The Cell & Genetics

Cells, DNA, genes and heredity — the microscopic machinery of life and how traits pass from one generation to the next.

The cell is the basic structural and functional unit of all living things.
DNA carries the genetic instructions for building and maintaining organisms.
Genes are segments of DNA that determine inherited traits.
The nucleus controls the cell's activities and stores its DNA.
Mitochondria are the powerhouses that produce energy for the cell.
Plant cells have a rigid cell wall that animal cells lack.
Chloroplasts in plant cells carry out photosynthesis.
Cells divide through a process called mitosis to grow and repair.
Proteins are built from chains of amino acids.
Chromosomes are tightly coiled structures made of DNA and proteins.
Humans typically have forty-six chromosomes in each body cell.
RNA helps translate genetic information into proteins.
Ribosomes are the cellular structures where proteins are assembled.
Mutations are changes in DNA that can be passed to offspring.
Bacteria are single-celled organisms lacking a true nucleus.
Offspring inherit one set of chromosomes from each parent.
The cell membrane controls which substances enter and leave the cell.
The cell membrane is composed mainly of a phospholipid bilayer.
Cytoplasm is the jelly-like fluid that fills the inside of a cell.
The endoplasmic reticulum transports materials throughout the cell.
Rough endoplasmic reticulum is studded with ribosomes that make proteins.
The Golgi apparatus modifies, sorts, and packages proteins for delivery.
Lysosomes contain enzymes that break down waste and worn-out cell parts.
Vacuoles store water, nutrients, and waste within a cell.
Plant cells often contain one large central vacuole for storage and support.
Centrioles help organize the spindle fibers during animal cell division.
The cytoskeleton gives the cell shape and supports internal movement.
Microtubules are hollow tubes that form part of the cytoskeleton.
Cilia are short hair-like projections that help move substances across cells.
Flagella are long whip-like structures used by some cells for movement.
The nucleolus inside the nucleus is the site of ribosome production.
The nuclear envelope is a double membrane surrounding the cell nucleus.
Nuclear pores allow molecules to pass between the nucleus and cytoplasm.
Eukaryotic cells contain a true nucleus and membrane-bound organelles.
Prokaryotic cells lack a nucleus and membrane-bound organelles.
Bacteria and archaea are the two main groups of prokaryotes.
Animal cells lack chloroplasts and cannot make their own food.
Photosynthesis converts carbon dioxide and water into glucose and oxygen.
Cellular respiration releases energy stored in glucose molecules.
ATP is the main energy-carrying molecule used by living cells.
Mitochondria have their own small ring of DNA separate from the nucleus.
Mitochondria are surrounded by a double membrane with inner folds called cristae.
Glycolysis breaks glucose into pyruvate within the cell cytoplasm.
The Krebs cycle takes place in the mitochondrial matrix.
Diffusion is the movement of particles from high to low concentration.
Osmosis is the diffusion of water across a semipermeable membrane.
Active transport moves substances against their concentration gradient using energy.
Passive transport moves substances without using cellular energy.
Endocytosis brings large particles into a cell by engulfing them.
Exocytosis releases materials from a cell using membrane-bound vesicles.
Phagocytosis is a form of endocytosis where cells engulf solid particles.
The cell wall in plants is made primarily of cellulose.
Fungal cell walls are made largely of a substance called chitin.
Stem cells can develop into many different specialized cell types.
Red blood cells carry oxygen and lack a nucleus in humans.
Neurons are specialized cells that transmit electrical signals through the body.
Muscle cells contain protein filaments that allow them to contract.
Cell differentiation is the process of cells becoming specialized for tasks.
Tissues are groups of similar cells working together for a function.
Organs are made of different tissues performing a common function.
The cell theory states that all living things are made of cells.
Robert Hooke first described and named cells in the year 1665.
Antonie van Leeuwenhoek observed living microorganisms with early handmade microscopes.
Matthias Schleiden concluded that all plants are made of cells.
