JK-TK/Newdata huggingface dataset:
Inversion:
A portion may break from a chromosome and then rejoin to it after turning though an angle-of 1800 . Translocation:
This is when a portion is joined to a non-homologous chromosome. Duplication:
A certain section of an intact chromosome replicates such that the genes are repeated. Gene Mutations
A gene mutation is a change in the structure of a gene. It may involve only a change in one base, e.g. adenine in place of thyamine yet the effect on the individual is profound e.g. sickle cell anemia . There are two main type of gene mutations:
Due to insertion or deletion of one or more (base) pairs. Substitution of base pairs e.g. purine for pyrimidine. Genetically inherited disorders in humans
Albinism is a mutation that alters the gene responsible for synthesis of skin pigment (melanin). The gene for albinism is recessive. Sickle cell anemia is a common condition in Kenya. Individuals with the sickle-cell gene produce abnormal haemoglobin. It is due to gene mutation caused by substitution of the base adenine for thymine. The result is the inclusion of the amino acid valine (in place of glutamic acid) in the haemoglobin synthesised. As a result the red blood cells become sickle shaped when oxygen concentration becomes low i.e. inside tissues. This leads to blockage of capillaries. Tissues do not get sufficient oxygen. Homozygous individuals are seriously anaemic and die in early childhood. Heterozygous individuals have a mixed population of normal and sickled red blood cells. They are not seriously anaemic and can lead fairly normal lives. Haemophila (bleeder's diseases) is due to lack of gene for production of proteins responsible for blood clotting. Practical Applications of Genetics
Study of genetics has been put into a wide variety of uses en-compasing plants and animals and in particular humans. Blood transfusion
Blood groups are genetically determined. As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, a patient may be given blood group A + when he/she is A-. First transfusion is fine since, by the time enough antibodies are produced most of the red blood cells of donor have completed their lifespan but a subsequent transfusion of A+ blood is fatal.
As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, a patient may be given blood group A + when he/she is A-. First transfusion is fine since, by the time enough antibodies are produced most of the red blood cells of donor have completed their lifespan but a subsequent transfusion of A+ blood is fatal. Plant and Animal breeding
Genetics is applied mostly in plant and animal breeding in order to produce varieties that are most suitable to man's needs. This is done through artificial selection. Varieties are developed that are resistant to pests, diseases or harsh climatic conditions. Genetic counselling
Genetic counselling involves advising about hereditary diseases and disorders so that they can make informed decisions. This is done through:
Taking family history. Screening for genotypes e.g. through amniocentesis. In amniocentesis, cells are obtained from amniotic fluid during pregnancy. Conditions such as Down's syndrome can be detected using microscopy. Genetic Engineering
This is a technology that involves the manipulation of the genotype of an organism to get the desired trait. It also involves the transfer of gene coding for the desired trait from one organism to another. Application of Genetic Engineering
Pharmaceutical industries:
Making of hormones e.g. Human insulin and human growth hormone. Enzymes e.g. Alph-Anti-Trypsin (AAT) used to treat emphysema. (c) Proteins. Drugs and vaccines. Agricultural industries:
Transgenic animals and plants are produced which are also called Genetically Modified Organisms (GMO's). A variety of tomato with improved paste and a longer shell life. Sheep for producing desired proteins in milk. Plants resistant to pests and diseases. Cloning
This is the making of identical copies of genes, DNA and whole organisms. Cloning is used in plants - that is tissue culture e.g. in development of various varieties of bananas and Eucalyptus trees. The first mammal to be cloned successfully was Dolly - the sheep. A nucleus from the cell obtained from the udder of the sheep was inserted in an unfertilised egg without a nucleus. This zygote was introduced into the uterus of a sheep and developed to full term. Gene therapy
Involves injecting genes into patients of certain diseases
e.g. Parkinson's diseases.
