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151 Cards in this Set

  • Front
  • Back
What are dendrites?
Cytoplasmic extensions that receive information and transmit it TOWARD the cell body (soma).
What is an axon?
A long cellular process that transmits impulses AWAY from the cell body (soma).
What is myelin? What is its function?
Myelin is an insulating substance that ensheaths most mammalian axons allowing axons to conduct impulses faster.
What are the two types of glial cells? What is their function?
Myelin is produced by cells known as glial cells.
Oligodendrocytes produce myelin in the CNS.
Schwann cells produce myelin in the peripheral nervous system.
What are synaptic terminals?
Axons end as swellings known as synaptic terminals.
Synaptic terminals release neurotransmitters into the synapse, or synaptic cleft, which is the gap b/t the axon terminals of one cell and of the dendrites of the next.
What is the resting potential of a neuron?
When a neuron is at rest, the potential difference b/t the extracellular space and the intracellular space is the resting potential.
At resting potential, is a neuron polarized?
Yes. Even at rest, a neuron is polarized. This potential difference is the result of an unequal distribution of ions b/t the inside and outside of the cell.
The inside of a neuron is more negative than the outside.
What creates the resting potential in a neuron?
The difference is due to ionic permeability of the neuronal cell membrane. It is maintained by the Na+/K+ pump (also called the Na+/K+ATPase).
The concentration of K+ is higher inside the cell, and the concentration of Na+ is higher outside the cell. Negatively charged proteins are also trapped inside the cell.
The resting potential is created b/c the neuron is selectively permeable to K+, so K+ diffuses down its concentration gradient, leaving a net negative charge inside.
The Na+/K+ pump transports howm much Na+ and K+ into and out of the cell?
The pump, using ATP energy, transports 3 Na+ out of the cell for every 2 K+ it transports into the cell.
The minimum level at which an action potential is initiated
The minimum threshold membrane potential
An action potential is generated when what process happens to the cell?
If the cell becomes sufficiently excited, or depolarized, an action potential is generated
If the inside of the cell becomes less negative, what process has occurred?
Describe how an action potential is generated
An AP begins when voltage-gated Na+ channels open in response to depolarization, allowing Na+ to rush down its electrochemical gradient into the cell, causing a rapid depolarization of that segment of the cell.
Voltage-gated Na+ channels then close, and voltage-gated K+ channels open, allowing K+ to rush out of the cell down its electrochemical gradient.
This returns the cell to a more negative potential, a process called repolarization.
If the cell shoots past the resting potential and becomes even more negative than normal, hyperpolarization has occurred.
Immediately following an AP, it may be very difficult or impossible to generate another AP, a period of time called the refractory period.
What is repolarization?
After depolarization, the voltage-gated Na+ channels close and voltage-gated K+ channels open, allowing K+ to rush out of the cell down its electrochemical gradient.
This returns to the cell to a more negative potential, a process called repolarization.
What is the all-or-none response.
Whenever the threshold membrane potential is reached, an AP w/ a consistent size and duration is produced.
Neuronal information is coded by the frequency and number of AP's rather than the size and duration of the AP's.
Connects the cell body of a neuron to the axon (nerve fiber)
Axon hillock
Describe how an impulse is propagated in a neuron
If there is an adequate stimulus, the AP will be initiated at the axon hillock.
Na+ rushes into the neuron and diffuses to adjacent parts of the axon, causing nearby voltage-gated Na+ channels to open (this occurs as previous segments are repolarizing). This chain of depolarization followed by a subsequent repolarization continues along the length of the axon.
What prevents the backward flow of the AP in an axon?
Synapses operate only in one direction b/c refractory periods make the backward travel of AP's impossible.
What is a synapse?
The gap b/t the axon terminal of one neuron (the presynaptic neuron) and the dendrites of another neuron (postsynaptic neuron).
What is a chemical synapse?
In chemical synapses, the nerve terminal contains thousands of membrane-bound vesicles full of chemical messengers called neurotransmitters.
How does a chemical synapse function?
When the AP arrives at the nerve terminal of a chemical synapse and depolarizes it, the synaptic vesicles fuse w/ the presynatpic membrane and release neurotransmitter into the synapse via a calcium-dependent process of exocytosis.
