* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 10.1 Methods of Recording Variation
Gene therapy of the human retina wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Saethre–Chotzen syndrome wikipedia , lookup
Medical genetics wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Genomic imprinting wikipedia , lookup
Epigenetics of neurodegenerative diseases wikipedia , lookup
Genetic testing wikipedia , lookup
Behavioural genetics wikipedia , lookup
Genetic drift wikipedia , lookup
Gene therapy wikipedia , lookup
Neuronal ceroid lipofuscinosis wikipedia , lookup
Koinophilia wikipedia , lookup
X-inactivation wikipedia , lookup
Gene expression profiling wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Genome evolution wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Frameshift mutation wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
History of genetic engineering wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Genetic engineering wikipedia , lookup
Gene expression programming wikipedia , lookup
Heritability of IQ wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Population genetics wikipedia , lookup
Point mutation wikipedia , lookup
Public health genomics wikipedia , lookup
Designer baby wikipedia , lookup
Human genetic variation wikipedia , lookup
F 6 Biology - Ch 10: Genetic Change and Variation Name:__________________________( ) Variation forms the basis of evolution. There are two basic forms: 1.Continuous variation where 2.Discontinuous variation where 10.1 Methods of Recording Variation 10.1.1 Table of data 10.1.4 Bar graph 10.1.5 Kite graph 10.1.2 Line graph 10.1.6 Pie chart 10.1.3 Histogram 1 F 6 Biology - Ch 10: Genetic Change and Variation Name:__________________________( ) 10.2 Types of Variation 10.2.1 Continuous variation - Characteristics within a population vary only very marginally between one individual and the next → a graduation from one extreme to the other - examples: - Characteristics which show continuous variation are controlled by the combined effect of a number of genes (polygenes) - a polygenic character - The random assortment of genes during metaphase I of meiosis ensures that individuals possess a range of genes from any polygenic complex: all tall genes → very tall all short genes → very short about 1/2 tall and 1/2 short genes → intermediate height 10.2.2 The normal distribution curve The mean (arithmetic mean) is the average of a group of values. The mode is the single value of a group which occurs most often. The median is the central or middle value of a set of values. The standard deviation is a value which gives an indication of the range of values on either side of the mean. 2 F 6 Biology - Ch 10: Genetic Change and Variation Name:__________________________( ) 10.2.3 Discontinuous (discrete) variation 3 - characters which do not show a gradation between extremes but fall into a number of distinct forms - usually controlled by a single gene which may have 2 or more alleles 10.3 The chi-squared test (not required in syllabus) 10.4 The t-test (not required in syllabus) 10.5 Origins of Variation 1. Environment 2. Genetic change: reshuffling of genes and mutation 10.5.1 Environmental effects Phenotype is the result of its _____________ and effect of ____________________. Because environmental influences are themselves very various and often form gradations, e.g. temperature, light intensity, etc., they are largely responsible for continuous variation within a population. 10.5.2 Reshuffling of genes - creating new combinations during sexual reproduction by: Mutation is any change in the structure or the amount of DNA of an organism. Most mutations occur in body cells and do not pass to offspring. Only those that affect gametes can be inherited and produce sudden and distinct differences between individuals → discontinuous variation 10.5.3 Changes in gene structure (point mutation) Gene mutation (point mutation) is gene mutation → wrong sequence of amino acids → no enzyme → absence of a character, e.g. pigment There are many forms of gene mutation: 1. Duplication 2. Addition (insertion) - 3. Deletion - 4. Inversion - 5. Substitution - F 6 Biology - Ch 10: Genetic Change and Variation Name:__________________________( ) example: sickle-cell anaemia is the result of but resistant to malaria ! 10.5.4 Changes in whole sets of chromosomes Polyploidy is the possession of more than ___________ sets of ___________________ e.g. triploid means ; tetraploid means Formation of tetraploid offspring: Formation of triploid offspring: Autopolyploidy - Autopolyploidy can be induced by colchicine (a chemical) which inhibits Triploids are sterile because they cannot If, however, a hybrid has a chromosome number which is a multiple of the original chromosome number, a new fertile species is formed, e.g. wheat (n=42) is the cross between wild grass (n=14) and emmer wheat (n=28) Allopolyploidy - Allopolyploidy is rare in _________________, but relatively common in __________, including many food plants, e.g. ________________________________________________ The polyploid variety often have advantages, e.g. 4 F 6 Biology - Ch 10: Genetic Change and Variation Name:__________________________( ) 10.5.5 Changes in chromosome number 5 Non-disjunction occurs when Down's syndrome: Down's syndrome often occurs in ova formation rather than sperms, especially in old age pregnancies. Turner's syndrome: Klinefelter's syndrome: 10.5.6 Changes in chromosome structure This occurs in meiosis when crossing over takes place. There are 4 types: 10.6 Causes of Mutations There is natural mutation rate which varies from one species to another. Animals with shorter life cycles show a greater rate of mutation because of more frequent meiosis. This natural mutation rate can be increased artificially by certain chemicals e.g. or energy sources (mutagens), e.g. F 6 Biology - Ch 10: Genetic Change and Variation Name:__________________________( ) 6 10.7 Genetic Screening and Counselling - not required in syllabus To risk for a mother to have babies with certain genetic diseases could be calculated, if enough information of the disease in the family is known, e.g. Down's syndrome, haemophilia. On the basis of this advice parents can choose whether or not to have children. Doctors can diagnose certain genetic defects, e.g. Down's syndrome, in a foetus, by studying samples of cells taken from the amniotic fluid which surrounds the foetus - a process called amniocentesis. Parents can then decide to have the pregnancy terminated. 10.7.1 Gene tracking To find out on which chromosome a defective gene is located. Blood groups are traced in families to act as gene markers. Correlation between certain blood groups alleles and the occurrence of a genetic disease can determine whether or not the gene for the disease is on the same chromosome as that for blood groups. If one genetic marker is not linked to the disease in question another must be tried and so on until the one which shows linkage with the disease is found. Linked markers are then used to work out if someone carries a disease. E.g. Huntington's disease (neuropsychiatric disorder leading to the loss of control of movements) fails to show itself until people are in the 40's or 50's. Any technique which allows the presence of the gene to be detected early helps individuals to decide whether or not to have children, and also shows the size of the risk of those children carrying the gene.