Genetics & Society Midterm Review

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Hypothesis

A testable and falsifiable statement used to explain observations that can be supported or rejected through experimentation

Theory

A well-supported explanation of natural phenomena based on repeated testing and a large body of evidence

Hypothesis Testing

Scientists test hypotheses through experiments

Scientific Communication

Scientists share findings through peer-reviewed journals for accuracy

Media Communication

The media communicates simplified versions of research findings to the public

Peer Review

Evaluation of research by experts before publication to ensure quality

Scientific Misconduct

Includes fabrication, falsification, plagiarism, and suppression

Misconduct Causes

Factors like career pressure, financial incentives, predetermined bias, and belief one won’t get caught

Ethical Behavior

Conducting science with honesty, integrity, and responsibility in research

Red Flags in Media

Warning signs like straw man, appealing to nature, burden switching, false balancing, and confirmation bias

Genome

The complete set of genetic instructions contained within a single cell

Protein

A molecule that drives chemical reactions and produces subcellular structures

Central Dogma

DNA is first replicated, then the replicated DNA is transcribed into RNA, which then gets translated and decoded into the protein

Prokaryotic Cells

Simple single-celled organisms without a nucleus or membrane-bound organelles

Eukaryotic Cells

Multicellular complex cells with a membrane bound nucleus

DNA Packaging

DNA wraps around histone proteins forming nucleosomes that coil into chromatin and chromosomes to fit inside the nucleus

Human Genome Size

About 3 billion base pairs

Genome Size vs Complexity

There is no consistent relationship between organism complexity and genome size

DNA Structure

DNA is made of nucleotides with a phosphate group, sugar group, and nitrogen base, including adenine, thymine, guanine, and cytosine

Base Pairs

Nitrogen bases on opposite strands bond specifically — A and T as well as G and C

Replication

The process of copying DNA before cell division

Transcription

The process of using a DNA template to make RNA

Translation

The decoding of mRNA into a specific sequence of amino acids to build a protein

Nucleotide

The basic building block of DNA or RNA composed of a sugar, phosphate, and nitrogen bases

Codon

A three-nucleotide sequence on mRNA that codes for a specific amino acid

Amino Acid

The building block of proteins linked together during translation

Promoter

A DNA region that signals where transcription begins and controls timing and tissue-specific expression

Exons

Coding regions of a gene that remain in mRNA and translate into protein

Introns

Non-coding regions removed during RNA processing

Gene Expression Control

Only necessary genes are active in each cell type to ensure proper function

Protein Functions

Proteins act as enzymes to speed reactions, structural proteins to provide support and shape to cells, and transport proteins to move molecules across membranes

Plasmid Gene Cloning

A gene is inserted into a plasmid using restriction enzymes and DNA ligase, introducing bacteria for replication

PCR Gene Cloning

Polymerase Chain Reaction amplifies DNA sequences using DNA polymerase, primers, and nucleotides

DNA Replication in Cells

DNA helicase unwinds the double helix, each strand being a template for a complementary strand, where DNA polymerase adds nucleotides and DNA ligase joins the fragments together

Polymerase

Enzyme that builds new DNA strands by adding nucleotides during replication

Ligase

Enzyme that joins DNA fragments with covalent bonds and seals inserted genes in cloning

Restriction Enzymes

Enzymes that cut DNA at specific sequences, as well as let scientists cut and pest genes into vectors for things like cloning and genetic engineering

Plasmids

Small circular DNA molecules that replicate independently and typically found in bacteria

DNA Insertion into Plasmids

Restriction enzymes cut plasmid and DNA, creating matching sticky ends, allowing ligase to seal inserted genes into the plasmid

Selectable Markers

Genes like ampicillin resistance used to identify bacteria that contain recombinant plasmids

Transformation

The process of introducing foreign DNA into bacterial cells such as E. coli

Transformation Method

Bacteria like E. coli are treated with calcium chloride and heat to allow plasmid DNA entry

Bacterial Pharmaceutical Production

A human gene (e.g. insulin) inserted in bacterial plasmid, which is introduced into bacteria, which use their cellular machinery to produce human protein (insulin), which is purified for medical use

PCR Steps

Denaturation separates template DNA strands, which are then annealed as primers bind to the complementary sequences on each DNA strand to indicate copying, leading to extension where Taq polymerase adds free nucleotides to the primers, building new DNA strands with the template DNA as guides

Denaturing

In PCR, template DNA is heated to separate two strands into single strands for copying

Annealing

In PCR, primers bind to the complementary sequences on each DNA strand to show where copying should start

Extension

In PCR, Taq polymerase adds free nucleotides to primers, building new DNA strands using the template DNA as a guide

PCR Components

Requires template DNA, primers, Taq polymerase, and free nucleotides

DNA and Traits

The sequence of nucleotides (ATCG) decides the sequence of amino acids in proteins, which the structure of them provide physical/biochemical traits of organisms, and gene expression can result in variations of these traits or diseases, caused by differences or mutations

Newborn Genetic Screening

Screening identifies serious genetic disorders early (like PKU), allowing early intervention before symptoms appear

Huntington’s Disease Testing

Adults may avoid testing to prevent emotional or psychological distress from knowing carrier status, as well as future plans

Huntington’s Disease Inheritance

If one parent carries the gene and the other does not (or both do)

Reporter Gene

A gene used in assays to visualize or measure gene expression by producing easily measurable products such as GFP in fruit flies

Animal Models

Used in genetics research to study human-like DNA, gene function, disease mechanisms, and therapies, as well as identify side effects before clinical trials

CRISPR Components

Cas9 protein cuts DNA while guide RNA (gRNA) directs Cas9 to the specific sequence by binding to complementary DNA and directing where to cut

guide RNA

Directs Cas9 to the specific sequence by binding to complementary DNA and directing where to cut

Cas9 protein

Cuts DNA in CRISPR

Off-Target Effect

Unintended DNA changes caused when CRISPR edits parts of the genome other than the target

Somatic Editing

Genetic modification in body cells after birth that cannot be inherited (widely acceptable)

Germline Editing

Genetic modification in reproductive or embryonic cells that can be inherited by offspring (not acceptable due to risks and ethics)

Editing Acceptance

Somatic editing is acceptable, germline is not

Helen Obando Case

Received ex vivo (cells edited outside body) somatic CRISPR therapy targeting sickle cell disease by editing the BCL11A repressor gene to increase fetal hemoglobin production

Sickle Cell Mutation

Caused by a single base-pair change in β-globin converting hydrophilic glutamic acid to hydrophobic valine, as it produces defective RBCs, hematologic disorder

CRISPR BCL11A Strategy

Upregulates fetal γ-globin and downregulates β-globin to restore healthy red blood cells in sickle cell disease

CPS1 Deficiency Therapy

In vivo CRISPR editing using lipid nanoparticles to deliver Cas9 and gRNA to the liver

CRISPR Non-Germline Disease Targets

Duchenne muscular dystrophy, melanoma modeling, retinitis pigmentosa, sickle cell disease

Duchenne muscular dystrophy

Muscle degeneration

Melanoma modeling

Cancer research model

Retinitis pigmentosa

Progressive vision loss

CPS1

Carbamoyl phosphate synthetase 1 deficiency where liver enzyme defects prevent ammonia breakdown