The neurotransmitter diffuses across the synapse and acts on receptor proteins embedded in the postsynaptic membrane.
The neurotransmitter can have a excitatory or inhibitory effect on the postsynaptic membrane.
How is a neurotransmitter removed from a synapse?
It may be taken up into the nerve terminal via a protein known as an uptake carrier where it may be degraded or reused.
It may be degraded by enzymes located in the synapse, or it may simply diffuse out of the synapse.
Afferent neurons
Sensory neurons
Efferent neurons
Motor neurons
Cell bodies in the brain are termed what?
Gray matter
Myelinated axons in the brain are termed what?
White matter
3 divisions of the brain
Forebrain, midbrain, hindbrain
The forebrain consists of what 2 divisions?
What processes is the cerebral cortex invovled in? Where is it located?
The cerebral cortex is the major component of the telencephalon in the forebrain.
The cortex process and integrates sensory input and motor responses and is important for memory and creative thought.
Right and left cerebral cortices communicate w/ eath other through the corpus callosum.
What processes is the thalamus invovled in? Where is it located?
The thalamus is a division of the diencephalon in the forebrain.
It is a relay and integration center for the spinal cord and cerebral cortex.
What process is the hypothalamus involved in? Where is it located?
The hypothalamus is a division of the diencephalon in the forebrain.
It controls visceral functions such as hunger, thirst, sex drive, water balance, b/p, and temperature regulation.
It also plays an important role in the control of the endocrine system.
What processes is the midbrain involved in?
The midbrain is a relay center for visual and auditory impulses.
It also plays an important role in motor control.
What are the 3 divisions of the hindbrain?
What processes is the cerebellum involved in? Where is it located?
The cerebellum is located in the hindbrain.
It helps to modulate motor impulses initiated by the motor cortex and is important in the maintenance of balance, hand-eye coordination, and the timing of rapid movements.
What is the function of the pons?
Located in the hindbrain, the pons acts as a relay center to allow the cortex to communicate w/ the cerebellum.
What is the function of the medulla? Where is it located?
The medulla (also medulla oblongata) is located in the hindbrain.
It controls many vital functions such as breathing, heart rate, and gastrointestinal activity.
What composes the brainstem?
Together, the midbrain, pons, and medulla constitute the brainstem.
What are the 4 regions of the spinal cord, proceeding from the brainstem to the tail?
The peripheral nervous system (PNS) consists of how many pairs of nerves?
12 pairs of cranial nerves which primarily innervate the head and shoulders. Exit from the brainstem
31 pairs of spinal nerves, which innervate the rest of the body. Exit from the spinal cord.
What are the 2 primary divisions of the PNS?
Somatic nervous system
Autonomic nervous system
Describe the somatic nervous system (SNS)
The SNS innervates skeletal muscles and is responsible for voluntary movement.
The SNS is also important for reflex action.
There are both monosynaptic and polysynaptic reflexes.
Motor neurons releases the neurotransmitter acetylcholine (ACh) into ACh receptors located on skeletal muscle.
What neurotransmitter do motor neurons in the SNS release? What effect does this have?
Motor neurons release acetylcholine (ACh) onto ACh receptors located on skeletal muscle.
This causes depolarization of skeletal muscle, leading to muscle contraction.
What is a monosynaptic reflex?. What is an example?
Monosynaptic reflex pathways have only one synapse b/t the sensory neuron and the motor neuron.
A classic example is the knee-jerk reflex.
What is a polysynaptic reflex? What is an example?
In polysynaptic reflexes, sensory neurons synapse w/ more than one neuron.
A classic example is the withdrawal reflex (When a person steps on a nail, the injured leg withdraws in pain, while the other leg extends to retain balance).
Describe the autonomic nervous system (ANS)
Regulates the body's internal enviroment w/o the aid of concious control, so sometimes called the involuntary nervous system.
The ANS innervates cardiac and smooth muscle.
ANS pathways are characterized by a two-neuron system.
2 subdivisions, the sympathetic and parasympathetic nervous systems.
