human development refers to
the biological and psychological development of a human being throughout their lifespan
t/f: slight changes in regulatory components have significant changes on development
true
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 anatomy. it is the 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
define differentiation
process by which a cell becomes dedicated to perform a specific function (ex liver, blood cell, neuron) takes during development that determines which genes are expressed and hence what type of cell will result
totipotency
ability of a single cell to divide and produce ALL of the differentiated cells in an organism (~32 trillion)
pluripotent
ability of a single cell to divide and produce some but not all kinds of differentiated cells in an organism
unipotent
ability of a single cell to divide and produce a SINGLE KIND OF DIFFERENTIATED CELL IN AN ORGANISM
alterations to key regulatory sequences often bring about
major developmental changes
pluripotent, embryonic stem cells originate as _ these stem cells can become an tissue in the body, excluding _
inner mass cells w/in a blastocyst; excluding a placenta
only the morula’s cells are _, able to become all tissues and a placenta
totipotent (16 cells)
hematopoietic stem cells are an example of _
multipotency; when the differentiate into myeloid or lymphoid progenitor cells, they lose potency and become oligopotent cells with the ability to give rise to only the cells of its lineage
many kinds of plants can be cloned from isolated single cells. thus _
none of the original genetic regulatory potential is lost during development
in order to clone an animal, _ must be reestablished
totipotency
describe how to clone an animal
- remove nucleus of donor cell and replaced w/ the nucleus from somatic cell
- give right environmental conditions to lead to development of organism (fertilization and meiotic events)
- replaced in uterus of a pseudo pregnant female animal
why is establishing polarity important
determines what goes where; once you know the poles you can begin segmentation ie pattern formation (where structure form) and going to have a unique set of genes at each pole
axes are important for
reference points; dorsal-ventral and anterior-posterior axis and this is how polarity is established
after axes are established, what happens next?
the number and orientation of the body segments are determined and the identity of each indiv segment is established
_ controls each of these 3 stages: axes, polarity, segmentation
different sets of genes
the developing embryo must have mechanisms to measure _ and _ in order to complete the developmental process w/ precision
time and location
in fruit flies, what genes are for developmental stage establishment of main body axes
egg-polarity genes
in fruit flies, what genes are for developmental stage determination of number and polarity of body segments
segmentation genes; genes get affected together in the right space and time because contain similar promoters
in fruit flies, what genes are for developmental stage establishment of identity of each segment
homeotic genes
egg-polarity genes have a _ origin
maternal origin; determination of anterior-posterior and dorsal-ventral axes of the embryo are initiated by mRNA from the mother
define morphogen
a protein that affects the developmental fate of the surrounding region through a concentration gradient
cell fate is a consequence of
saturation/concentration; dosage is important for genes and ratios need to be appropriately maintained as genes are dosage sensitive
_ gene in determination of the dorsal-ventral axis
dorsal gene
_ gene in determination of the anterior-posterior axis
bicoid gene, nanos gene, hunchback gene
gap genes are for
the body plan (affect large sections of the embryo)
homeotic genes in drosophilia
identity of segments
homeobox genes in other organisms
genes encoding DNA binding proteins; these proteins usually play a regulatory role (control development of segments/segmentation)
Hox genes
encode transcription factors (TFs) that help determine the identity of body regions
consequence if homeobox genes are expressed inappropriately
lead to inappropriate development of appendages/phenotypes in the wrong place
homeotic genes are expressed
sequentially; the arrangement of the genes on the chromosome corresponds to the sequence in which the genes are expressed along anterior-posterior axis of the body (fruit flies)
Hox genes are defined as having the following properties: (3)
- their protein product is a TF
- contain a DNA seq aka the homeobox (180 bp encodes a protein domain aka homeodomain which can bind DNA)
- organization of the Hox genes of the chromosome is physically the same as the order of their expression along the ant-post axis of developing animal
definition of homeobox-containing genes
genes that contain a highly conserved seq of 180 nucleotides called the homeobox which codes the 60 aa homeodomain found in homeodomain TF proteins
homeobox-containing genes characteristics (4)
- play a major role in vertebrates w/ regard to cranio-caudal segmentation, not only along main body axis but w/in the development of many organs
- activated in 3’-5’ direction (opp of transcription)
- loss of fcn mutations
- gain of fcn mutations
loss of fcn mutations in homeobox-containing genes
result in posterior to anterior transformations
gain of fcn mutations in homeobox-containing gens
result in anterior to posterior transformations
a _ of gene regulation establishes the polarity and identity of indiv segments of drosophila
cascade
humans have Hox genes in _ and Hox genes in mammals are _ to those found in drosophila
humans have Hox genes in 4 clusters and hox genes in mammals are similar to those found in drosophila
heterotaxy syndrome
aka atrial isomerism; lack of differentiation of right-sided and left-sided organs during fetal development. organs that are normally asymmetrically paired, w/ heterotaxy have a tendency to have symmetry (2 right lungs)
apoptosis
controlled, programmed cell death (orderly, signal received and DNA is cut in a specific and predictable manner, cell shrinks and is phagocytized)
necrosis
injured cells dying in an uncontrolled manner (cell swells and body is responsible to clean up lysis mess)
apoptosis in development/evolution
simplest and most energetically favorable way to induce change so organism can live in an environment and reproduce example is fish that has genes involved in eye development are overexpressed which led to apoptosis of the developing lens cells and lens degenerates as live in caves
t/f: precise regulation of gene expression is essential for development
true; inappropriate expression of the eyeless gene causes the development of an eye of the leg of a fruit fly
natural selection leads to environmental _ caused primarily by _
leads to environmental specialization caused primarily by changing expression levels of CALMODULIN which regulates the expression of many other developmental genes
a comparison of the chimpanzee genome to the human genome showed that the sequence differs by only 1.2% in terms of single-nucleotide changes to the genetic code. how can there be such a great physical difference?
there are a couple of thousand nucleotide differences in regulatory regions and thus contribute to subtle changes in developmental patterns that have significant role in the evolution of the human lineage
mutations in homeotic genes often cause:
structures to appear in the wrong places