Chapter Four : Excretion

The main concepts of chapter (4)
Excretion in living organisms

1- Excretion is getting rid of waste products of metabolism through the plasma membrane.

2- The main metabolic wastes are, CO₂ water vapour, volatile food substances salts and nitrogenous wastes.

3- Getting rid of nitrogen and defecation are not excretion processes.

4- The main excretory organs in animals are, the skin, the liver, the lungs and the kidneys.

5- The excretory organs in animals can regulate the body content of minerals.

6- The skin consists of the outer epidermis and the inner dermis.

7- The epidermis consists of epithelial cells, the surface cells have keratin and the melanin granules are found at the pigment cells.

8- The dermis has the sweat glands, the hair follicles, nerve endings and blood capillaries.
9- In lower vertebrates kidneys are long, thin extend along the two sides of the vertebral column.
10- Each human kidney is a bean shaped 12 cm long, 7 cm wide, 2.5 cm thick, the outer part is convex while the inner one is concave.

11- The renal artery and renal vein are on the inner side of each kidney.

12- Each kidney consists of thin outer cortex and inner broad medulla.

13- The functional unit of the kidney is the nephron.

14- Each kidney has almost one million nephron.

15- The nephron consists of Bowmman's capsule, first coiled tube, loop of Henel, second coiled tube and the collecting duct which opens in the pelvis from which the ureter emerges.
16- The urinary bladder is closed by a sphincter muscle.

17- Extraction of urine takes place in two main stages:
A- Ultra filtration
B- Selective reabsorption.

18- The total amount of blood which passes daily through the kidney is about 1600 litres.

19- The blood plasma is examined or filtered about 560 time per day.

20- Excretion in plants does not pose a serious problem Because:
a- The rate of catabolism is low.
b- green plants re-use their catabolic wastes.
c- Plant metabolism depends on carbohydrate which reproduce less toxic wastes.
d- some catabolic salts and acids are stored in the form of insoluble crystals.
e- excess calcium is accumulated in green leaves then they shed down.
f- excess water is removed by transpiration and guttation

21- There are three types of transpiration:
a- stomatal (about 90%)
b- cuticular (about 5%)
c- Lenticular (small quantity)

22- The most important functions of transpiration are:
a- decrease the plant temperature
b- ascent of water and salts.

