Biology: DNA Base Pairing Rules (Apple Tree, Car Garage) Practice
Practice matching A with T and C with G in DNA sequences
Biology: DNA Base Pairing Rules (Apple Tree, Car Garage) Practice
Practice matching A with T and C with G in DNA sequences
Biology - Grade 9-12
- 1
Use the Apple Tree and Car Garage mnemonics to explain the two DNA base pairing rules.
Apple Tree starts with A and T. Car Garage starts with C and G.
The Apple Tree mnemonic means adenine pairs with thymine, or A with T. The Car Garage mnemonic means cytosine pairs with guanine, or C with G. - 2
Write the complementary DNA strand for this sequence: ATCG
The complementary DNA strand is TAGC because A pairs with T, T pairs with A, C pairs with G, and G pairs with C. - 3
Write the complementary DNA strand for this sequence: GCTA
Match each base one at a time from left to right.
The complementary DNA strand is CGAT because G pairs with C, C pairs with G, T pairs with A, and A pairs with T. - 4
A section of DNA has the sequence AAGTCC. Write the complementary DNA strand.
The complementary DNA strand is TTCAGG because A pairs with T, G pairs with C, T pairs with A, and C pairs with G. - 5
A student writes that the complement of TACG is ATGC. Check the student's answer and explain whether it is correct.
Compare each base in the original strand with the base directly across from it.
The student's answer is correct. T pairs with A, A pairs with T, C pairs with G, and G pairs with C, so TACG pairs with ATGC. - 6
A student writes that the complement of CCGT is GGTA. Identify the mistake and write the correct complementary strand.
The answer is incorrect because G should pair with C and T should pair with A. The correct complementary strand for CCGT is GGCA. - 7
Complete the missing bases in this DNA pair: Original strand: A T C G A. Complementary strand: _ _ _ _ _.
Use Apple Tree for A-T and Car Garage for C-G.
The completed complementary strand is T A G C T because A pairs with T, T pairs with A, C pairs with G, G pairs with C, and A pairs with T. - 8
Complete the missing bases in this DNA pair: Original strand: G C T A C G. Complementary strand: _ _ _ _ _ _.
The completed complementary strand is C G A T G C because G pairs with C, C pairs with G, T pairs with A, A pairs with T, C pairs with G, and G pairs with C. - 9
A double-stranded DNA segment contains 18 adenine bases. How many thymine bases should it contain? Explain your answer.
In DNA, the number of A bases equals the number of T bases.
It should contain 18 thymine bases because adenine always pairs with thymine in double-stranded DNA. - 10
A double-stranded DNA segment contains 24 cytosine bases. How many guanine bases should it contain? Explain your answer.
It should contain 24 guanine bases because cytosine always pairs with guanine in double-stranded DNA. - 11
In a DNA sample, 30 percent of the bases are adenine. What percent of the bases are thymine? What percent are cytosine and guanine combined?
First match the percent of thymine to the percent of adenine, then subtract from 100 percent.
Thymine is also 30 percent because A pairs with T. The remaining 40 percent of the bases are cytosine and guanine combined because 100 percent minus 60 percent equals 40 percent. - 12
Look at this partially paired DNA segment: Top strand: A C G T T A. Bottom strand: T G C A A T. Explain why this is a correctly paired DNA segment.
This is a correctly paired DNA segment because each base follows the DNA base pairing rules. A pairs with T, C pairs with G, G pairs with C, T pairs with A, T pairs with A, and A pairs with T.