DNA & Protein Synthesis

DNA is the code to make

Proteins.

DNA is a double helix. What does that mean

Two strands wrapped around each other.

The monomers (repeating units) of DNA are called

Nucleotides.

A DNA monomer is composed of

A phosphate, sugar, and base.

What are the letters of the 4 different DNA bases

A, T, C, G.

Which bases are complementary to each other

Adenine & Thymine, Cytosine & Guanine.

What type of bond holds together the bases

Hydrogen bonds.

What is a hydrogen bond

There is a slight attraction between H on one base and O or N on a different base.

DNA strands are antiparallel. What does this mean

The two strands of DNA go in opposite directions. One strand is upside down compared to the other.

What are the notations for the different directions

5’ → 3’ (5 prime to 3 prime), 3’ → 5’ (3 prime to 5 prime).

What is the role of each enzyme/protein in DNA replication:

Helicase

Unzips the DNA double helix by breaking hydrogen bonds between base pairs, creating two single strands.

Single-strand binding proteins (SSBs)

Bind to and stabilize the separated DNA strands to prevent them from rejoining.

Primase

Synthesizes a short RNA primer to provide a starting point for DNA polymerase.

DNA polymerase III

Adds nucleotides to the 3’ end of the RNA primer and elongates the new DNA strand.

DNA polymerase I

Removes RNA primers and replaces them with DNA nucleotides.

Ligase

Joins Okazaki fragments on the lagging strand.

Replication fork

The Y-shaped region where the DNA is unwound and replication takes place.

DNA replication is semi-conservative. What does this mean

Each new double helix is composed of one new strand and one original.

Describe leading and lagging strand replication:

What direction is DNA built

5’ to 3’ direction.

What is a promoter

A specific DNA sequence where RNA polymerase binds to initiate transcription (the process of making RNA from DNA).

Which strand is made away from a fork

Lagging strand.

Which strand is made toward the fork

Leading strand.

Which strand is composed of Okazaki fragments

Lagging strand.