Anatomy and Physiology: Nervous System and Reproductive System, Lecture notes of Earth science

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CHAPTER 1: BODY REGULATION

Functions of Nervous system and Neurons

The nervous system is involved in most body functions. Some function of the nervous system are:

1. Gathers information from both inside and outside the body.
2. Transmits information to the processing areas of the brain and spine.
3. Process the information in the brain and spine.
4. Sends information to the muscles, glands and organs so they can respond appropriately. The nervous system divided into two divisions: **1. Central nervous system (CNS)
5. Peripheral nervous system (PNS) Stimuli** - is one of the many functions of the nervous system, anything that evokes a person reaction is called a “stimulus”. Homeostasis - is the body’s ability to maintain constant internal equilibrium by adjusting its physiological process. NEURON - is the basic cellular unit of the nervous system. It transmits impulses to and from the various parts of the body. Three types of neurons:
6. Sensory (afferent) neurons - receives information and send impulses to the spinal cord or the brains
7. Interneurons- which are scattered throughout the brain and the spinal cord. relay impulses or information from the sensory neurons to the motor neurons.
8. Motor (efferent) neurons- conduct impulses from the brain or the spinal cord to the muscles or glands throughout the body. Synapse - to move from one neuron to another, a message or impulse jumps across. Neurotransmitters - chemicals that help in transporting messages.

Neurons contain Nissl bodies the body sites of protein synthesis

and other important processes. Axon - which transmits impulses to motor neurons. Myelin sheath - which surrounds the axon, varies in thickness depending on its corresponding function, makes the axon look gray. Nerve fiber- is composed of an axon and its myelin sheath

outside the CNS it is surrounded by neurilemma.

Fiber tract - is made of bundled nerve fibers that are expanded to certain distance along the spinal cord and brain. Nerve - composed of bundles if nerve fibers outside the CNS surrounded

by the epineurium, a fibrous sheath of cells. Dendrites- shorter

extension of the cell body, receive stimulus and carries it impulses toward the cell body.

Transmission of Nerve Impulses Nerve impulse are

transmitted from one neuron to another through a synapse.  An axon splits into multiple branches upon approaching a synapse.  These branches terminate into a synaptic knob that is connected to another axon, a dendrite, or a cell body.  Hormonal secretions of

acetylcholine, melatonin, and

serotonin enable the

propagation of nerve impulses from the synapse.  Acetylcholine- carries signal from motor neurons to the body’s skeletal muscles  Norepinephrine - plays an important role in hoe your body responds to stress.  Dopamine- is related to muscular activity  Serotonin operates in bodily functions such as mood regulations, consciousness, and emotions.  Melatonin- regulates sleep and weak cycles. The Reflex

A Reflex is an involuntary and automatic response to a stimulus.

Sensory Receptors in your skin respond to the hot pan by sending an impulse to the spinal cord. The impulse passes to the interneurons in the spinal cord and sends an immediate response to the motor neurons to the muscles of your hand through a pathway called reflex arc so that you can remove your hand immediately without waiting for any command from the brain. DIVISION OF NERVOUS SYSTEM

• The major division of nervous system are Central nervous

system and Peripheral nervous system

A. CENTRAL NERVOUS SYSTEM

• Is composed of the brain and the spinal cord. BRAIN ▪ consists of about 100 billion neurons that do not regenerate once destroyed.

▪ The brain is protected by skull, while the spinal cord is

protected by vertebral column.

▪ These two structures are covered by the three layers of

membranes called meninges.

▪ The cerbrospinal fluid bathes the CNS and cushions it from bumps and thuds.

SPINAL CORD

▪ The spinal cord is a large, ropelike segment of nerve tissue extending from the medulla oblongata to the vertebral column. ▪ It serves as the connector mechanism for spinal reflexes and the connecting link between your peripehral nervous system and your brain. ▪ Through this, sensory and motor information pass through your brain and the other parts of your body. B. PERIPHERAL NERVOUS SYSTEM

• it helps the Central Nervous System to communicate to the rest of the body. It is made up Cranial nerves (12 pairs of nerve) attached to the undersurface of the brain and Spinal nerves ( 31 pairs of nerves) attached to the spinal cord **Two divisions of the PNS:

1. Somatic nervous system (voluntary** )
   • relays information from skin, sense organs, and muscles to CNS.
   • brings responses back to skeletal muscles for responses. 2. Autonomic nervous system ( involuntary )
   • regulates involuntary body functions such as breathing, urination, heartbeat, digestion, and salivation.
   • relays information to internal organs.

