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43 Cards in this Set
- Front
- Back
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What are the 3 other types of DNA, apart from protein coding?
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Housekeeping
Structural Regulatory |
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What does housekeeping DNA produce?
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Core metabolic functions.
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What does structural DNA produce?
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Genes required for function of specific cell types.
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What does regulatory DNA produce?
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Transcription factors, signalling proteins, etc.
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What are homeotic genes?
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A specialised group of transcription factors that organise other genes instead of interacting with the DNA hands on.
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What pigment in the snapdragon flower makes it red?
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Anthocyanin
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What is needed to make anthocyanin?
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A suite of specialised enzymes.
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What transcription factor mediates the genes that code for these enzymes?
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DELILA (binds to promoter of all genes)
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What is an example of a homeotic gene in drosophila that affects eye development?
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Eyeless
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What as an example of a homeotic mutation in flies?
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Bithorax mutant of the Ubx gene.
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What does the Ubx gene normally code for?
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The haltere (balancing organ) on the thorax of the fly.
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What gene codes for the haltere?
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T3
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What phenotype is seen in the bithorax mutation of the Ubx gene?
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Two thoraxes replacing the haltere and a normal abdomen and head.
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What is the name of the other genes that control the other segments of the fly? How many are there
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HOX genes, family of 8 adjacent genes.
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How many mutations are actually needed to see the bithorax phenotype? What are they (except 1)?
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3. One knocks out regulators (inhibitors of Ubx) in the anterior portion of the haltere, another in the posterior of the haltere. Other mutation is not needed!
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What is the bithorax complex?
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A group of homeotic genes (a homeobox) which are believed to control the differentiation of the abdominal and posterior thoracic segments.
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What are the three genes in the bithorax complex?
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Ubx, ABD-A, ABD-B
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What is observed when the bithorax complex is deleted?
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The abdominal segments are transformed into thoracic segments.
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What is the ANT-C complex?
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A homeobox which control the differentiation of the anterior segments.
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What does a mutant of a regulatory gene that results in the BX-C and ANT-C homeotic genes being more expressed throughout the embryo do to the embryo?
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Genes are more anterior than usual, so virtually all segments develop with the identity of 8 abdominal segments.
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Where are there more homeotic genes active? What happens when they're inactivated?
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In the posterior segment of the fly. When inactivated, the posterior resembles the anterior.
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What is co-linearity? Are the HOX genes of drosophila an example of this?
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When the order of expression along the body axis correlated to the order of genes in the two complexes. HOX genes are colinear.
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Where is Ubx expressed and what does is repress?
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In the abdomen (A1 and A2, look later), where it prevents limb formation.
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What does the distal-less gene do?
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Required for limb formation.
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What does the vestigial gene do?
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Required for wing formation.
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Where is the distal-less gene expressed?
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In the cells which are destined to become limbs (limb imaginal discs). Anterior (Ubx is posterior and distalless is anterior)
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Where is the vestigial-less gene expressed?
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In the cells which are destined to become winds (wing imaginal discs)
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What does Ubx do to distalless in the posterior region?
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Represses it (so distalless is present anteriorally, and limb formation can occur)
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How is the embryo split into segments and what are the names?
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Split into 5 segments, anteriorly to posteriorly. T1, T2, T3, A1 and A2.
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How can the fact that the repression of distalless causes limb formation be tested?
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Using a mutant that does not produce Ubx in the earliest posterior region (A1)?
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What is seen in a mutant that does not produce Ubx in the earliest posterior region (A1)?
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Extra leg formation at the segment (since distalless is no longer repressed)
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What is the difference in Ubx action in the centipede (which has many identical segments) and the fly?
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Ubx does not repress distalless, and so limb formation occurs throughout all the segments.
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What happens in the anterior portion of the embryo at later stages of development with regard to Ubx and distalless?
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Ubx is expressed more anteriorly (in the T3 segment but not further), but distalless has already been switched on and expressed, so it can no longer be repressed in that segment.
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What is the action of Ubx in the T3 portion of the embryo? What consequence does this have?
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Represses the vestigial gene, which is important in wing development. Halteres form instead of wings.
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Where is Ubx absent, allowing wings to form?
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In T1 and T2.
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Summary: What do the 8 homeotic genes in the two groups (ANT-C and BX-C) specify?
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Differences between segments along the anterior/posterior axis.
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Summary: How does UBX prevent limb development?
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By repressing distalless in A1-A8.
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How does UBX modify wing development in T3?
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Repressing targets such as wingless to promote haltere formation instead of wing.
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Are the homeobox genes conserved in vertebrates?
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Yes!
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How many Hox clusters are there in mice? Are they similar? Was the colineality conserved!
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4, yes and yes!
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Where are HOXB5, C8 and C6 expressed in the chick and python?
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Chick: B5 throughout, C8 thoracic and C6 cervical/thoracic.
Python: All express throughout. |
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What is gene knock down?
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Double stranded RNA for the gene in question is injected into the embryo, which leads to inactivation of the gene in question.
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What is another name for this?
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RNA interference
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