Question

name ____ date __ period ____
1 dna is made up of nucleotides. which 3 things are nucleotides composed of?
a. ______
b. ______
c. ______
2 what do scientists mean when they say the genetic code is universal?
a. all living things have the same sequence of nitrogenous bases.
b. amino acids are used to make dna in all living things
c. all living things have the same 4 letter nitrogenous bases in dna
d. nucleic acids contain all different nitrogenous bases in all living things
3 there are 3 enzymes used in the process of dna replication. match them to their
definition below

1. polymerase ______ a. the unzipper: separates the 2

strands of dna so replication can
begin

1. ligase ______ b. the builder: adds bases to the

complementary dna strand

1. helicase ______ c. the gluer: seals gaps in the new

dna strand to complete replication
4 using the same enzymes in the previous question, what is the order that each enzyme is
used in dna replication?
a. ______
b. ______
c. ______
5 dna polymerase is the enzyme responsible for adding bases to the complementary
dna strand. (using the original dna strand below, build a new strand using the
complementary base pairing rules for dna replication)
a. original dna strand: tca gat ggc atg
b. complementary strand ______

Explanation:

Question 1

Nucleotides, the building blocks of DNA, consist of three parts: a phosphate group, a deoxyribose sugar (a 5 - carbon sugar), and a nitrogenous base (adenine, thymine, cytosine, or guanine).

• Option a: Different living things have different sequences of nitrogenous bases, so this is incorrect.
• Option b: Amino acids are used to make proteins, not DNA. So this is wrong.
• Option c: The genetic code being universal means that all living things use the same 4 nitrogenous bases (A, T, C, G) in their DNA, and the same codon - amino acid relationships (with some minor exceptions). This option is correct.
• Option d: Nucleic acids (DNA and RNA) have a specific set of nitrogenous bases, and not all different ones in all living things. So this is incorrect.

• DNA Polymerase: Its main function is to add complementary bases to the growing DNA strand during replication, so it is the "builder" (matches with B).
• Ligase: It seals the gaps (like nicks) in the newly synthesized DNA strand, so it is the "gluer" (matches with C).
• Helicase: It unwinds the double - helix structure of DNA, separating the two strands, so it is the "unzipper" (matches with A).

Answer:

a. Phosphate group
b. Deoxyribose sugar
c. Nitrogenous base

Question 2