DNA Replication Lecture Notes

A set of vocabulary flashcards covering essential terms and definitions related to DNA replication, transcription, and translation.

DNA Replication

The process in a nucleus of a parental cell by which a cell duplicates its DNA molecules to ensure that each daughter cell receives an identical copy of the genetic material & occurs in the s stage of interphase before cell division. It involves unwinding the double helix and synthesizing new strands complementary to each original strand.

Chromosome

A DNA molecule that is tightly coiled and condensed, associated with proteins, present in the nucleus of eukaryotic cells.

46 DNA molecules

The total number of DNA molecules found in a human somatic cell, representing 23 pairs inherited from each parent.

DNA Polymerase III

The enzyme responsible for synthesizing new DNA strands by adding nucleotides to a DNA template during replication. C-G AND T-G OR A-T

Semi-Conservative Replication

A method of DNA replication in which each new double-stranded DNA molecule consists of one original strand and one newly synthesized strand.

Leading Strand

The continuously synthesized DNA strand that is produced in the same direction as the replication fork.

Lagging Strand

The discontinuously synthesized DNA strand that is produced in fragments opposite the direction of the replication fork.

Okazaki Fragments

Short strands of DNA produced on the lagging strand during replication, which are later joined together.

Helicase

An enzyme that unwinds the double-stranded DNA during replication, creating single-stranded regions for synthesis.

Single-Strand Binding Proteins

Proteins that stabilize unwound single-stranded DNA during replication, preventing it from re-forming double strands.

DNA Ligase

An enzyme that joins Okazaki fragments on the lagging strand by forming covalent bonds between adjacent DNA nucleotides.

Telomerase

An enzyme that adds nucleotide sequences to the ends of chromosomes (telomeres), preventing the shortening of DNA during replication.

Apoptosis

The process of programmed cell death that can be triggered by DNA damage or the presence of single-stranded regions.

RNA Primer

A short strand of RNA that provides a starting point for DNA synthesis, necessary for the activity of DNA polymerase. Consists of 5-10 nucleotides which will base pair with the template strand to initiate replication.

Transcription

The process of synthesizing RNA from a DNA template, in which only one of the DNA strands is used for coding.

Translation

The process by which ribosomes synthesize proteins based on the sequence of the messenger RNA.

Ribosomes

Cellular structures made of RNA and protein that facilitate the translation of messenger RNA into proteins.

Endoplasmic Reticulum

An organelle involved in the synthesis of proteins (rough ER) and lipids (smooth ER), playing a key role in the cell's functions.

Nucleic Acids

Biomolecules, including DNA and RNA, that are the genetic material of cells and are involved in the transmission of genetic information.

Primase

An enzyme that synthesizes the RNA primer needed to initiate DNA replication by DNA polymerase III.

Topoisomerase

An enzyme that breaks and rejoins the DNA strands to relieve the tension and supercoiling ahead of the replication fork.

Antiparallel Structure

The orientation of the two DNA strands running in opposite directions, one in the 5' to 3' direction and the other in the 3' to 5' direction.

Messenger RNA (mRNA)

A type of RNA that carries genetic information from the DNA in the nucleus to the ribosome for protein synthesis.

Transfer RNA (tRNA)

Small RNA molecules that carry specific amino acids to the ribosome and match them to mRNA codons during translation.

Codon

A triplet of nucleotides on an mRNA molecule that specifies a particular amino acid or a termination signal.

Anticodon

A triplet of nucleotides on a tRNA molecule that is complementary to a specific codon on messenger RNA.

Gene

A segment of DNA that contains the specific sequence of nucleotides required to produce a functional protein or RNA molecule.

Direction of DNA Synthesis

New DNA strands are always synthesized in the 5'\rightarrow 3' direction because DNA polymerase can only add new nucleotides to the free 3' hydroxyl (OH) group of the growing strand.

Replication Fork

The active, Y-shaped region where the double-stranded parental DNA is being actively unwound and separated by helicase into two single strands for replication.

Origin of Replication

A specific sequence of DNA within the genome where replication enzymes first bind and begin the process of unzipping the double helix to initiate copying.

Exonuclease Activity

A proofreading capability of several DNA polymerases that allows them to remove improperly paired nucleotides from the 3' end of a growing DNA strand and replace them with the correct ones.

Start Codon

The specific triplet sequence (AUG) on mRNA that signals the ribosome to begin translation and identifies the first amino acid incorporated into the protein (methionine).

Stop Codon

One of three nucleotide triplets (UAA, UAG, or UGA) that indicates the end of a protein-coding sequence and signals the ribosome to release the finished polypeptide chain.