• DIVIDED INTO TWO DIVISIONS: a) Sympathetic nervous system (fight or flight response)  in times of emergency response of fight or flight - by increasing blood flows in areas that are most likely to be used during emergency.  decrease blood flow to kidney and digestive tract. b) Parasympathetic nervous system (rest and digest)  opposes the actions of the sympathetic system.  when body is at rest or with normal functions.  normal everyday conditions.  increase blood flow to kidney and digestive tract. The sympathetic and parasympathetic nervous system regulate and control each other’s activity to maintain Homeostasis , a stable internal environment DISORDERS OF THE NERVOUS SYSTEM (Londo, Janima) VASCULAR DISORDERS - are those that are associated with the circulatory system which include stroke and hemorrhage in the brain. - Encephalitis .myelitis .meningitis STRUCTURAL DISORDERS - are injuries of the brain and spinal cord such as bell's palsy and carpal tunnel syndrome. DEGENERATIVE DISORDERS - such as Parkinson’s disease, Huntington’s disease, and Alzheimer’s disease are more common among elderly people. ENDOCRINE SYSTEM
• The chief function of the endocrine system is to secrete hormones that control activities such as metabolism, reproduction, and development in the human body.
• it secretes them into the blood. HORMONES
• Are your body’s chemical messengers.
• The hormones are released into the bloodstream and then carried to the receptor sites, where they await to be activated to perform their function. These specific sites affected by the hormones are called target cells.
• most hormones are either made of amino acids , including their more complex structures like peptides or proteins , or they’re derived from lipids , like cholesterol.
• most amino acids are water-soluble while lipids are lipid-soluble. THE ENDOCRINE GLANDS, HORMONES, AND THEIR FUNCTIONS. **1. Hypothalamus

2. Pituitary gland (posterior)**  oxytocin-causes contraction of the smooth muscle in the wall of the uterus; initiates milk ejection reflex.  antidiuretic hormone- stimulates water reabsorption by kidneys.
3. Pituitary gland (anterior )  growth hormone- stimulates body growth.  prolactin- promotes lactation.  follicle-stimulating hormone(FSH)- stimulates follicle maturation and production of estrogen; stimulates sperm production. REGION PART FUNCTION Hindbrain Medulla oblongata Cerebellum Pons

• It is responsible for maintaining an upright position and regulating most involuntary functions such as breathing and circulation.
• It coordinates fine muscle movemenet and balance.Extensive damage to the cerebellum can cause inability to stand up.
• It serves as the bridge to the midbrain.It is responsible for sleepregulation. Midbrain Reticular formation
• It relays signal, particularly those coming from the eyes and the ears, to the cerebellum. It is responsible for the general levels of lethargy or liveliness. Forebrain Cerebrum (Cerebral cortex) Thalamus Hypothalamus
• It is the seat of intelligence; it is responsible for one’s thinking, learning, emotions, consciousness,and voluntary movements.
• It sorts and relays incoming and outgoing information to the differences parts of the brain. It serves as the area of sensory integration.
• It monitors pleasurable activities such as eating and drinking. It influences the endocrine system,Particularly the pituitary gland, in secreting hormones in response to different emotions, stress, and rewarding feelings.

 luteinizing hormone (LH)-triggers ovulation and production of estrogen and progesterone by ovary; promotes sperm production.  thyroid-stimulating hormone(TSH)- stimulates release of triiodothyronine and thyroxine.  adrenocorticotropic hormone - promotes release of glucocorticoids and androgens from adrenal cortex.