Describe the sympathetic nervous system
A division of the ANS, it is responsible for the "fight or flight" responses that ready the body for action.
Increases b/p and heart rate and increases blood flow to skeletal muscles.
Preganglionic sympathetic neurons cause the adrenal medulla to releases epinephrine into the bloodstream.
Postganglionic neurons typically release norepinephrine.
Acetylcholine is used as a neurotransmitter.
Describe the parasympathetic nervous system
Acts to conserve energy and restore the body to resting activity levels following exertion
"Rest and digest"
Lowers heart rate.
One very important parasympathetic nerve is the vagus nerve which innervates many throacic and abdominal viscera.
Parasympatetic neurons origniate in the brainstem (cranial nerves) and the sacral part of the spinal cord.
Both preganglionic adn postganglionic neurons release acetylcholine.
What 3 types of sensory receptors does the body contain?
What is the function of interoceptors?
Interoceptos monitor aspects of the internal enviroment such as b/p, the partial pressure of carbon dioxide in the blood, and blood pH.
What is the function of proprioceptors?
Proprioceptors transmit information regarding the position of the body in spces.
Located in muscles and tendons to tell the brain where the limbs are in space and in the inner ear to tell the brain where the head is in space.
What is the function of exteroceptors?
Sense things in the external enviroment such as light, sound, taste, pain, touch, and temperature.
What is the thick, opaque layer that covers the eyeball (white of the eye)?
Describe the structure of the eye
The eyeball is covered by the sclera (white of the eye)
Beneath the sclera is the choroid layer, which helps to supplyh the retina w/ blood.
The innermost layer of the eye is the retina.
The transparent cornea is located at the front of the eye and bends and focuses light rays which travel through an opening called the pupil.
What is the function of the iris?
The muscular, pigmented iris controls the diameter of the pupil.
What is the function of the ciliary muscles?
Controls the shape of the lens.
What are the main types of photoreceptors in the eye?
Cones - respond to high intensity illumination and are sensitive to color.

Rods - Detect low intensity illumination and are important in night vision.
The cones contain 3 pigments that absorb what color wavelengths?
What is the blind spot of the eye?
The point at which the optic nerve exits the eye.
Called the blind spot b/c no photoreceptors are present there..
What is the fovea?
A small area of the retina that is densely packed w/ cones and is important for high acuity vision.
Trace the pathway of sound through the ear
Sound waves enter the auditory canal of the outer ear.
At the end of the auditory canal is the tympanic membrane, or eardrum of the middle ear. This membrane vibrates at the same frequency of the incoming sound.
Next, the three ossicles amplify the stimulus and transmit it through the oval window which leads to the fluid-filled inner ear.
Vibration of the ossicles exerts pressure on the fluid in the cochlea, stimulating the hair cells to transduce the pressure into AP's, which travel via the cochlear (auditory) nerve to the brain for processing.
What are the structures of the inner ear? What is their function?
The inner ear consists of the cochlea and the semicircular canals.
The cochlea contains the Organ of Corti, which has sensory cells called hair cells.
Vibration of the ossicles exerts pressure on the fluid in the cochlea, stimulating the hair cells to transduce the pressure into AP's.
What are the ossicles? What is their function?
Three bones, the malleus, incus, and stapes, that amplify the sound stimulus and transmit it through the oval window to the fluid-filled inner ear.
How does the ear function in the maintanence of equilibrium (balance) of the body?
The 3 semicircular canals are filled w/ a fluid called endolymph.
At the base of each canal is a chamber w/ sensory hair cells. Rotation of the head displaces endolymph in one of the canals, putting pressure on theh air cells in it.
This changes the nature of impulses sent by the vestibular nerve to the brain, which interprets this info to determine the position of the head.
What are the chemical senses?
Taste and smell
The chemical senses transduce chemical changes in the enviroment. Where specifically does this happen in the body? What types of sensory impulses do the generate?
The chemical senses, taste and smell, transduce chemical changes in the enviroment, specifically in the mouth and nose.
They transduce these changes into gustatory and olfactory sensory impulses, which are interpreted by the nervous system.
What is cleavage in terms of embryonic development?
Early embryonic development is characterized by a series of rapid mitotic divisions known as cleavage.
