* Tahia * 7. Formulate the definitions of the basic concepts of genetics: gene, allelic and non-allelic genes, genotype, phenotype, homozygosity, heterozygosity, hemizygosity. A gene: is a section of a DNA (or RNA) molecule that encodes a sequence of amino acids in a polypeptide chain or a sequence of nucleotides in transport RNA (t-RNA) and ribosomal RNA (rRNA) molecules. A genotype is a collection of all genes in an organism A phenotype: is a set of all the characteristics of an organism that are formed as a result of the implementation of a genotype under certain environmental conditions. Locus: is the region of the chromosome where the gene is located A homozygous: organism is an organism that has two identical allelic genes and produces one type of gamete. For example, organisms with genotypes AA and aa. Heterozygous organism : an organism that has two different allelic genes and produces two types of gametes. 11. The concept of dominance and recessiveness Dominance : is a form of relationship between alleles of one gene, in which one of them (dominant) suppresses (masks) the manifestation of the other (recessive) and thus determines the manifestation of a trait in both dominant homozygotes and heterozygotes >>> Recessiveness : is a form of relationship between two allelic genes, in which one of them, the recessive one, has a less strong effect on the other (dominat) recessive gene not appear in phenotype if there dominat gene because the dominant gene suppresses it, but appear just if there the same recessive gene __________________________________________ 13. Mendelian signs of a person In humans, mendelian signs are, for example, albinism ) lack of pigmentation caused by a recessive gene ; occurs in all human with a frequency of 1 in 20-30 thousand newborns) _ eye color_ hair character (curly or Smooth) _ group differences for various factors in the blood (see. Blood groups) _ Genes that cause hereditary diseases of a person also obey Mendel's laws _ there are concepts of mendelian traits (inherited according to Mendel's laws) and non-altering (inherited according to other laws) Mendelian signs in all organisms are large. Some mendelian signs in humans _____________________________________________________________ 12. Conditions for the Mendelian Characteristics. The statistical nature of Mendeleev's laws. Mendelian conditions:
