Gene Types

DNA material is found in chromosomes. Eukaryotic (higher level cells) chromosomes are each made of a single strand of DNA and several different kinds of proteins (Hale et al., 1995). These chromosomes exist in pairs (said to be diploid), except in some lower forms of algae or fungi that have single sets of chromosomes only (said to be haploid). Mammalian germ cells are also haploid. Some 

FIGURE 5,3.4 Polypeptides are formed at the ribosome through a process called translation. mRNA acts as a template, and tRNA acts as a scavenger, bringing the correct amino acids to the ribosome in the correct order determined by the mRNA. (From Campbell, N.A. et ah. Biology, 5th edn., Addison Wesley Longman, Menlo Park, CA, 1999. With permission.) 

FIGURE 5.3.5 Genetic outcomes from different crosses. 

The genetic makeup of a cell is called the genotype, and is determined fully when every allele is known. The physical appearance and apparent physiological traits of a cell is called the phenotype. In the case of Mendel s flowering peas, there were three separate genotypes resulting from a cross between two heterozygous individuals (purple-purple, purple-white, and white-white) there were, however, only two distinct phenotypes (purple or white). 

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Many bacteria have a second complete secretion system.481 This multi-gene type II system is present but usually inactive in E. coli. A third (type III) system is present in many pathogenic bacteria, and has evolved for delivery of specialized structural and regulatory proteins into host cells.48c 48d... 

For example, the native, capsular polysaccharide from Klebsiella aero-genes type K54 incubated with a bacteriophage-induced enzyme, gave an... 

Interferons are a group of pleiotropic cytokines with important proinflammatory functions required in defence against infections with bacteria, viruses and multicellular parasites along with fundamental functions in other processes such as cancer immuno-surveiUance, immune homeostasis and immunosuppression [209]. IFNs are classified into type I and type II IFNs [210]. Type I IFNs comprise multiple alpha IFNs (IFN-a), and single IFN-, -e, -k, - and -oo subtypes, all encoded by different genes. Type IIIFN consists of a single IFN-y gene. 

In the text area under Query genes, type the common name of the gene of interest... 

Britton et al 1997), we know that the native carotenoprotein, a-CR, has a molecular weight of about 320 kDa and that it is a multi-macromolecular 16-mer complex of protein subunits with 16 bound ASX molecules (Figure 8-2). These subunits are electrophoretically distinct components, each of approximate molecular weight of 20 kDa, classified by amino acid composition, size estimation, and peptide mapping into two groups Gene type I [CRTC] protein forms Al, Cl (predominant) and C2 and Gene type n [CRTA] protein forms A2 (predominant) and A3. 

The third element includes the transcription start site at position +1, but, in the case of eukaryotes, it is surrounded by a sequence called the initiator element (Inf). This sequence is not well conserved. For instance, the sequence for a particular gene type may be gWCAYYYYY g, in which Y indicates either pyrimidine, and A is the purine at the transcription start site (TSS). 

Another subject of interest is the influence of a specific gene type called apolipoprotein E, epsilon 4 allele (ApoE4). ApoE4 has been identified in roughly one-third of people with Alzheimer s disease. 

The position of a given DNA sequence with respect to the rest of the genetic material is critical to its status as a gene type-identical DNA sequences at different loci can play different hereditary roles - be different genes, if you like. So for a particular DNA sequence to be, say, a brown-eye gene, it must be in an... 

Type Gene Type Phenotype ) Gene ) Type Gene )... 

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