Matrix metalloproteinases (MMPs) are zinc-containing endopeptidases. They degrade proteins by cleavage of peptide bonds. More than twenty MMPs have been identified and are separated into six groups based on their structure and substrate specificity (collagenases, gelatinases, membrane type [MT-MMP], stromelysins, matrilysins, and others).
Confidence votes 164. Alleles are the different forms of a gene. Alleles are corresponding pairs of genes located at specific positions in the chromosomes. Together, alleles determine the genotype. Alleles which determine some aspect of the phenotype, the physical appearance of an organism, are said to be coding alleles.
Genes are segments of DNA arranged along a chromosome. A single chromosome can have hundreds or even thousands of genes. Most sexually reproducing organisms, like people and pigeons, have two copies of each chromosome, called homologous chromosomes. Humans have 23 chromosome pairs, or 46 chromosomes in all. Homologous chromosomes have the same genes arranged in the same order, but they have slightly different DNA sequences. Different versions of the same gene are called alleles (uh-LEELZ); homologous chromosomes often contain different alleles.