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Creado por louisa.slinger4825
hace alrededor de 11 años
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| Pregunta | Respuesta |
| Distinguish between homozygous and heterozygous genotypes in monohybrid crosses | Alternative factors for the same characteristics are called alleles, for each there are at least 2 factors controlling the phenotype. Factors that are the same are called homozygous; TT or tt and factors that are different are called heterozygous; Tt or tT |
| Describe the chemical nature of chromosomes and genes | Chromosomes are strands of DNA, a gene is a short length of a chromosome, so a gene is a short length of DNA. |
| Explain how an understanding of the source of variation in organisms has provided support for Darwin's theory of evolution by natural selection | The sources of variation (mutations, crossing over, random segregation, random fertilization) provide support for natural selection by showing how new alleles, or combinations of genes can be formed. These genes are the raw materials for variation. If some of the variants are more favourable in a particular environment, and increase survival, then they are more likely to be passed onto following generations. These variations provide the source for variations Darwin refers to in his theory. |
| Discuss the potential impact of the reproductive technologies on the genetic diversity of species using a named plant example that has been genetically altered | Reproductive technologies, such as cloning, and the engineering of transgenic species have the potential to both increase and decrease genetic diversity. By moving genes from species to species, the genetic diversity is being increased. Crops, such as rice, have been genetically engineered to suit a particular climate and topography, making then resistant to herbicides and pesticides commonly used in a particular region |
| Discuss the potential impact of the reproductive technologies on the genetic diversity of species using a named animal example that has been genetically altered | Transgenic animals present greater problems with lower success rates so far. One important use is seen to be the preservation of numbers of endangered species. The first cloned endangered mammal was a guar (an endangered wild ox from SE Asia), but unfortunately it did not survive. It is hoped that reproductive technologies such as cloning and sperm and embryo banks can be used to preserve stocks of threatened species. |
| Describe the process of DNA replication | During replication the DNA unwinds and the double helix separates into two single strands due to an enzyme. These two single strands act as a template for the creation of a complimentary strand. The cytoplasm of the cell contains many free nucleotides, which then forms bonds with the unzipped DNA strands. They join, the strand rewinds, and the two molecules of DNA have been created from one molecule. |
| Describe the significance of DNA replication | The significance of this process is that large amounts of genetic information can be copied accurately and passed on to the next generation providing continuity of the species. |
| Discuss evidence for the mutagenic nature of radiation | A mutagen can be a natural or human-made agent which can alter the structure or sequence of DNA. There is much evidence for the mutagenic nature of radiation, environmental factors ( X-rays, ultraviolet rays) may increase the rate of mutation. Radiation was the first mutagenic agent known. |
| Outline the reasons why the importance of Mendel's work was not recognised until some time after it was published | Mendel began his work in 1858, published his results in 1866 but it wasn't discovered until the 1900's this could have been due to various reasons: He was not a recognised high member of the scientific community, he presented his paper to only a few people, other scientists did not understand the significance of his work, very little was known at that time about cells, chromosomes - the study of genetics didn't exist, he used quantitative data. |
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