Pair-rule genes in Drosophila development

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In summary, the gap genes produce global positional signals that control the expression of other genes, while the pair-rule genes produce local positional signals that control the details of patterning.
  • #1
sven222
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Hey guys,

So I have an exam tomorrow afternoon on developmental bio (ugh ), and i have been going over my notes and have run into something I'm struggling to understand.

The topic is Drosophila development, and the brick wall I have run into involves the way in which pair-rule genes work their magic.

I can understand the way in which Gap genes work, however when it comes to pair-rule genes it goes way over my head. The notes I have explaining them are quite bad, so I was wondering if you guys have an explanation that would be much more useful.

Cheers guys :smile:
 
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  • #2
Well:

The products of the egg-polarity genes provide the global positional signals in the early embryo. These cause particular gap genes to be expressed in particular regions. The products of the gap genes then provide a second tier of positional signals that act more locally to regulate the finer details of patterning through the expression of yet other genes, including the pair-rule genes.

Does that answer your question?

Gap genes (at least 6): the products mark out coarse subdivions of the embryo. Mutations in a gap gene eliminate one ro more groups of adjacent segments, and mutations in different gap genes cause different but partially overlapping defects.

Pair-rule genes (8): mutations in these cause a series of deletions affecting alternate segments, leaving the embryo with only half as many segments as usual. While all the pair-rule mutants display this two-segment periodicity, they differ in the precise positioning of the deletions relative to the segmental or parasegmental borders.

Segment polarity genes (10): mutations in these genes produce larvae with a normal number of segments but with a part of each segment deleted and replace by a mirror-image duplicate of all or part of the rest of the segment.

Then the homeotic selector genes serve to define and preseve the differences between one segment and the next.

Source: Alberts et al, Molecular Biology of The Cell
 
  • #3
That helped a bit. Thanks monique :smile:
 

1. What are pair-rule genes and how do they function in Drosophila development?

Pair-rule genes are a group of genes that play a crucial role in the early development of Drosophila, also known as the fruit fly. These genes are responsible for dividing the body segments of the fly into distinct regions, called segments. They do this by regulating the expression of other genes involved in the formation of body segments.

2. How many pair-rule genes are there in the Drosophila genome?

There are a total of 14 pair-rule genes identified in the Drosophila genome. These include genes such as even-skipped, fushi tarazu, and odd-paired, among others.

3. What is the role of gap genes and segment polarity genes in relation to pair-rule genes?

Gap genes and segment polarity genes are important in the process of establishing the initial body segmentation in Drosophila. They work together with pair-rule genes to regulate the expression of other genes involved in body segment formation. Gap genes define broad regions of the embryo, while segment polarity genes further refine these regions into distinct segments.

4. How are pair-rule genes regulated during Drosophila development?

Pair-rule genes are regulated by a complex network of interactions between other genes and signaling pathways. This includes interactions with gap genes, segment polarity genes, and other transcription factors. The precise timing and levels of expression of these genes are crucial for proper body segmentation.

5. What happens if there is a mutation in a pair-rule gene?

A mutation in a pair-rule gene can lead to developmental defects and abnormalities in the segmentation of the fly's body. This can result in missing or duplicated body segments, which can have severe consequences for the survival and function of the fly. Mutations in pair-rule genes have also been linked to certain genetic disorders in humans, highlighting the importance of understanding their role in development.

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