Question

the diagram represents a section of double - stranded dna. the bottom strand is complementary to the top strand. what letter belongs in each blank to complete the complementary sequence? enter your answers in the boxes. dna segment 3 g a t c c a t g a g 5 c t

Explanation:

Step1: Recall DNA base pairing

In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). The top strand is \( 3' - G A T C C A T G A G - 5' \) (let's parse the given sequence: first base \( 3' \) is G, then A, T, C, C, A, T, G, A, G? Wait, looking at the diagram: the top strand (3' to 5'? Wait, no, the bottom strand is 5' to 3' (since 5' is on the left for bottom). Wait, the bottom strand is \( 5' - C T \) [blank] [blank] [blank] [blank] [blank] [blank] [blank] [blank] \( - 3' \)? Wait, no, the diagram shows top strand: 3' end has G, A, then T, C, C, A, T, G, A, G (wait, the boxes are below the top strand's bases. Let's list the top strand bases (from 3' to 5'? Or 5' to 3'? Wait, DNA is antiparallel, so top strand 3' to 5' and bottom strand 5' to 3'. So the top strand (let's take each base: first (3' end) G, then A, then T, C, C, A, T, G, A, G (wait, the diagram has: 3' G A T C C A T G A G? Wait, the bottom strand is 5' C T [box1] [box2] [box3] [box4] [box5] [box6] [box7] [box8] 3'? Wait, no, the bottom strand starts with 5' C T, then the boxes. Let's take each base of the top strand and find the complement:

Top strand (let's assume the top strand is 3' to 5' as per the 3' label on the left top, and bottom is 5' to 3' (5' on left bottom). So top strand bases (from 3' to 5'): G, A, T, C, C, A, T, G, A, G? Wait, the boxes are below each top base. Let's list each top base and its complement:

1. Top base: G (3' end first base) → complement is C (since C pairs with G)
2. Top base: A → complement is T
3. Top base: T → complement is A
4. Top base: C → complement is G
5. Top base: C → complement is G
6. Top base: A → complement is T
7. Top base: T → complement is A
8. Top base: G → complement is C
9. Top base: A → complement is T
10. Top base: G → complement is C

Wait, but the bottom strand starts with 5' C T. Let's check the first two bottom bases: 5' C T. The top base above the first bottom C is G (since C is complement of G), and T is complement of A (so top base above T is A). So top strand starts with 3' G A... Then the next top base is T (above the first box). So:

First box (below T): T's complement is A? Wait, no: top base is T, so bottom (complement) is A? Wait, no: A pairs with T, T pairs with A; C pairs with G, G pairs with C.

Wait, let's re-express:

Top strand (3' to 5'): G (first), A (second), T (third), C (fourth), C (fifth), A (sixth), T (seventh), G (eighth), A (ninth), G (tenth)

Bottom strand (5' to 3'): C (first, complement of G), T (second, complement of A), [complement of T (third top base)] → A, [complement of C (fourth top base)] → G, [complement of C (fifth top base)] → G, [complement of A (sixth top base)] → T, [complement of T (seventh top base)] → A, [complement of G (eighth top base)] → C, [complement of A (ninth top base)] → T, [complement of G (tenth top base)] → C

Wait, but the bottom strand is written as 5' C T [box1] [box2] [box3] [box4] [box5] [box6] [box7] [box8] 3'? Wait, the diagram shows bottom strand: 5' C T, then 8 boxes? Wait, maybe I miscounted. Let's look at the diagram again:

Top strand (3' end): G A T C C A T G A G (10 bases? Wait, the user's diagram:

Top: 3' G A T C C A T G A G? Wait, the bottom: 5' C T [box1] [box2] [box3] [box4] [box5] [box6] [box7] [box8]? Wait, no, the boxes are:

After 5' C T, there are 8 boxes? Wait, maybe the top strand has 10 bases: G, A, T, C, C, A, T, G, A, G (10), and bottom has 10: C, T, [A], [G], [G], [T], [A], [C], [T], [C]

Wait, let's do each position:

1. Top base: G (3' first) → bottom complement: C (matches the given bottom first base: 5' C)
2. Top base: A → bottom complement: T (matches given bottom second base: T)
3. Top base: T → bottom complement: A (first box)
4. Top base: C → bottom complement: G (second box)
5. Top base: C → bottom complement: G (third box)
6. Top base: A → bottom complement: T (fourth box)
7. Top base: T → bottom complement: A (fifth box)
8. Top base: G → bottom complement: C (sixth box)
9. Top base: A → bottom complement: T (seventh box)
10. Top base: G → bottom complement: C (eighth box)

So the bottom strand (5' to 3') is: C T A G G T A C T C

Wait, but let's check again. Wait, maybe the top strand is 3' G A T C C A T G A G (10 bases), so bottom strand (5' to 3') is 5' C T A G G T A C T C 3'

So the boxes (after C T) are: A, G, G, T, A, C, T, C

Wait, but the diagram has 8 boxes? Wait, the original diagram: bottom strand is 5' C T, then 8 boxes. So the first two are C T, then 8 boxes. So the top strand has 10 bases (G, A, T, C, C, A, T, G, A, G), so bottom has 10 (C, T, A, G, G, T, A, C, T, C). So the boxes (positions 3 to 10 of bottom) are A, G, G, T, A, C, T, C

But maybe the question is about the first box (after C T). Let's confirm the base pairing: A-T, C-G. So for each top base:

- G (top) ↔ C (bottom)
- A (top) ↔ T (bottom)
- T (top) ↔ A (bottom)
- C (top) ↔ G (bottom)
- C (top) ↔ G (bottom)
- A (top) ↔ T (bottom)
- T (top) ↔ A (bottom)
- G (top) ↔ C (bottom)
- A (top) ↔ T (bottom)
- G (top) ↔ C (bottom)

So the bottom strand (5' to 3') is: C (complement of G), T (complement of A), A (complement of T), G (complement of C), G (complement of C), T (complement of A), A (complement of T), C (complement of G), T (complement of A), C (complement of G)

So the sequence of the bottom strand (complementary) is \( 5' - C T A G G T A C T C - 3' \)

So the first box (after C T) is A, second G, third G, fourth T, fifth A, sixth C, seventh T, eighth C.

But maybe the question is asking for each box. Let's assume the first box (under T) is A, second (under C) is G, third (under C) is G, fourth (under A) is T, fifth (under T) is A, sixth (under G) is C, seventh (under A) is T, eighth (under G) is C.

Step2: Fill each box

1. Under T (top base T): complement is A → box1: A
2. Under C (top base C): complement is G → box2: G
3. Under C (top base C): complement is G → box3: G
4. Under A (top base A): complement is T → box4: T
5. Under T (top base T): complement is A → box5: A
6. Under G (top base G): complement is C → box6: C
7. Under A (top base A): complement is T → box7: T
8. Under G (top base G): complement is C → box8: C

Answer:

The sequence of the complementary (bottom) strand is \( 5' - C T A G G T A C T C - 3' \), so the boxes (from left to right) contain: A, G, G, T, A, C, T, C (depending on the box position, but following base pairing: A-T, C-G). For the first box (after C T), the answer is A; second G, etc. (Assuming the first blank box is under T, so A.)