Question

from the shape of dna

1
like most other scientists, pauling was not interested in dna until 1952, even though swiss biologist friedrich miescher had discovered dna in 1869. but what was dna? scientists knew only a little. it came in long strands, and each strand had a phosphorus - sugar backbone. there were also nucleic bases, which stuck out from the backbone like knobs on a spine. but the shape of the strands and how they linked up were mysteries—important mysteries. as pauling showed with hemoglobin, shape can affect how molecules work. soon the shape of dna became the most important question in biology.

2
and pauling, like many others, assumed he was the only one smart enough to answer this question. this wasn’t, or at least wasn’t only, arrogance: pauling had simply never been beaten before. so in 1952, pauling sat down at his desk in california to crack dna. he decided, incorrectly, that the bulky nucleic bases sat on the outside of each strand with the phosphorus - sugar backbone toward the molecule’s core. pauling also reasoned that dna was a triple helix, with three ribbons of the phosphorus - sugar backbones forming a spiral. unfortunately for pauling, his data came from a dried - out dna sample, which made the molecule seem more complicated. but on paper, all this seemed possible.

3
everything was humming along nicely until pauling asked a graduate student to check his calculations. the student did and was soon tying himself in knots trying to see where he was wrong and where pauling was right. eventually, the student pointed out to pauling that something about his theory didn’t seem quite right.

4
the graduate student explained his thinking, and pauling, being pauling, politely ignored him. it’s not clear why pauling bothered to have someone

part a
which sentence states a central idea of the passage?

1. linus pauling became a highly regarded scientist even though he failed to discover the double helix.

1. most of what is known about the shape of dna today is due to the work of the scientist linus pauling.

1. the double helix allows pairs of nucleic acids to fit tightly together in a sort of twisted ladder structure.

1. discovering the structure of dna involved several blunders and a heated competition among scientists.

part b
which two sentences from the passage best help develop the central idea in the correct answer from part a?

1. \as pauling showed with hemoglobin, shape can affect how molecules work.\ (paragraph 1)

1. \pauling probably would have solved dna...\

Explanation:

Part A

• Option 1: Focuses on Pauling's reputation, not the central idea about DNA structure discovery.
• Option 2: The passage shows Pauling made mistakes, so most DNA shape knowledge isn't due to him. Eliminate.
• Option 3: Describes DNA structure, not the process of discovery (with blunders and competition). Eliminate.
• Option 4: The passage details Pauling's blunder (wrong structure, ignored student) and implies competition (he thought he was the only one), so this states the central idea of discovery involving blunders and competition.

To support the central idea that DNA structure discovery had blunders and competition, we need sentences showing blunders (e.g., Pauling's wrong theory, ignored student feedback) and competition (e.g., his belief he was the only one).

• Sentence 2 (if it's about Pauling's potential and implies competition/blunder) and another sentence (e.g., about his wrong DNA structure or ignored student) would support. For example, if there's a sentence like "Pauling also reasoned that DNA was a triple helix... (blunder)" and "Pauling, like many others, assumed he was the only one... (competition)", these would be the two.

Answer:

1. Discovering the structure of DNA involved several blunders and a heated competition among scientists.

Part B (assuming Part A's correct answer is 4, we analyze the options to find two that support "discovery with blunders and competition"):

(Note: Since the passage is partially shown, we analyze based on visible info and typical central idea support. Let's assume the following for visible options: )

• Option 1: Talks about shape affecting molecules, not blunders/competition. Not supportive.
• Option 2: (If it's about Pauling's potential and maybe competition/blunder context) and another option (not fully shown, but let's assume a second relevant one). But with given visible options, if we consider the passage's focus on Pauling's blunder (wrong theory, ignored student) and competition (his assumption he was the only one), sentences showing his blunder (like his wrong DNA structure reasoning, student finding error) and competition - related (his assumption) would support. But with the given checkboxes, if we assume:

Let's say Option 2 (about Pauling's potential to solve if not for... ) and another (e.g., a sentence about his wrong structure or ignoring student) support. But with the visible part, if we take the two that relate to blunders (his wrong theory, ignoring student) or competition (his self - assurance). However, since the full passage isn't here, but based on Part A's answer, the two sentences should relate to blunders in discovery and competition among scientists.
(Note: Since the user's passage for Part B is cut off, but following the format, we'll assume the two correct options based on the central idea. For example, if there's a sentence about Pauling's wrong DNA structure (blunder) and a sentence about multiple scientists trying (competition), those would be the two. But with the given visible checkboxes, if we assume Option 2 and another (say a sentence about his wrong calculation or ignored student) are correct. But as the passage is partial, we'll proceed with the analysis based on the central idea.)