Chapter Five: Sensitivity

The main concepts of chapter six: Sensitivity

1- Sensitivity is one of the biological functions of the lliving organism that mentain its life.
2- Senstivity is the coordination between the body and the environment.
3- Forms of sensitivity in plants are:
A- Response to touch and darkness.
B- Tropisms. [phototropism - Geotropism - Hydrotropism]
4- Mimosa plant and some leguminous plants are hold in a horizontal position, but at night the leaflets hang down ward and fold their upper surfaces upward, i.e undergo sleeping movement.
5- The sleeping movement can be explained due to cell turgidity.
6- At the base of each mimosa leaf there is a swallen structure called pulivinus, when the leaf is touched the water in the lower side of pulvinus escape to the neighboring tissues and after the removal of the stimulus these cell regain their turgidity so pulvini act as joints.
7- The cell walls of the lower half of pulvini are more senstive than those of the upper half.
8- Boysen johnson found that oat coleoptile loses its ability to bend towards light if 1 - 2 cm of its tip is cut off but it regains this ability if the cut part is fixed again to the tip with gelatin.
9- Unequal distribution of light around the plant leads to unequal in the distribution in aucxins which in turn leads to unequal in plant growth that the side away of light has more auxins concentration so it is stimulated to grow more than the other side that leads to be bend towards light which we call the plant stem is positive phototropic.
10- The high concentration of auxins in plant root (in one side) leads to the inhibition (decrease) of its growth.
11- Plant hormones (Auxins) can diffuse through gelatin but not through mica.
12- The plant root is negative phototropic.
13- Herman's exp. Proved that the total amount of auxins in the tip of oat coleoptile does not change but change their position that:
A- In vertical position equal amount of auxins move into the two halves of the tip.
B- In horizontal postion more auxins diffuse or accumulate into the lower half. So the plant stem is negative geotropic and plant root is positive geotropic.
14- The plant root is positively Hydrotoropic if the water is not equally distributed around its two sides, the side facing water has more concentration of auxins and this inhibits its growth, while the other side grows faster and it has less auxins, so it bends towards water.
15- Sensitivity, coordination and response to a stimulus are called irritability.
16- In animals receptors and effectors are linked together and their action is coordinated by the nervous system.
17- Man can not feel all the stimuli like X- rays. Polarized rays - ultraviolet and infera red because man has no nerve cells which are affected by these stimuli.
18- The animal can not preceive all stimuli picked up by its sense organs, but it can preceive changes in them.
19- The external stimuli that most of the animals respond to are:
Heat - gravity - pressure - chemicals - sound - water - light.
20- The nerve cell is the building unit of the nervous system.
21- The nerve cell consists of a cell body or cyton and long axon which is surrounded by two fatty layers [Myelin and schwann] these layers accelerate the speed of nerve impulses that reaches 120 m/sec.
22- The nerve cells are neither divide nor renewed.
23- Myelin and schwann's layer are interrupted at regular intervlas by the nodes of ranvier.
24- According to the function there are three types of nerve cells:
A - sensory neurons: which transmit nerve impulses from receptors to the central nervous system.
B - Motor neurons: which transmit the motor impulses to the effectors from central nervous system.
C- Connector neurons: which carry impulses from one neuron to another.
25- The nerve cord: It is a bundel of axons which is surrounded by a sheath of fatty material [myelin and schwann] in addition to the outer nerve sheath.
26- The nerve: It is a long nerve cord.
27- The nerve impulse is a sequence of electro - chemical changes propagated along a nerve fiber and transmitted across synapses.
28- The nerve fiber is surrounded by a plasma membrane which is semipermeable so positive ions are accumulated at the outer surface while negative ions are accumulated at the inner side i.e the membrane has two poles or polarized; this is at rest.
