Study Notes: DNA replication, Types of Mutations, Natural & Artificial Selection Flashcards

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Mutation

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A mutation is any change in the DNA sequence of a gene or chromosome. Mutations can be harmful, neutral, or beneficial and may affect protein structure and organism traits.

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Substitution

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A substitution is a mutation where one nucleotide is replaced by another. This can change a single amino acid or be silent depending on the codon and may alter protein function.

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Insertion

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An insertion is a mutation that adds one or more nucleotide bases into DNA. Insertions often cause frameshifts, changing downstream codons and potentially producing nonfunctional proteins.

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Deletion

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A deletion removes one or more nucleotide bases from DNA. Like insertions, deletions can shift the reading frame and drastically alter the resulting protein.

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Frameshift

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A frameshift mutation occurs when insertions or deletions change the reading frame of codons. This typically alters every amino acid downstream and often yields a nonfunctional protein.

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Inherited mutation

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An inherited mutation is passed from parent to offspring through sex cells and is present in every cell of the organism. These mutations can affect traits across generations.

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Acquired mutation

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An acquired mutation arises during an individual's lifetime and may be caused by environmental factors or DNA replication errors. These are present only in some cells and usually are not inherited unless in sex cells.

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Jumping genes

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Jumping genes (transposable elements) are DNA sequences that can move to new genome locations. Their movement can change gene expression or disrupt genes, contributing to variation and evolution.

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DNA replication

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DNA replication is the process by which a cell makes an exact copy of its DNA before cell division. The double helix unwinds, each strand serves as a template, and complementary bases are added to form two identical molecules.

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Base pairing

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Base pairing rules state that adenine pairs with thymine (A–T) and cytosine pairs with guanine (C–G) in DNA. These rules ensure accurate complementary copying during replication.

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Template strand

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During replication, each original DNA strand acts as a template for a new complementary strand. This semiconservative process yields two DNA molecules each with one old and one new strand.

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When replication occurs

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DNA replication occurs before cell division so that each new cell receives an identical set of genetic instructions. It is essential for growth, repair, and replacement of cells.

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Natural selection

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Natural selection is the process where individuals with favorable heritable traits survive and reproduce more successfully. Over time, populations change as advantageous traits become more common.

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Artificial selection

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Artificial selection is when humans choose which individuals breed to promote desired traits. It accelerates changes across generations, as seen in domesticated crops and animals.

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Selective breeding

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Selective breeding is a technology of artificial selection where humans mate individuals with preferred traits to enhance those traits in future generations. Farmers and breeders have used it for thousands of years.

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Directional selection

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Directional selection favors individuals at one extreme of a trait distribution, causing the population's average trait value to shift. An example is pollution favoring larger fish in a population.

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Stabilizing selection

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Stabilizing selection favors average phenotypes and reduces extremes in a population. Human birth weight often shows stabilizing selection because average weights have higher survival.