D2.2 Gene Expression

Question 1

How does gene expression relate to phenotypes

Answer 1

it is the mechanism through which info in genes has effects on the phenotype

Question 2

What are transcription factors

Answer 2

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

Question 3

What are enhancer sequences

Answer 3

regulatory sequences that enhance the transcription of an associated gene when bound by transcription factors

Question 4

Where are regulatory sequences found

Answer 4

usually upstream of the gene being transcribed but can sometimes be downstream

Question 5

what is the most common form of gene control

Answer 5

regulation of transcription

Question 6

How is the control of the degradation of mRNA a means of regulation translation

Answer 6

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

Question 7

what is epigenesis

Answer 7

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

Question 8

What is epigenetics

Answer 8

the study of heritable changes in gene activity that are not caused by changes in DNA base sequences

Question 9

what are the mechanisms through which gene activity is changed

Answer 9

DNA methylation and histone modifications

Question 10

what is altered in epigenetic changes

Answer 10

the phenotype

Question 11

what is the proteome

Answer 11

refers to all the proteins expressed within a cell, tissue or organism at a certain time

Question 12

What is the genome

Answer 12

the whole of the genetic info of an organism
It is unique

Question 13

how does the uniqueness of the genome affect the proteome

Answer 13

because its unique, the proteome it expresses is also unique

Question 14

how can genome stay the same and proteome change

Answer 14

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

Question 15

what is the transcriptome

Answer 15

the range of mRNA transcripts produced in a specific cell/tissue at a particular time

Question 16

how are genome, transcriptome and proteome related

Answer 16

transcriptome will determine which proteins are synthesized within a cell, which means it is dependent on which parts of the genome are activated

Question 17

what is methylation

Answer 17

the addition of a methyl group within the chromatin , to the DNA molecule itself at the promoter

Question 18

what are epigenetic tags and where are they found

Answer 18

the methyl group which is attached to the cytosine
occurs while DNA is wrapped around the histone proteins

Question 19

what does methylation do

Answer 19

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

Question 20

what can be the reason for methylation

Answer 20

external conditions which lead to the switching off of certain genes

Question 21

what happens once methylation has occurred

Answer 21

it can remain like that from cell division to cell division

Question 22

what is epigenetic inheritance

Answer 22

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

Question 23

what is the result of epigenetic inheritance

Answer 23

phenotypic changes in a cell or organism can be passed on to daughter cells or offspring without changes

Question 24

what can modify DNA and histone methylation patterns

Answer 24

air pollution , chemicals
can lead to CV diseases, asthma

Question 25

what is the purpose of epigenetic reprogramming

Answer 25

remove epigenetic changes that might be caused by the environment. Evolved to prevent changes from being transmitted across generations

Question 26

what is imprinting

Answer 26

when epigenetic tags survive and pass unchanged from parent to offspring, through imprinting

Question 27

how does imprinting work in sperms and eggs

Answer 27

in sperm development, maternal tags are silenced and in egg development, paternal tags are silenced

Question 28

how does the way lions mate affect the genes passed on

Answer 28

female lions mate with multiple males , so male lions pass on growth encouraging gene
females evolved genes that are antigrowth

Question 29

how does the way tigers mate affect the genes passed on

Answer 29

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

Question 30

what happens if a female tiger is crossed with a male lion

Answer 30

a liger is produced which is bigger than parents because no limit to growth

Question 31

what happens if male tiger and female lion is crossed

Answer 31

a tigon is produced which is same size or smaller than both parents because female has anti growth genes

Question 32

what are differences within family due to

Answer 32

genetic factors - controlled by genes
environmental factors
combination of both

Question 33

why can monozygotic twins not be distinguished by DNA fingerprinting

Answer 33

they came from the same dividing cell so are genetically identical

Question 34

what steroid hormones affect gene expression

Answer 34

oestradiol, progesterone and testosterone
bind to receptors in cytoplasm and then bind to DNA

Question 35

what are operons

Answer 35

regions of DNA that contain a group of closely related genes consisting of structural genes and regulating elements

Question 36

regulatory sequences

Answer 36

include promoter, operator and terminator

Question 37

why is operator position important

Answer 37

its regulation enables or prevents the transcription of genes into mRNA

Question 38

E. Coli and how it helps in lactose metabolism

Answer 38

found in gut, helps avoid wasting energy by only producing appropriate enzyme when the nutrient is available

Question 39

what ensure E coli only produces the enzyme required when lactose is present

Answer 39

lactose operon

Question 40

what happens when lactose is present , how is it metabolised

Answer 40

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

Question 41

what does it mean by lac operon is a inducible operon

Answer 41

transcription is turned on by the rpesence of a small effector molecule called the inducer
concentration of inducer determines the activity of the operon

Question 42

what does tryptophan function as

Answer 42

a co repressor that cooperates with a repressor protein to switch an operon off

Question 43

what happens as more tryptophan accumulates

Answer 43

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