Intro to Nucleic Acids

Write the complementary sequence for the following DNA sequence, in order from 3' to 5': 5′−CGATATTGAGCTAAGCTT−3′

3′-GCTATAACTCGATTCGAA −5

List three structural characteristics of DNA.

-Structural features of DNA include that it is shaped like a double helix. -It contains a sugar-phosphate backbone, the nitrogen-containing bases are hydrogen bonded between strands, and the strands run in opposite directions. -G forms three hydrogen bonds to C, and A forms two hydrogen bonds to T.

Replication fork

Point in DNA where nucleotides add to daughter DNA strand

Complete the following vocabulary exercise related to DNA replication.

1. Okazaki fragmentsare the short sections of DNA that are synthesized on the lagging strand of the replicating DNA. 2. The enzyme that can replicate DNA is called DNA polymerase. 3. The new DNA strand that grows continuously in the 5' to 3' direction is called the leading strand. 4. After replication is complete, the new DNAs, called daughter DNA, are identical to each other. 5. During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a replication fork.

Why are there no base pairs in DNA between adenine and guanine or between thymine and cytosine?

Adenine and thymine can form two hydrogen bond(s), whereas guanine and cytosine form three hydrogen bond(s). Because each base pair contains a pyrimidine and a purine, the distance between the two DNA strands is equal. Other combinations of base pairs would not maintain a(n) equal distance along the DNA polymer.

Complete the sentences to explain the function of the enzyme DNA polymerase in DNA replication.

DNA polymerase catalyzes the formation of phosphodiester linkages between the nucleotides. DNA polymerase forms bonds between the 5' phosphate of one nucleotide and the 3' hydroxyl of the next.

Lagging strand

Daughter DNA synthesized from short sections called Okazaki fragments

What is meant by double helix?

Double helix refers to the helical shape of the double chain of DNA that consists of two polynucleotide strands winding about each other like a spiral staircase with a sugar-phosphate backbone on the outside and base pairs on the inside.

Order the steps of DNA replication, starting with the first step and ending with the production of a DNA copy.

First Step: -partial unwinding of double-stranded DNA to expose the nucleotides on the template strand -DNA polymerase adds nucleotides to the leading strand, which is synthesized in the 5'-->3' direction as a continuous strand -DNA polymerase add nucleotides to the lagging strand, which is synthesized in the 3'-->5' direction as Okazaki fragments Last Step: -Okazaki fragments are joined to form a continuous strand

What is meant by complementary base pairing?

In complementary base pairing, three hydrogen bond(s) form between each G and C while there is (are) two hydrogen bond(s) between each A and T.

Complete the sentences to explain how the bases cytosine and uracil differ.

In cytosine, the functional group attached to carbon 4 in the ring is an NH2 group, whereas uracil has a carbonyl functional group on carbon 4. Within the ring of cytosine, there is a double bond between carbon 4 and the adjacent nitrogen. However, within the ring of uracil, there is a single bond between carbon 4 and the adjacent nitrogen.

What is the difference in the 3' end and the 5' end of a polynucleotide chain?

One end of a nucleic acid polymer consists of a sugar with a free 5' phosphate group, and the other end consists of a sugar with a free 3' hydroxyl group.

Primase

Synthesizes primers at the replication fork

Rank the following base pairs according to their stability.

The base pair adenine-cytosine occurs very rarely in nature. It only happens during a mutation event. When the DNA is replicated, one of the two daughters will contain a guanine-cytosine base pair in the location of the mutation, and the other daughter will contain an adenine-thymine base pair.

What component in a nucleic acid determines the 3' free end?

The free 3' end is determined by the free hydroxyl group on the 3' carbon of the sugar of a nucleic acid

What component in a nucleic acid determines the free 5' end?

The free 5' end is determined by the free phosphate group on the 5' carbon of ribose or deoxyribose of a nucleic acid

What component in the backbone of a nucleic acid is bonded to a nitrogen base?

The nitrogen base is bonded to a 1' carbon atom of the ribose or deoxyribose sugar in the backbone of the nucleic acid.

What nucleic acid subunits are connected in a 3',5' phosphodiester linkage in a polynucleotide?

The nucleotides in nucleic acid polymers are held together by phosphodiester linkages between the 3' hydroxyl group of a sugar (ribose or deoxyribose) and the phosphate group on the carbon 5' carbon of another sugar.

Helicase

Unwinds the DNA helix