This zygote was introduced into the uterus of a sheep and developed to full term. Gene therapy
Involves injecting genes into patients of certain diseases
e.g. Parkinson's diseases. The injected gene alters metabolism to bring about the cure of the disease. Practical Activities
To demonstrate Continuous variations
Height of students
Students should work in pairs, use chalk and metre rule to mark level of top of head onto the wall
Or door as one student stands straight without shoes, next to the wall or door. The height for each student is recorded on chalk board. The frequency distribution of height is recording as the height is grouped into various classes. A histogram to represent frequency against height is drawn. The normal bell shaped curve is observed. Discontinuous variations - ability to roll tongue
The number of students who can roll their tongue is recorded as well as the number of non-tongue rollers. The ratio of tongue-rollers to non tonguerollers is worked out. Gene for the ability to roll the tongue is dominant, therefore is expected more tongue rollers. Demonstration of Mitosis and Meisosis
Mitosis
Plasticene is used to represent number and shapes of various chromosomes e.g. 8 in Drosophila melanogaster. Each stage of mitosis illustrated e.g. interphase,
Each is rolled to appear long is and coiled, prophase is each made into a ball and then shaped to the appropriate length; and split into two to represent chromatids. Centromeres for different chromosomes can be illustrated in different positions. Each stage of mitosis is illustrated and telophase can be illustrated by surrounding the "chromosomes" with a long many drawn plasticene to represent cell membrane. It is manipulated to show how telophase takes place. Meiosis
The same procedure is followed. Plasticine with contrasting colours is used to show clearly gene mixing in crossing over. Each pair of homologous chromosomes is represented by plasticene with two different colours e.g. red (paternal) blue for maternal chromosome. All the steps in the two stages of meiosis are illustrated up to the production of four haploid gametes. Human Finger Prints
The finger prints for each student's thumb, forefinger and middle fingers of the left hand is imprinted on a white paper. A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad. For best results students work in pairs.
Human Finger Prints
The finger prints for each student's thumb, forefinger and middle fingers of the left hand is imprinted on a white paper. A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad. For best results students work in pairs. Observations are made at all forefingers, thumb prints and differences noted. The main patterns are noted. It is also noted that no two, fingerprints are exactly similar. end
EVOLUTION
Meaning of Evolution and Current Concepts
Evolution is the development of organisms from pre-existing simple organisms over a long period of time. It is based on the similarities in structure and function that is observed in all organisms. All are made up of cells, and similar chemical compounds are present. This indicates that all organism may have had a common origin. Evolution seeks to explain the diversity of life and also to answer the question as to the origin of life, as well as its present state. The Origin of Life
Human beings have tried to explain how life began. Currently held views are listed below:
Special creation -life was created by a supernatural being within a particular time. Spontaneous generation life originated from non-living matter all at once. e.g. maggots arise from decaying meat. Steady state - life has no origin. Cosmozoan - life on earth originate from elsewhere, outer space. Bio-chemical evolution-life originated according to chemical and physical laws. Only special creation and chemical evolution will be discussed. Special Creation
The earliest idea is that of special creation which is recorded in the old testament (Genesis 1: 1-26). It states that God created the world and all living things in six days. Some hold the six days literally, while others say it may represent thousands of years. According to his theory, the earth and all organisms were created mature. Similarities in structure and function denote the stamp of a "common Designer"
Evidence for this view arises from observations of life itself. Faith explains it all. By faith we understand that the universe was created by the command of God. Several scientists hold this view and their research confirms accounts in the old testament of a universal flood explains the disappearance of dinosaurs as vegetation decreased.
Faith explains it all. By faith we understand that the universe was created by the command of God. Several scientists hold this view and their research confirms accounts in the old testament of a universal flood explains the disappearance of dinosaurs as vegetation decreased. Chemical Evolution
The following is the line of thought held in this view to explain origin of life:
The composition of atmospheric gases was different from what it is today:
There was less oxygen, more carbon (IV) oxide, hence no ozone layers to filter the ultra-violet light. The high solar energy reached the earth and brought together hydrogen, carbon (IV) oxide and nitrogen to make organic compounds. These were: hydrocarbons, amino acids, nucleic acids, sugars, amino acids and proteins. The proteins coalesced and formed colloids. Proteins and lipids formed a "cell membrane" that enclosed the organic compounds, to form a primitive cell. The cell was surrounded by organic molecules that it fed on
heterotrophically. This took place in water. From this cell progressively autotrophs evolved. That were similar to blue-green algae. They produced oxygen and as more oxygen was evolved ozone layer formed an blocked ultra violet radiation. This allowed formation of present day photo-autotrophs. Evidence for Organic Evolution
Most of the evidence for evolution is indirect . i.e. it is based on studies carried out on present-day animals and plants. Direct evidence is obtained from studying the remains of animals and plants of the past. Fossil Records
The study of fossils is called paleontology. Fossils are remains of organisms that lived in ancient times. Most fossils are remains of hard parts of the body such as bones, teeth, shells and exoskeletons. Some fossils are just impressions of the body parts, e.g. footprints, leaf-vennation patterns, etc. Fossils are usually found in sedimentary rocks which have been formed by deposition of sediments over millions of years. The deeper the layer of sediments, the older the fossils found in that layer. Modem man, Homo sapiens, evolved from ape-like creatures 25 million years ago. These evolved to upright, tool using creature called Australopithecus afarensis which had a cranial capacity of 400-500 cc. This evolved through several intermediates; Homo habilis and Homo erectus to modem day human. Homo sapiens has a cranial capacity of 1350 - 1450 cc.
