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Human Genetics (week 10)
Terms in this set (21)
What is a gene? What two types of functional product do genes encode?
A segment of DNA that encodes a functional product- either a polypeptide or a functional RNA molecule (such as rRNA, tRNA, snRNA, miRNA, for example).
What happens during the process of transcription
The sequence of DNA nucleotides in a gene is copied (transcribed) to a sequence of RNA nucleotides.
Which enzyme transcribes DNA to RNA? How many different types of RNA polymerase are there in humans?
RNA polymerase transcribes DNA to RNA. Humans have 3 different RNA polymerase enzymes
What is the name of the region where RNA polymerase binds to the DNA to initiate transcription?
The promoter region.
At which location of a gene do the GTFs and RNA polymerase bind to initiate transcription?
The promoter region
What is a consensus sequence?
consensus sequence lists the most common nucleotide at each position:
What is the role of the Mediator complex?
Mediator interacts with the regulatory transcription factors, and it regulates phosphorylation of the carboxyl terminal domain (CTD) of RNA pol II, which is the switch between transcription initiation and elongation.
What are regulatory transcription factors (RTFs)? Do all genes transcribed by a particular RNA polymerase (e.g., RNA polymerase II) require the same set of RTFs, or do different genes use different RTFs?
Regulatory transcription factors control the rate of gene transcription. Genes transcribed by a particular RNA polymerase are controlled by different combinations of regulatory transcription factors.
What effect to activators have on gene expression? What sequence do activators bind to?
Activators promote gene transcription. Activators bind to enhancer sequences in DNA.
What effect do repressors have on gene expression? What sequence to repressors bind to?
Repressors inhibit gene transcription. Repressors bind to silencer sequences in DNA.
Describe 3 ways in which activators and repressors act to affect gene expression.
-Promote or inhibit the binding to TFIID to the promoter region.
-Interact with Mediator to promote or inhibit phosphorylation of the carboxyl terminal domain (CTD) of RNA pol II.
-interact with proteins complexes that alter chromatin structure to make the DNA more or less accessible to GTFs and RNA pol
Which base in DNA is methylated to affect gene expression?
Methylation is associated with gene silencing. Methyl groups can be added to cytosine (C) bases.
What are the base pairing rules between DNA and RNA during transcription?
A in DNA pairs with U in RNA, T in DNA pairs with A in RNA, G in DNA pairs with C in RNA and C in DNA pairs with G in RNA.
of the template strand is the promoter located?
The promoter is located at the 3' end of the template strand.
Do all genes use the same DNA strand as the template strand?
Different genes located on the same chromosome may use a different DNA strand as the template strand, but any individual gene always uses the same DNA strand as the template strand.
What causes RNA polymerase to end transcription?
Transcription ends after RNA polymerase transcribes the polyA signal sequence. RNA is cleaved after this sequence and RNA polymerase dissociates a short way downstream.
What are introns and exons?
-Exons are coding regions that encode amino acids (i.e., expressd regions). -Introns are non-coding intervening regions that do not encode amino acids.
The spliceosome removes introns. What two types of molecules is the spliceosome composed of?
The spliceosome is composed of multiple subunits that are each composed of proteins and a type of functional RNA called small nuclear RNA (snRNA).
It seems wasteful for organisms to use energy to transcribe introns only to remove them. What is an advantage of having genes that contain introns?
Genes can be alternatively spliced to produce different polypeptides by using different combinations of exons.
What is RNA editing? What is the result of RNA editing?
After transcription, one base is converted to a different base. RNA editing alters the structure and/or properties of the resulting polypeptide
What is the role of micro RNA (miRNA)? How can one micro RNA control gene expression of many genes?
miRNAs are functional RNA molecules that bind to target mRNAs and repress translation.
-Therefore, one miRNA can have many target mRNAs that all share the same short nucleotide sequence in the 3' UTR that is complementary to the seed region.
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