29- When the nerve fiber is stimulated at a certain point, it loses it selective permeability at this point and becomes fully permeable, as a result of that the positive ions move to the inside and the membrane is said to be depolarized.
30- The time needed for the entry of sodium ions and the exit of potassium ions is from 0.002 to 0.005 seconds.
31- A period of about 0.001 - 0.003 sec. elapses between the end of impulse transmission through a certain point and the beginning of a new impulse this period is the refracotry period.
32- Synapse can be defined by two ways:
A: Anatomically it is the site at which the terminal arborization of a neuron axon lie very close to the dendrites of a neighboring neuron.
B: Physiologically: It is the functional connection between neurons.
33- The synaptic knob or cleft is formed for transmission of nerve impulses.
34- The synaptic knob contains many transmitting substances like nor-adrenaline- acetyl choline - and sympathin.
35- The nervous system in vertebrates consists of highly developed structures these are:
A- Sensory receptors [sense organs]
B- Nerve fibers [transmit impulses]
C- Nerve centres. [in brain]
36- The nervous system in vertebrates and also in man consists of:
A- The central nervous system which includes the brain and the spinal cord.
B- The peripheral nervous system which includes 31 pairs of spinal nerves and 12 pairs of cranial nerves.
37- Physiologically the nervous system includes:
Somatic nervous system (central and peripheral): which controls the voluntary actions.
B- Autonomic nervous system: which controls the involuntary actions.
38- The human brain weights about 1300 - 1400 grams, protected by the cranium bones, and surrounded by three membranes:
A: Dura matter:
a strong fibrous tissue adhering to the cranium.
B: Pia matter:
a transparent one adhering to the brain and contains blood vessels.
C: Archnoid membranse:
intermediate delicate layer of connective tissue, a transparent fluid passes through it, it contains proteins, glucose, sodium and potassium salts, it is used to feed and protect the brain.
39- Meningitis leads to the inflammation of the three membranes around the brain.
40- The human brain consists of:
A: The cerebrum [the two cerebral hemispheres.]
B: The cerebellum
C- pons varolii
D- Medulla oblongata.
41- The two cerebral hemispheres are the ceutre of high mental activities thought - memory - and reasoning.
42- Lab animals, car victims, brain tumor patients are used to make a map for the centres on the cerebral hemispheres that:
The thinking and memory centres lie at the anterior part followed by voluntary movements centres, followed by the skin sensation, at the back the centre of vision hearing, smell, and taste lie at the two sides.
43- The nerve centres in the right hemisphere control the left sided organs and vice versa.
44- The nerve centres exist in identical locations in both of the two hemispheres except speech and writing centres.
45- The cerebellum coordinates the different voluntary muscle movements, also maintains the balance and posture of the body.
46- Pons varolii transmits impulses from the hemispheres and cerebellum to the medulla oblongata and vice versa.
47- The medulla oblongata transmits the impulses from the hemispheres to the spinal cord also controls the main involuntary actions.
48- The spinal cord transmits both sensory and motor impulses from the body to the brain and vice versa, it also contains the nerve centres which control the reflex actions.
49- The peripheral nervous system consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves.
50- The ability of nerves to transmit the impulses is affected by the amount of oxygen and decreases by the effect of some chemicals such as alcohol ether and other drugs.
51- The reflex action is the unit of the nervous activity.
52- Reflex actions include, constriction of the iris, blinking of the eyes, secretion of digestive juice and jerking of the leg if it is struck below the knee cap.
53- Reflex action is involuntary rapid response to a stimulus threatening the body with danger without brain involvement.
54- Reflex actions may take place during sleep or mild anesthesia.
55- The intensity of reflex action depends upon the general state of the body, it is affected by durgs.
56- Reflex actions may stop completely under the effect of strong anaesthetic substances; certain reflex actions may decrease the effect of another reflex actions.

