DNA Replication

Semiconservative replication

Each half of an original DNA molecule serves as a templete for a new strand, and the two new DNA molecules each have one old and one new strand.

Primer

Sequence of RNA nucleotides bound to a region of single-stranded DNA to initiate DNA replication.

double helix

The form of DNA, referring to its two strands wound into a spiral shape.

DNA Polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule

direction of continuous replication

5' to 3' direction; In DNA synthesis, DNA strands always elongate in a 5' to 3' direction.

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

point of origin

Specific sequence of DNA where DNA synthesis begins.

DNA ligase

enzyme which connects the individual okazaki fragments on the lagging strand by forming covalent bonds

5' or 3'

the number stands for where on the deoxyribose sugar is attached to a phosphate

DNA Replication

the process of making identical copies of DNA before cell division

leading strand

the strand of DNA that is continuously synthesized. 5' to 3' direction

replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

deoxyribonucleic acid

A molecule that consists of nucleotide monomers used for transmitting genetic information from one generation to the next

adenine

A nitrogen base found in DNA and RNA. It pairs with thymine in DNA and with uracil in RNA

guanine

A nitrogen base found in both DNA and RNA; pairs only with cytosine.

cytosine

A nitrogenous base found in DNA and RNA; pairs with guanine

thymine

A nucleotide that pairs with adenine. Found only in DNA.

nucleotide

A subunit of nucleic acids formed from a simple sugar, a phosphate group, and a nitrogenous base.

hydrogen bond

A weak chemical bond used to hold complementary base pairs together

Primase

An enzyme that creates a short RNA primer for initiation of DNA replication.

DNA helicase

An enzyme that unwinds the double helix of DNA and separates the DNA strands in preparation for DNA replication.

base pairs

Any of the pairs formed between complementary bases in the two nucleotide chains of DNA, such as A-T and C-G (DNA); A-U and C-G (RNA)

nucleic acid

Macromolecules that includes DNA and RNA.

lagging strand

The strand that is synthesized away from the replication fork , in fragments using sections called Okazaki fragments. 3' to 5' direction

Point of origin is identified by certain sequences. Heliase comes in and unwinds the double strand DNA. This step is also called initiation.

What is happening in step 1?

This is where Primase comes in and makes the primer needed for DNA polymerase to start . This is where elongation of the DNA molecule begins.

What is happening in step 2

DNA Polymerase gets to work. The enzyme adds DNA nucleotide (bases) to the open strand. DNA polymerase can only work on the 5' to 3' strand called the leading strand. The building is continuous. The two strands that complement each other but they are opposite base pairs (A-T) and (C-G).

What is happening in step 3

The lagging strand is being built. This is the 3' to 5" strand where little fragments of DNA is build..these fragements are called Okazaki fragments. Once the strand is ready, DNA Ligase comes in and "glues" the fragments together to complete the DNA. TERMINATION is happening here. The DNA is 1/2 old and 1/2 new which is now called a Semi-Conservative strand of DNA

What is happening in step 4?