Chapter 18 Flashcards
Even though human cells share the same genome, why do they look and function differently from one another?
Because each type of cell expresses different sets of genes.
Where can gene regulation take place?
- through chemical modification of chromatin or histones
- during transcription
- during RNA processing
- during translation
what is gene regulation?
Gene regulation is the process of controlling which genes in a cell’s DNA are expressed (used to make a functional product such as a protein).
what can alter gene expression?
nucleosomes
what is chromatin and function in gene regulation
a coiled complex of DNA, RNA, and proteins that gives chromosomes their structure.
Chromatin must unravel to allow space for transcription
Coiling is facilitated by histone complexes called
nucleosomes
DNA coiled around the nucleosome is inaccessible for
transcription (genes are ‘silenced’)
what is chromatin remodelling?
nucleosomes are repositioned to expose different stretches of DNA.
what is Methylation?
addition of a methyl group to cytosine bases adjacent to
guanosine bases on a DNA strand (CpG)
Use of methylation
Methylation is a way to turn genes on or off
Heavy methylation leads to gene repression
what is epigenetic effects?
alterations that affect how DNA expressed (rather than to the DNA sequence itself)
what does Methylation or Histone modification do?
These changes sometimes cause changes in gene expression.
They can be inherited but are often reversible and responsive to changes in the environment.
How is high vs. low licking is ‘inherited’ epigenetically
Mothers lick their newborn offspring
Offspring of ‘high licking’ (i.e. good) mothers are good
mothers themselves
what is dosage compensation?
Sex-specific regulation of X chromosome
Inactivation of one X chromosome in females is called
X inactivation
Explain X inactivation
How does transcription factors regulate gene expresion?
•Transcription factors regulate gene expression
•Enhancers bind at enhancer sequences near the
promotor region
•Recruit RNA polymerase complex
•Silencers bind and repress transcription
How does RNA processing helps with gene regulation
RNA splicing provides an opportunity for regulating gene expression.
what is alternative splicing?
The same primary transcript can be spliced in different ways to yield different proteins, a phenomenon called alternative splicing
Hows does small regulatory RNA regulate expression?
•Binding to transcripts and blocking
translation
•Blinding to transcripts causing degradation
what RNA folds back on itself to form a hairpin?
microRNAs and small interfering RNAs (siRNA)
Function of Post-translational modifications
serve to regulate structure and function of proteins
•Regulates protein activity
•e.g. phosphorylation
The lac operon image
Lac operon is a controlled cascade
Mutations & the lac operon