Chapter Six: Hormonal co-ordination in living organism

Main concepts of chapter 7

Hormonal coordination in Living organisms

1- Starling gave the name hormones for these chemicals that coordinate between body organs.
2- Auxins are plant hormones which regulate plant growth because they act as catalysts for important growth enzymes.
3- Endocrine glands are those that secrete their hormones directly into the blood current.
4- Endocrine glands are chracterized by:
A- ductless
B- Provided with plenty of blood
C- Each gland has a specific secretion which contain one or more hormones.

5- The most important endocrine glands in man are:
a- pituitary gland or the master gland.
b- Thyroid gland or the activity gland
c- Parathyroid gland
d- Adrenal gland
e- Pancrease.
f- gonads [ovaries - testes]
7- The pituitary gland is a small oval shaped body 12 mm long, half gram in mass. It consists of two lobes.
8- The anterior lobe is more important than the posterior lobe because it produces more than nine hormones some of them act as activating hormones for other glands.
9- From the hormones of the anterior lobe are growth hormone, TSH, ACTH, FSH, LH, and lactoginic hormone.
10- From the hormones secreted by the posterior lobe are oxytocin hormone which is responsible for controlling involuntary muscles like uterine muscles during delivary and antidiuretic hormone which regulates urine formation and excretion.
11- The deficiency of the growth hormone before puberty leads to dwarfism but after puberty it causes impotence.
12- The excessive secretion of the growth hormone in early childhood causes gigantism but if it happens in adults it causes acromegaly.
13- The thyroid gland lies infront of and on both sides of trachea at the base of the neck; it consists of two small lobes joined together by an isthmus, it is about 6 cm long and weighs 30 - 60 grams.
14- The enlargement of the thyroid gland is called goitre.
15- In case of simple goitre, the enlargement is accompanied by dificiency of the secretion which leads to the decrease of body activities, body temp. and heart beats.
16- In adults, dificiency leads to myxedema, but in infancy it leads to cretinism.
17- The exophthalmic goitre, the enlargement is accompanied by an excessive secretion of the hormone which leads to the increase in the body activities, increase the rate of stored food combustion.
18- Deficiency in the secretion of thyroxine is treated by adding iodine to food, or using the extract of cettle thyroid, excessive secretion is treated by the surgical removal of the enlarged part.
18- The parathyroid glands are 4 small bodies each is as big as wheat grain.
19- Each two bodies are located on one side of the trachea and behind the thyroid gland.
20- Parathyroid gland secretes parathormone hormone.
21- Parathormone hormone regulates caclium and phosphorus levels and keep them constant in the blood.
22- Both calcium and phosphorus are essential for bone, teeth and blood formation.
23- Deficiency of parathormone leads to excitability.
24- Excessive secretion leads to a rise in the calcium and phosphorus level in the blood and they are excreted in large amounts in the urine, this is due to the withdrawal of these elements from the bones which become fragile and more exposed to fractures.
25- The adrenal gland is called emotional galnd or supra renal glands.
26- There are two adrenal glands, each one is completely attached to each kidney.
27- The adrenal gland is yellow, pyramid shaped body about 3 cm long and about 6 - 12 gm.
28- The person will die if the adrenal glands are infected with a disease or removed.
29- Each gland consists of an outer certex and inner medulla.
30- The medulla part secretes adrenaline and the cortex secretes a group of hormones the most important one is the cortisone.
31- The adrenaline causes:
a- Constriction of skin and visceral blood vessels.
b- increase the heart beats causing rise in blood pressure.
c- Muscle blood vessels become wider
d- An increase in breathing movements.
e- conversion of stored glycogen into sugar.
f- secondary symptoms appear like white skin, widening of iris, mouth muscles contract, and fingers tremble.
32- The cortisone hormone has some functions:
a- It keeps sodium and potassium constant in the body.
b- Regulates the fats and carbohydrated metabolism.
c- Increase the ability of the body to resist climatic and psychic disturbances.
33- The increase in the activity of the cortex leads to early sexual maturity in males and appearance of musculine characteristics on females.
34- Pancreas an exocrine gland which secretes the pancreatic juice through the pancreatic duct.
35- Pancreas is also endocrine because there are patches of cells scatterd in the pancreatic tissue which secrete insulin directly into the blood.
36- The scientist langerhans discovered some patches of cells in the pancreatic tissue.
37- The role of insuline is:
a- Keep the percentage of of sugar in the blood constant 0.1% i.e. 100 m.gm of glucose in 100 gm of blood.
b- help the body cells to use glucose for energy production.
c- Stimulate the hepatic cells to absorb the glucose and convert it to glycogen to be stored till needed.
38- In 1922 Banting siolate insuline from the pancreas.

Chapter Seven: Support and Movement

The amin concept of chapter 5
Support and movement in living organisms

1- In plants there are two main types of support:
a- physiological support e.g cell turgidity.
b- Structural support, [by deposition of hard substances such as cellulose lignin, cutin, subrin on or in the cellwalls].

2- The cell wall becomes stronger if cellulose or lignin are deposited.

3- The human skeletal system consists of bones and cartilages [206 bones].

4- Bones form about 18% of the total body weight.
5- The bone is hollow and covered by periosteum rough membrane.

6- The bone marrow inside the bone cavity contains blood capillaries and nerves, it forms new blood cells.

7- Bones which perform the same function are identical in structure.

8- Ligaments which are rough tissues attache between bones, they exist in movable joints.

9- The tips of articulated bones are covered with cartilage.
10- The synovial fluid prevents or reduces friction between bones.

11- The skeletal system in man consists of:
a- Axial skeletal system:
[ vertebral column - rib cage - skull]
B- Apendicular skeletal system:
[ The upper limbs - the lower limbs the pectoral girdle - the pelvic girdle]
12- The vertebral column consists of 33 vertebrae which differ in shape and size in different regions of the body:
a- 7 cervical.
b - 12 thoracic.
c- 5 lumber.
d- 5 sacral. Fused"
e- 4 coccyx "fused"

13- Each vertebra has a neural canal or arch through which the spinal cord passes.

14- The skull consists of two main parts the cranium which is made up of 8 serrated bones, and the facial part which includes face bones, jaws and dense orbits of ears, eyes and nose.

15- At the base of the cranium there is a large hole known as the foramen magnum through which the spinal cord passes.

16- The thoraic cage consists of:
12 thoracic vertebrae, the sternum and 12 pairs of ribs.

