19.3 Body plans Flashcards
(17 cards)
What is morphogenisis
The regulation of the pattern of anatomical development
What are homeobox genes
A group of regulatory genes that contain a length of DNA made up of 180 base pairs they produce proteins called homeodomains
What’s a homeodomain
A high conserved 60 amino acid sequence that binds to DNA and switches other genes on and off
What’s a hox gene
Homeobox genes only present in animals
Responsible for the correct positioning of body parts
Found in gene clusters
The order in which the genes appear are the order in which the genes are expressed
Regulate mitosis and apoptosis
How many hox genes do humans have
39 in 4 clusters
What are diploblastic animals
Have two primary tissue layers
What are triploblastic animals
Have three primary tissue layers
What controls the development of wings, limbs & ribs?
Hox genes in the thorax
What controls the development of mouthparts
Hox genes in the head
What are somites
Segmented blocks of tissue that later differentiate into vertebrae, ribs, and skeletal muscles
The somites are directed by hox genes to develop in a particular way depending on their position in the sequence
What’s radial symmetry
Symmetry about a central axis in diploblastic animals like jellyfish
There is no right or left side, only a top and a bottom
Factors affecting the expression of regulatory genes
Expression is infulenced by internal and external environment
- Stress (caused by: temperature, light, hormones & psychological stress)
- Drugs
Role of mitosis in body plans
Results in cell division and cell proliferation
Leads to growth
What’s bilateral symmetry
Arrangement of body parts so there are distinct left and right halves that mirror each other rather than just a top and a bottom
What’s asymmetry
Seen in sponges which have no lines of symmetry
Apoptosis and it’s role in body plans
Programmed cell death
Important in shaping different body parts by removing unwanted cells and tissues
Cells undergoing apoptosis can also release chemical signals which stimulate mitosis and cell proliferation leading to the remodelling of tissues
Why are animals segmented
Segmentation of the body plan is important for allowing free movement and development of certain body parts
It also allows for regeneration in specific individuals
Segments are specialised to perform different functions
