IBDP Bio (2025) - D1.1 DNA Replication

Complementary base pairing

is the standard arrangement of bases in nucleotides in relation to their opposite pairing, such as cytosine paired with guanine and adenine with thymine (or uracil in RNA).

DNA polymerase

an enzyme that catalyses the elongation of new DNA during replication.

Genetic code

the order of bases in DNA that determines the sequence of amino acids in proteins.

Helicase

an enzyme involved in DNA replication, responsible for unwinding the double helix.

Hydrogen bonds

a chemical bond in which a hydrogen atom of one molecule is attracted to an electronegative atom of another molecule.

Nucleotides

the building blocks of nucleic acids consisting of a five-carbon sugar, a nitrogenous base, and a phosphate group.

Polymerase chain reaction (PCR)

a technique for amplifying DNA in vitro.

Polypeptides

a polymer of amino acids joined together by peptide bonds.

Replication of DNA

making a copy of a DNA molecule.

Semi-conservative replication is

the process of DNA synthesis each original strands of the molecule acts as a template on which a new complementary strand is created.

Taq DNA polymerase

a heat resistant enzyme found in the bacillus Thermus aquaticus, which lives in hot springs, that can endure the high temperatures of the polymerase chain reaction.

Adenine

The base that pairs with Thymine in DNA

Thymine

The base that pairs with Adenine in DNA

Cytosine

The base that pairs with Guanine with DNA

Guanine

The base that pairs with Cytosine in DNA

Double Helix

two strands of nucleotides wound about each other; structure of DNA

dispersive replication

a disproved model of DNA synthesis suggesting more or less random interspersion of parental and new segments in daughter DNA molecules

conservative replication

A disproved model of DNA synthesis suggesting that one-half of the daughter DNA molecules should have both strands composed of newly polymerized nucleotides.

Supercoiled DNA

DNA is further twisted to save space

Histones

protein molecules around which DNA is tightly coiled in chromatin

Nucleosome

repeating subunit of chromatin fibers, consisting of DNA coiled around histones

Naked DNA

DNA not associated with histones or histone-like proteins.

Denaturation Phase (PCR)

when the temperature is increased to cause the separation of the 2 strands of DNA.

Annealing Phase (PCR)

when the temperature is lowered to allow primers to base pair to the complementary DNA

Amplification/Extension Phase (PCR)

when heat resistant Taq polymerase replicates the DNA strand

primers in PCR

needed to start new strand synthesis, determines where amplification starts

Free nucleoside triphosphates

made of a N-base and sugar and 3 phosphates; removal of 2 of the phosphates allows it to be bound to the current strand to continue its length during replication.

gel electrophoresis

Procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel

restriction endonucleases

an enzyme that cuts DNA at specific sites, producing small fragments used in genetic engineering.

buffer solution

a solution made from a weak acid and its conjugate base that neutralizes small amounts of acids or bases added to it

DNA ladder

set of known DNA fragments with different sizes in base pairs or kilo bases. these DNA fragments are separated and visualized as DNA bands on a gel. used to determine the size and quantity of DNA fragments

ethidium bromide

a DNA stain (indicator); glows orange when it is mixed with DNA and exposed to UV light; abbreviated EtBr

Genome

the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes

tandem repeats

short, adjacent segments of DNA within a gene that are repeated several times

Taq polymerase

A DNA synthesis enzyme that can withstand the high temperatures of PCR

DNA profiling

A procedure that analyzes DNA fragments to determine whether they come from a specific individual.