4U Molecular Genetics Unit Test Review

Flashcards covering key terms and scientist contributions from the 4U Molecular Genetics Unit Test Review notes.

Nucleotide

The basic building block of nucleic acids, consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Chargaff’s rule

The observation that in DNA, the amount of adenine equals thymine ($A = T$) and the amount of cytosine equals guanine ($C = G$).

Complementary base-pairing

The specific hydrogen bonding between nitrogenous bases: Adenine pairs with Thymine (or Uracil in RNA) and Cytosine pairs with Guanine.

Antiparallel

The arrangement of the two strands in a DNA double helix, where one strand runs in the $5' \rightarrow 3'$ direction and the other in the $3' \rightarrow 5'$ direction.

Genome

The complete set of genetic material or DNA sequence present in an organism.

Gene

A specific sequence of DNA that contains the instructions to produce a functional product, such as a protein or RNA molecule.

Nucleoid

The irregularly shaped region within a prokaryotic cell that contains all or most of the genetic material.

DNA supercoiling

The over- or under-winding of a DNA strand, which allows the long DNA molecule to be compacted within a cell.

Regulatory sequence

A segment of DNA where regulatory proteins such as transcription factors bind to control the rate of gene expression.

Histone

A highly alkaline protein around which DNA wraps to form nucleosomes, aiding in DNA packaging in eukaryotic cells.

Nucleosome

The fundamental subunit of chromatin, consisting of a segment of DNA wrapped around a core of eight histone proteins.

Chromatin

A complex of DNA and protein found in eukaryotic cells that packages DNA into a smaller volume to fit in the nucleus.

Chromosome

A thread-like structure of nucleic acids and protein found in the nucleus, carrying genetic information in the form of genes.

DNA replication

The process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.

Semi-conservative replication

The mechanism of DNA replication in which each of the two new DNA molecules contains one original parent strand and one newly synthesized strand.

Replication origin

A particular sequence in a genome at which DNA replication is initiated.

Helicase

An enzyme that breaks the hydrogen bonds between the two strands of the DNA double helix, 'unzipping' the molecule for replication.

DNA polymerase III

The primary enzyme in prokaryotes that adds nucleotides to the $3'$ end of a growing DNA strand during replication how okazaki fragments are created

DNA polymerase II

An enzyme involved in DNA repair and the restart of replication after DNA damage.

DNA polymerase I

An enzyme that removes RNA primers and replaces them with DNA nucleotides during replication.

RNA primer

A short segment of RNA that serves as a starting point for DNA synthesis by providing a free $3'$ hydroxyl group.

Primase

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

Okazaki fragments

Short, discontinuous segments of DNA synthesized on the lagging strand during DNA replication.

DNA ligase

An enzyme that joins the phosphate-sugar backbones of DNA fragments, such as Okazaki fragments, creating a continuous strand.

Mismatch repair

A cellular mechanism that identifies and corrects errors in DNA replication where incorrect bases have been paired.

Telomeres

The repetitive nucleotide sequences at the ends of eukaryotic chromosomes that protect the ends of the DNA from deterioration.

Messenger RNA (mRNA)

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

Genetic code

The set of rules by which information encoded in genetic material is translated into proteins by living cells.

One gene/one polypeptide hypothesis

The theory that each gene is responsible for the production of a single specific polypeptide.

Triplet hypothesis (codon)

The proposal that a sequence of three nucleotides (a codon) specifies a single amino acid.

Central dogma

The framework for understanding the flow of genetic information: DNA is transcribed into RNA, which is then translated into protein.

Gene expression

it is like switch. When a gene is turned on it creates a protein so gene is expressed by us.

Transcription

The process of synthesizing a complementary RNA strand from a DNA template.

Translation

The process by which ribosomes in the cytoplasm or ER create proteins using the mRNA sequence as a guide.

RNA polymerase

The enzyme responsible for copying a DNA sequence into an RNA sequence during transcription. can only copy a few sequences at once also how fragments occur

Promoter region

A specific DNA sequence where RNA polymerase binds to initiate transcription.

Precursor mRNA (pre-mRNA)

The initial RNA transcript synthesized from DNA before it undergoes processing to become mature mRNA.

Mature mRNA

mRNA that has undergone processing (capping, tailing, splicing) and is ready for translation.

5’ cap

A modified guanine nucleotide added to the $5'$ end of a pre-mRNA molecule to protect it and aid in ribosome binding.

