Bio Lecture 15 - DNA Replication

anti-parallel

Describes the opposite orientation of two strands of DNA or RNA, where one strand runs 5' to 3' and the other runs 3' to 5'. This arrangement is crucial for the formation of the double helix structure.

double stranded

Refers to the structural form of nucleic acids like DNA, where two complementary strands are held together by base pairing and twist into a helical shape.

single stranded

Refers to nucleic acid molecules consisting of only one strand, such as certain viruses or RNA, which do not have a complementary strand.

5’ end of DNA or RNA

The end of a DNA or RNA strand that has a free phosphate group attached to the fifth carbon of the sugar molecule, typically involved in the synthesis direction during transcription and replication.

3’ end of DNA or RNA

The end of a DNA or RNA strand that has a free hydroxyl group attached to the third carbon of the sugar molecule, important for nucleic acid synthesis.

complementary

Refers to the relationship between nucleotides in DNA or RNA where specific bases pair with each other, such as adenine with thymine (or uracil in RNA) and guanine with cytosine.

base pairing

The specific hydrogen bonding between nucleotide bases on opposite strands of DNA or RNA, where adenine pairs with thymine (or uracil in RNA) and cytosine pairs with guanine.

Template strand

The strand of DNA that serves as a guide for the synthesis of a complementary strand during DNA replication or transcription.

daughter strand

The newly synthesized strand of DNA that is complementary to the template strand during DNA replication.

polarity

In DNA and RNA, polarity refers to the distinct directional orientation of the nucleic acid strands, where one end has a free phosphate group (5' end) and the other end has a free hydroxyl group (3' end). This polarity is crucial for the synthesis and function of nucleic acids.

origin of replication

The specific location on the DNA strand where replication begins, allowing the separation of the two strands and the initiation of DNA synthesis.

leading strand

The DNA strand that is synthesized continuously in the same direction as the replication fork, allowing for smooth addition of nucleotides during DNA replication.

lagging strand

The DNA strand that is synthesized discontinuously in short segments (Okazaki fragments) opposite to the direction of the replication fork, requiring eventual joining of these segments.

primer

A short RNA sequence that provides a starting point for DNA synthesis during replication.

DNA polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides to a pre-existing chain during DNA replication.

primase

An enzyme that synthesizes RNA primers needed for DNA replication, facilitating the initiation of new DNA strand synthesis.

ligase

An enzyme that facilitates the joining of DNA strands together by catalyzing the formation of phosphodiester bonds, crucial for DNA replication and repair. JOINS OKAZAKI FRAGMENTS

helicase

An enzyme responsible for unwinding the DNA double helix ahead of the replication fork, allowing the two strands to be copied during DNA replication.

single strand binding protein (similar to topoisomerase)

Proteins that bind to single-stranded DNA during replication to prevent re-annealing and protect it from degradation.

telomere

The repetitive nucleotide sequences at the ends of chromosomes, which protect them from deterioration and prevent fusion with neighboring chromosomes. Telomeres play a key role in cellular aging and replication.

telomerase

An enzyme that adds repetitive nucleotide sequences to the ends of telomeres, helping to maintain their length and protect chromosomes from deterioration during cell division.

purine

A type of nitrogenous base found in DNA and RNA, consisting of adenine and guanine, which has a two-ring structure.

pyrimidine

A type of nucleotide base that includes cytosine, thymine, and uracil, characterized by a single-ring structure.