These divisions lead to an increase in cell number without a corresponding growth in cell protoplasm (the total volume of cytoplasm remains constant).
What is the results of cleavage?
Cleavage results in progressively smaller cells, w/ an increasing ratio of nuclear-to-cytoplasmic material.
Also increases the surface-to-volume ratio of each cell, thereby improving gas and nutrient exchange.
What is an indeterminate cleavage?
Cleavage that results in cells that maintain the ability to develop into a complete organism.
Identical twins are the result of an indeterminate cleavage.
What is determinate cleavage?
A cleavage that results in cells whose future differentiation pathways are determined at an early developmental stage.
(Differentiation is the specializaition of cells that occurs during development).
When do the cleavages of the zygote occur?
The first complete cleavage occurs approx. 32 hours after fertilization.
Second cleavage occurs after 60 hours.
Third cleave after approx. 72 hours, at which point the 8-celled embryo reaches the uterus.
What is a morula?
A solid ball of embryonic cells that is formed as cell division continues following the first 3 cleavages of the zygote.
What is blastulation?
Blastulation begins when the morula develops a fluid-filled cavity called the blastocoel, which by the 4th day becomes a hollow sphere of cells called the blastula.
What is a blastocyst? What does it consists of?
The mammalian blastula is called a blastocyst.
Consists of 2 cell groups: the inner cell mass and the trophoblasts.
The inner cell mass protrudes into the blastocoel.
The trophoblast surrounds the blastocoel and later gives rise to the chorion.
What is blastulation? When does it occur?
The embryo implants in the uterine wall during blastulation, approx. 5-8 days after fertilization.
What hormone prepared the uterus for implantation?
What is the gastrula?
Once implanted, cell migrations transform the single-cell layer of the blastula into a three-layered structure called a gastrula.
What is gastrulation?
The transformation of the single-cell layer of the blastula into a 3-layered structure called a gastrula.
An inpocketing forms as cells continue to move toward the invagination, eventually eliminating the blastocoel.
Results in a 2-layered cup, w/ the outer layer called the ectoderm, and an inner cellular layer called the endoderm.
The newly formed cavity of the gastrula is called the archenteron, which later develops into the gut.
Proliferation and migration of cells intot he space b/t the ectoderm and endoderm gives rise to the mesoderm.
What are the 3 primary germ layers? What is their function?
These germ layers are responsible for the differential development of the tissues, organs, and systems of the body at later stages of growth.
What structures develop from the ectoderm?
Integumentary - includes the epidermis, hair, nails, and epithelium of the nose, mouth, and anal canal.)
Lens of the eys
Nervous system
What structures develop from the endoderm?
The epithelial linings of the digestive and respiratory tracts (including the lungs).
Parts of the liver, pancreas, thyroid, and bladder.
What structures develop from the mesoderm?
Musculoskeletal system, circulatory system, excretory system, gonads.
Connective tissues throughout the body.
Portions of the digestive and respiratory organs.
All embryonic cells are derived from a single zygote and therefore have the same DNA. So how do cells and tissues differentiate to perform their specialized functions?
Most differentiation is accomplished through selective transcription of the genome.
As the embryo develops, different tissue types express different genes.
(Most of the genetic info w/in any given cell is never expressed)
What is induction in terms of embryonic development?
The influence of a specific group of cells, sometimes known as the organizer, on the differentiation of another group of cells.
Most often mediated by chemical substances called inducers which are passed from the organizer to adjacent cells.
What is neurulation?
By the end of gastrulation, regions of the germ layers begin to develop into a rudimentary nervous system ina process known as neurulation.
Describe neurulation
The notochord, a rod of mesodermal cells, develops along the longitudinal axis just under the dorsal layer of the ectoderm.
The notocord causes the overlying ectoderm to bend inward and form a groove along the dorsal surface of the embryo w/ the dorsal ectoderm folding on either side.
These neural folds grow upward and fuse forming a closed tube.
This is the neural tube which gives rise to the CNS.
Once the neural tube is formed, it detaches from the surface ectoderm.
The cells at the tip of each neural fold are called the neural crest cells. These cells give rise to many components of the PNS, including the sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells.