4. Thyroid gland  Triiodothyronine (T 3 ) and thyroxine (T 4 ) - increases metabolism and blood pressure and regulates tissue growth.  calcitonin - regulates blood calcium levels through uptake by bone. 5. Parathyroid gland  parathyroid hormone - increases blood calcium levels through action on bone, kidneys, and intestines

6. Pancreas  insulin - reduces blood sugar levels by increasing glucose uptake  glucagon - increases the blood sugar levels 7. Adrenal glands (medulla)  epinephrine and nonepinephrine - short-term stress response; increases blood sugar levels, regulates blood pressure, and increases heart rate and blood diversion. 8. Adrenal glands (cortex)  glucocorticoids - long-term stress resposnse; blood volume and pressure maintenance and sodium and water retention by kidneys 9. Gonads (testes) androgen testosterone- affects reproductive maturation and sperm production. 10. Gonad (ovaries)  estrogen - affects reproductive maturation and regulation of menstrual cycle.  progesterone - affects regulation of menstrual cycle; maintains pregnancy. 11. Pineal gland melatonin- circadian rhythm.
7. Thymus thymosin- development of T lymphocytes. NEGATIVE FEEDBACK MECHANISM ( USMAN, NORHAFIZAH M.)
   • The Endocrine glands send information back and forth within itself in order to control and regulate the amount of hormone it produces. This is called negative feedback mechanism, once the target cell has responded to the hormones, it sends chemical signal back to the glands such that the gland may stop or slow down hormone production. When the hormone level in the blood drops, the will secrete the hormone again. This way the hormone level is kept constant. THE FIGHT-OR-FLIGHT RESPONSE (Rahman, Anie Sahara)
   • Each time you sense danger, your body automatically tries to protect you. ADRENALINE is a chemical that gives you a quick rush of energy, is released into your bloodstream. Your pupils dilate, your heart rate accelerates, your blood pressure rises, and your breathing speeds up. You become alert and highly sensitive to your surroundings. This combination of reacts is called the fight-or-flight response. How you react to this response can improve situations or make them worse.
   • Fight-or-Flight response, response to an acute threat to survival that is marked by physical changes, Including nervous and endocrine changes, that prepare a human or an animal to react or to retreat. The functions of this response were first described i n the early 1900s by American neurologist and physiologist Walter Bradford Cannon.
     • Sympathetic system initiates what we call the fight-or-flight reaction by activating the hormones responsible for this response and keeping the brain alert and the body ready to take action. The Adrenal Medulla is stimulated to release the emergency or stress hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream. In turn, these stress hormones cause changes in the body, including increase of heart rate and blood pressure. What effect will these changes have? An increase in heart rate and blood pressure will assure that cells will receive the much needed oxygen and glucose to produce the body’s fuel.
     • ATP (adenosine triphosphate) is responsible for taking immediate action, as well as removing waste as a consequence of this energy production. These changes will give you strength whether you just stand up or run away from the danger. INSULIN MANAGEMENT AND DISORDERS INSULIN - is a hormone made by an organ located behind the stomach called pancreas. It regulates glucose level in the blood.  Insulin prevents the glucose from rising to dangerous levels.  Glucagon prevents the glucose from falling too low.  Islets of Langerhans are made up of different types of cell that male hormones, the commonest ones are beta cells, which produce insulin.  Glycemix Index a number or value (0-100) that tells how a particular food affects blood glucose level ENEDOCRINE DISORDERS Disorders of the endocrine may be grouped into two main categories :
8. Category result from the overproduction or underproduction of a hormone, leading to hormonal imbalance. Ex : diabetes, gigantism, dwarfism, hyperthyroidism,hypothyroidis
9. Category is caused by the development of an injury or tumor in the endocrine gland. Ex : thyroid nodules, goiter, adrenal cancer, pancreatic cancer, ovarian cancer, and pituitary tumor.

