Membrane Receptors Signaling between cells, cells and matrix, tissues, and systemically, is key to the developmental and differentiation process. While there are a large number of known methods of signaling these all fall into a few broad classes. Signaling also depends upon having an initial source for the signal and cells which can interpret the signal. To see how these mechanisms are employed you should look at embryo axes formation or the specific pages within each set of notes that refer to early development or system development (these pages are listed on Molecular Development homepage).
Some signals act internally (More? cell cycle) or over a short distance (between ajoining cells or to the cell itself), others act in a distance dependent manner (changing concentration of the signal will alter the response), others act by cascading (signaling from one cell to the next, to the next), and finally some signals act at a distance (between one tissue and a distant cell population).
Signaling in many cases precedes any observable change in cell shape and motility. Please note as an introduction the notes below have been extensively simplified. More details can be gained by clicking on specific links.
Page Links: Introduction | Starting Out | Mechanisms | System Notes Molecular | Glossary
receptors- Tyrosine kinase
receptors- 7 membrane
channels
steroidal growth factors
adhesive interactions-cell/extracellular matrix
adhesive interactions- cell/cell
cell junctions
transcription factors
The first page of Developmental and System Notes usually contains some information about mechanisms of development that include molecular mechanisms. In order to keep the introductory page simple, detailed molecular mechanisms have been placed on a separate page (Page 11) of each section of notes. Below is a list of direct links to specific Molecular Development Pages.
| Molecular System Notes |
|
| Axis Formation | Early | Limbs |
|
Signaling during development, though complex, can also be grouped into a few specific classes. These mechanisms have also been listed and described briefly on Signaling Mechanisms page.
Lecture Notes |
Please note that these notes only relate to an earlier Course and not all Lecture notes and research material have been transferred. |
| |
Simple pictures illustrating the early events of fertilization. |
| |
Figures and text relating to early events of spinal cord formation. |
| |
Text relating to the molecular events of sex determination in the embryo. |
| |
A short comparison of establishing positional information in embryos. |
| |
The fly mutation that opened the field of Hox Genes and the conservation of pattern formation control mechanisms between species in embryonic development. |
antisense- a sequence of DNA that is complementary usually to coding sequence of DNA or mRNA. Has been used experimentally to perturb or block gene expression. Also a mechanism that has been found to occur naturally as a regulatory mechanism.
autosomal inheritance- some hereditary diseases are described as autosomal which means that the disease is due to a DNA error in one of the 22 pairs that are not sex chromosomes. Both boys and girls can then inherit this error. If the error is in a sex chromosome, the inheritance is said to be sex-linked.
base- another term for nucleotide (usually a t c g).
base pair- Double stranded DNA has nucleotides A-T, C-G, paired by hydrogen bonds (2 for AT, 3 for GC). Note this means that GC is harder to separate that AT.
DNA- DeoxyriboNucleic Acid. The genetic material found in mammalian chromosomes and mitochondria. Consisting of 4 nucleic acids (ATCG) that combine in a triptych (3 nucleotide) code for protein amino acids (3nt=1aa).
DNA duplex- double stranded base-paired DNA forming a helix.
dominant inheritance-With autosomal dominant inheritance, there is an error in one of the 22 chromosome pairs. But the damaged gene dominates over the normal gene received from the other parent. If one of the parents has a disease caused by an autosomal dominant gene, all the children will have a 50 per cent risk of inheriting the dominant gene and a 50 per cent chance of not inheriting it. The children who do not inherit the damaged dominant gene will not themselves suffer from the disease, nor will they be able to pass the gene on to future children. This type of inheritance is present for example in Huntington's disease.
exon- a block of protein encoding sequence of DNA in a gene. Many proteins are made of several exons "stitched" or spliced together by editing out non-coding (intron) sequences.
fasta- a format for listing DNA sequence, where the first line has descritive information followed on the next line by the sequence without numbering.
GC repeat- a string of GC sequence repeated several times. Also associated with GC expansion, a mutational process that may lead eventually to serious gene expression effects.
gene- a sequence of DNA that encodes an individual protein.
genetic code- the 3 nucleotide sequence that forms a codon for a single amino acid or stop. See the gene code.
genome- the complete genetic information in the form of DNA available to a specific species.
hairpin loop- a folding of RNA generated by base pairing making a "===()" structure, the end loop and or stem of this structure can then interact with proteins or other RNA.
intron- a block of DNA within a gene not encoding a protein. Edited, spliced, out during transcription into mRNA. Originally thought not to contain any information, but more and more this appears not to be the case. Some intron sequences have been shown to regulate gene expression during development (eg c elegans, Lin 14)
mRNA- messenger, transcribed from DNA in the nucleus and in mitochondria. Is translated by the ribosome in the cytoplasm (or mitochondrial matrix). Intermediate step in gene expression. (DNA-> mRNA-> protein).
mutation- any process which results in the alteration of the DNA sequence. Some conservative mutations may have no effect on the final amino acid encoded.
point mutation- a change in a single nucleotide.
recessive inheritance-With autosomal recessive inheritance, the diseased individual has inherited the same gene damage from both father and mother. The damage is found on both chromosomes in the pair. But as this is not ´dominant gene damageª, neither father nor mother show any sign of disease, they are healthy carriers of the gene. We are all carriers of about five recessive genes of this type, but as spouses are seldom carriers of exactly the same damaged gene(s), all will probably go well in the next generation.
ribosome- complex of rRNA and ribosomal proteins, bind mRNA and translate it into protein.
RNA- RiboNucleic Acid. The intermediate nucleic acid involved in gene expression. It comes in 3 forms: tRNA, mRNA, rRNA.
rRNA- ribosomal, translates mRNA into protein. rRNA provides the "scaffolding" on which many ribosomal proteins are assembled as 2 subunits that themselves assemble to form a ribosome. rRNA genes are localized to the nucleolus in the nucleus, a sometimes visible region of DNA usually constantly being transcribed.
telomere- regions at the end of chromosomes. Shortening of the telomeres is thought to be associated with cellular aging. The enzyme that maintains the telomere is called telomerase. Introducing this gene into a cell can extend the cells lifespan.
transcription factor- a protein which binds to DNA activating (usually) gene expression. There are many different ways and forms that this activation can take place, but most transcription factors fall into specific classes (eg zinc fingers, helix loop helix).
tRNA- transfer, binds single amino acids acts as a "donor' for protein synthesis.
Home Page
Embryo stages
Fetal Dev
Dev Notes 1
Dev Notes 2
System Notes
Acknowledgements
Introduction
Axes Formation
Signalling
Early Axis
Rostro/Caudal Axis
Anterior/Posterior Axis
Left/Right Axis
Limb Axes
Spinal Cord Axes
Sex Determination
Reviews
Movies
Class Notes
Serial Images
K12 Students
Abnormal
Embryology in the News
Histology
Site Map
School of Med Sci
UNSW Medicine
University of NSW
UNSW Cell Biology
NCBI Books
Dev Biol (Gilbert)
We have come a long way from just observing development to now wanting to understand how the complex program of development is controlled. Using new research tools and some excellent animal models researchers have discovered common themes and mechanisms that tie all embryonic development together.
Molecular mechanisms of development is an exciting area and requires a variety of different skills. This page introduces only a few examples and should give you a feel for the topic.
Note that each section of system notes has a "page 11" covering molecular Development in that system.
Please email Dr Mark Hill if you wish to make a comment about this current project.