What gives rise to the brain and spinal cord (the CNS)?
The neural tube which is formed during neurulation.
What gives rise to many of the components of the PNS?
Neural crest cells.
Give rise to sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells.
When is the embryo referred to as a fetus?
After 8 weeks of gestation
What are the components of the fetal respiration system?
Umbilical cord
(Both of these structures develop in the first few weeks following fertilization)
What are the extra-embryonic membranes formed during development?
Yolk sac
What is the amnion?
A thin, tough membrane containing a water fluid called amniotic fluid which acts as a shock absorber of external and localized pressure from uterine contractions during labor.
What is the chorion?
Membrane that completely surrounds the amnion.
About 2 weeks after fertilization, the chorion extends villi into the uterine wall.
These chorionic villi become closely associated w/ endometrial cells, developing into the spongy tisse of the placenta.
What is the allantois?
Extra-embryonic membrane that develops as an outpocketing of the gut.
The blood vessels of the allantoic wall enlarge and become the umbilical vessels, which will connect the fetus to the developing placneta.
What is the umbilical cord? What does it develop from?
The allantois and yolk sac are eventually enveloped by the amnion, forming the primitive umbilical cord, the initial connection b/t the fetus and placenta.
The mature umbilical cord consists of the umbilical vessels, which developed fromt eh allantoic vessels, surrounded by a jellylike matrix.
What is the site of nutrition, respiration, and waste disposal for the fetus?
The placenta
How does fetal hemoglobin (Hb-F) compare to adult hemoglobin (Hb-A)?
Hb-F has a greater oxygen affinity than Hb-A does. Therefore, oxygen preferentially diffuses into fetal blood.
Concurrently, metabolic wastes and carbon dioxide diffuse in the opposite direction, from fetal blood into the maternal blood.
Are the circulatory systems of the mother and fetus connected?
Not directly, so maternal and fetal blood do not mix
Where does gas exchange in the fetus occur?
Across the placenta.
Fetal lungs do not become functional until birth.
How does the placenta function as an endocrine gland?
The placenta produces the hormones progesterone, estrogen, and human chorionic gonadotropin (hCG) which are all essential for maintaining a pregnancy.
How does fetal circulation differ from adult circulation?
The major difference is that in fetal circulation, blood is oxygenated in the placenta (fetal lungs are nonfunctional prior to birth) while in adults, blood is oxygenated in the lungs.
The fetal circulatory route contains 3 shunts that divert blood flow away from the developing fetal liver and lungs.
Fetal circulation can be considered the opposite of adult circulation. Why?
Umbilical veins carry oxygenated blood from the placenta to the fetus.
Umbilical arteries carry deoxygenated blood back to the placenta.
Human pregnancy
What are the divisions of gestation?
3 trimesters
What happens during the first trimester of gestation?
During the first weeks, major organs begin to develop.
Heart begins to beat at approx. 22 days.
Soon after, the eyes, gonads, limbs, and liver start to form.
Cartilaginous skeleton begins to turn into bone by the 7th week.
By 8 weeks, most organs have formed, the brain is fairly developed, and the embryo is now a fetus.
What happens during the 2nd trimester?
The fetus does a tremendous amount of growing.
By the end of the 6th month, the fetus is 30-36 cm long.
What happens during the third trimester?
7th and 8th months are characterized by rapid growth and further brain development.
During the 9th month, antibodies are transported by highly selective active transport from the mother to the fetus for protection against foreign matter.
Describe the 3 stages of labor.
First stage - cervix thins out and dilates, amniotic sac ruptures. Contractions are mild.
Second stage - Rapid contractions, resulting in the birth of the baby.
Third stage - Uterus contracts expelling the placenta and the umbilical cord.
What are alleles?
Alternate forms of a gene.
What is a genetic testcross, or backcross?
An organism w/ a dominant phenotype of unknown genotype (Ax) is crossed w/ a phenotypically recessive organism (aa).
In a testcross, the appearance of the recessive phenotype in the progeny indicates that the phenotypically dominant parent is genotypically heterozygous.
Can be used to determine the unknown genotype of an organism w/ a dominant phenotype.