17- The last two pairs of ribs are short and do not reach the sternum and are known as floating ribs.

18- Ribs can move anteriorly and laterally to increase the thoracic cavity.

19- The pectoral girdle or shoulder bones consists of the scapula and clavical.

20 - Bones of the upper limb are:
Humerus - radius and ulna - carpals meta carpals - phalanges.

21- The lower limb consists of:
femur - tibia - fibula - tarsals - metatarsals - phalanges.

The pelvic girdle and the sacrum together form the pelvis in the region of the hips.

23- Each pelvic girdle consists of 3 bones which are ilium ischium, and pubis.
24- The main types of movement in living organisms:
a- cytoplasmic streaming
b- Positional movement of some organs e.g peristalsis
c- The movement of insectivorous plant leaves.
d- The movement of animals from one place to another.
25- The skeleton may be endoskeleton or exoskeleton.

26- Some plant leaves respond to touch and move e.g mimosa.
27- Leaves of legumes and mimosa move as a response to light and darkenss.
28- Different plant parts repsond to different stimuli like light, water and gravity this is called tropism.
29- Haptotropism is responding to a support which is seen in tendrils of peas.

30- If the tendrils do not meet a support they will welt and die.

31 - The pull movement is seen in subterranean stems and bulbs, the pulling roots contract pulling them downwards.

32- The body parts move as a system of levers:
a- Nodding of the head represents a lever of the first order.
b - Movement of foot on the ankle represents a lever of the second order.
c- Bending your hand upward represents a lever of the third order.

Chapter Eight: Reproduction

(1) There are two main theories about the origin of life.
(2) Reproduction in living organisms takes place in two main levels:
A- Molecular duplication in which the cellular molecules multiply.
B- The whole organism.
(3) There are two main methods of reproduction:
A- A sexual reproduction that includes:
1- Binary fission e.g Amoeba; paramecium simple algae and bacteria.
2- Budding e.g yeast, hydra, sponge
3- Regeneration e.g: Sponge, Hydra star fish - planaria.
4- Sporogony e.g: Mushroon - some algae, bread mould, and some ferns.
5- Parthenogensis e.g some worms, crustaceans and insects.
6- Tissue culture: e.g carrot, tobacco.
B- Sexual reproduction which may be:
1- By conjugation e.g spirogyra alga
2- By gametes e.g higher plants and animals.
(4) Alternation of generation is the phenomenon through which some living organisms reproduce sexually followed by one or two cycles asexually. e.g plasmodium (protozoan), schistosoma (worms) and fern plants (Adiantum), from the benefits of alternation of generation is the production of great number of life stages because most of them are lost or damaged during the life cycle, the two types of reproduction enable the living organism to adapt with changes in environmental conditions.

(5) The flower emerges from the axil of a leaf called bract (may be absent)
(6) A typical flower has four floral whorls
A- Calyx "Sepals"
B- Corolla "petals"
C- Androecium "Stamens" male organs
D- Gynoecium "Carpals" female organs
(7) Flowers of most monocot plants the calyx leaves are hardly differentiated from the corolla leaves so they are called perianth.
(8) Monoecious plants are those that carry male and female flowers.
(9) Diecious plants are those that male flowers exist on one plant and female ones exist on another plant. e.g palm tree
(10) Flowers are divided according to their symmetry into:
A- Actinomorphic e.g. onion.
B- Zygomorphic e.g. petunia
(11) The function of the flower is reproduction, the stages of reproduction in flowering plants are:
1- Formation of pollen grains
2- Formation of ovules
3- Pollination
4- Fertilization.
(12) Pollination could be:
A- Self pollination
B - Cross pollination which takes place when:
1- The flowers are unisexual
2- Early maleness or early femaleness
3- Height of another is lower than the stigma.
(13) The pollin grain germinates on the stigma forming a pollen tube which penetrates the stigma and passes through the style till it reaches the ovule micropyle, the tube nucleus degenerates and the generative nucleus divides forming two male nuclei, one of them fuses with the two polar nuclei (or embryo sac nucleus) forming the endosperm nucleus which divides to give the endosperm tissue, it supplies the embryo with food, the other male nucleus fuses with the egg cell forming the zygote.
This process is called double fertilization.
(14) We can divide seeds into:
A- endospermic seeds e.g wheat, dates
B- exoendospermic seeds e.g bean, pea
(15) After fertilization
a- The two integuments will form the testa
b- The ovary wall becomes the pericarp
c- The ovary will form the fruit
d- Other floral whorls wither and fall down except in cases that they share in fruit formation.
(16) If the two integuments are fused with the ovary wall "pericarp" This forms single seeded fruit or grain e.g. Maize - wheat.