These evolved to upright, tool using creature called Australopithecus afarensis which had a cranial capacity of 400-500 cc. This evolved through several intermediates; Homo habilis and Homo erectus to modem day human. Homo sapiens has a cranial capacity of 1350 - 1450 cc. Homo sapiens is more intelligent. Main features in human evolution include bipedal posture, is an omnivore and has an opposable thumb. Limitations of the Fossil Evidence
Only partial preservation was usually possible because softer parts decayed. The fossil records are therefore incomplete. Distortion - parts of organisms might have become flattened during sedimentation. Subsequent geological activities e.g. erosion, earthquakes, faulting and uplifting may have destroyed some fossils. Geographical Distribution
Until about 250 million years ago, all the land masses on earth formed a single land mass (Pangaea). This is thought to have undergone continental drift, splitting into different continents. Consequently, organisms in certain regions became geographically isolated and did not have a chance to interbreed with other organisms in other regions. Such organisms underwent evolution in isolation and have become characteristically different from organisms in other regions. For example, pouched mammals (e.g. kangaroo, wallaby, koala bear) are found almost exclusively in Australia. The opossum is the only surviving representative of the pouched mammals in North America. Comparative Embryology
During the early stages of development, the embryos of different vertebrates are almost indistinguishable. Fish, amphibian, bird and mammalian embryos have similar, features, indicating that they arose from a common ancestor. Similarities include:
Visceral clefts, segmental muscle blocks (myotomes) and a single circulation. Comparative Anatomy
Comparative anatomy is the study of organs in different species with the aim of establishing whether the organism are related. Organisms which have the same basic features are thought to have arisen from a common ancestor. The vertebrate pentadactyl limb evolved in different ways as an adaptation to different modes of life. e.g. as a flipper in whales, as a wing in bats and as a digging hand in moles. Such organs are said to be homologous, i.e. they have arisen from a common ancestor but they have assumed different functions. This is an example of divergent evolution . The wing of a butterfly and that of a bird are said to be analogous.
they have arisen from a common ancestor but they have assumed different functions. This is an example of divergent evolution . The wing of a butterfly and that of a bird are said to be analogous. i.e. they have originated from different ancestors but they perform the same function. This is an example of convergent evolution. Cell Biology
All eucaryotic cells have organelles such as mitochondria, membrane-bound nuclei, ribosomes, golgi bodies. Thus indicating that different organisms have a common ancestor. The presence of chloroplasts and cellulose cell walls indicates that green plants have a common ancestor. Blood pigments are conjugated proteins with a metal group. Similar pigments are found in different animal groups . e.g. haemoglobin is found in all vertebrates and in annelida (earthworm). This shows that all animals have a common origin. Mechanism of Evolution
The mechanism of evolution can be described as a process of natural selection acting on the heritable variations that occur among the members of a population. A population consists of a group of individuals of the same species. Each individual has a set of hereditary factors(genes). All the genes in a population constitute a gene pool. When reproduction takes place, genes pair with one another randomly. Genes which occur in great numbers in the gene pool, will occur in greater numbers in the next generation. Several theories have been proposed over the years to explain how evolution took place. Lamark’s theory
Lamark had observed that if a part of the body of an organism was used extensively, it became enlarged and more efficient;
If a part of the body was not fully used, it would degenerate. By use and disuse of various body parts, the organism would change and acquire certain characteristics. He suggested that these characteristics would them be passed on to the offspring(next generation). In 1809, lamark published his book ‘’Theory Of Evolution’’. He proposed that new life forms arise from use and disuse of parts of existing organisms and through the inheritance of acquired characteristics. Lamark’s theory has been disapproped in that although use and disuse of parts does lead to acquired characteristics, such characteristics are not inheritable since they are effects produced by the environment and not by genes. Evolution by natural selection
In 1859, charles Darwin published his theory of evolution’ in a book called origin of species by means of natural selection’.
He proposed that new life forms arise from use and disuse of parts of existing organisms and through the inheritance of acquired characteristics. Lamark’s theory has been disapproped in that although use and disuse of parts does lead to acquired characteristics, such characteristics are not inheritable since they are effects produced by the environment and not by genes. Evolution by natural selection
In 1859, charles Darwin published his theory of evolution’ in a book called origin of species by means of natural selection’. Darwin’s theory was based on the following evidence;the population of a given species remains constant over a long period of time. The number of young ones is more than the number of adults. More offsprings are produced than can possibly survive. Variation occurs withing a given population,i.e all members of the same species are not alike. On the basis of these observations. Darwin made the following conclusions;
There is a struggle for existence among individuals in a given population. Individuals who are not suitably adapted (e.i. who have unfavourable variations)are less able to pass their characteristics to the next generation. Natural selection operates on the population, selecting those individuals with favourable variations;
i.e. environment favours individuals that are more adapted. They win competition e.g. for food and survive.i.e. ‘’survival of the fittest’’. They attain sexual maturity and pass on the characteristics to their offsprings. Natural selection
Peppered moth (Industrial melanism)
The peppered moth, Biston betularia, exists in two distinct forms;
A speckled white form(the normal form) and the melanic, dark form. The moths normally rest on the tree trunks and branches wherre they are camouflaged against predators. The first melanic moths were observed in 1848 around Manchester in Britain. Since that time, their numbers has increased tremendously, out-numbering the speckled white form. The increase in the population of the melanic form is correlated with environmental changes brought about by industrialization and pollution. Smoke and soot from factories have darkened the tree trunks over the years. This has resulted in the preservation of the mutation in Biston betularia leading to the evolution of the melanic form. This form is almost invisible against the dark background of the tree trunks and is less subject to predation than the speckled form.
