Molecular Genetics

Deoxyribonucleic Acid (DNA)

A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins

Anti-parallel

A term used to describe the opposite orientations of the two strands of a DNA double helix

Ribonucleic Acid (RNA)

A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses.

Deoxyribose

A five-carbon sugar that is a component of DNA nucleotides

Ribose

A five-carbon sugar present in RNA

Adenine (A)

A nitrogenous base that pairs with Thymine (T) in DNA and Uracil (U) RNA

Thymine (T)

Nitrogenous base that pairs with Adenine (A) in DNA; only present in DNA

Uracil (U)

A nitrogenous base that pairs with Adenine (A) in RNA; is only found in RNA

Guanine (G)

A nitrogenous base that pairs with Cytosine (C) in DNA and RNA

Cytosine (C)

A nitrogenous base that pairs with Guanine (G) in DNA and RNA

Purine Nucleotide

Adenine (A) and Guanine (G); Bigger nitrogenous bases

Pyrimidine Nucleotide

Thymine (T), Cytosine (C), and Uracil (U); Smaller nitrogenous bases

Gene

A segment of DNA that codes for a protein

Nucleotide

A sub-unit of DNA that consists of a phosphate, sugar, and nitrogenous bases

Replication

Copying process by which a cell duplicates its DNA

Transcription

The organic process whereby the DNA sequence in a gene is copied into mRNA

RNA Polymerase

The enzyme that synthesizes mRNA from DNA (*ONLY ADDS NUCLEOTIDES TO THE 3’ END)*

Promoter

A specific nucleotide sequence in the DNA of a gene that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place

Transcription Unit

A region of DNA that is transcribed into an RNA molecule

Terminator

A sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA; Only found in bacteria cells

Transcription Factors

Regulatory proteins that bind to DNA to mediate the transcription of genes by RNA polymerase

Transcription Initiation Complex

The completed assembly of transcription factors and RNA polymerase bound to a promoter

TATA Box

A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex

Initiation

RNA polymerase bonds to the promoter and unwinds the DNA strands to initiate mRNA synthesis from the DNA template strand

Elongation

RNA polymerase moves downstream, unwinding the DNA and elongating the mRNA using new nucleotides complementary to the template strand

Termination

The mRNA is released from RNA polymerase and the enzyme detaches from the DNA

Polyadenylation Signal (AAUAAA)

A sequence of nucleotides in eukaryotic pre-mRNA that signals proteins within the nucleus to cut the RNA transcript away from the enzyme so it can undergo processing

5’ Cap

A modified guanine nucleotide attached to the 5’ end of eukaryotic pre-mRNA after the first 20-40 nucleotides have been transcribed

Poly-A Tail

50-250 extra adenine nucleotides added to the 3’ end of eukaryotic pre-mRNA as it leaves the nucleus

Introns

Non-coding segments of mRNA that lie between coding regions

Exons

Coding regions of mRNA

Untranslated Regions (UTRs)

Non-coding segments of mRNA at the 5’ and 3’ ends of the mRNA that remain because they aid in activities like ribosome binding

RNA Splicing

The process in which introns are removed

Alternative RNA Splicing

A primary transcript can be modified to code for different amino acids based on which segments are considered introns or exons

Spliceosomes

A large complex of proteins and RNA molecules that remove introns from mRNA

Ribozyme

An RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing

Messenger RNA (mRNA)

A type of RNA, synthesized from DNA and attached to ribosomes in the cytoplasm; it specifies the primary structure of a protein

Translation

The process whereby genetic information coded in mRNA directs the formation of a specific protein at a ribosome in the cytoplasm

Transfer RNA (tRNA)

An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA

RIbosomal RNA (rRNA)

Type of RNA that makes up the major part of ribosomes

Origin of Replication

The location on the DNA where replication begins

Replication Bubble

An unwound and open region of a DNA helix where DNA replication occurs

Replication Fork

The area where the replication of DNA will actually take place

DNA Polymerase

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

RNA Polymerase

Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription

Phenotype

An organism's physical appearance, or visible traits

Extended Phenotype

Structures constructed by organisms that can influence their performance or success

Stem Cell

Unspecialized cell that can give rise to one or more types of specialized cells

Genetic Engineering

Process of making changes in the DNA code of living organisms

Chargaff's Rule

Rule #1: In DNA, percent guanine will match percent cytosine, and percent thymine will match percent adenine

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Rule #2: Composition of DNA varies between species

Helacase

Enzyme that takes apart DNA strands by breaking the hydrogen bonds between nitrogenous bases

Primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template (Conductor)

Primer

A short piece of RNA

Ligase

An enzyme that connects two fragments of DNA to make a single fragment (Gluer) *ONLY ACTS ON LAGGING STRAND*

Topoisomerase

Relieves strain in DNA ahead of the replication fork

Nuclease

Cuts out mismatched or damaged nucleotides

Telomeres

Caps of noncoding nucleotides at the end of eukaryotic DNA; Protects DNA from erosion

Telomerase

Extends telomeres in germ cells (ovary, testes)

Leading Strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

Lagging Strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

Okazaki Fragments

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

Semi-Conservative

In each new DNA double helix, one strand is from the original molecule, and one strand is new

Frederick Griffith Experiment

The different strains of Streptococcus pneumoniae have different effects on mice; the rough strain did not affect the mice, the smooth strain did affect the mice, the heat

Transforming Factor

The molecular agent of transformation; DNA

Avery, McCarty, Macleod Experiment

Concluded which of the different major structures of the bacteria could be the transforming factor; Found that RNA and protein could not be a transforming factor because they transformed when different enzymes were added, but DNA could be the transforming factor because it was not transformed with certain enzymes

Hershey-Chase Experiment

Confirmed that DNA is the genetic material because only radiolabeled DNA could be found in bacteriophage-infected bacteria

James Watson and Francis Crick

Men credited with discovering the structure of DNA

Plasmid

A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome

Central Dogma

DNA-transcription-RNA-translation-protein

Codon

A specific sequence of three adjacent bases on a strand of mRNA that provides genetic code information for a particular amino acid

Anticodon

A group of three bases on a tRNA molecule that are complementary to an mRNA codon

Mutation

A change in a gene or chromosome

Hemoglobin

The main protein in red blood cells

Sickle-Cell Anemia

A genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle shape

Gene Therapy

The insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder

Biotechnology

The application of technology in biological sciences

Substitution

A mutation that causes one base in the DNA to be changed (Ex. A 🠞 T)

Deletion

A mutation in which one base is deleted from the gene (Ex. ATG 🠞 A_G)

Addition

A mutation in which one base pair is added to the gene (Ex. TAG 🠞 TATG)

Inversion

A mutation in which the order of the bases switches (Ex. GAT 🠞 TAG)

Rearrangement

A mutation in which the bases within the gene are moved to different places (Ex. ATC CAG 🠞 CAG ATC)

Translocation

A mutation in which the bases within the gene are moved to different places (Ex. ATC CAG 🠞 CAG ATC)

Frameshift Mutation

Mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

Mutagen

Any substance (chemical or radiation) that can cause a gene or chromosomal mutation

Mutagenic Agent

Any substance (chemical or radiation) that can cause a gene or chromosomal mutation