What is the relationship between form and function in biology

Function (biology) - Wikipedia

what is the relationship between form and function in biology

What biological processes allow them to inhabit and survive in their our understanding of the fascinating relationship between the form and function of life . Key Course Themes 1. Form and Function Examples? 2. Maintenance of Homeostasis Example?. Form and function, then, are areas of deep and intrinsic interest to extreme complexity of biological processes mate relationship between anatomy and.

These studies suggest that organization of genes into heterochromatin can lead to transcriptional repression; however, they do not demonstrate the means by which this silencing is achieved Fig. The studies discussed above have revealed a correlation between the activity of a gene and its proximity to CH.

In all of the cases, the genes that are ultimately sequestered at heterochromatin are significant in the differentiation of the involved cell type.

That is, the genes localized to PCH are oftentimes the genes whose suppression is necessary in that cell type, or in that stage of cell development. It is likely, then, that PCH-association facilitates the formation of a repressive chromatin structure and that the examples described above are, in effect, facultative heterochromatin.

The active recruitment to PCH may therefore be reserved for those genes that must be silenced for differentiation to occur, or those whose regulation must be modulated to ensure the precise developmental progression.

Despite integration into PCH and localization to the outside of CH clusters, the transgenes demonstrate position effect variegation PEV in pre-B cells, indicating that proximity to CH does not preclude activity.

Form follows function: the genomic organization of cellular differentiation

However, loss of a potent HS site results in the internalization of the transgene into CH in fibroblasts cells in which the gene is inactive and in the reduction of expression in pre-B cells, although remaining at the surface of CH. Therefore, the formation of facultative heterochromatin at PCH may lead to the progressive silencing of genes that are obligately repressed for cellular differentiation, reflecting the need to localize silenced genes in a particular nuclear subcompartment to preclude their response to the fluctuating concentrations of regulatory proteins.

Interestingly, the FH that forms during terminal erythroid differentiation coincides with a large-scale relocation of proteins associated with gene repression e. Modifications to the N termini of histones can regulate the binding of proteins involved in chromatin organization and gene regulation Felsenfeld and Groudine HP1 is perhaps the best-understood protein involved in the transcriptional repression by heterochromatin, having been shown to localize to CH clusters and to mediate gene silencing Eissenberg and Elgin Studies of HP1 have shed light on a potential mechanism for the maintenance and spreading of repressive heterochromatin.

Furthermore, this association is dependent on the activity of histone methyltransferases HMTs that specifically modify histone H3 on Lys 9 Rea et al. Because HP1 and the HMTs are colocalized in heterochromatin domains, these results suggest a means for transcriptionally repressive chromatin structures to be maintained as well as spread to adjacent cis sequences. In addition, it is also possible that this mechanism may function in trans, silencing genes brought to heterochromatin domains by heterochromatin-associating proteins, like Ikaros Fig.

Nuclear periphery Despite early indications that transcription may be localized to the nuclear periphery Hutchison and Weintraub and a recent demonstration that boundary activities BAs, which protect the expression status of active domains involve the tethering of active chromatin to the nuclear pore complex NPC; Ishii et al. The nuclear periphery's role in repression has been well established in budding yeast.

Engaging with Molecular Form to Understand Function

A number of studies have collectively demonstrated that yeast telomeres form clusters at the nuclear periphery, which leads to an enrichment of the Sir proteins known to be involved in gene silencing Cockell and Gasser The ability of this peripheral compartment to repress transcription was tested in a study in which a reporter gene was tethered to the nuclear envelope.

An analysis of the murine Ig loci during lymphocyte development has shown the involvement of the nuclear periphery in the regulation of these intricately regulated gene arrays Kosak et al. During early B-cell development, both loci are relocalized to the nuclear center, which may represent a transcriptionally permissive nuclear environment.

what is the relationship between form and function in biology

Interestingly, the IgH locus undergoes compaction wherein distal ends of the 3-Mbp array colocalize, implying a looped structure when it is centrally located in the nucleus and is poised to undergo long-range V D J recombination.

A recent study has further delineated the steps involved in the compaction of the locus, indicating that the B-cell regulatory protein Pax-5 in conjunction with an unknown B-cell-specific factor may induce the close juxtaposition of the ends of the IgH array Fuxa et al.

FISH analysis of whole chromosomes in human nuclei has revealed that a gene-poor chromosome 18 is preferentially localized to the nuclear periphery, whereas a gene-rich chromosome 19 is more centrally disposed in the nucleus Croft et al.

Structure and Function in Biology

This preferential association is maintained, even in the context of a balanced translocation between the two chromosomes, with the translocated portions of 18 and 19 residing peripherally and centrally, respectively.

Further analysis of genedense and gene-poor chromosomes has confirmed the tendency for gene-poor chromosomes to be positioned at the nuclear periphery Boyle et al. Cross-species analysis has revealed that this behavior is not restricted to the human nucleus Tanabe et al. As described below, gene-rich chromosomal domains are the most highly expressed regions of the human genome; therefore, the demonstrations of gene-rich chromosomes organized into the nuclear center may simply be a reflection of their overall level of activity.

