The structure of DNA
Grade 9 Science Worksheet
Circle the best answer.
Bottom strand directly beneath it: six bases, ends not labeled. Luz writes the bottom strand under 3′-TACGGA-5′. Which choice gives the bottom strand, read from its own 5′ end?
- 5′-ATGCCT-3′
- 5′-TCCGTA-3′
- 5′-CGTAAG-3′
- 5′-TACGGA-3′
Read this first
Use this
Ladder (model, not to scale).
Milo writes the bottom strand under 5′-GATCCG-3′, left to right as it sits beneath. Which choice is correct, with its end labels?
- 3′-GATCCG-5′
- 3′-CTAGGC-5′
- 3′-AGCTTA-5′
- 5′-CTAGGC-3′
Pia completes the bottom strand under 3′-ATGGCA-5′. Which letters fill the blanks, left to right?
- C, A, G
- A, G, T
- T, C, A
- A, C, T
Ladder (model, not to scale). Bottom strand directly beneath: five bases, to find. Zee counts the hydrogen bonds in a short stretch whose top strand is 3′-GATTC-5′. How many hydrogen bonds join the five base pairs?
- 13
- 12
- 15
- 10
(model, not to scale). Ari studies one nucleotide of the top strand. Arrow Y points to the part that faces the other strand. What is Y?
- The hydrogen bond, which is a part of each single nucleotide
- The sugar, which links to the other strand
- The base, which pairs with a base on the other strand
- The phosphate, which links to the other strand
Use this
Model data card, percent of the bases in a two-stranded sample. A: 28. T: ?. G: ?. C: ?. Total: 100.
Bo reads a model sample of two-stranded DNA. Adenine is 28% of the bases. What percent of the bases is guanine?
- 28%
- 22%
- 44%
- 36%
Model data card, number of bases in a two-stranded sample. A: 240. T: ?. G: ?. C: ?. Total: 1,000. Jun counts the bases in a model sample of two-stranded DNA with 1,000 bases. Adenine is 240 of them. How many bases are cytosine?
- 260
- 240
- 380
- 520
Sketch by a classmate (model, not to scale). Noah sketches DNA with the bases on the two outer lines and the sugar-phosphate chains as the crosspieces. What should change?
- Swap them: the chains form the outer lines and the bases meet in the middle
- Pair each A with G and each C with T, to keep the width even
- Add a third strand in the middle to hold the sketch together
- Nothing: the bases must be on the outside to reach each other
Use this
Who-did-what card (real facts from OpenStax Biology 2e and NIH NLM). Columns: person, place, work. Rosalind Franklin with Raymond Gosling, King's College London, X-ray photo of the B form of DNA in 1952, labeled 51. James Watson and Francis Crick, University of Cambridge, built the double-helix model in 1953 using Franklin's X-ray data.
Esme says Watson and Crick took the X-ray photo labeled 51. Using the card, which reply is best?
- Not correct: the photo was made in 1962, after the prize
- Correct: Watson and Crick took it at Cambridge in 1952
- Not correct: Franklin and Gosling made the photo, and the model used it
- Not correct: Franklin joined the work after the 1953 model
Use this
History card (real dates). 1952: Rosalind Franklin with Raymond Gosling, at King's College London, make an X-ray photo of the B form of DNA, labeled 51. 1953: James Watson and Francis Crick, at the University of Cambridge, publish a double-helix model built with Franklin's X-ray data on 25 April; Franklin and Gosling publish a paper in the same issue of Nature. 1962: Francis Crick, James Watson and Maurice Wilkins receive the Nobel Prize in Physiology or Medicine; Franklin is no longer living, and the prize is not awarded after death.
Kira says Franklin missed the 1962 prize because her data were not used. Using the card, which reply is best?
- Correct: Watson and Crick did the X-ray work themselves
- Not correct: her data were used, and the prize is not awarded after death
- Correct: the prize was given before her 1952 photo
- Correct: her X-ray work was not needed for the model