Theodor Schwann proposed that all animals are made of cells.
Rudolf Virchow stated that all cells arise from pre-existing cells.
DNA stands for deoxyribonucleic acid, the molecule of heredity.
RNA stands for ribonucleic acid and helps express genes.
DNA has a double-helix structure resembling a twisted ladder.
James Watson and Francis Crick described the DNA double helix in 1953.
Rosalind Franklin's X-ray images were crucial to discovering DNA's structure.
DNA is built from repeating chemical units called nucleotides.
A nucleotide consists of a sugar, a phosphate group, and a base.
The four DNA bases are adenine, thymine, guanine, and cytosine.
Adenine always pairs with thymine in the DNA double helix.
Guanine always pairs with cytosine in the DNA double helix.
In RNA, the base uracil replaces thymine found in DNA.
RNA is usually single-stranded while DNA is typically double-stranded.
The sugar found in DNA molecules is called deoxyribose.
The sugar found in RNA molecules is called ribose.
Complementary base pairing allows DNA to be copied accurately.
DNA replication produces two identical copies of a DNA molecule.
DNA polymerase is the enzyme that builds new DNA strands.
Helicase unwinds the DNA double helix during replication.
The genome is the complete set of genetic material in an organism.
A gene codes for a specific protein or functional RNA molecule.
The genetic code is read in three-base units called codons.
Each codon specifies a particular amino acid or a stop signal.
Transcription copies a gene's DNA sequence into messenger RNA.
Translation builds a protein using the sequence in messenger RNA.
Messenger RNA carries genetic instructions from DNA to the ribosomes.
Transfer RNA brings amino acids to the ribosome during translation.
Ribosomal RNA is a major structural component of ribosomes.
The start codon AUG signals the beginning of protein synthesis.
Stop codons signal the end of protein synthesis at the ribosome.
There are twenty common amino acids used to build proteins.
Proteins fold into specific shapes that determine their biological function.
Enzymes are proteins that speed up chemical reactions in cells.
Each enzyme typically acts on a specific substrate molecule.
Mitosis produces two daughter cells that are genetically identical.
Interphase is the longest phase of the entire cell cycle.
During interphase the cell grows and copies its DNA.
Prophase is the first stage of mitosis when chromosomes condense.
Metaphase is the stage when chromosomes line up at the cell center.
Anaphase is the stage when sister chromatids separate to opposite poles.
Telophase is the stage when two new nuclei form during division.
Cytokinesis is the division of the cytoplasm into two separate cells.
Meiosis produces four sex cells that are genetically varied.
Meiosis reduces the chromosome number of a cell by half.
Gametes are the reproductive cells, such as sperm and egg.
Sperm and egg cells in humans each carry twenty-three chromosomes.
Fertilization combines two gametes to form a single zygote.
A zygote is the first cell of a newly forming organism.
Diploid cells contain two complete sets of chromosomes.
Haploid cells contain only a single set of chromosomes.
Crossing over during meiosis exchanges genetic material between chromosomes.
Homologous chromosomes carry the same genes in the same order.
Sister chromatids are identical DNA copies joined at a centromere.
The centromere is the region where sister chromatids are connected.
Gregor Mendel is widely considered the founder of modern genetics.
Mendel studied inheritance using pea plants during the 1860s.
An allele is one of the alternative forms of a gene.
A dominant allele masks the effect of a recessive allele.
A recessive allele is expressed only when two copies are present.
Genotype refers to the genetic makeup of an organism.
Phenotype refers to the observable physical traits of an organism.
Homozygous means having two identical alleles for a single gene.
Heterozygous means having two different alleles for a single gene.
A Punnett square predicts the likely outcomes of a genetic cross.
Mendel's law of segregation states that allele pairs separate during gamete formation.
Mendel's law of independent assortment describes how genes sort separately.
In codominance, both alleles are fully expressed in the phenotype.
Human ABO blood types are an example of multiple alleles.
