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View Article1.6 Summary
The number of chromosomes is characteristic of each species and can vary enormously between species.Sexual reproduction always includes two distinctive processes: the production of gametes, which...
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6 Inheritance of more than one pair of contrasting characters
We have considered the inheritance of one pair of contrasting characters that involves the segregation of the two copies of one gene in maize. A single chromosome carries many genes, of the order of 2...
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5 Why not an exact 3:1 ratio?
Before we leave the maize breeding experiments we will look more closely at some actual values obtained for the F2 generation and how closely they fit the expected phenotypic ratio of 3:1. Table 2...
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1.3.4 Predicting the outcome of crosses
By knowing the pattern of inheritance of genes as described above, it is possible to make some predictions about the phenotypes and genotypes of each generation in breeding experiments. This section...
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1.3.3 A breeding experiment: stage two
We now turn to the second stage of the breeding experiment, but this time we will follow the phenotypes and genotypes simultaneously. The purple (Gg) grains of the F1 generation are planted and when...
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1.3.2 A breeding experiment: stage one
In the first stage of the breeding experiment, shown in Figure 5, plants from the pure-breeding purple-grained variety are crossed with (fertilised by) plants from the pure-breeding white-grained...
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1.3.1 Inheritance of colour in maize
We can trace the inheritance of characters in animals and plants by following the phenotype from generation to generation, in breeding experiments. We will describe work with maize (Zea mays),...
View Article1.2 Like begets like
It is possible to follow a character, such as eye colour or hair colour in humans, that is handed down from generation to generation. Such characters are said to be inherited characters (or heritable...
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1.1.2 Sexual reproduction
Sexual reproduction includes two distinctive processes:The production of haploid gametes, such as sperm and ova, which involves the specialized nuclear division called meiosis. The fusion of gametes at...
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1.1.1 Chromosomes and the life cycle
The type of nuclear division called meiosis is intimately linked to the life cycle of organisms that reproduce sexually.Chromosomes are present in the cells of all eukaryotes. Their number varies...
View Article1 Unit introduction
Living organisms use the components of the world around themselves and convert these into their own living material. An acorn grows into an oak tree using only water, oxygen, carbon dioxide, some...
View ArticleLearning outcomes
After studying this unit you should know:the number of chromosomes is characteristic of each species and can vary enormously between speciesgenetics is based on the concept of the gene as the unit of...
View ArticleIntroduction
This unit looks at how units if inheritance are transmitted from one generation to the next. First you will look at what happens to the chromosomes of animals and plants during the process of sexual...
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