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• What is genetic variation?


  The genetic difference between individuals that contributes to a species’ adaptation to its environment.
• How many chromosomes do the egg and sperm each contain?


  23 chromosomes each.
• What determines the sex of the offspring?

  The Y chromosome from the sperm cell determines the sex of the offspring.
• What are traits?


  Visible characteristics controlled by genes, such as eye color and hair color.
• What is an allele?


  A specific version of a gene that affects a trait.
• What is the difference between genotype and phenotype?


  Genotype is the genetic makeup, while phenotype is the inherited physical characteristics.
• What is a dominant allele?


  An allele that expresses a trait even when only one copy is present.
• What is a recessive allele?


  An allele that does not produce a trait when only one copy is present.
• What does polygenic mean?


  Traits controlled by more than one gene.
• What is a mutation?


  A sudden, permanent change in a gene.
• What are the three types of gene-environment interactions?


  Passive, evocative, and active gene-environment correlations.
• What does the range of reaction assert?


  Genes set boundaries for potential, influenced by the environment.
• What is epigenetics?


  The study of how the same genotype can be expressed in different ways.
• How do identical twins develop?


  From a single fertilized egg that splits.
• What is the primary function of the nervous system?


  To send messages back and forth between the brain and the body.
• What are glial cells?


  Cells that support neurons by providing insulation and nutrients.
• What is the function of the myelin sheath?


  To insulate axons and speed up neural impulse transmission.
• What are neurons?


  Specialized cells for transmitting information in the form of electrical impulses.
• What is a nerve?


  A bundle of axons from different neurons.
• What is the soma of a neuron?


  The cell body where the nucleus is located.
• What are dendrites?


  Input sites where signals are received from other neurons.
• What is the function of terminal buttons?


  To release neurotransmitters that carry neural messages to adjacent neurons.
• What are neurotransmitters?


  Chemical messengers of the nervous system.
• What is the role of receptors in neurons?


  Proteins on the cell surface where neurotransmitters attach.
• What do sensory neurons do?


  Transmit information about the outside world to the spinal cord and brain.
• What is the function of motor neurons?


  Convey messages from the brain and spinal cord to the muscles and glands.
• What are interneurons?


  The most common type of neuron that connects neurons to neurons.
• How do neurons communicate?


  Through an electrochemical event involving ion movement.
• What is resting potential?


  The state of a neuron when it is not active, about -70 mV.
• What happens during depolarization?


  Positively charged sodium ions rush into the cell, making it less negatively charged.
• What is action potential?


  The rapid change in electrical charge from negative to positive in a neuron.
• What is repolarization?


  The process of a neuron returning to its resting state after firing.
• What is hyperpolarization?


  When the cell becomes more negative than its resting state.
• What is the refractory period?


  The temporary state when a neuron is unable to fire again after an action potential.
• What is a synapse?


  The tiny gap that separates one neuron from another.
• What are excitatory effects of neurotransmitters?


  They make an action potential more likely to occur.
• What are inhibitory effects of neurotransmitters?


  They make an action potential less likely to occur.
• What is reuptake?


  The process of recycling excess neurotransmitters in the synapse.
• What is the role of enzymes in the synapse?


  To break down neurotransmitters for elimination from the body.
• What is the function of acetylcholine?


  Involved in muscle action and memory.