Sex chromosomes determine the biological sex of an organism.
Human females typically have two X chromosomes in each cell.
Human males typically have one X and one Y chromosome.
Sex-linked traits are carried on the X or Y chromosomes.
Color blindness is a common X-linked recessive trait in humans.
Hemophilia is an inherited disorder that affects blood clotting.
A pedigree chart traces the inheritance of traits through families.
Polygenic traits are controlled by several different genes at once.
Human height and skin color are examples of polygenic traits.
A carrier has a recessive allele but does not show the trait.
Down syndrome results from an extra copy of chromosome twenty-one.
A point mutation changes a single nucleotide in a DNA sequence.
A frameshift mutation results from inserting or deleting nucleotides.
Silent mutations do not change the resulting protein at all.
Sickle cell anemia is caused by a single mutation in a hemoglobin gene.
Mutations can be caused by radiation, chemicals, or copying errors.
A mutagen is an agent that increases the rate of mutation.
Cystic fibrosis is an inherited disorder affecting the lungs and digestion.
Heredity is the passing of traits from parents to their offspring.
Variation refers to the differences among individuals in a population.
Asexual reproduction produces offspring genetically identical to the single parent.
Sexual reproduction combines genetic material from two different parents.
Binary fission is how bacteria reproduce by splitting in two.
Viruses are not cells and cannot reproduce on their own.
A virus consists of genetic material enclosed in a protein coat.
Viruses must infect a living host cell in order to replicate.
The chromosome number remains constant within a given species.
A karyotype is an organized display of an organism's chromosomes.
Genetic engineering involves altering an organism's DNA directly.
Recombinant DNA combines genetic material from two different sources.
Genetically modified organisms have had their DNA deliberately changed.
Restriction enzymes cut DNA at specific recognition sequences.
DNA ligase joins separate fragments of DNA together.
The polymerase chain reaction makes many copies of a DNA segment.
Gel electrophoresis separates DNA fragments by their size.
DNA fingerprinting can identify individuals from their unique genetic patterns.
Cloning produces an organism genetically identical to another organism.
Dolly the sheep was the first mammal cloned from an adult cell.
The Human Genome Project mapped all human genes by the year 2003.
CRISPR is a powerful tool used to edit specific sequences in DNA.
Gene therapy aims to treat disease by altering a patient's genes.
Insulin can be produced by genetically modified bacteria for medical use.
Selective breeding chooses parents with desirable traits over many generations.
Hybridization crosses two genetically different parents to produce offspring.
Epigenetics studies changes in gene activity without DNA sequence changes.
Gene expression determines which proteins a particular cell produces.
Some genes are switched on or off depending on the cell type.
Chromatin is the loose combination of DNA and proteins in the nucleus.
Histones are proteins around which DNA wraps to form chromatin.
Telomeres are protective caps located at the ends of chromosomes.
Telomeres become shorter each time a cell divides.
Apoptosis is the process of programmed and controlled cell death.
Cancer results from the uncontrolled division of abnormal cells.
Oncogenes are mutated genes that can contribute to causing cancer.
The cell cycle is regulated by checkpoints that ensure proper division.
Photosynthesis occurs in the chloroplasts of green plant cells.
Chlorophyll is the green pigment that captures light energy in plants.
Stomata are tiny pores in leaves that allow gas exchange.
Aerobic respiration requires oxygen to release energy efficiently.
Anaerobic respiration releases energy from glucose without using oxygen.
Fermentation is an anaerobic process that produces alcohol or lactic acid.
A protein's function depends largely on its three-dimensional folded shape.
Denaturation destroys a protein's shape and its biological function.
Carbohydrates are sugars and starches used by cells for energy.
Organelles are specialized structures that perform functions within a cell.
A single chromosome carries many different genes along its length.
Identical twins develop from a single fertilized egg that splits.

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The Cell & Genetics

Cells, DNA, genes and heredity — the microscopic machinery of life and how traits pass from one generation to the next.

