Unit 6 - Gene Expression and Regulation

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70 Terms

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Helicase

Unwinds the DNA double helix by breaking hydrogen bonds

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Topoisomerase

Prevents supercoiling ahead of the replication fork

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Single-Strand Binding Proteins

Prevent separated DNA strands from reannealing

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Primase

Adds RNA primer to start DNA replication

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DNA Polymerase III

Adds nucleotides to the new DNA strand (5’ to 3’)

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DNA Polymerase I

Replaces RNA primers with DNA

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Ligase

Seals gaps between Okazaki fragments

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RNA Polymerase

Synthesizes mRNA from DNA template

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Transcription Factors

Help RNA polymerase bind to promoter

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Helicase (transcription)

Unwinds DNA to form transcription bubble

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Spliceosome

Removes introns and joins exons

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snRNPs

Help spliceosome cut out introns

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Poly(A) Polymerase

Adds poly-A tail to mRNA’s 3’ end

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Capping Enzymes

Add 5’ cap to mRNA

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Ribosome

Assembles proteins by reading mRNA

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DNA replication

The process by which a cell copies its DNA before cell division

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Leading Strand

Continuous replication in the 5’ to 3’ direction

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Lagging Strand

Discontinuous replication with Okazaki fragments

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Conservative Replication

Original DNA stays intact, new molecule is fully new

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Semi-Conservative Replication

Each DNA has one old strand and one new strand

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Dispersive Replication

DNA is a mix of old and new fragments throughout both strands

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Transcription

DNA is copied into mRNA in the nucleus

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Translation

Ribosomes read mRNA to build proteins in the cytoplasm

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Promoter

Region where RNA polymerase binds to start transcription

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Operator

On/off switch that controls access to genes by binding repressors

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Regulatory gene

Codes for repressor protein that controls the operon

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Repressor

Protein that binds to the operator to block transcription

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TATA box

A repeating DNA sequence in the promoter that helps position RNA polymerase for transcription

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Transcription bubble

Opened section of DNA where RNA polymerase reads the template strand to make mRNA

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Phosphodiester bonds

Strong covalent bonds that link nucleotides together in DNA and RNA strands.

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Template strand

The DNA strand used as a guide to build mRNA during transcription

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Alternative Splicing

Creates different mRNAs by including/excluding exons

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Messenger RNA (mRNA)

Carries genetic instructions from DNA to ribosomes

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Ribosomal RNA (rRNA)

Forms the ribosome and helps assemble proteins

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Transfer RNA (tRNA)

Brings amino acids to the ribosome based on mRNA codons

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5’ Cap

Added to mRNA to protect it and help ribosome binding

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Poly-A Tail

Added to mRNA’s end to stabilize and export it from nucleus

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A site

Holds incoming tRNA with an amino acid

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P site

Holds tRNA with the growing polypeptide chain

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E site

Where empty tRNA exits the ribosome

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Codon

A 3-nucleotide sequence on mRNA that codes for a specific amino acid (e.g. AUG = start/methionine)

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Anticodon

A 3-nucleotide sequence on tRNA that pairs with the mRNA codon to bring the correct amino acid

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Retroviruses

Viruses that have RNA as their genetic material and use reverse transcriptase to convert RNA into DNA

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Reverse Transcriptase

An enzyme that converts RNA into DNA

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Operons

Clusters of genes in prokaryotes that work and are regulated together

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Inducible Operon

An operon that is normally off but can be turned on by an inducer (e.g., lac operon)

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Repressible Operon

An operon that is normally on but can be turned off by a repressor (e.g., trp operon)

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Tryptophan

A type of amino acid used in the trp operon; its presence can turn off the operon

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Euchromatin

Loosely packed chromatin that is active in gene expression.

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Heterochromatin

Tightly packed chromatin that is usually inactive and not expressed

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Histone Proteins

Proteins that help package DNA into a compact form

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Epigenetics

Study of changes in gene expression without altering the DNA sequence

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miRNA

Small RNA molecules that regulate gene expression by binding to mRNA and preventing translation.

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siRNA

Small interfering RNA that helps degrade mRNA and prevents gene expression

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Induction

The process by which one cell or tissue influences the development of another

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Morphogenesis

The process by which cells and tissues develop into their correct shape and size

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Transcriptional Co-repressors

Proteins that bind to repressors and help turn off gene transcription

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Transcription Factors (TFs)

Proteins that help initiate or regulate gene transcription

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Point Mutations

A change in a single nucleotide in the DNA sequence

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Silent Mutation

A mutation that does not change the amino acid sequence

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Missense Mutation

A mutation that changes one amino acid in the protein sequence

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Nonsense Mutation

A mutation that introduces a premature stop codon, leading to a truncated protein

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Insertions and Deletions

Mutations where nucleotides are added (insertion) or removed (deletion), which can cause frameshift mutations

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Transformation

The process by which a cell takes up foreign DNA from its environment

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Transduction

The process by which a virus transfers DNA between bacteria

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Conjugation

The process by which bacteria transfer genetic material through direct contact

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DNA Cloning

The process of making multiple copies of a specific DNA fragment

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Gel Electrophoresis

A technique used to separate DNA, RNA, or proteins based on size and charge

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PCR (Polymerase Chain Reaction)

A method to amplify (make many copies of) a specific DNA segment

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Biopiracy

The unethical use of biological resources or traditional knowledge from indigenous communities without fair compensation