Biology and Society: Module 11 – Complex Genetics and GMOs

Protein synthesis

The process of turning a gene’s instructions into a protein; happens in two steps—transcription (making RNA) and translation (making protein)

Transcription

The process of copying a section of DNA into mRNA inside the nucleus so the message can leave and be used to make protein

Translation

The step where ribosomes read the mRNA code and link amino acids together to build a protein chain

mRNA (messenger RNA)

A temporary copy of DNA that carries the genetic code from the nucleus to the ribosome

tRNA (transfer RNA)

A helper molecule that brings amino acids to the ribosome and matches them to the correct codon on the mRNA

Codon

A group of three bases on mRNA that tells the ribosome which amino acid to add next

Anticodon

A group of three bases on tRNA that pairs with the codon on mRNA to make sure the right amino acid is added

Ribosome

A cell structure that builds proteins by reading mRNA and connecting amino acids in order

Ribosome subunits

The small subunit reads the mRNA, and the large subunit connects the amino acids into a growing chain

DNA

The molecule that holds all genetic instructions; it’s double-stranded, uses thymine (T), and stays inside the nucleus

RNA

A molecule that helps make proteins; it’s single-stranded, uses uracil (U) instead of thymine, and can leave the nucleus

Genetic code

The system that shows which codons code for which amino acids; it’s redundant (more than one codon can mean the same thing) and universal (used by all living things)

Mutation

A change in the DNA sequence that can affect how a protein is made or works

Base-substitution mutation

One DNA base is swapped for another; it might change one amino acid or have no effect at all

Neutral mutation

A mutation that doesn’t change how the protein works, often because the codon still codes for the same amino acid

Frameshift mutation

When a base is added or deleted, shifting how the genetic code is read and usually ruining the protein

Deletion mutation

A mutation where bases are removed from DNA, often causing a frameshift and changing the whole protein

Gene regulation

The process of turning genes on or off so cells only make the proteins they need

Prokaryotic gene regulation

Bacteria control genes by using repressors that block RNA polymerase from starting transcription

Eukaryotic gene regulation

Cells use activators to start transcription and also control genes by folding DNA, cutting mRNA, or breaking down old proteins

Protein effect of mutation

A mutation can have no effect, make the protein stop working, or create a new version that works differently

PCR (Polymerase Chain Reaction)

A lab technique that makes millions of copies of a specific DNA segment by heating, cooling, and using Taq polymerase to build new strands

Purpose of PCR

Used to amplify small amounts of DNA for profiling, genetic testing, or research

DNA fingerprint (DNA profiling)

A unique pattern of DNA fragments created by analyzing variable regions like STRs to identify individuals

Short Tandem Repeats (STRs)

Repeating DNA sequences found in noncoding regions; the number of repeats varies between people and is used in DNA profiling

Restriction enzymes

Proteins that cut DNA at specific sequences, creating fragments with sticky ends that can join to other DNA pieces

Gel electrophoresis

A method that separates DNA fragments by size using an electric current through a gel; smaller fragments move faster

Plasmid

A small circular piece of bacterial DNA used as a carrier to transfer genes in genetic engineering

Cloning

The process of making a genetically identical copy of a cell, gene, or organism

Steps of cloning

Remove the nucleus from a donor egg, insert the nucleus from a body cell, then place the embryo into a surrogate mother

Gene cloning

Copying a specific gene by inserting it into a plasmid and growing it in bacteria

Recombinant DNA

DNA formed by joining genetic material from two different sources, such as inserting a human gene into bacterial DNA

rBGH (recombinant bovine growth hormone)

A growth hormone gene from cows inserted into bacteria so it can be mass-produced for agriculture

Genetic modification (GMOs)

Changing an organism’s DNA to give it new traits like faster growth, pest resistance, or higher nutrition

How genes are added to plant cells

Using a Ti plasmid or a gene gun that shoots DNA-coated particles into plant cells

How genes are added to animal cells

Injecting the gene directly into a fertilized egg or using viruses as carriers

CRISPR

A precise gene-editing tool that uses a guide RNA to find a DNA sequence and an enzyme to cut and replace it

Uses of CRISPR

Used to fix mutations, improve crops, create disease-resistant animals, and potentially treat human genetic disorders

Gene therapy

Replacing or fixing a faulty gene to treat genetic diseases

Somatic cell gene therapy

Fixes genes only in specific body cells; treatments need to be repeated over time

Germline gene therapy

Replaces genes in an embryo so all future cells have the corrected gene

Benefits of cloning

Can help preserve endangered species, produce genetically identical animals for research, and grow organs for transplants

Ramifications of cloning

Raises ethical concerns about individuality, genetic diversity, and potential misuse in humans

Stem cells

Undifferentiated cells that can turn into many different types of specialized cells in the body

Totipotent stem cells

Stem cells that can develop into any cell type, including an entire organism

Pluripotent stem cells

Stem cells that can become almost any type of cell but not an entire organism

Adult stem cells

Stem cells found in mature tissues that repair and replace damaged cells; limited in what types they can become

Sources of adult stem cells

Found in bone marrow, blood, skin, liver, and other tissues throughout the body

Embryonic stem cells

Stem cells taken from early-stage embryos that can become any cell type in the body

Therapeutic cloning

Using stem cells to grow healthy tissues or organs to replace damaged ones

Uses of stem cells

Can treat diseases like Parkinson’s, Alzheimer’s, heart damage, or joint injuries by regenerating tissue

Limitations of adult stem cells

Found in small numbers, divide only a few times, and are hard to grow in labs

Ethical issues with embryonic stem cells

Involves destroying embryos, which raises moral and legal debates about human life

Benefits of stem cell research

Advances medicine, allows tissue regeneration, and helps study disease development

Gene therapy

Replacing defective genes with normal ones to treat or prevent diseases

Germline gene therapy

Fixes genetic problems in embryos so all future cells carry the corrected gene

Somatic gene therapy

Targets and repairs defective genes only in certain body cells; effects are temporary

Cloning in animals

Creating a new organism genetically identical to another using nuclear transfer

Nuclear transfer

Taking the nucleus from a body cell and inserting it into an egg cell with its nucleus removed

Purpose of cloning

Used for research, agriculture, medicine, and preserving endangered species

Ethical concerns of cloning

Risks of defects, reduced genetic diversity, and moral issues about human cloning

Benefits of cloning

Can produce identical animals for testing, help create organs for transplants, and advance genetic research

Polygenic traits

Traits controlled by several genes, each adding a small effect; examples include height, skin color, and eye color

Quantitative traits

Traits that show continuous variation instead of clear categories; often influenced by both genes and environment

Heritability

The percentage of variation in a trait within a population that’s caused by genetic differences rather than environment

High heritability

Means genes strongly influence the trait, but environment can still affect how it appears

Low heritability

Means the environment has a stronger effect than genes on how the trait develops

Twin studies

Used to estimate heritability by comparing identical (monozygotic) and fraternal (dizygotic) twins

Epigenetics

The study of how the environment changes gene expression without changing the DNA sequence

DNA methylation

Adds chemical tags to DNA that turn genes on or off; these changes can sometimes be passed to offspring

Polymorphism

A DNA region that varies greatly between individuals; used in DNA profiling

DNA fingerprinting (profiling)

A method of identifying people based on unique patterns in their DNA, often using STRs

Short Tandem Repeats (STRs)

Short DNA sequences repeated several times in a row; the number of repeats differs from person to person

PCR in DNA profiling

Copies small DNA samples to make enough for analysis

Restriction enzymes in DNA profiling

Cut DNA into fragments at specific sequences for comparison

Gel electrophoresis in DNA profiling

Separates DNA fragments by size using an electric current through a gel

Interpreting gel bands

Each person’s pattern of bands is unique; a child’s DNA bands must come from one or both parents

Environmental influence on genes

Even traits with strong genetic control can be shaped by environment, like diet or sunlight exposure

Example of environment and genetics

Skin color darkens with sun exposure even though it’s genetically determined

Importance of DNA profiling

Used in criminal cases, paternity tests, and identifying remains

Example of DNA profiling

Used to identify the remains of the Romanov family by matching DNA to living relatives

Epigenetic example

Agouti mice changed coat color and health when their mothers were fed diets that altered DNA methylation