The cell is the basic structural and functional unit of all living things.
DNA carries the genetic instructions for building and maintaining organisms.
Genes are segments of DNA that determine inherited traits.
The nucleus controls the cell's activities and stores its DNA.
Mitochondria are the powerhouses that produce energy for the cell.
Plant cells have a rigid cell wall that animal cells lack.
Chloroplasts in plant cells carry out photosynthesis.
Cells divide through a process called mitosis to grow and repair.
Proteins are built from chains of amino acids.
Chromosomes are tightly coiled structures made of DNA and proteins.
Humans typically have forty-six chromosomes in each body cell.
RNA helps translate genetic information into proteins.
Ribosomes are the cellular structures where proteins are assembled.
Mutations are changes in DNA that can be passed to offspring.
Bacteria are single-celled organisms lacking a true nucleus.
Offspring inherit one set of chromosomes from each parent.
The cell membrane controls which substances enter and leave the cell.
The cell membrane is composed mainly of a phospholipid bilayer.
Cytoplasm is the jelly-like fluid that fills the inside of a cell.
The endoplasmic reticulum transports materials throughout the cell.
Rough endoplasmic reticulum is studded with ribosomes that make proteins.
The Golgi apparatus modifies, sorts, and packages proteins for delivery.
Lysosomes contain enzymes that break down waste and worn-out cell parts.
Vacuoles store water, nutrients, and waste within a cell.
Plant cells often contain one large central vacuole for storage and support.
Centrioles help organize the spindle fibers during animal cell division.
The cytoskeleton gives the cell shape and supports internal movement.
Microtubules are hollow tubes that form part of the cytoskeleton.
Cilia are short hair-like projections that help move substances across cells.
Flagella are long whip-like structures used by some cells for movement.
The nucleolus inside the nucleus is the site of ribosome production.
The nuclear envelope is a double membrane surrounding the cell nucleus.
Nuclear pores allow molecules to pass between the nucleus and cytoplasm.
Eukaryotic cells contain a true nucleus and membrane-bound organelles.
Prokaryotic cells lack a nucleus and membrane-bound organelles.
Bacteria and archaea are the two main groups of prokaryotes.
Animal cells lack chloroplasts and cannot make their own food.
Photosynthesis converts carbon dioxide and water into glucose and oxygen.
Cellular respiration releases energy stored in glucose molecules.
ATP is the main energy-carrying molecule used by living cells.
Mitochondria have their own small ring of DNA separate from the nucleus.
Mitochondria are surrounded by a double membrane with inner folds called cristae.
Glycolysis breaks glucose into pyruvate within the cell cytoplasm.
The Krebs cycle takes place in the mitochondrial matrix.
Diffusion is the movement of particles from high to low concentration.
Osmosis is the diffusion of water across a semipermeable membrane.
Active transport moves substances against their concentration gradient using energy.
Passive transport moves substances without using cellular energy.
Endocytosis brings large particles into a cell by engulfing them.
Exocytosis releases materials from a cell using membrane-bound vesicles.
Phagocytosis is a form of endocytosis where cells engulf solid particles.
The cell wall in plants is made primarily of cellulose.
Fungal cell walls are made largely of a substance called chitin.
Stem cells can develop into many different specialized cell types.
Red blood cells carry oxygen and lack a nucleus in humans.
Neurons are specialized cells that transmit electrical signals through the body.
Muscle cells contain protein filaments that allow them to contract.
Cell differentiation is the process of cells becoming specialized for tasks.
Tissues are groups of similar cells working together for a function.
Organs are made of different tissues performing a common function.
The cell theory states that all living things are made of cells.
Robert Hooke first described and named cells in the year 1665.
Antonie van Leeuwenhoek observed living microorganisms with early handmade microscopes.
Matthias Schleiden concluded that all plants are made of cells.
Theodor Schwann proposed that all animals are made of cells.
