D2.2 Gene Expression Flashcards
How does gene expression relate to phenotypes
it is the mechanism through which info in genes has effects on the phenotype
What are transcription factors
they are proteins that bind to specific sequences of DNA to control transcription
Each has a DNA binding site that allows it to bind to enhancer or promoter sequences
What are enhancer sequences
regulatory sequences that enhance the transcription of an associated gene when bound by transcription factors
Where are regulatory sequences found
usually upstream of the gene being transcribed but can sometimes be downstream
what is the most common form of gene control
regulation of transcription
How is the control of the degradation of mRNA a means of regulation translation
for mRNA to be broken down, the 3’ poly A tail must be degraded before the mRNA is broken down.
Ensures proteins are only synthesized when needed and mRNA is removed afterwards
what is epigenesis
the development of an organism by differentiation from an undifferentiated zygote
Essentially, the development of patterns of differentiation in the cells of a multicellular organism
What is epigenetics
the study of heritable changes in gene activity that are not caused by changes in DNA base sequences
what are the mechanisms through which gene activity is changed
DNA methylation and histone modifications
what is altered in epigenetic changes
the phenotype
what is the proteome
refers to all the proteins expressed within a cell, tissue or organism at a certain time
What is the genome
the whole of the genetic info of an organism
It is unique
how does the uniqueness of the genome affect the proteome
because its unique, the proteome it expresses is also unique
how can genome stay the same and proteome change
genome is the same in all cells of the same organism but diff tissues have different proteins
This means proteomes vary with the function, location or environmental conditions of the cell
what is the transcriptome
the range of mRNA transcripts produced in a specific cell/tissue at a particular time
how are genome, transcriptome and proteome related
transcriptome will determine which proteins are synthesized within a cell, which means it is dependent on which parts of the genome are activated
what is methylation
the addition of a methyl group within the chromatin , to the DNA molecule itself at the promoter
what are epigenetic tags and where are they found
the methyl group which is attached to the cytosine
occurs while DNA is wrapped around the histone proteins
what does methylation do
methylation of amino acids in histones either enables or disables the recruitment of regulatory proteins to the chromatin, causing transcription to be repressed or activated
what can be the reason for methylation
external conditions which lead to the switching off of certain genes
what happens once methylation has occurred
it can remain like that from cell division to cell division
what is epigenetic inheritance
the acquisition of characteristics gained by a parent in their lifetime and passed onto their offspring.
this happens through modification of chromatin via epigenetic tags
what is the result of epigenetic inheritance
phenotypic changes in a cell or organism can be passed on to daughter cells or offspring without changes
what can modify DNA and histone methylation patterns
air pollution , chemicals
can lead to CV diseases, asthma
what is the purpose of epigenetic reprogramming
remove epigenetic changes that might be caused by the environment. Evolved to prevent changes from being transmitted across generations
what is imprinting
when epigenetic tags survive and pass unchanged from parent to offspring, through imprinting
how does imprinting work in sperms and eggs
in sperm development, maternal tags are silenced and in egg development, paternal tags are silenced
how does the way lions mate affect the genes passed on
female lions mate with multiple males , so male lions pass on growth encouraging gene
females evolved genes that are antigrowth
how does the way tigers mate affect the genes passed on
female only mates with one male, who is equally related to all cubs
no growth encouraging gene and female has no anti growth imprinting gene
what happens if a female tiger is crossed with a male lion
a liger is produced which is bigger than parents because no limit to growth
what happens if male tiger and female lion is crossed
a tigon is produced which is same size or smaller than both parents because female has anti growth genes
what are differences within family due to
genetic factors - controlled by genes
environmental factors
combination of both
why can monozygotic twins not be distinguished by DNA fingerprinting
they came from the same dividing cell so are genetically identical
what steroid hormones affect gene expression
oestradiol, progesterone and testosterone
bind to receptors in cytoplasm and then bind to DNA
what are operons
regions of DNA that contain a group of closely related genes consisting of structural genes and regulating elements
regulatory sequences
include promoter, operator and terminator
why is operator position important
its regulation enables or prevents the transcription of genes into mRNA
E. Coli and how it helps in lactose metabolism
found in gut, helps avoid wasting energy by only producing appropriate enzyme when the nutrient is available
what ensure E coli only produces the enzyme required when lactose is present
lactose operon
what happens when lactose is present , how is it metabolised
lactose molecule reacts with the regulator protein, preventing it from binding with the operator gene, allowing it to be transcribed and lactose metabolised by the cell
after digestion, repressor molecule blocks transcription again
what does it mean by lac operon is a inducible operon
transcription is turned on by the rpesence of a small effector molecule called the inducer
concentration of inducer determines the activity of the operon
what does tryptophan function as
a co repressor that cooperates with a repressor protein to switch an operon off
what happens as more tryptophan accumulates
more tryptophan molecules can bind to the trp repressor, which can then bind to the trp operator and inhibit the synthesis of enzymes involved in tryptophan biosynthetic pathway
