It has remained in all descendent species throughout evolutionary history
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What are Homeobox genes?
Regulatory genes
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What is a Homeobox Sequence?
A stretch of 180 DNA base pairs (excluding introns) encoding a 60 Amino-acid sequence called a Homeodomain sequence
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What is a Homeodomain Sequence?
A protein that acts as a transcription factor, it folds into a certain shape and binds to DNA switching other genes on or off
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What shape does the Homeodomain sequence fold into?
H-T-H , 2 alpha helices (H) connected by one turn (T)
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What does this Homedomain shape do?
Recognises the TAAT sequence on enhancer region of a gene to be transcribed
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What are Hox genes?
a group of homeobox genes only present in animals
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What are Hox genes responsible for?
the formation of anatomical features in the correct location of body plans (parts)
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What is morphogenesis?
The regulation of the pattern of anatomical development
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What are Hox genes arranged in?
Clusters, each cluster containing up to 10 genes
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What is Colinearity?
The correspondence of sequential and temporal development of various body parts with the sequential and temporal order of gene expressions
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How are Hox genes regulated?
By other genes called gap genes and pair-rule genes, which are regulated by maternally supplied mRNA from cytoplasm
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How is Mitosis Regulated?
with the help of Homeobox and Hox genes
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What do Homeobox and Hox genes do for mitosis?
Ensure each new daughter cell contains the full genome and is a clone of the parent cell
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What is the 1st stage of Apoptosis?
Enzymes breakdown the cell cytoskeleton
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What is the 2nd stage of Apoptosis?
The cytoplasm becomes dense with tightly packed organelles
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What is the 3rd stage of Apoptosis?
The cell surface membrane changes and small protrusions called blebs form
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What is the 4th stage of Apoptosis?
Chromatin condenses, nuclear envelope breaks and DNA breaks into fragments
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What is the 5th stage of Apoptosis?
Cells break into vesicles and are ingested by phagocytic cells
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Why must the cell fragments be ingested by Phagocytic cells?
So cell debris doesn't damage any other cells or tissues
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Recall the first 4 stages of Apoptosis:
Enzymes breakdown the cell cytoskeleton, The cytoplasm becomes dense with tightly packed organelles, The cell surface membrane changes and small protrusions called blebs form, Chromatin condenses, nuclear envelope breaks and DNA breaks into fragments
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What happens after DNA breaks into fragments?
Cells Break into vesicles and are ingested by phagocytic cells to prevent damage to other cells and tissues
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When may signalling molecules that help control apoptosis be released?
When genes that are involved in regulating the cell cycle and apoptosis respond to internal cell stimuli and external stimuli such as stress
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Name 3 signalling molecules:
Cytokines, Nitric oxide and hormones
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How may Nitric Oxide induce Apoptosis?
Making the inner mitochondrial membrane more permeable to hydrogen ions
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What effect does Nitric oxide have on the proton gradient?
It dissipates it
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How can proteins promote Apoptosis?
By entering the cytoplasm and binding to apoptosis inhibiting proteins, allowing apoptosis to occur
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How is Apoptosis involved in the development of the immune system?
By removing ineffective or harmful T-lymphocytes
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What can a lack of Apoptosis lead to?
The formation of tumours
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What can too much Apoptosis lead to?
Cell loss and degeneration
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How many primary tissue layers do Diploblastic animals have?
2
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How many primary tissue layers do Triploblastic animals have?
3
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What are Somites?
Segments in the embryo where the individual vertebrae and associated structures have all developed
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What is Radical symmetry?
No left and right just top and bottom
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What is Bilateral Symmetry?
Both left and right sides and a head and a tail
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What is Asymmetry?
No lines of symmetry e.g. sponges
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What effect did Thalidomide have on pregnant women?
Prevented the normal expression of a particular Hox gene resulting in shortened limb babies
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Other cards in this set
Card 2
Front
What does Conserved mean?
Back
It has remained in all descendent species throughout evolutionary history
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