Rudolf Virchow stated that all cells arise from pre-existing cells.
DNA stands for deoxyribonucleic acid, the molecule of heredity.
RNA stands for ribonucleic acid and helps express genes.
DNA has a double-helix structure resembling a twisted ladder.
James Watson and Francis Crick described the DNA double helix in 1953.
Rosalind Franklin's X-ray images were crucial to discovering DNA's structure.
DNA is built from repeating chemical units called nucleotides.
A nucleotide consists of a sugar, a phosphate group, and a base.
The four DNA bases are adenine, thymine, guanine, and cytosine.
Adenine always pairs with thymine in the DNA double helix.
Guanine always pairs with cytosine in the DNA double helix.
In RNA, the base uracil replaces thymine found in DNA.
RNA is usually single-stranded while DNA is typically double-stranded.
The sugar found in DNA molecules is called deoxyribose.
The sugar found in RNA molecules is called ribose.
Complementary base pairing allows DNA to be copied accurately.
DNA replication produces two identical copies of a DNA molecule.
DNA polymerase is the enzyme that builds new DNA strands.
Helicase unwinds the DNA double helix during replication.
The genome is the complete set of genetic material in an organism.
A gene codes for a specific protein or functional RNA molecule.
The genetic code is read in three-base units called codons.
Each codon specifies a particular amino acid or a stop signal.
Transcription copies a gene's DNA sequence into messenger RNA.
Translation builds a protein using the sequence in messenger RNA.
Messenger RNA carries genetic instructions from DNA to the ribosomes.
Transfer RNA brings amino acids to the ribosome during translation.
Ribosomal RNA is a major structural component of ribosomes.
The start codon AUG signals the beginning of protein synthesis.
Stop codons signal the end of protein synthesis at the ribosome.
There are twenty common amino acids used to build proteins.
Proteins fold into specific shapes that determine their biological function.
Enzymes are proteins that speed up chemical reactions in cells.
Each enzyme typically acts on a specific substrate molecule.
Mitosis produces two daughter cells that are genetically identical.
Interphase is the longest phase of the entire cell cycle.
During interphase the cell grows and copies its DNA.
Prophase is the first stage of mitosis when chromosomes condense.
Metaphase is the stage when chromosomes line up at the cell center.
Anaphase is the stage when sister chromatids separate to opposite poles.
Telophase is the stage when two new nuclei form during division.
Cytokinesis is the division of the cytoplasm into two separate cells.
Meiosis produces four sex cells that are genetically varied.
Meiosis reduces the chromosome number of a cell by half.
Gametes are the reproductive cells, such as sperm and egg.
Sperm and egg cells in humans each carry twenty-three chromosomes.
Fertilization combines two gametes to form a single zygote.
A zygote is the first cell of a newly forming organism.
Diploid cells contain two complete sets of chromosomes.
Haploid cells contain only a single set of chromosomes.
Crossing over during meiosis exchanges genetic material between chromosomes.
Homologous chromosomes carry the same genes in the same order.
Sister chromatids are identical DNA copies joined at a centromere.
The centromere is the region where sister chromatids are connected.
Gregor Mendel is widely considered the founder of modern genetics.
Mendel studied inheritance using pea plants during the 1860s.
An allele is one of the alternative forms of a gene.
A dominant allele masks the effect of a recessive allele.
A recessive allele is expressed only when two copies are present.
Genotype refers to the genetic makeup of an organism.
Phenotype refers to the observable physical traits of an organism.
Homozygous means having two identical alleles for a single gene.
Heterozygous means having two different alleles for a single gene.
A Punnett square predicts the likely outcomes of a genetic cross.
Mendel's law of segregation states that allele pairs separate during gamete formation.
Mendel's law of independent assortment describes how genes sort separately.
In codominance, both alleles are fully expressed in the phenotype.
Human ABO blood types are an example of multiple alleles.
Sex chromosomes determine the biological sex of an organism.
Human females typically have two X chromosomes in each cell.
