cytochrome c is a protein that helps release energy from food and is produced by nearly all organisms. the table shows a short sequence of the amino acids in cytochrome c for several species.

identify the organisms that is most closely related to tuna and explain your reasoning using evidence from the table. think about the information carefully!

Question

cytochrome c is a protein that helps release energy from food and is produced by nearly all organisms. the table shows a short sequence of the amino acids in cytochrome c for several species.

identify the organisms that is most closely related to tuna and explain your reasoning using evidence from the table. think about the information carefully!

Accepted Answer

# Brief Explanations:
To determine the organism most closely related to tuna, we compare the amino acid sequences of cytochrome c. The more identical amino acids in the sequence, the closer the evolutionary relationship (since fewer mutations imply a more recent common ancestor).
- Tuna's sequence: Glycine (9), Aspartic acid (10), Valine (11), Alanine (12), Lysine (13).
- Chicken: Glycine (9), Aspartic acid (10), Isoleucine (11) – different at position 11.
- Neurospora: Glycine (9), Aspartic acid (10), Serine (11) – different at 11; Lysine (12) – different at 12.
- Gray whale: Glycine (9), Aspartic acid (10), Valine (11), Glutamic acid (12) – different at 12; Lysine (13) – same as tuna at 13, but 12 differs. Wait, re - check: Tuna (12: Alanine), Gray whale (12: Glutamic acid) – different. Wait, no, let's re - list each position (9 - 13) for each organism vs tuna:
    - Tuna: 9 = Gly, 10 = Asp, 11 = Val, 12 = Ala, 13 = Lys.
    - Chicken: 9 = Gly, 10 = Asp, 11 = Ile (diff), 12 = Glu (diff), 13 = Lys.
    - Neurospora: 9 = Gly, 10 = Asp, 11 = Ser (diff), 12 = Lys (diff), 13 = Lys.
    - Gray whale: 9 = Gly, 10 = Asp, 11 = Val (same), 12 = Glu (diff), 13 = Lys (same).
    - Silkworm moth: 9 = Gly, 10 = Asp (wait, no: Silkworm moth 10 is Asparagine? Wait, no, the table: Tuna 10: Aspartic acid; Silkworm moth 10: Asparagine – different. Wait, I misread earlier. Let's correct:
Tuna:
9: Glycine
10: Aspartic acid
11: Valine
12: Alanine
13: Lysine

Gray whale:
9: Glycine (same as tuna)
10: Aspartic acid (same as tuna)
11: Valine (same as tuna)
12: Glutamic acid (different from tuna's Alanine)
13: Lysine (same as tuna)

Chicken:
9: Glycine (same)
10: Aspartic acid (same)
11: Isoleucine (different from Valine)
12: Glutamic acid (different from Alanine)
13: Lysine (same)

Wait, no, maybe I messed up the silkworm moth. Wait, Silkworm moth: 9: Glycine (same), 10: Asparagine (different from Aspartic acid) – so position 10 differs.

Wait, another approach: count the number of matching amino acids at positions 9 - 13.
- Tuna vs Gray whale: Positions 9 (Gly - Gly: match), 10 (Asp - Asp: match), 11 (Val - Val: match), 12 (Ala - Glu: no), 13 (Lys - Lys: match). So 4 matches.
- Tuna vs Chicken: 9 (match), 10 (match), 11 (no), 12 (no), 13 (match). 3 matches.
- Tuna vs Neurospora: 9 (match), 10 (match), 11 (no), 12 (no), 13 (match). 3 matches.
- Tuna vs Silkworm moth: 9 (match), 10 (no, Asp vs Asparagine), 11 (no, Val vs Alanine), 12 (no, Ala vs Glutamic acid), 13 (no, Lys vs Asparagine). Wait, no, Silkworm moth 13: Asparagine – different from Lys. So fewer matches.

Wait, I think I made a mistake earlier. Let's re - extract the table correctly (assuming the columns are Organism, 9,10,11,12,13):

| Organism   | 9       | 10          | 11       | 12          | 13    |
|------------|---------|-------------|----------|-------------|-------|
| Tuna       | Glycine | Aspartic acid | Valine   | Alanine     | Lysine|
| Chicken    | Glycine | Aspartic acid | Isoleucine| Glutamic acid| Lysine|
| Neurospora | Glycine | Aspartic acid | Serine   | Lysine      | Lysine|
| Gray whale | Glycine | Aspartic acid | Valine   | Glutamic acid| Lysine|
| Silkworm moth| Glycine | Asparagine  | Alanine  | Glutamic acid| Asparagine|

Now, compare each to Tuna:
- Tuna: [Gly, Asp, Val, Ala, Lys]
- Chicken: [Gly, Asp, Ile, Glu, Lys] → differences at 11,12 → 3 matches (9,10,13).
- Neurospora: [Gly, Asp, Ser, Lys, Lys] → differences at 11,12 → 3 matches (9,10,13).
- Gray whale: [Gly, Asp, Val, Glu, Lys] → differences at 12 → 4 matches (9,10,11,13).
- Silkworm moth: [Gly, Asn, Ala, Glu, Asn] → differences at 10,11,12,13 → 1 match (9).

So Gray whale has 4 matches (positions 9,10,11,13) – only position 12 (Ala vs Glu) differs. This is more matches than Chicken (3) or Neurospora (3) or Silkworm moth (1). In evolutionary biology, the similarity of protein (like cytochrome c) amino acid sequences is a key indicator of relatedness (molecular homology). Fewer sequence differences mean the organisms share a more recent common ancestor, so Gray whale is most closely related to tuna. Wait, but wait, earlier I thought Gray whale's 12 was Glutamic acid vs Tuna's Alanine – that's one difference, but Chicken has two differences (11 and 12), Neurospora two (11 and 12), Silkworm moth four. So Gray whale has the most identical amino acids in the cytochrome c sequence, so it is most closely related.

# Answer:
Gray whale. The amino acid sequence of cytochrome c in Gray whale has the most matches with Tuna's sequence (4 out of 5 positions: 9,10,11,13 are identical; only position 12 differs), indicating a closer evolutionary relationship (fewer mutations, more recent common ancestor) compared to other organisms (Chicken: 3 matches, Neurospora: 3 matches, Silkworm moth: 1 match).

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Organism	9	10	11	12	13
Chicken	Glycine	Aspartic acid	Isoleucine	Glutamic acid	Lysine
Neurospora	Glycine	Aspartic acid	Serine	Lysine	Lysine
Gray whale	Glycine	Aspartic acid	Valine	Glutamic acid	Lysine
Silkworm moth	Glycine	Asparagine	Alanine	Glutamic acid	Asparagine