D2.2 Flashcards
Gene Expression
Define genotype
the alleles of an organism.
Define phenotype
the characteristics of an organism.
List the common stages in the process of gene expression
Transcription - during which the genetic code is transcribed into mRNA. …
Translation - when the genetic code is translated into proteins at ribosomes.
The function of the protein product, such as an enzyme, which will affect the phenotype.
Explain the regulation of transcription by a transcription factor binding to the promoter sequence of DNA
Sets of transcription factor proteins bind to specific DNA sequence in or near a gene and promote or repress its transcription into an RNA
Compare the function of enhancer and silencer DNA sequences
An enhancer is a specific region of DNA that promotes trnascription, wherease a region of DNA that causes a decrease in gene activity is called a silencer.
Compare the function of repressor and activator transcription factors
Activator proteins bind to an enhancer and enables it to form a complex that interacts with the promoter region and aids the binding of RNA polymerase whereas repressors recruit corepressors that lead to transcriptional repression.
Outline how the length of the poly A tail on mRNA impacts degradation of mRNA by nucleases
Guanine caps and poly A tails increase the stability of mRNA increasing its persitence, the tail is shortened over time which makes mRNA easier to be degraded.
Outline how the degradation of mRNA is a mechanism of regulating translation.
The faster mRNA is degraded the less time it has to cause proteins to be produced, and different mechanisms exist to degrade mRNA at different rates.
Define epigenesis Define epigenesis and epigenome
Epigenesis: The process by which organisms develop from an undifferentiated zygote through the interaction between DNA and environmental factors
Epigenome: all the epigenetic tags in an organism
Compare genome, transcriptome and proteome
The genome represents the entire set of genetic instructions for an organism, all cells of an organism share an idential genome.
The transcriptome represents the genetic instructions that have been actively transcribed into RNA molecules, it includes rRNA, tRNA, and mRNA sequences. The proteome represents all proteins expressed within a cell, tissue, or organism. The proteome is larger than the transcriptome as proteins may be modified to become additional variants.
Describe the ipact of methylation of DNA in the promoter of DNA on gene expression.
Regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcroption factors to DNA.
Describe the impact of acetylation and methylation of histone proteins on gene expression
Methylation of DNA and histones cause nucleosomes to pack tightly together, transcription factors cannot bind the DNA, and genes are not expressed.
Histone acetylation results in loose packing of nucleosomes. Transciption factors can bind the DNA, and genes are expressed.
