6.4 Inheritance
.Essential idea: The inheritance of genes follows patterns.
Nature of Science: Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data. Understandings: 6.4.1 Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed. 6.4..2 Gametes are haploid so contain only one allele of each gene. 6.4.3 The two alleles of each gene separate into different haploid daughter nuclei during meiosis. 6.4.4 Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles. 6.4.5 Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects. 6.4.6 Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. 6.4.7 Some genetic diseases are sex-linked. The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes. 6.4.8 Many genetic diseases have been identified in humans but most are very rare. 6.4.9 Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer. Applications and Skills 6.4.10 A: Inheritance of ABO blood groups. 6.4.11 A: Red-green colour blindness and hemophilia as examples of sex-linked inheritance. 6.4.12 A: Inheritance of cystic fibrosis and Huntington’s disease. 6.4.13 A: Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl. 6.4.14 S: Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses. 6.4.15 S: Comparison of predicted and actual outcomes of genetic crosses using real data. 6.4.16 S: Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases. Guidance/International Mindedness Guidance: Alleles carried on X chromosomes should be shown as superscript letters on an upper case X, such as Xh |
Light Energy into Chemical Energy
Producers absorb sunlight using chlorophyll and other pigments. This makes the light energy convert into chemical energy which is used to make carbon compounds. Producers can release energy by cell respiration and then use it for cell activities. Energy released is usually later lost to the environment because energy cannot be recycled. The largest part of energy remains in the cells and tissues which is later passed on to consumers. Each cell in the body contains 23 pairs of chromosomes. One chromosome from each pair is inherited from your mother and one is inherited from your father. Genetic mutations occur when DNA changes, altering the genetic instructions. This may result in a genetic disorder or a change in characteristics.
Mutations can be caused by exposure to specific chemicals or radiation. Mutations can also occur when DNA fails to be copied accurately when a cell divides. Mutations can have three different effects. They may:
Examples of genetic conditions inherited in this way include:
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