Smoke and soot from factories have darkened the tree trunks over the years. This has resulted in the preservation of the mutation in Biston betularia leading to the evolution of the melanic form. This form is almost invisible against the dark background of the tree trunks and is less subject to predation than the speckled form. The peppered form is more abundant in areas away from the soot and smoke of factories. This is because it is well camouflaged by the lichen-covered tree trunks against which it rests and is therefore not easily detected by predators. The existence of two or more distinct forms within a species (as exemplified by Biston betularia) is called polymorphism. Resistance to Drugs
Certain strains of organisms have developed resistance to drugs and antibiotics. Following continued use of such drugs and antibiotics, some of the individuals in a population of bacteria or other microorganisms survive and are able to pass their characteristics to the next generation. When a patient fails to take full dosage of the antibiotics prescribed the pathogen develops resistance to the drugs hence become difficult to control. Some mosquitoes have developed resistance to certain pesticides. Practical Activities
Comparison of Vertebrate Limbs
Limbs of various vertebrates are provided:
e.g. fish- Tilapia, amphibian-frog reptiles, lizard; bird - domestic fowl (chicken), mammal- rabbit. Their anatomy can be studied. The following can be noted:
That all limbs have five sets of bones;
A single upper bone- the femur in hind limb and the humerus in fore limb
Two lower limb bones -i.e. the tibia & fibula in the hind limb & ulna & radius in the forelimb. Small bones - i.e. ankle (tarsals) and wrist bones (carpals)
The bones making the foot and hand are metatarsals and metacarpals respectively. The bones of toes and of fingers i.e. phalanges
Observe the various modifications of these bones in the various animals. Limbs of different mammals e.g. rabbit, cow, donkey reveal that the anatomy is adapted to mode or type of movement . e.g. the horse has a single digit. An outdoor activity to observe various sty les of movement in different mammals can be studied. It is noted that some move on tips of toes (donkey) others on the whole leg (rabbit).
the horse has a single digit. An outdoor activity to observe various sty les of movement in different mammals can be studied. It is noted that some move on tips of toes (donkey) others on the whole leg (rabbit). Comparision of Wings of bird-and insect
Wings of birds and insects (grasshopper, butterfly or moth) are obtained. A hand lens or a dissecting microscope is used to observe the specimens. The differences in their anatomy is noted. Insect wings are membranous while those of birds are made up of feathers that interlock. Education tour to Archeological site/local Museum
Visits to the local museum yield important information that greatly supplement study of evolution. The National museum in Nairobi has many fossils. Visit to the various archeological sites that exist in Kenya is recommended. end
RECEPTION, RESPONSE AND CO-ORDINATION
IN PLANTS AND ANIMALS
Introduction
The structures involved in detecting the changes may be located far away from the ones that respond. There is need for a communication system within the body. The nervous system and the endocrine system perform this function,
i.e. linking the parts of the body that detect changes to those that respond to them. Irritability
Living organisms are capable of detecting changes in their internal and external environments and responding to these changes in appropriate ways. This characteristic is called irritability, and is of great survival value to the organism. Stimuli
A stimulus is a change in the internal or external environment to which an organism responds. Examples of stimuli include light, heat, sound, chemicals, pH, water, food, oxygen and other organisms. Response
A response is any change shown by an organism in reaction to a stimulus. The response involves movements of the whole or part of the body either towards the stimulus or away from it. It also results in secretion of substances e.g. hormones or enzymes by glands. Co-ordination
Co-ordination is the working together of all the parts of the body to bring about appropriate responses to change in the environment. Reception
Reception is the detection of changes in the environment through receptors. Irritability in Plants
Response in plants is not as pronounced as in animals. This does not in anyway diminish the importance of irritability in plants. It is as important to their survival as it is in animals. Plants respond to a variety of stimuli in their environment. These stimuli include light, moisture, gravity and chemicals.