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Genetics and Evolution Summary Notes

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Year 10 Genetics and Evolution Summary Notes
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  Genetics and Evolution Summary Notes Describe the process of meiosis. Meiosis is the process of sex cell formation. (1) MITOSIS MEIOSIS Function Mitosis is the process of normal cell division. Growth :  multi-cellular organisms grow in size and complexity by making more cells Repair:  old and damaged cells are continuously replaced by the division of cells Genetic Stability:  Daughter cells contain same number and kind of chromosomes as the parent cell. For sexual reproduction. Occurs in the testes and ovaries. It produces the gametes. There are two types of gametes. Egg cells and sperm cells. When does it happen? Mitosis occurs only in eukaryotes. When the sperm and the egg unite. Where does it happen? Mitosis occurs in most cells Sex cells How many cell divisions? 1 cell division 2 divisions How many cells? 2 cells. (two daughter cell swish the same chromosome number as the  parental cell. 4 cells How many chromosomes? 46 chromosomes each 23 chromosomes Is there variation in offspring? Mitosis is the copying of cells. Sometimes there might be an error after the egg fertilization. There is variation because the chromatids exchange DNA sections. Uses and results of their use Mitosis is the process by which all cells divide. Many cells have a limited life span, and mitosis allows them to  be renewed on a regular basis. Mitosis is also responsible for generating the many million of cells that are needed for an embryo to develop into a foetus, an infant, and finally an adult. Meiosis functions to reduce the number of chromosomes to one half .Each daughter cell that is produced with have one half as many chromosomes as the parent cell. Meiosis is important in assuring genetic diversity in sexual reproduction.  Identify genes as units of heredity (carriers of genetic information). (2) - A gene  is a unit of heredity in a living organism. It is normally a stretch of DNA that codes for a type of protein. Describe the structure of DNA in terms of four bases; the double stranded backbone, and the double helix shape. (3) DNA - Deoxyribonucleic acid - DNA carries the genetic information  and passes it from one generation to the next . DNA carries the code  to make proteins  (that contribute to determining eye colour and hair colour) to enable the cell to reproduce and perform its function. The Double helix - In 1953, James Watson, Francis Crick and Rosalind Franklin discovered that the structure of DNA was a double helix Structure: - Two strands intertwine like a spiral staircase to form a structure called a double helix. - Sides: Deoxyribose sugar and a unit of phosphate forms the upright supports along the sides. Each sugar  joins with a base. - Bases form the rungs of the staircase - The sugar (deoxyribose) + phosphate + a base = a nucleotide. Outline the connection between chromosomes, genes and DNA and particularly identify that information is transferred as DNA when cells reproduce themselves and explain the advantages of DNA replicating exactly. (4) ABOUT: Chromosomes, Genes and DNA - Within each cell is a nucleus  which controls all the activities of the cells. - Inside the nucleus of each of your cells is your unique set of 46 chromosomes.   - Each of these is a long, thread-like structure made up of DNA ( deoxyribonucleic acid ). - Sections of DNA on the chromosomes that contain complete messages are called genes . - The message in a gene is a coded formula needed by the cell to produce one protein . E.g. hair. - The DNA molecule is made up of simple bases called nucleotides.   Base Matching base Adenine Thymine Guanine Cytosine Thymine Adenine Cytosine Guanine  - Each nucleotide is made up of three chemical groups: a Sugar , a Phosphate,  and a Base . - The order in which the bases are strung along the chain forms the basis of the genetic code . Appreciate the role that environmental factors have in determining the features of an organism. (5) The environment plays a big role in the appearance of an organism. The environment includes all surrounding forces of an organism, such as diet, nutrition, climate, exposure to disease. It can affect the expression of genes. Identical genotypes (twins) do not always produce the same  phenotypes because the environment can affect the expression of genes.  Example: Identical twins have exactly the same genes, such as for tall height and strong muscles. If one twin is brought up in a poor family he may eat very little, be thin, not very tall, he may suffer from malnutrition resulting in rickets (bandy legs), scurvy (vitamin C deficiency), and poor teeth, he may be unable to play sport. If the other twin is brought up on a good nutritious diet in a wealthy family he may reach his full height, be fit and strong with good legs and teeth, or if he was brought up on hamburgers and chips he maybe obese.  Environmental Factors influencing your phenotype: - Diet -  Nutrition - Exposure to disease - Climate - Temperature - Sunlight  Environmental Factors promoting Cancer - Smoking  –   lung cancer    - Drinking  –   liver cancer    - Exposure to UV light  –   skin cancer    - Exposure to radiation  –   thyroid caner  Environmental Factors promoting rickets Vitamin D is found in fish and vegetables. When the sun shines on our skin we can also make vitamin D. When children do not get enough vitamin D, the bones in their legs bend, this is called rickets.  Plants Climatic factors - such as rainfall, temperature or exposure to wind - can be important, as well as soil composition and the availability of nutrients. What affects the growth of plants: -   availability of water -   nutrition in the soil -   availability of sunlight -   fertilisers -   climate   Examples: -   The pH of soil can affect the hydrangea plant. -   Those grown in acidic soil produce blue flowers whilst those grown in basic soil produce  pink flowers Distinguish between a gene and an allele. (6) A gene is a unit of heredity and is a section of DNA whereas, alleles refer to different versions of the same gene (e.g. if the height will be short or tall) Define dominant and recessive genes and explain their influence in determining phenotype given the inherited genotype. (7) DOMINANT:  The genes which determines the physical traits of a person. They dominate over recessive genes. RECESSIVE:  A recessive gene is a gene that produces an effect in the organism only when it is homozygous, having identical alleles for a single trait. Genotype:   - Refers to the genetic traits in an organism. - It has to do with the genetic coding of an organism. = - Such coding is inheritable .   - The genotype is the genetic load that is copied every time a cell divides, and therefore is inherited   down to the next generation. Genotype  is something you can't see with your eyes (e.g.. dominant, recessive, heterozygous). Phenotype:   - Refers to observable, physical manifestations of an organism. - The phenotype  includes physical characteristics, behaviours corresponding to such species, structures, organs, behaviours, reflexes, etc. Phenotype  is things that can be seen with your eyes. (ex. colours, growth). The genotype  is the genetic programming  that provides the phenotype. Define biotechnology and explain that genetic engineering is a form of biotechnology. (8)  Biotechnology - Biotechnology is the practice of using plants, animals and micro-organisms such as bacteria, as well as biological processes - such as the ripening of fruit or the bacteria that break down compost - to some benefit.  Genetic Engineering - the deliberate modification of the characteristics of an organism by manipulating its genetic material to improve certain characteristics. Outline the engineering of pest resistance into cotton plants or the production of human insulin by bacteria as examples of genetic engineering. Use these as examples of where developments in Science have led to new technologies. (9) When the gene is inserted into cotton plants, they produce toxic proteins called Bt toxins that kill the bollworm caterpillars. The poison stays in the leaves and does no harm until the bollworm
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