Theme 3- Module 3 Flashcards
Development of a eukaryotic organism from a single fertilized zygote is dependent on the ____________
Molecular communication between cells
What determines the fate of an embryonic cell?
The signals that are exchanged
Which genes are switched on or off at specific times
On what type of cell did differentiation occur (that eventually led to the variation in specialized cell types)?
Stem cells
What does the body use to control which genes get activated along the chromosome during development?
Transcription factors (det pathway)
Proteins (that can result in various changes in gene expression)
All embryonic stem cells are
a) Different
b) The same
B) The same
Muscle cells and liver cells are different because:
a) They have different DNA blueprints
b) They were transcribed differently
c) They removed unnecessary genes from the genome
b) They were transcribed differently
How does winding the DNA into chromatins affect gene expression?
Genes within this tightly wound heterochromatin are usually not expressed. To be able to transcribe a specific gene product, it is necessary to unwind the DNA.
Describe the structure of a nucleosome
Octamer of 8 histone proteins around which approximately 150 DNA base pairs wrap around
Describe the basic steps of chromatin remodeling
1) Activator protein recruits histone acetyltransferase (or methyltransferase, etc)
2) Add acetyl group to lysine (or specific amino acid) along histone tails
3) (+) charge of tails reduced
4) Interaction b/w histones and DNA are weakened
What is the histone code?
Degree of modifications to histone tails controls activation and repression of transcription
Does acetylation and methylation with a single methyl group allow for transcriptional activation or repression?
Activation
Does methylation with three methyl groups allow for transcriptional activation or repression?
Repression
Why are transcription factors able to recognize and bind to nucleic acid sequences in DNA?
Bc of structural and chemical complementarity between the proteins and DNA
Most transcription factors are classified based on what?
The structures of their distinct DNA binding motifs (basically, they’re classified based on their structure and how it helps them bind to DNA)
What are the four different types DNA binding motifs?
Basic helix- loop-helix
Helix-turn-helix
Zinc finger
Leucine zipper
Most of these transcription factors have _________ that tend to fit nicely within the major grooves of DNA
Alpha-helical domains
What is the core promoter?
Binding site that is required for binding of RNA polymerase and associated transcription factors
What elements are part of the core promotor?
TATA box
BRE region
Transcriptional start site
The TATA box region is usually recognized by the __________ subunit of the transcription factor ___________
TATA-binding protein (or TBP)
TFIID
What is another region that is recognized by TFIID?
BRE (B recognition element)
- closely related to the TATA box
How are enhancer regions able to facilitate the formation of the transcriptional complex?
Enhancer regions are able to bind cell or region specific transcription factors. These transcription factors interact with the basal machinery at the promoter to enhance the transcription of a gene
What binds to enhancer regions?
a) Transcriptional activator proteins
b) General transcription factors
a) Transcriptional activator proteins
What binds to promotrr regions?
a) Transcriptional activator proteins
b) General transcription factors
b) General transcription factors
How do transcriptional activator proteins and general transcription factors work together to help regulate transcription?
Loop the DNA and bring regulatory sequences (which are situated far from the actual transcription sites) close to transcription sites
