Question

part iii. true or false?
indicate if each of the statements below is true or false by writing the word on the line provided. if it is false,
make a correction to the underlined word.

1. ________ cytosine, guanine, thymine and adenine are referred to as phosphates.
2. ________ dna is in the shape of a double helix.
3. ________ a nucleotide is made up of a sugar, phosphate and two nitrogen bases.
4. ________ replication is performed prior to cell division.
5. ________ adenine always pairs with guanine.
6. ________ complementary base pairing matches up complementary sugars.
7. ________ the sides of the dna molecule are made up of repeating nitrogen bases and sugars.
8. ________ replication results in two strands of dna, each of which has half of the original strand.

part iv. short response
answer the following:

1. the proportions of the bases are consistent within a species, however they do vary between

species. using the base - pairing rules, complete the following table to show the percentage of each
type of base in the five different organisms.

Explanation:

1. Statement 1: Cytosine, guanine, thymine, and adenine are nitrogen - containing bases, not phosphates.
2. Statement 2: DNA has a double - helix structure, which is a well - established fact in molecular biology.
3. Statement 3: A nucleotide is composed of a sugar, a phosphate, and one nitrogen base, not two.
4. Statement 4: DNA replication occurs before cell division to ensure that each daughter cell gets a complete set of genetic information.
5. Statement 5: Adenine always pairs with thymine, not guanine (guanine pairs with cytosine).
6. Statement 6: Complementary base pairing matches up complementary nitrogen bases (e.g., A - T, G - C), not sugars.
7. Statement 7: The sides of the DNA molecule are made up of repeating phosphate and sugar units (the sugar - phosphate backbone), not nitrogen bases and sugars.
8. Statement 8: DNA replication is semi - conservative, resulting in two DNA molecules, each with half of the original strand (one old and one new strand).

For the table in Part IV:

• Human: Since adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). If A = 31%, then T=31%, and since C = 19%, G = 19%.
• Chicken: A = 28%, so T = 28%; G = 22%, so C = 22%.
• Frog: T = 29%, so A = 29%; and since A + T+G + C=100%, G + C=100-(29 + 29)=42%, and since G = C, G = C = 21%.
• Wheat: A = 27%, so T = 27%; and since A + T+G + C=100%, G + C=100-(27 + 27)=46%, and since G = C, G = C = 23%.
• Bacteria: G = 17%, so C = 17%; and since A + T+G + C=100%, A + T=100-(17 + 17)=66%, and since A = T, A = T = 33%.

Answer:

1. False, change “phosphates” to “nitrogen - containing bases”.
2. True.
3. False, change “two” to “one”.
4. True.
5. False, change “guanine” to “thymine”.
6. False, change “sugars” to “nitrogen bases”.
7. False, change “nitrogen bases” to “phosphates”.
8. True.

Table (Part IV):

Organism	Adenine	Guanine	Cytosine	Thymine
Chicken	28	22	22	28
Frog	29	21	21	29
Wheat	27	23	23	27
Bacteria	33	17	17	33