Lecture 25 Flashcards
Define differentiation
Process by which a cell becomes dedicated to perform a specific function, as in the case of a liver or blood cell, or a neuron; takes place during development and determines which genes are expressed and hence what type of cell will result
Define totipotent
Ability of a single cell to divide and produce ALL of the differentiated cells in an organism
Define pluripotent
Ability of a single cell to divide and produce some, but not ALL kinds of differentiated cells in an organism
Define unipotent
Ability of a single cell to divide and produce a single kind of differentiated cell in an organism
Describe the steps in cloning a mammal
- Donor cell is taken from a sheep’s udder and an egg cell is taken from an adult female sheep
- The nucleus of the egg is removed and the 2 cells are fused together using an electric shock
- The fused cell begins dividing normally and the embryo is placed in the uterus of a foster mother
- Embryo develops normally into a lamb (Dolly)
Explain how egg polarity is established and its significance
Determination of anterior-posterior (bicoid, nanos, hunchback genes) and dorsal-ventral (dorsal gene) axes of the embryo are initiated by mRNA from the mother; allows for proper formation of an organism
Slides 19-23
What role does homeobox-containing genes play in vertebrate development?
Play a major role in vertebrates with regard to cranio-caudal segmentation, not only along the main body axis but within the development of many organs
Compare loss-of-function mutations to gain-of-function mutations
LOF: result in posterior to anterior transformations
GOF: result in anterior to posterior transformations
Describe the organization of the human Hox complex
Organization of the Hox genes of the chromosome is physically the same as the order of their expression along the anterior-posterior axis of the developing animal
Compare the Hox gene complex in mammals to that in Drosophila
Very similar; this is highly conserved over time; drosophila can survive and develop with the Hox genes from a chicken, for example
Define the role that apoptosis plays in development
The fish Mexican tetras lives in caves have lost their eyes through a change in gene expression; genes in the sonic hedgehog pathway are overexpressed which leads to apoptosis of the developing lens cells and the lens degenerates
What is somatic cell nuclear transfer?
Transfering the nucleus of a somatic cell to a germ cell that had its nucleus removed; used in cloning
What is a morphogen?
Protein that affects the developmental fate of the surrounding region through a concentration gradient
What is heterotaxy?
Also known as atrial isomerism; refers to the lack of differentiation of right-sided and left-sided organs during fetal development; malformations often occur in multiple systems including the heart, liver, lungs, intestine, and spleen
Define developmental genetics
Study of the regulatory processes that control cell growth, differentiation, and morphogenesis, which is the process that gives rise to tissues, organs, and the anatomy; study of cell fate, cell determination, and differentiation and pattern formation
Define determination
Process by which a cell or part of an embryo becomes restricted to a given developmental pathway
Distinguish between the homeobox and the homeodomain
Homeobox is about 180 bases that encodes the homeodomain, which when expressed can bind DNA
What genes are responsible for establishing the main body axes?
Egg-polarity genes
What genes are responsible for determining the number and polarity of body segments?
Segmentation genes
What genes are responsible for establishing the identity of each segment?
Homeotic genes
Define necrosis
Injured cells dying in an uncontrolled manner
