Flvs Biology 3.1

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3.0 Chromosomal structure provides the key to inheritance The evidence that chromosomes contain hereditary material on genes, which is passed on to successive generations, is important to our understanding of life. It is well known that it is the sequence of nucleotides on the DNA that carries the genetic information, and that mutations are caused by changes in DNA structure. Mendel’s laws: Law of segregation Inherited characteristics are controlled by genes that occur in pairs. Each gamete contains one gene from each pair. The offspring therefore will regain a gene pair (one from each parent). There is usually more than one alternative allele for each characteristic. The dominant allele will always be expressed when present, but the…show more content…
Since the chromosome pairs carry different genes, the daughter cells (sex cells) produced by meiosis are almost always genetically different. See Biozone. 3.5 Explain the role of gamete formation and sexual reproduction in variability of offspring Genetic variability of offspring occurs for a number of reasons: 1. During sexual reproduction, two sex cells join together in a process called fertilization. Which sex cells join together during fertilization is a random process. New combinations of genes occur, producing genetic variation 2. During meiosis, chromosome pairs sort themselves independently and randomly (this is called random segregation). This produces genetic variation also. 3. When genes for different characteristics are found on the same chromosome, they are called linked genes. Linked genes will usually be inherited together. Exceptions to this linkage occur when crossing over happens. Crossing over is a swapping of chromatid parts of homologous chromosomes early in meiosis, resulting in chromosomes with new combinations of genes and results in increased variation across resulting

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