(17) Parthenocarpy means that some ovaries can develop naturally into seedless fruits without pollination or fertilization. E.g. Banana, pine, Apple, it can be carried out artificially e.g. tomato and cucumber by some stimulants e.g. indole acetic acid or naphthol acetic acid.
(18) The male reproductive system in man has two functions:
A- Production of sperms. (300 - 500 millions for each ejaculation)
B- Production of male hormone which is responsible for the appearance of secondary sexual characters.
(19) The position of testes outside the body exists in some mammals like primates and ungulates, because spermatogenesis needs lower temp.
(20) The female reproductive system in human consists of:
a- Two ovaries.
b- Two oviducts
c- The uterus
d- the vagina.
(21) The female reproductive system has the following functions:
a- Production of ova ("about 400 ova" during the fecundity period)
b- production of female hormones estrogen and progesterone.
c- safe place for the development of the embryo.
(22) The breeding cycle of placental mammals is a period where the ovary becomes active and the uterus becomes ready for fertilization, this cycle is periodic and coincide with mating and reproduction:
a- Lion and tiger its annual (12 month)
b- Cats and dogs biannual (6 month)
c- Rabbits - rats every month.
d- Human being every 28 days.
(23) The menstrual cycle is differentiated into ovarian cycle and uterine cycle.
(24) Menstruation cycle is divided into 3 phases:
1- Phase of proliferation (10 days)
2) Phase of ovulation (14 days)
3- Phase of menstruation (3 - 5 days)
(25) Pregnancy occurs if the ovum is fertilized in the second phase (ovulation).
(26) During pregnancy the corpus luteum remains to secrete the progesterone and estrogen, these two hormones inhibit the ovulation, preserve the endometrium and stimulate the mammary glands to secrete milk after delivary.
(27) Contraceptive methods of birth control:
A- The oral contraceptives "pills" which are combination of synthetic estrogen and progesterone.
B- Intra uterine device "Coil" which is inserted into the lumen of the uterus and prevents the implantation of the ovum.
(28) The inner membrane "amnion" and the outer membrane "chorion" are formed around the embryo in addition to the extension of the endometrium.
(29) Both the chorionic villi and the endometrium intermingle to form the placenta.
(30) After short time both margins of the amnion join forming the umbilical cord which extends from the placenta to the intestine of the embryo.
(31) The mother's blood and foetus blood do not mix but their vessels are only adjacent to allow movement of substances by diffusion.
(32) There are two types of twins:
A- Fraternal "Two ova and two sperms".
B- Identical "one ovum and one sperm"
- One mature ovum and one sperm, then dividing cells separate into two masses they are similar in all genetic characters, some time they are attached together form the head. Abdomen or chest this case is called siamese.
- Extra - uterine fertilization "test tube babies" is done in 1977 when scientists succeeded to get a mature ovum from a wife's ovary and fertilized it externally with the husband's semen in a certain nutritive medium.
- Embryo culture exp. have been conducted on rabbits and mice, the cells from their early embryonic stages were separated and cultured as separate masses of cells in a female's uterus to proudce complete individual.
- Renucleation is a type of embryo cutlute through which the nucleus is removed from an embryo body cell of an Amphibian. Then the nucleus of an unfertilized ovum is destroyed by radiations, then the nucleus from the somatic cells of the embryo is implaned in the ovum which develops normally and give individuals identical to individual from which the cultured nucleus was taken.
- Gamete banks are used to store gametes of selected animals to keep them available for external fertilization.
- The gametes are stored in, frozen conditions up to 20 years.
- Centrifugation or exposure to limited electric field can separate the sperms with X chromosomes from sperms with Y chromosomes.