What is Mendel's Law of Independent Assortment?
The alleles of unlinked genes assort independently during meiosis.
The principles of the monohybrid cross can be extended to a dihybrid cross in which the parents differ in two traits, as long as each trait assorts independently.
If the genotype TTPP is crossed with the genotype ttpp (TTPP x ttpp), what will be the resulting genotype(s)?
100% TtPp
In diploids (species that have chromosome pairs) the alleles for a given trait are segregated. What does this mean?
One allele is located on one chromosome, and the other allele is found on its homologue.
How does Mendelian segregation and independent assortment occur?
It is the consequence of chromosomal behavior during meiosis.
Prior to meisos, each chromosome is replicated, but the daughter copy remains attached to the parental chromosome via the centromere, forming sister chromatids.
The sister chromatids pair w/ their homologues and align at the equatorial plate during metaphase 1.
During the first meiotic division, the homologous pairs separate and following cytokinesis, the number of chromosomes per cell is reduced from 2N to N.
This is when segregation and independent assortment occur.
Each gamete receives the haploid (N) complement of chromosomes (one sister chromatid from every homologous pair).
The fusion of 2 gametes during fertilization restores the diploid number, 2N.
When does segregation and independent assortment occur?
During the first meiotic division, the homologous pairs separate and following cytokinesis, the number of chromosomes per cell is reduced from 2N to N.
This is the step in meiosis during which segregation and independent assortment occur.
What is nonindependent assortment?
Not all traits assort independently in a dihybrid cross.
Can be due to genetic linkage, or when two genes are linked (located on the same chromosome and inherited together).
What is genetic linkage?
When two genes are linked, or located on the same chromosome. Usually inherited together.
Can lead to nonindependent assortment.
Genetic linkage is a direct result of the organization of genes along chromosomes. Linked genes are located on the same chromosome.
How does the degree of genetic linkage affect recombination
If the degree of linkage is tight and complete, no recombinant phenotypes. Tightly linked genes recombine at a frequency close to 0%.
If degree of linkage is weak, the number of recombinants in the F1 progeny approaches the number expected from independent assortment. Weakly linked genes recombine at frequencies approaching 50%.
What are recombinant chromosomes?
Linked genes can recombine to produce recombinants.
The recombinant chromosomes arise through physical exchange of DNA b/t homologoues chromosomes during meiosis, a process called crossing over or genetic recombination.
Crossing over can unlink linked genes.
What process can unlink linked genes?
Crossing over, or genetic recombination.
What is meant by the degree of genetic linkage?
The degree of genetic linkage is a measure of how far apart 2 genes are on the same chromosome.
The probability of a crossover and exchange occuring b/t 2 points is directly proportional to the distance b/t the points.
For example, pairs of genes that are far apart on a chromosome have a higher probability of being separated during crossing over.
When does crossing over occur?
When the homologous chromosomes pair up into tetrads during prophase 1.
What is incomplete dominance?
An allele is incompletely dominant if the phenotype of the heterozygote is an intermediate of the phenotypes of the homozygotes.

Homozygous red crossed w/ homozygous white producing 100% pink progeny.
What is codominance?
Codominance occurs when multiple alleles exist for a given gene and more than one of them is dominant.
ABO blood groups in humans is a classic example.
What determines the gender of a zygote?
The genetic contribution of the male gamete
Examples of sex-linked (X chromosome) recessives in humans are the genes for hemophilia and color blindness. What are these genes much more frequently found in males?
Females have 2 X chromosomes, and males have only one. Therefore, recessive genes on the X chromosome will produce the recessive phenotypes whenever they occur in males, since no dominant allele is present to mask them. Thus, the recessive phenotype will be much more frequently found in males.
What chromosome are sex-linked genes usually found on?
X chromosome
What is a pedigree?
A family tree depicting the inheritance of a particular genetic trait over several generations.
Conventionally, males are indicated by squares and females by circles.
When analyzing a pedigree, look for the recessive phenotype (you'll know the genotype, must be homozygous recessive) and work from there. If only males are affected, suspect sex linkage.
What is nondisjunction?
Either the failure of homologous chromosomes to separate properly during meiosis 1 or the failure of sister chromatids to separate properly during meiosis 2.
