Chapter 3 - Differential Gene Expression

each somatic cell nucleus of an organism has the same chromosomes as every other somatic cell nucleus in that organism

what is genomic equivalence

differential gene expression

if genomic equivalence is true how o we get different cell types

1) every somatic cell nucleus of an organism contains the complete genome established in the fertilized egg. The DNA of all differentiated somatic cell is identical.

2) The unexpressed genes in differentiated cells are neither destroyed nor mutated; they retain the potential to be expressed

3) Only a small percentage of the genome is expressed in each cell type and a portion of the RNA synthesized in each cell is specific for that cell type.

what are the 3 pillars of differential gene expression

1) differential gene transcription (whether DNA is made into RNA)

2) selective pre-mRNA processing

3) selective mRNA translation (mRNA has left the nucleus but doesn’t mean it’s translated)

4) differential posttranslational protein modification

what are the 4 ways in which gene expression is modulated

Drosophila polytene chromosomes

what was the first piece of evidence for genomic equivalence

all cells had the same banding pattern (physical arrangement of DNA), but the cells of the same cell type would have the same genes being transcribed which was indicated by the chromosome puffing out (polytene chromosomes)

how did the Drosophila chromosomes give evidence of genomic equivalence

they were easy to visualize under the microscope

why did researchers use Drosophila polytene chromosomes during research

through nucleic acid hybridization which involves staining specific genes in DNA → Globin genes which are only expressed in blood cells were stained and were present in pancreatic tissue even through not expressed in pancreatic cells

how was genomic equivalence later proved in mammalian tissue

that the nucleus of any somatic cell in the body should be able to direct the entire development if put into an enucleated egg (since every cell’s nucleus is identical to the zygote nucleus) → this is the idea of cloning

what was the hypothesis given the results of genomic equivalence

somatic nuclear transfer

what is cloning also known as

cloning of an animal

what was the solid proof of genomic equivalence

oocyte donor → giving the egg

nuclear donor → giving adult differentiated cell (utter cell in this case)

what were the 2 donors used in the cloning of Dolly the sheep

1) remove eggs from oocyte donor and remove the nucleus from an egg to have an enucleated egg

2) remove udder cells from nuclear donor, place in culture to grow in G1 phase, then transfer the cell into the enucleated egg

3) fuse egg and cell with electric current

4) embryo cultured for 7 days until reaches blastocyst form then planted back into the oocyte donor

explain the process of cloning Dolly the sheep

the nuclear donor (the sheep that donated its utter cells)

who was Dolly identical to

epigenetics and differences in environmental factors

why might cloning organisms face differences in development

information flow from the end product back to the beginning of production

what is reverse engineering a protein

an octamer of histone proteins wrapped with 2 loops of DNA

what is a nucleosome

how eukaryotic genes are held and is a complex of DNA and proteins

what is chromatin

heterochromatin is tightly condensed chromatin that prevents transcription

euchromatin is loosely packed chromatin that allows transcription

heterochromatin vs euchromatin