SIBC Radio Broadcasts
- 8 May, 2020: Population and Urban Drift 1
- 15 May, 2020: Population and Urban Drift 2
- 22 May, 2020: Probability 1
- 29 May, 2020: Probability 2
- 5 June, 2020: Literature – Poetry 1
- 12 Jun, 2020: Literature – Poetry 2
- 19th June, 2020: Science – Genetics
- 3rd July, 2020: Economics and Commerce
- 10th July, 2020: Accounting
- 17th July, 2020: Agriculture
- 24th July, 2020: Animal Production
- 24th August, 2020: New Testament Study
19th June, 2020: Science – Genetics
Script, prepared and compiled by Cephas Teiraru for radio program
Hello and welcome to all of you who are listening to this radio program from across our country Solomon Islands and especially to you form 4, form 5 and form 6 students. Whether you are attending classes in your schools now, after the Covid-19 break, or just staying at home, this program has been prepared for you.
My name is Cephas Teiraru and I am part of a team of senior secondary teachers who are presenting this radio program geared towards students learning at home particularly at this time when we are under the threat of Covid 19. For me in particular I shall be presenting the science component especially on the biology – strand, sub-strand Genetics. I chose this topic because genetics is covered in the F4/5 science syllabus and also in form 6 Biology.
What is Genetics?
Genetics is a branch of biology concerned with the study of genes, genetic variation and heredity in organism. In a nut-shell genetics is the study of heredity in general and of genes in particular. The concepts in genetics are very theoretical. However its application is very practical in agriculture, medicine and biotechnology.
In our (F4/5) science syllabus, the study of genetics is very brief and general. We look at the structure of chromosomes and genes and how sex chromosomes determined the sex of an individual. We study meiosis and mitosis cell division especially their functions and finally application of genetics.
At the Form 6 level, the content is broader. We look at the structure of DNA and RNA, the relationship of DNA and genes in protein synthesis which is important in our understanding of inheritance. We study the steps in mitosis and meiosis cell division and their importance especially in regards to genetic variation that makes us unique. Finally we look at the type of genes in an organism (dominant or recessive, incomplete and co-dominance) and how the genes express themselves in the appearance (phenotype) of the organism.
First of all let me briefly go through the learning outcome of the study of genetics in the F4/5 science syllabus and the study of genetics at the F 6 level
After completing the unit on genetics the students in F4/5 should be able to:
- Describe the structure of chromosome and genes
- Explain how sex chromosomes determine, the sex of an individual
- Describe how cells divide by mitosis or meiosis and the importance of these divisions in the life of organisms
- State the functions of mitosis and meiosis cell division, and why the divisions are important to the survival of organisms
- Describe how genes are inherited (dominant and recessive gene)
The learning outcomes in the biology prescription at the form 6 level on genetics are:
Students should be able to;
- Describe the structure of DNA and RNA in terms of sugar, phosphate, bases, nucleotides, and base pairing
- Explain the relationship between a gene and protein synthesis
- Describe the process of transcription and translation
- Describe the relationship between chromosomes, DNA and genes
- Describe the events in mitosis and meiosis
- Describe the roles of mitosis and meiosis in the life of an organism
- Explain inheritance in organisms (Mendelian Genetics)
- Explain the application of genetics in agriculture, medicine and biotechnology (genetic engineering)
For the purpose of this radio program I shall consider selected learning outcomes, that is common at the F4/5 science syllabus and the F6 Biology prescription and merge them together. In this way I hope I shall be able to present to you through this presentation, a clearer understanding of genetics for the learner.
Secondly by doing this I should be able to bridge the gap between F4/5 genetics to F6 genetics and possibly beyond to tertiary level
Having done that the combined outcomes now reads as follows
- Describe the relationship between chromosomes, DNA and genes
- Describe the structure of DNA and Chromosome
- Describe mitosis and meiosis cell division
- State the function of mitosis and meiosis and their importance in the survival of an organism
- Describe and demonstrate mendelian inheritance
- Describe application of genetics
First of all, I will brief you on what genes are in relation to chromosomes and DNA. Second I shall take about how genes are inherited and finally I shall highlight some of the application of genetics.
What are genes?
Before we discuss what genes are there basically three things that the study of genetics is specifically concerned about. These are the number and type of chromosomes in an organism, the type of nucleic acid and structure (DNA or RNA) and of course the type of genes- dominant, recessive, co-dominance, and incomplete dominance
I shall start by explaining what genes are, and after I shall explain what is DNA and lastly what chromosomes are. Finally I will explain the relationship between chromosomes, DNA and genes as they apply in inheritance.
Genes: Genes are chemical components of a very large molecule called deoxyribose-nucleic acid, in short DNA found in the cells of every living creature, human beings and all animals, plants, fungus, bacteria etc. Genes are the instructions inside your DNA. Your genes control how you look (Shape and structure) how your body works (function) and your behavioural pattern (attitude). Genetically speaking, what you are and who you are is the expression of your genes. Part of what makes you unique or different from another person is your genes. Apart from our mere physical structure our overall personality; how we think, feel and behave is controlled by our genes.