The studies described above strongly suggest that the nuclear periphery may represent a transcriptionally repressive nuclear compartment distinct from CH, which often resides in perinuclear clusters.

what is the relationship between form and function in biology

For example, the peripheral localization of silent Ig loci does not involve association with PCH Kosak et al. In fact, this study indicates that the nuclear lamina itself may play a role in the sequestration and inactivity of perinuclear loci. The major components of the nuclear lamina are the lamins, type-V intermediate filament proteins that polymerize to form the lamin network that is juxtaposed to the inner nuclear membrane of the nuclear envelope. There are two classes of lamins, A type and B type.

Expression of the A-type lamins is developmentally regulated, whereas the B-type lamins are ubiquitously expressed Mounkes et al. The nuclear lamina, through lamin B, interacts directly with DNA and chromatin, as well as indirectly through lamin-binding proteins Gotzmann and Foisner In addition, proteins demonstrated to be involved in gene silencing have also been shown to associate with the lamina, including HP-1 Kourmouli et al. Therefore, although much works need to be done before a causative effect in gene silencing can be attributed to localization at the nuclear periphery, growing evidence supports the idea that it represents a transcriptionally repressive nuclear subcompartment Fig.

Of particular interest is how mutation of a single gene that is broadly expressed in differentiated tissues could result in several tissue-specific disease phenotypes.

Chromatin mobility The organization of the transcriptional machinery and the compartmentalization of silenced genes suggest that genes must be mobile within the nucleus to be appropriately positioned.

Form follows function: the genomic organization of cellular differentiation

Currently, the study of chromatin mobility has yielded conflicting results in the comparison of human and yeast nuclei. In humans, small movements of 0. However, in light of the IC model, these small movements may be sufficient to localize a gene to a relevant nuclear body or repressive compartment.

Also, use of the lac operator-repressor system which allows visualization of chromatin through arrays of lac-binding sites revealed that a late-replicating, heterochromatic domain undergoes large-scale movement from the nuclear periphery to the interior prior to replication Li et al. In yeast and Drosophila0.

Furthermore, the movement of loci in yeast has been shown to be energy dependent, unlike the small-scale movements in humans. Despite the differences between human and yeast, the evidence for short, diffusional movements are compatible with the role of nuclear localization in gene regulation. Chromosome organization Beyond the movement of individual genetic loci, there is evidence that chromosomes may themselves be mobile.

Two recent studies utilized an H2B—GFP fusion protein and photobleaching to analyze the overall order of chromosomes through the cell cycle. In an analysis of HeLa cells, chromosomes were shown to maintain their localization in daughter cells in approximately half the nuclei studied Walter et al.

Furthermore, chromosomes were shown to be mobile during the early Gap 1 cell cycle G1. A similar analysis that modeled a random and nonrandom organization of chromosomes to be expected from the photobleaching experiment showed that the organization of chromosomes is significantly nonrandom, or maintained, during mitosis Gerlich et al.

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Despite the discrepancies between these results, they both argue that an inherent chromosome organization may exist that is remembered upon cell division. In support of the suggestion of a defined chromosomal organization in the nucleus, studies of the chromosomes and gene loci involved in translocations that lead to leukemia have revealed a propensity for translocation partners to be spatially proximal Parada et al.

These results argue for a functional organization of the genome at the level of the chromosome. You are encouraged to visit this blog site. If you press the "Like" button shown below, your Facebook page will provide you with short notifications and summaries of new blog posts as they become available.

When one describes patterns in nature, one needs to define the environment in which the pattern resides, the pattern's architecture, and its internal dynamics or processes. It is important to describe a pattern in this way because of the strong connectedness between between the context environment in which the pattern resides, its architecture formand its dynamics function.

Form, function, and context cannot be separated, neither of them is more important than the other. One cannot exist without the others.

Historically, there has been little study of relationships between form, function, and context.

Engaging with Molecular Form to Understand Function

In biology "morphology" is the study of the form, structure and configuration of an organism. This would include shape, structure, color, and pattern of plants and animals. In contrast, physiology is the study of function. This separated "reductionist" approach to the study of patterns does not consider the connectivity of all things in nature. Taking a more integrated view, a dynamic process can form a pattern's architecture.

Architecture can guide or direct a process. The surrounding environment serves to control and evolve. It is within this interplay between form, function, and context that we start getting clues as to how patterns are formed. Together, form, function, and context become a interrelated unity. Examples of this interplay between formfunction, and context are rivers, ant colonies, and sponges.

In the flow of rivers, the source is a branching structure connecting to a central and larger flow of water.

what is the relationship between form and function in biology

Here, the shape of the land a context called geomorphology provides a structural template form that shapes the flow of water. But, then the river path in the terrain becomes shaped by the dynamic flow function of water and other ecological processes.

what is the relationship between form and function in biology

Form and function become interrelated. Through the interplay of form and function, a pattern in nature is formed.