What is trisomy?
3 copies of a chromosome
Somatic cells will have 2N+1 chromosomes.
What chromosomal breakage?
When a chromosome loses a fragment.
May occur spontaneously or be induced by enviromental factors, such as mutagenic agents or X-rays.
The chromosome that loses a fragment is said to have a deficiency.
Fragment may join w/ its homologous chromosome, resulting in a duplication.
It may join w/ a nonhomologous chromosome, an event termed translocation.
May also rejoin its original chromosome but in the reverse position, called inversion.
What is the basic unit of DNA?
Nucleotides - composed of deoxyribose (a sugar) bonded to both a phosphate group and a nitrogenous base.
How is DNA unwound?
The enzyme helicase unwinds the helix.
Single-strand binding protein (SSB) binds to the single strands and stabilized them.
DNA gyrase enhances the action of helicase by the introduction of negative supercoild into the DNA.
What is the function of primase?
Primase is an RNA polymerase that synthesizes the primer, which binds to a segment of DNA to which it is complementary and serves as the site for nucleotide addition.
The first nucleotide binds to the 3' end of the primer chain.
What is the function of DNA polymerase?
Catalyzes DNa synthesis.
How is RNA different from DNA?
Sugar is ribose
Contains uracil instead of thymine
Single stranded
What is the function of mRNA?
Carries the complement of a DNA sequence and transports it from the nucleus to the ribosomes, where protein synthesis occurs.
One mRNA strand codes for one polypeptide.
What is the functiono of tRNA?
Found in the cytoplasm, tRNA aids in the translation of mRNA's nucleotide code into a sequence of amino acids.
tRNA brings amino acids to the ribosomes during protein synthesis.
At least one type of tRNA for each amino acid.
What is the function of rRNA?
A structural component of ribosomes and the most abundant of all RNA types.
Synthesized in the nucleous.
What is transcription?
Process where info coded in the base sequence of DNA is transcribed into a strand of mRNA.
The strand of mRNA is synthesized from a DNA template in a process similar to DNA replication.
How is mRNA synthesized?
mRNA is synthesized by the enzyme RNA polymerase.
RNA polymerase binds to sites on the DNA called promoters to begin RNA synthesis.
Synthesis continues until the polymerase encounters a termination sequence.
mRNA then leaves the nucleus through nuclear pores.
Coding sequences in a gene are termed what?

EXons are EXpressed!!
Noncoding sequences in a gene are termed what?

INtrons are cut OUT!!
RNA processing occurs where?
In the nucleus.
What is translation?
Processs where mRNA codons are translated into a sequence of amino acids.
Occurs in the cytoplasm.
What is a point mutation?
Occurs when a single nucleotide base is substituted by another.
If the substitution occurs in a noncoding region, or if the substitution is transcribed into a codon that codes for the same amino acid, there will be no change in the amino acid sequence called a silent mutation.
Point mutations do not result in a change of length of the genome of gene. POINT MUTATIONS ARE ALWAYS JUST SUBSTITUTIONS!!
What are frame shift mutations?
The addition or loss of a nucleotide(s) (except in multiples of three) will change the reading frame of the mRNA and is known as a frameshift mutation.
The protein, if synthesized at all, will most likely be nonfunctional.
What is mutagenesis?
Mutagenesis is the creation of mutations.
Can be caused by internal genetic "mistakes" or by external, cancer-causing agents called mutagens.
Mobile pieces of DNA called transposons can insert themselves in genes and cause mutation.
A mutation will only be inherited if it occurs in the germ (sex) cell line.
What are transposons?
Mobile pieces of DNA that can insert themselves in genes and cause mutation.
What must be present for a virus to infect a cell?
A surface receptor for the virus' capsid (protein coat) must be present.
What are retroviruses?
A special group of RNA viruses that use their genome as a template for DNA synthesis rather than for RNA synthesis.
DNA is synthesized by the enzyme reverse transcriptase.
The retroviral DNA becomes integrated into the host DNA
What is the term for when viral DNA becomes integrated into host DNA?
Provirus for animal viruses

Prophage for bacterophages