Chapter10 Flashcards
the genetic code
is not the blueprint of life
all cells contain
a complete copy of an organisms genetic info but for development to occur, there must be some form control over the expression of that info
cells develop into
skin, nervous system
muscles, bones, blood, gonads
digestive system, lungs
processes that occur during development
- cell division
- cell specialization ( the expression of different genes)
- cell heredity
- cell movement
- spatial patterning
control over cell division
most eukaryotic cells do not have the ability to divide
growth factors
(protiens) must be present to complete the cell cycle
in eukaryotes most specialized cell are in the G1 phase
growth factors may be produced externally or internally
contact between cells can affect the
production of growth factors
cancer results from unregulated cell division
can result when cells do not respond properly to growth factors
ex) proteins producing a signal without a growth factor present
genes that cause cancer may develop from genes that are normally involved in controlling cell division
cell specialization
occurs through the turning off and on (expression) of genes
during development cells become increasingly specialized
undifferented cells–> germ layer–> tissues (cells with similar function)–> specialized cells
3 processes lead to cell specialization
- chromosome inactivation
- single gene inactivation
- gene expression
inactivation of chromosome
proteins bound to whole chromosome prevents transciption
ex) inactivation of one x chromosome in females. maternal or paternal chromosomes are deactivated at random
usually occurs after zygote has started to divide
chromosome inactivation occurs
through DNA packing
all daughter cells will have the same chromosome de-activated
paternal and maternal chromosomes
express different alleles
paternal and maternal x chromosomes deactivated
results in regions of the organism with different alleles being expressed
inactivation of individual genes
molecules bind to DNA
prevents transciption from taking place but does not prevent DNA from being copied
cell heredity
once a gene is inactivated in a cell, all daughter cells have the gene activated
during DNA replication
the binding of molecules to either whole chromosomes or individual nucleotides is also copied
inactivation of genes results in cell heredity
undifferentied cells–> germ layers–> tissues (cells with similar function)–> specialized cells
ex) of control gene expression
lactose degrading genes in prokaryotes
when lactose is not present the enzymes are not produced
when lactose is present the enzymes that break it down are produced
in ekaryotes most genes are in an
inactive state
many regulatory protiens may be
required for transciption to take place
two forms of heredity within organisms (from parent to daughter cells)
- genetic code
- cell state
includes: inactivated genes quality of cytoplasm (regulatory protiens)
cells states need to be re-set for gamete production
- antiquity- 1830
atomistic principal:
different body parts provided material for the offspring of an individual
aristoltle
compared reproduction and development among animals
- in mammals semen provides a drive (edios) to the devlopment of menstrual blood
- the traits in anew individual are the result of a struggle between material from the mother and the father
- 1830- early 20th century
discovery of cells
fertilization- union of sperm and egg
desciption of cell specilazation:
-development of germ layers and tissues
- development of cell heredity
3 competing ideas about sexual reproduction and dvelopment of multicelled organisms
- pangenesis
- preformation
- epigenesis
pangenesis
every cell contribute genetic info to reproductive cells
preformation
miniture version of adult is present in either egg or sperm
epigenesis
development starts from undifferentiated cells
some external force caused development and cell specialization to take place
only certain genes passed from one cell to another during development, except games
early 20th century- present
undertanding of how genetic info is a pass from parent to offspring (meiosis)
understanding of haploid/diploid phases of the life cycle
focus on relationship between gene expression and development