CHAPTER 2: THE HUMAN REPRODUCTIVE SYSTEM

THE MALE REPRODUCTIVE SYSTEM

Performs the following function:  Secretion of male hormones  Production of sperm cell  Transfer of sperm cell

PARTS OF MALE REPRODUCTIVE SYSTEM:

1. TESTES - it is a male gonads also called as testicles, which hang in scrotum. The testes have compartments that contain tightly coiled tubes called seminiferous tubules. Sperm cells develop from the cells that line the coiled tubes. The premature cell are transport;  SCROTUM- a sac skin-fold encloses the testes.
2. PENIS - The tip is expanded as the glans penis which is also covered by the skin fold called prepuce .it is also the external organ that allows the trans fer of the semen into the vagina of the female. 3. Duct system composed of the following:  EPIDIDYMIS - 6cm to 20ft long coiled tube located on the surface of the testes which as storage of sperm cell.Sperm are routinely stored here for 1month and are then released during ejaculation(is the process which the semen passes through the urethra).  VAS DEFERENS/ VAS DEFERENTIA - conveys the sperm to the abnominal cavity through the inguinal canal where it joins the urethra.  EJACULATORY DUCT - short duct where vas deferens joins with the seminal vesicle.  URETHRA - the outlet tube functioning both for excretion(passage of urine) and reproduction(passage of semen). it runs through the penis and opens at the tip of the penis. THREE GLANDS:  SEMINAL VESICLES - secrete a thick fluid that contains nutrients  PROSTATE GLAND - secrete a thick, milky alkaline fluid to counteract the acidic vagina and urethra and activate the sperms  BULBOURETHRAL or COWPER’S GLAND - produces the lubricating effect. The sperm cell and the fluid make up the SEMEN. THE MALE SEX HORMONE It is the main male sex hormone secreted by the testes.  It is responsible for the normal development of the organs of the male reproductive system. It is also necessary for the maturation of the sperm cells with the aid of another hormone, follicle-stimulating hormone (FHS).  Testosterone brings about the changes experienced by males during puberty. These changes, called secondary sex characteristics, appear at around 10 to 14 years of age and distinguish a male from a female.  Secondary sex characteristics in males include: 1. Hair growth in the face, underarm, genital area, and other parts of the body 2. Enlargement of the voice box 3. Deepening of the voice 4. Development of the male musculature 5. Increased secretion of sweat and oil  Testosterone is responsible for males’ muscular strength. This is why some athletes use steroids that contain testosterone or other similar compounds. However, taking steroids have been produce harmful effects including mental problems. SPERM is described as tadpole-like. A mature sperm has (3) three parts: the tai l, the middlepiece or neck , and the head.

• The tail propels the sperm as it swims in the fluid.
• The middle piece contains the mitochondria , which provides the sperm with energy during its journey to the female body.
• The head of the sperm contains enzymes that break the hyaluronic acid of the egg’s membrane. It also houses the genetic material which will eventually unite with the egg’s nucleus during fertilization. THE SPERM CHALLENGE When a man ejaculates, about 200 to 500 million sperm cells are in the semen. Only less than one percent of thece reach the egg for the following reasons:  Millions already die in the vagina due to its acidic environment.  Some sperm cells lose energy along the journey.  Some sperm cells go to the oviduct or fallopian tube, which does not contain the egg.  Some sperm cells are blocked by the mucus covering the cervix.  Abnormal sperms relating from its mass production are unable to fertilize an egg. THE FEMALE REPRODUCTIVE SYSTEM PERFORMS THE FOLLOWING FUNCTION: a. Production of female sex hormones – estrogen and progesterone. b. Production of egg cells. c. Transfer of sperms from the male sex organ. d. Protection and nourishment of the developing embryo. PARTS OF FEMALE REPRODUCTIVE SYSTEM

1. Ovaries - paired primary sex female which lie on the right and left depression of the upper pelvic cavity, produce the mature egg cell.  Fimbriae - is a finger-like projections at the ends of each of the fallopian that sweeps the matured eggs to the fallopian tube (oviduct)
2. Fallopian Tubes (oviduct) - are narrow tubes that are attached to the upper part of the uterus and serve as pathways for the ova (egg cell). It is where the normal fertilization happens.
3. Uterus (womb) - a hollow muscular organ where the zygote is implanted. The site where an egg cell is fertilized and baby grows. Layers of the Uterine Wall:  Endometrium - is the inner lining of the uterus.  Myometrium - is the thick middle muscle layer of the corpus and fundus. Consist of 3 layers of smooth muscles and gives strength to the uterus.  Perimetrium - the external coat of serous membrane. The uterus (womb) accomplishes the 3 important functions:

 Menstruation - sloughing away of compact and spongy layers of endometrium – by bleeding.  Pregnancy - implantation of embryo in the endometrium and embryonic development.  Labor - consists of powerful, rhythmic contractions of the muscular uterine walls that results in the expulsion of the fetus at birth.

