What is mitosis and why do cells undergo it?

Mitosis is a type of cell division that produces two genetically identical daughter cells — it is used for growth, tissue repair, and replacing worn-out cells Mitosis produces four genetically unique cells and is used to make sperm and eggs Mitosis only occurs in plants — animals use a different type of cell division Mitosis is the process by which cells produce energy from glucose

What is meiosis and how does it differ from mitosis?

Meiosis produces four genetically unique sex cells (gametes) each with half the normal chromosome number — it introduces genetic variation through recombination and random assortment Meiosis is another name for mitosis — both produce two identical daughter cells Meiosis occurs in all cells for normal growth and repair Meiosis produces one large egg cell and three smaller cells that are discarded

What is a protein and why are proteins so important?

Proteins are large molecules made of chains of amino acids folded into specific 3D shapes — they carry out nearly every biological function: enzymes catalyze reactions, structural proteins build tissues, hormones signal between cells, antibodies fight infection Proteins are the primary energy source for cells — they are burned like fuel in mitochondria Proteins store genetic information — each protein contains one copy of a gene Proteins are only found in animal cells — plant cells use carbohydrates instead

What is a mutation?

A mutation is a change in the DNA sequence — it can be a substitution (one base changed), insertion (extra bases added), or deletion (bases removed), and may be harmless, beneficial, or harmful A mutation is always harmful and causes cancer or genetic disease A mutation only occurs in cancer cells — healthy cells never have DNA changes Mutations are deliberate changes made by the cell when it needs to adapt to a new environment

What is the difference between a genotype and a phenotype?

Genotype is the actual DNA sequence (the genetic instructions); phenotype is the observable physical result (appearance, behavior, biochemistry) — the same genotype can produce different phenotypes depending on the environment Genotype refers to appearance; phenotype refers to the underlying genetic code Genotype and phenotype are identical — what is in the DNA is always expressed Genotype is determined by the environment; phenotype is set at birth by DNA

How does a single fertilized egg become a complex human body?

Through repeated cell division (mitosis) and differentiation — all cells share the same DNA, but gene expression differs by cell type, producing over 200 specialized cell types from the same genome Different cells contain different DNA — nerve cells have nerve genes, muscle cells have muscle genes The fertilized egg divides differently depending on which body part it will become — left-side cells go on to form the left side of the body Cell differentiation happens only during puberty when the body undergoes major changes

What is genetic variation and why does it matter?

Genetic variation is the differences in DNA sequences between individuals of the same species — it is the raw material for natural selection and allows populations to adapt to changing environments Genetic variation is always harmful — it leads to disease and reduced fitness Genetic variation only occurs between different species, not within a species Genetic variation is caused only by environmental factors, not by DNA changes

What causes siblings to look different from each other even though they have the same parents?

Each parent has two copies of every chromosome — during meiosis, random assortment and crossing over mean each egg and sperm carries a unique combination, so siblings inherit different subsets of their parents' genetic variants Siblings look different because they receive mutations from the environment that change their DNA after birth Parents always pass down the same genes to all their children — differences come from nutrition Siblings look different because the second child always inherits recessive traits from both parents

What makes every living thing on Earth unique?

The specific sequence of DNA bases in an organism's genome — even a single base difference distinguishes one individual from another, and the combinations of variants are astronomically large Every organism is unique because no two organisms can ever eat exactly the same food Organisms are not truly unique — all members of a species have identical DNA Uniqueness comes entirely from the environment — genetics is the same for everyone

What is the 'central dogma' of molecular biology?

The central dogma describes the flow of genetic information: DNA is transcribed into RNA, which is translated into protein — information flows from DNA to RNA to protein, not in reverse The central dogma states that all life evolved from a single common ancestor The central dogma states that proteins are more important than DNA in controlling cell behavior The central dogma describes how chromosomes pass from parent to offspring during reproduction