minisatellite DNA

Microsatellite DNA

short dispersed elements

long discrete elements

hairpin structure

palindrome

In a multigene family, some members do not produce functional gene products. These genes are called pseudogenes.

The first pseudogene was discovered in 1977 while studying the ribosomal 5S RNA gene of Xenopus laevis.

Regulate gene expression

deletion or insertion

Sequential changes in intron- and exon-adjacent regions

Defects in the 5′ end initiation region

In structural genes, coding sequences called exons express portions of the polypeptide chain. Non-coding sequences are called introns, also known as insertion sequences.

Introns can also be transcribed but not translated

Different structural genes contain very different numbers of introns and exons.

Within a gene, the lengths of different introns and exons are different

Some genes in eukaryotes do not have introns and they mostly exist in the form of gene clusters. Most yeast structural genes also do not have introns.

Eukaryotic introns and exons are not completely fixed, and are sometimes a certain DNA sequence on the same DNA chain. When it is a gene encoding a certain polypeptide chain, it is actually an exon, and when it is encoding another polypeptide chain, it is an intron.

Features