4. Cervix - the neck of the uterus leading to the vaginal canal.
5. Vagina - is a long, elastic, muscular canal where menstrual blood and tissue are expelled from the body. It receives the penis during copulation; serves as passageway of the baby during normal delivery. The Menstrual Cycle The menstrual cycle encompasses the ovarian and uterine cycles. The Ovarian Cycle: ➢ It consists of 2 phases: a) Follicular (pre-ovulatory) b) Luteal (post-ovulatory) ➢ At the beginning of the cycle, the pituitary gland secretes increased amounts of FSH and allows an ovarian follicle to mature. As the follicle cells develop, they secrete the female sex hormone estrogen. ➢ The multiplication of follicle cells signals an increased level of estrogen in the blood, inducing the pituitary gland to secrete luteinizing hormones. LH, together with FSH, bring about the follicle’s final maturation, which culminates in ovulation, the release of a mature egg. ➢ Ovulation usually occurs on the fourteenth day of the cycle. The egg is viable for fertilization within 24 hours from its release. Still under the influence of LH, the cells of the ruptured follicle develop into yellow body called corpus luteum. ➢ This yellow body then produces more estrogen and another female sex hormones, progesterone. Both hormones prepare the uterine wall for possible implantation of a fertilized egg. ➢ the first period (called menarche ) occurs at around 12 years of age and continues for about 30–45 years. Menstrual cycles end at menopause , which is usually between 45 and 55 years of age. The Uterine Cycle: ➢ It consists of 3 phases: a) Menstruation (menstrual) b) Proliferative c) Secretory ➢ While events take place in the ovary, a series of hormone- influenced changes also happens in the uterus. ➢ With low levels of progesterone, the surface of the endometrium or uterine wall begins to disintegrate and the blood vessels rupture. ➢ Blood and some accompanying endometrial tissues flow out of the vagina in a process called menstruation. The menstrual phase lasts for about five days. ➢ After the menstrual period, the endometrium starts to build up due to the increasing amount of estrogen by the developing follicles in the ovary. ➢ Proliferative phase, which happens on days 6 to 14. The formation of the corpus luteum and the secretion of progesterone trigger the endometrium to increase its thickness and prepare itself for a developing embryo. ➢ The uterine glands become mature and produce a thick secretion (secretory phase). ➢ The secretory phase of the uterine cycle begins on the fifteenth day of the cycle until before the onset of the next menstrual phase. ➢ This cycle, maybe interrupted by stress, health problems, and pregnancy. Female Sex Hormones: ✔ Estrogen- regulates the menstrual cycle ✔ Progesterone- promotes the secondary sex characteristics ✔ Follicle-stimulating hormone- stimulate the production of egg cells and estrogen. ✔ Luteinizing Hormone- triggers the ovulations and stimulates the production of progesterone. Hormone Feedback and Pregnancy When a sperm cell successfully penetrates their nuclei fuse, a zygote (fertilized egg cell that results from the union of the female gamete with a male gamete) or fertilized egg is formed. A fertilization membrane also develops to prevent other sperms to further penetrate the egg. This process whereby the sperms’ nucleus and the ovum’s nucleus unite is called fertilization. It usually takes place while the egg is travelling along the oviduct or fallopian tube (slender tubes that connect the ovaries to the uterus). It will take about 7 to 10 days for an egg (fertilized or not) to reach the uterus. Upon successful implantation of the developing embryo in the endometrium, the developing embryo and the uterine lining jointly form a special organ called the placenta. This will provide nourishment for the embryo as well as secretion of hormone called human chorionic gonadotropin (HCG), which is related to luteinizing hormone (LH) since they act on the same receptor. Recall that LH maintains the corpus luteum. With the corpus luteum intact, progesterone production is maintained and the uterine wall will not break down. Hence, a pregnant woman will not menstruate. HCG passes in the uterine. It is the same hormone detected in pregnancy test. The symbols used to indicate pregnancy vary kit to kit. Some kit, like this one, indicates a positive results with two parallel lines. If the embryo is abnormal or if it dies, HCG will drop and the endometrium will disintegrate causing a woman to have a miscarriage. CHAPTER 3: DNA: THE THREAD OF LIFE 3.1: DNA and Protein Synthesis DNA (Deoxyribonucleic acid)