Chapter One

Main concepts of chapter 9

Genetics

1- Methods of studying genetics:
A- Bredding and crossing in which organisms with well known characters are grown and crossed and then we follow the inheritance of their characters.
B- Family pedigree
This is a diagram in which males are represented by squares and females by circles, the shaded squares or circles indicate to the studied character.
C- Cytological and biochemical studies.

2- Mendel's first law:
When two homozygous individuals different in a pair of allelomorphic characters are corssed, only the dominant character appears in F1 generation while the two characters appear in F₂ by 3: 1

3- Mendel's second law:
When two homozygous individuals different in two pairs of allelomorphic characters are crossed, each pair is assorted randomly and inherited independantly from the other pair, the ratio of the second generation is 9: 3: 3: 1

4- In case of lack of dominance there is no gene that completely dominates over the other, so together they produce an intermediate character. e.g. colour in Antirrhinum flowers.

5- Incase of incomplete dominance the recessive gene shows the character in certain conditions only e.g sickle-cell onemia in man.

6- Complementary genes "qualitative". This is a genetic case through which the character is controlled by 2 pairs of genes, the dominant character appears if at least one dominant gene is found in each pair. The ratio is 9: 7 in the second generation. e.g some strains of pea flowers.

7- Lethal genes are genes which cause the death of forth of the offspring when they are in a pure state

8- Multiple alleles is a case in which the genetic traits are controlled by more than one pair of allelomorphic genes but each individual carries only two genes e.g. inheritance of fur colour in rabbits and blood groups in man.

9- Blood groups in man represents three genetic cases.
A- Complete dominance because both gene A and B dominate over 0.
B- Lack of dominance because gene A and gene B give AB.
C- Multiple alleles because there are three genes A, B, O but the share of each individual is only one pair.

10- Blood groups in man are A, B, AB, O and they are determined according to the antigens and antibodies "chemical bases"

11- Rhesus factor is an antigen, it is found in about 85% of human beings which are RH⁺ the other 15% are RH^-, there are three pairs of genes that control the production of rhesus antigens, they are very similar in their effect.

12- Linked genes are genes that carried on the same chromosome and transferred from parents to their off spring as one unit Mendel ratio can not be applied e.g. the inheritance of wing length and body colour in drosophila fly.

13- In some cases linkage between genes is broken due to the crossing over which occurs during meiosis.

14- The chromosomal maps was done by Morgan and they represent the chromosome and the arrangement of genes on these chromosomes and the distances between genes.

15- In each somatic cell there is the total number of chromosome, they are divided into one pair called sex chromosomes and the rest are called autosomes.

16- In man there are 46 chromosomes 44 autosomes + XX for females, 44 autosomes + xy for males.

17- The reproductive cells or gametes contain half the number of chromosomes.

18- There are some abnormal cases
A- Down's syndrome: male 45xy, female 45xx
B- Klinefeltersyndrome: 44xxy
C- Turner's syndrome: 44x
D- Multiple sex genes: 44xxx or 44 xxxx

19- Barr body is a sex chromosome x which is compact and can be stained it is used to determine the sex of some players or competitors at the Olympics.

20- Sex-lined inheritance means that the trait is determined by the genes located or carried on the sex chromosome x examples: White eye colour in drosophila, colour blindness in man, hemophili. The female passes these traits to her sons and the sick man passes them to his grand sons through his daughters.

21- Sex influenced inheritance means the genes are carried on the autosomes but the action of genes is influenced by sex hormones. Examples: Sheep horns [dorset-suffolk] and premature baldness in man.

22- The environment has an effect on the genes and their characters e.g. orbanch has no genes for chlorophyll formation so it can not make photosynthesis even if it is exposed to light.

23- The appearance of any character in a living organism depends on:
A- The presence of its genes
B- Suitable environmental conditions.

24- The effect of heat on genetic characters is seen in the following:
A- The white fur changed to black in low temp. in Himalayan rabbits.
B- The drosophila wings grew curved in high temp. (25^o C)

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