Term
| What is so special about drosophila zygotes once they start to develop? |
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Definition
A number of nuclei are produced through multiple mitotic divisions but these proceed without cytoplasmic division |
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Term
| What happens to the free-floating nuclei in the drosophila zygote and what do they form? |
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Definition
The nuclei start to migrate towards the edge of the embryo where they undergo cellularization (in which cellular membranes form around the nuclei). They end up forming a blastoderm which is a flat, hollow ball of about 6,000 cells |
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Term
| How do the blastoderm cells in d. mel already know what kinds of cells they will become? |
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Definition
They've already undergone signaling which was induced by the mother. The embryonic fly does not start transcribing its own genes until the ninth round of cell division and each specific maternal mRNA is distributed in a very specific pattern in the oocyte and early embryo |
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Term
| What is one crucial factor to note about embryonic genes in D. mel? |
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Definition
Since embryonic genes don't turn on right away, early development in D. mel embyros depends on the genotype of the mother |
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Term
| What are maternal effect genes and zygotic genes and how are they related to each other? |
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Definition
Maternal effect genes are genes that function in the mother and are needed for development of the embryo. Zygotic genes are developmental genes that function in the embryo. Zygotic genes intrepret and respond to the info laid out in the egg by the MEGs |
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Term
| What are maternal effect genes in regards to their oocytes? |
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Definition
Maternal effect genes are required for females to be able to form functional oocytes |
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Term
| What phenotype will result in the abnormal development of offspring in D. mel in regards to maternal effect mutations? |
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Definition
If a mutant allele is represented by m then the phenotype m/m in the mother will result in abnormal development of offspring. These genes work independently of the father and a m/+ or +/m individual will produce normal offspring since they have at least one copy of the normal gene |
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Term
| What are the various separations in the D. mel larva and how are they separated? |
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Definition
There are 3 head segments (C1-C3), 3 thoracic segments (T1-T3) and 8 abdominal segments (A1-A8). These segments are all separated by denticles which are pigmented tooth-like projects |
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Term
| What are parasegments in the D. mel embryo and what is important to note about each |
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Definition
They're important boundaries for gene expression. Each is the posterior end of one segments and the anterior end of another |
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Term
| What is polarity and what are the corresponding terms for top, bottom, head and rear? |
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Definition
Polarity refers to the directional information available to cells. The top is dorsal, the bottom is ventral, the head is anterior and the rear is posterior |
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Term
| What are coordinate genes? |
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Definition
Coordinate genes are genes that establish the main body axis of the embyro. They're maternal effect genes |
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Term
| What is the role of bicoid in developing D. mel? |
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Definition
Bicoid determines which end of the embryo will become the anterior end. High expression of bicoid will result in this decision |
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Term
| What is the role of Nanos in developing D. mel? |
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Definition
Nanos is a posterior gene which regulates development of the abdominal segments |
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Term
| How to bicoid and nanos affect the transcription of the hunchback gene sequence? |
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Definition
Bicoid actives and nanos represses the transcription of hunchback |
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Term
| What is the main role of coordinate genes and what do torso and dorsal genes regulate? |
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Definition
The main role of coordinate genes is the regulate gap genes. Torso genes regulate terminal genes and dorsal genes regulate dorsal/ventral genes (dorsal genes can regulate themselves) |
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Term
| What are gap genes and how are they expressed? |
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Definition
Gap genes are genes that define the major segments with the D. mel larva. They are expressed in sets of contiguous segments with a segment for each region of the adult D. mel individual |
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Term
| What happens when a gap gene is mutant? Also, give an example of this in D. mel |
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Definition
If a gap gene is mutant the segments that require that specific gene won't develop. In hunchback D. mel mutants, there is a "gap" instead of the T2 and T3 segments |
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Term
| What are pair-rule genes and what do they affect? |
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Definition
Pair-rule genes are genes that affect alternating segments. They're expressed in alternating segments and therefore differentiate segments from adjacent segments |
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Term
| What are segment polarity genes? |
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Definition
Segment polarity genes are genes which create spatial differentiation within each segment. Cells in the anterior portion of each segment don't express the affected gene |
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Term
| What are imaginal disks in D. mel individuals? |
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Definition
Imaginal disks are sections of the larval body that develop into specific body parts during metamorphosis |
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Term
| What are homeotic (HOX) genes? Give a brief overview of what exactly they do |
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Definition
Homeotic genes become actie and determine the identity of individual segments after the segmentation genes establish the number and orientation of those segments. They encode regulatory proteins which contains the conserved domain called the homeobox. The regulatory proteins then bind to the DNA which encodes 60 amino acids of the DNA binding domain |
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Term
| What is the antennapedia complex in developing D. mel? |
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Definition
The antennapedia complex is a cluster of homeotic genes which affects the development of the head and anterior thorax segments |
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Term
| What is the bithorax complex in developing D. mel? |
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Definition
The bithorax complex is a cluster of homeotic genes that affects development of the posterior thorax and abdominal segments |
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Term
| Why is the arrangement of genes on the chromosome important in developing D. mel? |
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Definition
The arrangement corresponds to the sequence in which the genes are expressed along the anterior-posterior axis of the body |
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Term
| What is so interesting about hox gene inheritance? |
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Definition
| Hox genes are simlar in sequence to the homeotic genes in drosophila and they're in the same order |
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Term
| What is combinatorial control of gene expression? |
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Definition
The combinatorial control of gene expression is the type of gene expression in which more than one gene affects the resulting phenotype |
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Term
| What are classes of mutants and how can they be compared? |
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Definition
Classes of mutants have characteristic mutations which they share in common so instead of being grouped as several different mutations they're grouped as one single classification. A simple chart can be constructed to see which classes are opposite each other (and therefore likely repress each other) and also which classes are the distinct outliers |
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