs D → ✘
→ 3 differences

58–104: T G E E T L M E S A A C S K
→ Differences:
- 58: I vs T → ✘
- 62: D vs E → ✘
- 65: M vs M → ✔️
- 66: E vs E → ✔️
- 100: K vs S → ✘
- 101: A vs A → ✔️
- 102: T vs C → ✘
- 103: N vs S → ✘
- 104: E vs K → ✘
→ Let’s list them:
- 58: I vs T → ✘
- 62: D vs E → ✘
- 100: K vs S → ✘
- 102: T vs C → ✘
- 103: N vs S → ✘
- 104: E vs K → ✘
→ 6 differences

✔ Total for Frog: 3 + 6 = 9

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## 🦈 Shark:

42–57: Q A Q F S T D K S K G I
→ Differences:
- 44: P vs Q → ✘
- 46: Y vs F → ✘
- 50: A vs D → ✘
- 54: N vs S → ✘
→ 4 differences

58–104: T Q Q E T L R I K T A A S
→ Differences:
- 58: I vs T → ✘
- 60: G vs Q → ✘
- 61: E vs Q → ✘
- 62: D vs E → ✘
- 63: T vs T → ✔️
- 64: L vs L → ✔️
- 65: M vs R → ✘
- 66: E vs I → ✘
- 100: K vs K → ✔️
- 101: A vs T → ✘
- 102: T vs A → ✘
- 103: N vs A → ✘
- 104: E vs S → ✘
→ That’s a lot!

List:
- 58: I vs T → ✘
- 60: G vs Q → ✘
- 61: E vs Q → ✘
- 62: D vs E → ✘
- 65: M vs R → ✘
- 66: E vs I → ✘
- 101: A vs T → ✘
- 102: T vs A → ✘
- 103: N vs A → ✘
- 104: E vs S → ✘
→ 10 differences

✔ Total for Shark: 4 + 10 = 14

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## 🐢 Turtle:

42–57: Q A E F S T E K N K G I
→ Differences:
- 44: P vs E → ✘
- 46: Y vs F → ✘
- 50: A vs E → ✘
→ 3 differences

58–104: T G E E T L M E D A T S K
→ Differences:
- 58: I vs T → ✘
- 62: D vs E → ✘
- 65: M vs M → ✔️
- 66: E vs E → ✔️
- 100: K vs D → ✘
- 103: N vs S → ✘
- 104: E vs K → ✘
→ List:
- 58: I vs T → ✘
- 62: D vs E → ✘
- 100: K vs D → ✘
- 103: N vs S → ✘
- 104: E vs K → ✘
→ 5 differences

✔ Total for Turtle: 3 + 5 = 8

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## 🐒 Monkey:

42–57: Q A P Y S T A K N K G I
→ Exactly same as human!
→ 0 differences

58–104: T G E D T L M E K A T N E
→ Exactly same as human!
→ 0 differences

✔ Total for Monkey: 0 + 0 = 0

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## 🐰 Rabbit:

42–57: Q A V F S T D K N K G I
→ Differences:
- 44: P vs V → ✘
- 46: Y vs F → ✘
- 50: A vs D → ✘
→ 3 differences

58–104: T G E D T L M E K A T N E
→ Same as human!
→ 0 differences

✔ Total for Rabbit: 3 + 0 = 3

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## ✔ Final Answer Table:

| Animal | Number of Amino Acid Differences Compared to Human Cytochrome C |
|---------|---------------------------------------------------------------|
| Horse | 5 |
| Chicken | 7 |
| Tuna | 12 |
| Frog | 9 |
| Shark | 14 |
| Turtle | 8 |
| Monkey | 0 |
| Rabbit | 3 |

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## 📌 Summary:

This exercise shows how closely related animals are based on protein sequence similarity. The fewer the differences, the more closely related the species are to humans.

- Monkey has 0 differences → very close evolutionary relationship.
- Rabbit has 3 → fairly close.
- Horse has 5 → moderately close.
- Chicken has 7 → more distant.
- Turtle, Frog → more distant still.
- Shark has 14 → most distant among these.

This is exactly how scientists use molecular data (like cytochrome c) to build evolutionary trees!

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✔ All done! You can now fill in the table accordingly.