Molecular Genetics: DNA, RNA, Replication, Transcription, Translation, Mutations, Molecular Genetics of Bacteria

Flashcards for review of Molecular Genetics: DNA, RNA, Replication, Transcription, Translation, Mutations, Molecular Genetics of Bacteria

DNA

Contains hereditary information of the cell; composed of 4 types of nucleotides (A, T, G, C). It is double stranded, in the structure of a complementary and antiparallel double helix

RNA

Functions vary by molecule type; composed of 4 types of nucleotides (A, U, G, C).

mRNA (Messenger RNA)

Single-stranded template for protein synthesis.

tRNA (Transfer RNA)

Clover-shaped RNA that transports amino acids to its mRNA codon.

rRNA (Ribosomal RNA)

Globular RNA that forms part of the ribosomes.

DNA Replication

Copying of genetic information in cells.

Leading strand

Synthesized continuously as DNA unzips.

Lagging strand

Synthesized discontinuously (producing Okazaki fragments).

Okazaki fragments

Short stretches of nucleotides formed as the lagging strand is synthesized.

Primase

Enzyme that creates a small strip of RNA primer, which DNA polymerase needs to begin synthesizing a new strand of DNA.

DNA Polymerase III

Synthesizes new DNA strand in 5’ → 3' direction by adding nucleotides to an RNA primer.

DNA Polymerase I

Removes RNA primer and replaces it with newly synthesized DNA.

Ligase

Seals the gaps in the phosphodiester backbone of DNA between the Okazaki fragments.

Telomere

Segment of DNA that are added to the ends of chromosomes to prevent loss of genomic info as chromosome ends wear down.

Telomerase

Enzyme that creates telomeres.

Origin of replication

Specific nucleotide sequence where DNA replication starts.

Helicase

Separates the DNA double helix into single stranded DNA, forming a replication fork.

Topoisomerase

Relieves the stress caused by unwinding DNA by breaking and rejoining strands.

Single stranded binding proteins

Proteins that bind to the single-stranded DNA near the replication fork to keep the two strands of DNA apart.

Transcription

Process of synthesizing RNA from a DNA template; in transcription, we bind and transcribe a specific gene.

Transcription factors

Proteins that bind to the promoter sequence and other regulatory sequences to control transcription of a target gene; needed by Eukaryotic RNA Polymerases to help initiate transcription.

Promoter region

Sequence RNA polymerase attaches to; upstream of DNA that gets transcribed.

Post-transcriptional processing

Adding 5' cap sequence to 5' end and poly-A tail to 3' end of mRNA for stability; RNA splicing.

RNA Splicing

The process of removing sections of pre-mRNA transcript that are absent in the mature mRNA and reconnecting the remaining exons

Exons

Protein-coding regions of the genome.

Introns

Non-coding regions in mRNA that do not encode functional proteins.

Alternative splicing

Process occurring during gene expression that allows for production of multiple protein types from a single gene when different combinations of exons are used.

Translation

The synthesis of proteins based on the sequence of mRNA nucleotides.

Initiation (Translation)

Small ribosomal subunit binds to mRNA, and methionine-tRNA binds to AUG start codon; large ribosomal subunit joins to form a complete ribosome.

Elongation (Translation)

tRNAs bring amino acids to a growing polypeptide chain—enter at A site, then shift to P site, and finally to E site for removal.

Termination (Translation)

Translation terminates when the stop codons (UAG, UAA, UGA) are encountered. These are recognized by release factors, which cause the newly made polypeptide chain to be released.

Elongation (Transcription)

RNA Polymerase synthesizes RNA nucleotides using one DNA strand as template.

Termination (Transcription)

RNA Polymerase reaches a special sequence, detaches from the DNA, and disassembles.

Point mutation

A single nucleotide change causing substitution, insertion, or deletion.

Insertion (mutation)

Addition of a nucleotide.

Deletion (mutation)

Removal of a nucleotide.

Substitution (mutation)

Change of one nucleotide to a different nucleotide; can create silent, missense, or nonsense mutations.

Silent mutation

The codon is changed, but due to the redundancies in codons, the same amino acid gets incorporated as normal; protein function remains unchanged.

Missense mutation

Results in a new codon that encodes a new amino acid.

Nonsense mutation

Converts an existing codon encoding an amino acid into a stop codon, prematurely signaling the cell to stop building a protein; it produces a truncated, usually non-functioning protein.

Forward mutation

Changes a wild type allele to a mutant allele.

Backward mutation

Reverts a mutant allele to a wild type allele.

Frameshift mutation

Results in a shifted reading frame of RNA transcript, causing different amino acids to be translated and resulting in impaired protein structure.

Plasmids

Small, circular double stranded DNA molecules that are separate from the main prokaryotic DNA; carry genes that are non-essential but may be beneficial for survival and replicate independently.

Operons

Gene clusters that control transcription and consist of promoter, operator, structural genes.

Promoter (prokaryotic)

DNA sequence where RNA Polymerase attaches to in prokaryotes.

Operator (prokaryotic)

Region that can block the action of RNA Polymerase if occupied by a repressor in prokaryotes.

Structural genes (prokaryotic)

Genes that code for proteins that are to be produced in prokaryotes.

Regulatory genes (prokaryotic)

Genes that encode products that control the expression of other genes in prokaryotes.

Repressor (prokaryotic)

Protein that binds to the operator of prokaryotic genes to decrease transcription.

Activator (enhancer) [prokaryotic]

Protein that binds to prokaryotic operators to increase transcription and assists the attachment of RNA Polymerase to promoter.

Lac Operon

Operon in prokaryotic cell that encodes genes required for processing of lactose; presence of lactose induces the operon to produce lactose breakdown enzymes.

Trp Operon

A group of genes necessary to synthesize tryptophan in prokaryotic cells.

Conjugation (bacterial)

DNA is transferred from a living donor bacterium to a living recipient bacterium by cell-to-cell contact using a pilus (bridge) to send its DNA or plasmid to the recipient.

Transformation (bacterial)

A competent recipient bacterium takes up free DNA from the surrounding.

Transduction (bacterial)

DNA is transferred from one bacterium to another by a bacteriophage (virus that infects bacteria).

Genome

Complete genetic information for an organism; majority of the human genome consists of non-coding DNA.

Transcriptome

Set of all RNA molecules that can be produced by a cell.

Proteome

Complete set of proteins in an organism that are expressed.