Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
List a few exceptions to the genetic code.
A gene is a unit of genetic material present on the strand of DNA (Deoxyribonucleic acid). DNA complexes with histone proteins to form chromatin fiber. Double stranded, helical structure of DNA contains four nitrogenous bases, ribose sugar and phosphate group which together form negatively charged phosphate backbone. These nitrogenous bases if arranged in correct order are responsible for expressing amino acids.
Genetic code is a sequence of nitrogenous bases printed on the DNA strand which encodes various amino acids for the functioning of living organisms. These sequences follow some rule in order to be expressed and synthesized in the cell.
- Genetic code is universal: Genes are the universal unit of hereditary. The code encoding amino acids are universal in all animals and plants.
- The code is in triplet form: The genes present on the DNA are in form of threes (triplet). These triplet codes are called as codons. They are the coding regions of DNA. There are also some codes which are non-coding they are called non-codons.
- The code is unambiguous: Each triplet specifies a single amino acid
- Genetic code is degenerate: One amino acid can be encoded by more than one codon. For example; UUU and UUC both expresses phenylalanine amino acids.
- The code is non-overlapping: the last base of any triplet code is not shared overlapped with consecutive triplet.
- Start and stop codon: Every stretch of a DNA contains an initiation/start codon and a termination/stop codon for the process of termination and replication. Start codon is usually AUG which codes for methionine whereas, termination codons are UAA, UAG and UGA
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