• contains the sequence that provides all information necessary for the proper functioning of an organism.
• made up of building blocks called NUCLEOTIDES, which consist of **three subunit molecules:

1. Deoxyribose sugar
2. Phosphate group
3. Nitrogenous bases.**

In 1953 , British scientists James Watson and Rosalind Franklin , and US biochemist Francis Crick unveiled the most accurate description of the structure of the DNA molecule. Three main features of the double-helix model:

• The DNA structure is a double-stranded helix, with the two strands connected by hydrogen bonds.
• The two strands of the DNA are antiparallel---the 5' end of one strand is paired with the 3' end of its complementary strand and (vice versa).
• Not only are the DNA base pairs connected by hydrogen bonds, the outer edges of the nitrogen-containing bases are also exposed and are available for possible hydrogen binding. Protein Synthesis
• is the process in which cells make proteins. It occurs in two stages: Transcription and Translation. 3.2 RNA Ribonucleic acid (RNA) is names after ribose, the five-carbon sugar group that makes up RNA’s backbone. Just like DNA, RNA also has nucleotides composed of a sugar-phosphate backbone attached to a nitrogen base. However, RNA is single-stranded and does not have thymine. Instead, its adenine pairs with a nitrogen base called uracil. RNA may also found in the nucleus and the cytoplasm of a cell. The three major types of RNA are the messenger RNA (mRNA) , the ribosomal RNA (rRNA) , and the transfer RNA (tRNA). RNA dictates what proteins are to be synthesized, becomes part of the ribosomes which create proteins, and moves the amino acid (building blocks of proteins) to the ribosomes. All three of the RNA’s ( mRNA, tRNA and rRNA), together with DNA, works to build the proteins needed by the body. Compare DNA to RNA: The Three Major Types of RNA: 3.3: DNA and it's Relation to Heredity and Diversity
  • Humans Grow and Develop according to the Instructions in our Genes. A gene is a segment of DNA that may code for the protein of your hair or a Protein like Insulin , which Controls the level of glucose or sugars in the blood. A DNA molecule is Very Long and may contains hundreds of even thousands of genes. It is Responsible for your Uniqueness and why you share some features with your Family Members. However, before the information in your genes becomes Useful, the Segment of The DNA coding for a Particular trait should be cracked. The code dictates order by which amino acids will be assembled to form a protein.
  • DNA accounts for the unity, as well as the Diversity among Living organisms. Heredity is about how traits are passed down from Parents to Offspring. 3.4 REPLICATION AND TRANSCRIPTION CENTRAL DOGMA MOLECULAR BIOLOGY
  • is the production of proteins from DNA which includes Replication, Transcription, and Translation. REPLICATION
  • is the process by which a copy of the original genetic is duplicated so that the new cell has exactly the same information and the parent's cell.

TYPES CHARACTERISTICS FUNCTIONS

Messenger RNA (mRNA) Produced in the nucleoplasm, using DNA as the template; sequenced as Trinucleotide called codon. Brings the code for synthesis of proteins from DNA in the nucleus To the ribosomes in the cytoplasm. Transfer RNA (tRNA) Clover-shaped structure in the cytoplasm with three exposed bases, called anticodons, on one end and an amino acid on the other. Picks up amino acids in the cytoplasm and fits them into the proper place in the growing chain of polypeptide inside a ribosome. Ribosomal RNA (rRNA) Made in the nucleolus (dark area of the nucleus). Forms an important structural component of the ribosome.

STEPS OF DNA REPLICATION

1. Topoisomerase binds an relaxes the double helix.
2. Helicase unwinds and parental double helix.
3. Single stranded binding proteins stabilize the unwound parental DNA
4. The leading strand is synthesized continually in the 5' to 3' direction by DNA polymerase III.
5. The lagging strand is synthesized discontinuously. Primase synthesizes a short RNA primer, which is extended by DNA polymerase I to form and Okazaki fragment.
6. After the RNA primer is replaced by DNA polymerase, DNA ligase joins the Okazaki fragment to the growing chain.  TRANSCRIPTION

• is the process by which the DNA molecule ( genetic material and hereditary information) is copied to form a single Stranded molecule messenger RNA (mRNA).Transcription takes place in the STEPS IN DNA TRANSCRIPTION

1. INITIATION
2. ELONGATION
3. TERMINATION 3 .5 TRANSLATION  TRANSLATION - Is the second step in gene expression, When the mRNA strand reaches the cytoplasm, it enters a ribosome to start the translation which is the beginning of protein synthesis. And is where the codons (three consecutive nitrogen bases) are read and translated into amino acids. A functional ribosome is divided into a small subunit and a large subunit. The small subunit reads the mRNA and binds with the large subunit, while the large subunit binds with the transfer RNA (tRNA) and joins the minor acids to form a polypeptide chain. Transfer RNA (tRNA) has an anticodon; it carries a specific amino acid complementary to the mRNA (codon) at the ribosome. A specific codon signals the beginning of the translation process so that the whole base sequence in the mRNA will be read correctly. This codon Called the initiation codon ( AUG ) also the codon for the amino acid Methionine. The tRNA picks up the amino acid Methionine according to its triple bases, or anticodon attached to one end of the tRNA. The anticodon end of the tRNA binds with the AUG codon at the P site of the large subunit of the ribosome. The next mRNA codon is lined up at the a site. An enzyme joins the first two amino acids in the chain with a peptide bond. The First tRNA, now empty and moves to the e site and leaves to pick up another molecule. During Elongation process,The Translated codon moves to the p site so that the next codon will be in position at the a site. The sequence repeats and polypeptide chain grows until the ribosome reads any of the “stop” codons ( UAA, UGA, UAG ).A Releasing factor binds with the stop codon and release the mRNA from the ribosome. The polypeptide goes to the Golgi complex to combine with fats, minerals, or carbohydrates to make complex proteins. GENETIC CODE  Proteins made by joining amino acids into long chains called polypeptides.  There are 20 different amino acids.  Codon - three consecutive nucleotides that specify a single amino acid. Nucleus of the eukaryotic cells, then after modification, the mature mRNA leaves the nucleus and enters the cytoplasm through the nuclear pore.

Key: Ala = Alanine Leu = Leucine Arg = Arginine Lys = Lysine Asn = Asparagine Met = Methionine Asp = Aspartate Phe = Phenylalanine Cys = Cysteine Pro = Proline Gln = Glutamine Ser =Serine Glu = Glutamate Thr = Threonine Gly = Glycine Trp = Tryptophan His = Histidine Tyr = Tyrosine lle = Isoleucine Val = Valine EXAMPLE: DNA CODE: TAC CCA CCG TTA GGA ACG CAT GGT (^) … mRNA: AUG GGU GGC AAU CCU (^) … Codon 1 Codon 2 Codon 3 Codon 4 Codon 5 Codon 6 Codon 7 Codon 8 Codon 9 tRNA: UAC CCA CCG UUA GGA (^) … Anticodon 1 Anticodon 2 Anticodon 3 Anticodon 4 Anticodon 5 Anticodon6 Anticodon 7 Anticodon 8 Anticodon 9 Protein: m ethionine G lycine G lycine Asparagine Proline

…

Amino acid 3.5 Mutation

• Is a permanent change in a gene or a chromosome. In simple words, it is defined as sudden and abrupt changes to the genetic material of organisms. Mutagen - Agents that cause mutation. They include radioactive substances, x-rays, UV radiation, and certain chemicals. Genetic mutations and their effects on the DNA molecule:
  1. Substitution - a base is replaced by one of the other three bases. In sickle cell anemia, codon GAG mutates to GTG.
  2. Deletion - one or more base pairs are lost or deleted in the DNA.
  3. Insertion - one or more base pairs are added to the DNA. The number may range from one to a thousand. Huntington's disease results from this type of mutation.
  4. Inversion - It is a 180° - rotation of a piece of DNA.
  5. Frame shift - this occurs when inversions and deletions completely change a gene such that its message can no longer be decoded correctly.