Chromosomes are substances in the nucleus that are easily dyed dark by alkaline dyes. Chromosomes consist of deoxynucleotides and protein. Deoxynucleotide means that DNA is the carrier of genetic information, which mainly exists in the nucleus, and DNA molecules have double helix structure.
Effective DNA fragments that determine biological characteristics are called genes. Genes determine the characteristics of organisms. A chromosome contains a DNA molecule, and there are many genes on a DNA molecule. Therefore, genes are DNA fragments on chromosomes that control biological traits.
Extended data:
gene mutation
Genetic variation refers to the sudden heritable variation of genomic DNA molecules.
From the molecular level, gene variation refers to the change of base pair composition or arrangement order of genes in structure. Although genes are very stable and can accurately replicate themselves during cell division, this stability is relative.
Under certain conditions, a gene can suddenly change from the original existing form to another new existing form, that is, a new gene suddenly appears at a site to replace the original gene, which is called a mutant gene.
Therefore, new traits that ancestors never had suddenly appeared in the performance of future generations. For example, Queen Victoria's family had never found a hemophiliac before, but one of her sons suffered from hemophilia and became the first member of her family to suffer from hemophilia.
Later, several hemophiliacs appeared among her grandchildren. Apparently, her father or mother's hemophilia gene has mutated. The mutant gene was passed on to her. She is heterozygote, so the phenotype is still normal, but it was passed on to her son through her.
The consequences of gene mutation can not only cause genetic diseases through the formation of the above-mentioned pathogenic genes, but also cause stillbirth, spontaneous abortion and premature death after birth, which is called fatal mutation; Of course, it may not affect the human body, but only cause genetic differences between normal people; It may even bring some benefits to the survival of individuals.
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