Let me suggest a simple observational experiment you can do this evening. When you and your other family members or household come together for dinner, observe their skin colour. At first glance they may seem to all have brown skins, but upon closer observation you will notice that each individual have different shades of brown, even amongst the same siblings. You can also go to the central market and observe the shape, height and length of the eyes of 100 people. You will notice that no two persons have the same eye shape and dimension.
We are unique. Every single person has slightly different genes therefore everyone has a slightly different set of instructions. This makes us unique and different from one another.
To summarize we say, genes are components of DNA and has instructions that control how you look and how your body works. Since everyone has slightly different genes, everyone has a different set of instructions and this makes us unique.
What is DNA?
DNA is an abbreviation for deoxyribose-nucleic acid. It is a chemical substance that is located in the nucleus of every cell. DNA contains the genes that we have looked at previously.AS you aware by now, it is the genes or the instructions in our DNA that make us different from another individual and also what make each type of living creature unique. For example a dog is different from a crocodile; a fish is different from a bird and so on.
What are Chromosomes?
Chromosomes are physical structures (thread-like) located inside the nucleus of cells. Each chromosome is made of protein and a single molecule of DNA.
Relationship between Chromosome, DNA and genes
Chromosomes are the visible structure that contain the DNA which contain the genes.
To better understand the relationship between chromosomes, DNA and genes let me put it this way. Consider an ice cube, which is frozen water. The ice cube is made of water molecules (2 hydrogen atoms joined to and atom of oxygen). A chromosome is like the ice cube, which you can see, DNA is like the molecule of water and the genes are the two atoms of hydrogen and one atom of oxygen.
Structure of DNA and Chromosomes
Chromosomes are found in the nucleus of every cell. Chromosomes are made up of a chemical substance called DNA which contains the genes. Chromosomes are not normally visible but when a cell is about to divide they can be observed using a high powered microscope as threads
Each chromosome consists of two threads joined together at the middle like the letter X. The two parts of the letter X are called chromatids. Let me remind you that presenting a chromosome like the letter X is just the usual way of showing a chromosome in many biology text books. It can be drawn otherwise. The only chromosome that resembles the letter X is the sex chromosome X. It is called the X chromosome because its shape is like the letter X. The important thing to remember is that a chromosome consists of two chromatids joined together. The genes are located at various points on the chromosome.
In human beings we have a total of 46 chromosomes with their genes in all the body cells, except for the sperm and egg cells which contain only 23 chromosomes. However when a sperm cell combines with an egg cell during fertilization to form the zygote, the chromosomes from the egg and those from the sperm come together to give a total of 46. Hence the zygote inherits the chromosomes along with their genes from both the mother and father
Structure of DNA
DNA as you might recall is the chemical substance that makes up the chromosomes. Each chromosome consists of a single molecule of DNA. DNA is a very large molecule consisting of many different atoms. However a molecule of DNA is made up of only 3 groups of chemicals: phosphate, sugar and nitrogenous bases joined together repeatedly to form a very long chain. There are 4 bases in a molecule of DNA ; these are adenine, thymine, guanine and cytosine. These bases join to each other in the following order. Adenine pairs with thymine and guanine pairs with cytosine.
Open your book to a blank page.
One the left side draw a circle- Below the circle, draw a pentagon. Connect the two shapes with a straight line. To the right of the pentagon draw a rectangle. Draw a line to connect the pentagon and the rectangle. Label the circle, phosphate, label the pentagon sugar and the rectangle nitrogenous base. You have just drawn the basic component of DNA.
Now let us continue our drawing. Below the pentagon draw another circle and connect them with a line. Below the circle draw another pentagon. Connect the circle and the pentagon with a line. On the right of the second pentagon, draw a rectangle and connect them with a line. Label the first base adenine and the second base cytosine. Now let us complete our model. To the right of the base labeled adenine, draw another rectangle and label it thymine. Join the two bases with a line. To the right of the base labeled cytosine, draw another rectangle and label it guanine. Again connect the two bases with a line. Finally connect the base labeled thymine to another pentagon drawn at its right side. Also connect the base labeled guanine with a line to another pentagon shape drawn on its right side. Draw a circle above the top pentagon on the right side and also another circle below the second pentagon on the right. Connect the circles to the pentagons. You have just constructed a model of a DNA.
The structure of DNA is comparable to a ladder. The two sides of the ladder are the strands of DNA which consist of phosphate and sugar and the rungs of the ladder are the nitrogenous bases. The bases connect the two strands.
The diagram you have drawn is just a segment of DNA. The actual DNA molecule is like the model you have drawn but repeated millions of times to make a very long chain.