3’ poly-A tail

A string of adenine nucleotides added to the $3'$ end of a pre-mRNA molecule to increase stability and facilitate transport.

Introns

Non-coding sections of an RNA transcript that are removed by splicing before the RNA is translated into a protein.

Exons

The coding sequences of an RNA transcript that remain after splicing and are expressed in the final protein.

Splicing

The process of removing introns and joining exons together in a pre-mRNA molecule.

Transfer RNA (tRNA)

The RNA molecule that transports specific amino acids to the ribosome during translation.

Anticodon loop

The region of a tRNA molecule that contains a triplet of nucleotides complementary to a specific mRNA codon.

Acceptor stem

The part of a tRNA molecule where an amino acid is covalently attached.

aa-tRNA synthetase

An enzyme that attaches the correct amino acid to its corresponding tRNA molecule.

Ribosome

The cellular structure consisting of RNA and protein that serves as the site of protein synthesis.

Ribosomal RNA (rRNA)

The type of RNA that, together with proteins, makes up the structure of ribosomes.

Polyribosome

A group of several ribosomes translating the same mRNA molecule simultaneously.

Start codon

The first codon of an mRNA transcript translated by a ribosome, typically AUG (Methionine).

Reading frame

A way of dividing the sequence of nucleotides in a nucleic acid molecule into a set of consecutive, non-overlapping triplets.

Peptide bond

The covalent bond formed between the carboxyl group of one amino acid and the amino group of another.

Mutation

A permanent change in the DNA sequence of a cell's genome.

Single-gene mutation

A mutation that affects a single gene, often through changes in one or more nucleotides.

Chromosomal mutation

Large-scale changes in chromosome structure or number, often affecting many genes.

Point mutation

A mutation that involves a change in a single nucleotide base pair.

Frameshift mutation

A mutation caused by the insertion or deletion of nucleotides that shifts the reading frame of the genetic message.

Silent mutation

A point mutation that changes a codon but result in the same amino acid due to the redundancy of the genetic code.

Missense mutation

A point mutation that results in the substitution of one amino acid for another in a protein.

Nonsense mutation

A point mutation that changes an amino acid codon into a premature stop codon.

Mutagen

A physical or chemical agent that increases the frequency of mutations in an organism.

Transposon

A DNA sequence that can change its position within a genome, sometimes creating or reversing mutations.

Gene regulation

The wide range of mechanisms used by cells to increase or decrease the production of specific gene products (protein or RNA).

Constitutive gene

A gene that is transcribed continually at a relatively constant rate regardless of environmental conditions.

Operon

A cluster of genes in prokaryotes that are under the control of a single promoter and transcribed as a single mRNA.

Operator

A DNA segment within an operon where a repressor protein binds to inhibit transcription.

Repressor

A protein that binds to the operator or promoter of a gene to prevent transcription.

Activator

A protein that binds to DNA and stimulates the transcription of a specific gene.

Transcription factor

A protein that controls the rate of transcription by binding to specific DNA sequences.

RNA interference

A biological process in which RNA molecules inhibit gene expression or translation by neutralizing targeted mRNA molecules.

Friedrich Meischer

The scientist who first isolated 'nuclein' (now known as DNA) from the nuclei of white blood cells.

Fred Griffith

Discovered the 'transforming principle' by showing that non-virulent bacteria could become virulent when mixed with heat-killed virulent bacteria.

Avery, McLeod, and McCarty

Demonstrated that DNA, rather than protein, was the transforming principle responsible for Griffith's observation.

Hershey and Chase

Used radioactive labeling of sulfur (protein) and phosphorus (DNA) in bacteriophages to prove that DNA is the genetic material.

Watson and Crick

Developed the first accurate double-helix model of DNA structure.

Meselson and Stahl

Conducted the 'elegant' experiment using heavy ($^{15}N$) and light ($^{14}N$) nitrogen isotopes to prove the semi-conservative model of DNA replication.

Beadle and Tatum

Formulated the one gene-one enzyme hypothesis by studying nutritional mutants in the mold Neurospora crassa.

Lac Operon

An inducible operon in E. coli that encodes enzymes for lactose metabolism; it is repressed in the absence of lactose.

Trp Operon

A repressible operon in E. coli that encodes enzymes for tryptophan synthesis; it is inhibited when tryptophan levels are high.