the gene where transcription begins, it is said to be at the 5' end of the gene; thus, the promoter region is also called the 5' regulatory region (Figure 8-7a). The first transcribed base is always at the same location, designated the initia- tion site. The promoter is referred to as upstream of the initiation site because it is located ahead of the initiation site (5' of the gene), in the direction opposite the direction of transcription. A downstream site would be located later in the direc- tion of transcription. By convention, the first DNA base to be transcribed is FIGURE 8-6 The MRNA sequence is complementary to the DNA template strand from which it is transcribed and therefore matches the sequence of the nontemplate strand (except that the RNA has U where the DNA has T). This sequence is from the gene for the enzyme B-galactosidase. Sequences of DNA and transcribed RNA Nontemplate strand 5' CTGCCATTGTCAGACATGTATACCCCGTACGTCTTCCCGAGCGAAAACGATCTGCGCTGC- 3 Coding strand DNA Template strand 3' Noncoding strand GACGGTAACAGTCTGTACATATGGGGCATGCAGAAGGGCTCGCTTTTGCTAGACGCGACG - 5' 5 CUGCCAUUGUCAGACAUGUAUACCCCGUACGUCUUCCCGAGCGAAAACGAUCUGCGCUGC-3' MRNA
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.
In Figure 8-6, describe where the gene promoter is
located.
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