Human males typically have one X and one Y chromosome.
Sex-linked traits are carried on the X or Y chromosomes.
Color blindness is a common X-linked recessive trait in humans.
Hemophilia is an inherited disorder that affects blood clotting.
A pedigree chart traces the inheritance of traits through families.
Polygenic traits are controlled by several different genes at once.
Human height and skin color are examples of polygenic traits.
A carrier has a recessive allele but does not show the trait.
Down syndrome results from an extra copy of chromosome twenty-one.
A point mutation changes a single nucleotide in a DNA sequence.
A frameshift mutation results from inserting or deleting nucleotides.
Silent mutations do not change the resulting protein at all.
Sickle cell anemia is caused by a single mutation in a hemoglobin gene.
Mutations can be caused by radiation, chemicals, or copying errors.
A mutagen is an agent that increases the rate of mutation.
Cystic fibrosis is an inherited disorder affecting the lungs and digestion.
Heredity is the passing of traits from parents to their offspring.
Variation refers to the differences among individuals in a population.
Asexual reproduction produces offspring genetically identical to the single parent.
Sexual reproduction combines genetic material from two different parents.
Binary fission is how bacteria reproduce by splitting in two.
Viruses are not cells and cannot reproduce on their own.
A virus consists of genetic material enclosed in a protein coat.
Viruses must infect a living host cell in order to replicate.
The chromosome number remains constant within a given species.
A karyotype is an organized display of an organism's chromosomes.
Genetic engineering involves altering an organism's DNA directly.
Recombinant DNA combines genetic material from two different sources.
Genetically modified organisms have had their DNA deliberately changed.
Restriction enzymes cut DNA at specific recognition sequences.
DNA ligase joins separate fragments of DNA together.
The polymerase chain reaction makes many copies of a DNA segment.
Gel electrophoresis separates DNA fragments by their size.
DNA fingerprinting can identify individuals from their unique genetic patterns.
Cloning produces an organism genetically identical to another organism.
Dolly the sheep was the first mammal cloned from an adult cell.
The Human Genome Project mapped all human genes by the year 2003.
CRISPR is a powerful tool used to edit specific sequences in DNA.
Gene therapy aims to treat disease by altering a patient's genes.
Insulin can be produced by genetically modified bacteria for medical use.
Selective breeding chooses parents with desirable traits over many generations.
Hybridization crosses two genetically different parents to produce offspring.
Epigenetics studies changes in gene activity without DNA sequence changes.
Gene expression determines which proteins a particular cell produces.
Some genes are switched on or off depending on the cell type.
Chromatin is the loose combination of DNA and proteins in the nucleus.
Histones are proteins around which DNA wraps to form chromatin.
Telomeres are protective caps located at the ends of chromosomes.
Telomeres become shorter each time a cell divides.
Apoptosis is the process of programmed and controlled cell death.
Cancer results from the uncontrolled division of abnormal cells.
Oncogenes are mutated genes that can contribute to causing cancer.
The cell cycle is regulated by checkpoints that ensure proper division.
Photosynthesis occurs in the chloroplasts of green plant cells.
Chlorophyll is the green pigment that captures light energy in plants.
Stomata are tiny pores in leaves that allow gas exchange.
Aerobic respiration requires oxygen to release energy efficiently.
Anaerobic respiration releases energy from glucose without using oxygen.
Fermentation is an anaerobic process that produces alcohol or lactic acid.
A protein's function depends largely on its three-dimensional folded shape.
Denaturation destroys a protein's shape and its biological function.
Carbohydrates are sugars and starches used by cells for energy.
Organelles are specialized structures that perform functions within a cell.
A single chromosome carries many different genes along its length.
Identical twins develop from a single fertilized egg that splits.

Learn this lesson, not just read it

Load these facts straight into the free Class Coupon Speed Learning app — they become fast, playful study activities with audio and translation in 100+ languages.

Get the Speed Learning app →