Presentation on theme: "Genetics & Inheritance SCN 4-14c: I can use my understanding of how characteristics are inherited to solve simple genetics problems and relate this to."— Presentation transcript:
Genetics & Inheritance SCN 4-14c: I can use my understanding of how characteristics are inherited to solve simple genetics problems and relate this to my understanding of DNA, genes and chromosomes.
Activity 1 1.I will be able to define the terms fertilisation, species, variation and chromosome and gene. 2. I will be able to relate my understanding of the process of fertilisation to the passing on of chromosomes.
Definition “If organisms belong to the same species they can interbreed to produce fertile offspring.”
Friday, April 17, 2015Friday, April 17, 2015Friday, April 17, 2015Friday, April 17, Donkey Horse Mule Horses and donkeys can mate to produce a mule – but mules are not fertile so horses and donkeys are separate species. This is a HYBRID.
In the wild tigers and lions are enemies likely to kill each other. Most lions are in Africa and most tigers are in Asia. These types of cross occur in captivity
17/04/2015Variation “Variation” is the name given to differences between individuals of the SAME species. Variation is due to GENETIC or ENVIRONMENTAL causes. For example, consider identical twins: 1)Ways in which Patty and Selma are the same (caused by genes): 2)Ways in which Patty and Selma are different (caused by environment): Selma Bouvier Patty Bouvier
Variation Human examples – height, pulse, blood type, hand span, etc.. This variation within a species can either be CONTINUOUS or DISCONTINUOUS.
If the variation in a characteristic… can not be put into distinct groups has a continuous range of values it shows a wide range of values between the maximum and minimum measurements = CONTINUOUS VARIATION.
Continuous Variation e.g. Height
If the variation in a characteristic…. -allows individuals to be placed into distinct groups -does not show a range of values -has clear cut differences between individuals = DISCONTINUOUS VARIATION.
Discontinuous Variation e.g. ear lobes Attached lobeUnattached lobe
17/04/2015 Where is this information stored? Section of a chromosome: Genes for eye colour Genes for hair colour Genes for blood group: Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell.
Friday, April 17, Variation in Humans Human species have 23 pairs of chromosomes in every cell except the gametes. There is an enormously large number of combinations of chromosomes to form zygotes because fertilisation is random. This means that all zygotes are different. (It depends on which gamete does the fertilising!)
Fertilisation All of our cells contain one set of chromosomes from the mother and one set of chromosomes from the father – this make the 2n! This means there is one set of genes from the mother and one set of genes from the father.
Karyogram –shows the Chromosomes found in a male and female human. What do you notice about them?
Activity 2 I can define the term allele and give examples of alleles for different characteristics.
23 Alleles Genes control the characteristics of an organism, e.g. flower colour in peas. Alleles are different forms of the same gene. –A–An allele is a different form of that gene, e.g. red flower or white flower. chestofbooks.com Flickr.com
24 Examples of allelesOrganismGene Different Alleles Pea plantHeightTall or dwarf HumansBlood typeA or B or O Fruit flyWing typeNormal or vestigial MaizeSeed colourPurple or yellow Labrador DogCoat colourGolden or black BudgerigarFeather colourBlue or green
E.g. Pea Flower Colour
rothamsted.ac.uk E.g. Human Characteristics
Think & Discuss: So for each of your characteristics there are 2 genes controlling it – one from your mother and one from your father. If these lists show the genes in a sperm and in an egg, what genes would you expect to find in the new human?
Answer: They would have all of them! So what would they look like?
Activity 3 I can define the terms genotype, phenotype, dominant and recessive.
Genotype V Phenotype Genotype is the sum of all the genes you possess (represented by letters). Phenotype is the actual physical characteristics you have because of those genes (represented in words). Not all the genes in your genotype can or will show up in your phenotype – why not?
Genotype and Phenotype seniorapbiologyreview.wikispaces.com
Dominant V Recessive The gene in each pair which is dominant always shows through. Imagine the following scenario: The tall gene is dominant to the short gene so the person would be? Tongue rolling is dominant to non-tongue rolling so the person would be? The persons eye colour would be?
33 A dominant allele will always show up in the appearance of an organism. A recessive allele will only show up if it is paired with another recessive allele. When describing an allele, for convenience, we usually give it a symbol, generally the first letter of the dominant allele.
35 If it is dominant it gets the capital letter and if it is recessive it gets the lower case of the same letter. E.g. in pea plants tall is dominant over dwarf, and so the tall allele is given the letter T, and the dwarf allele the letter t. The genotype of the organism is the alleles it carries for that particular characteristic. Complete the “Symbols for Alleles” sheet Tt
36 TT is a genotype and the plant phenotype will be tall. Tt is a genotype and the plant phenotype will be tall, because the T is dominant over the t. Recessive genes have no effect when paired with dominant genes. tt is a genotype and the plant phenotype will be dwarf. The outward appearance of one of its characteristics i.e.What the plant actually looks like (how the genes are expressed) is called its phenotype.