Topic 8 - The Control Of Gene Expression Flashcards

Question

Answer 1

A

Change in DNA base sequence of a gene
mainly occurs in DNA replication
occur spontaneously, but frequency is increased by exposure to mutagenic agents
can result in different amino acid sequence in primary structure - causes hydrogen and ionic binds to from in different locations - results in different tertiary structure and therefore different 3D shape - different shape results in different function or non-functioning protein
alterations to genes can result in a mutation that causes cancer

Answer 2

A

Addition
Deletion
Substitution
Inversion
Duplication
Translocation of bases

Answer 3

A

One extra base is added to sequence
Original - TAC TTC AGG TGG
Mutation - TAC ATT CAG GTG G
all subsequent codons are altered (frame shift) - all altered codes could potentially code for different amino acids and result in very different sequence if amino acids resulting in a non-functioning protein

Answer 4

A

deletion of a base in a sequence
Original - TAC TTC AGG TGG
Mutation - TAC TCA GGT GG
Causes frame shift to the left - could result in different polypeptide chain and a non-functioning protein

Answer 5

A

one base changed for different base
Original - TAC TTC AGG TGG
Mutation - TAC ATC AGG TGG
results in only one codon changing and due to genetic code being degenerate it may still code for same amino acids and result and therefore have no impact. If mutation is in the introns it would also have not changed the amino acids coded for

Answer 6

A

section of bases detach from DNA sequence, but when they rejoin they are inverted, so section of code is back to front. Results in different amino acids being coded for in this region
Original - TAC TTC AGG TGG
Mutation - TAC GGA CTT TGG

Answer 7

A

One particular base duplicated at least once in the sequence. Causes frame shift to the right and a different sequence of amino acids are coded for
Original - TAC TTC AGG TGG
Mutation - TAC TTT TCA GGT GG (2 duplications)

Answer 8

A

Section of bases on one chromosome detaches and attaches to different chromosome
Substantial alteration and can cause significant impacts on gene expression and therefore resulting phenotype

Answer 9

A

multicellular organisms have a diverse range of specialised cells that all originate as undifferentiated stem cells
stem cell are undifferentiated cells that can continually divide and become specialised
differentiation is process by which stem cells become specialised

Answer 10

A

Each type of stem cell have different differentiation abilities.
- totipotent
- pluripotent
- multipotent
- unipotent

Answer 11

A

Can divide and produce any type of body cell
Totipotent cells occur only for a limited time in early mammalian embryos

Answer 12

A

found in embryos
an divide into unlimited numbers
used in treating human disorders

Answer 13

A

found in mature mammals
can divide to form a limited number of different cell types

Answer 14

A

found in mature mammals
can divide to form a limited number of different cell types
used to make cardiomyocytes

Answer 15

A

produced from adult somatic cells using appropriate protein transcription factors to overcome some of the ethical issues with using embryonic stem cells
to do this, genes that were switched off to make cell specialised must be switched back on. This is done using transcriptional factors

Answer 16

A

In eukaryotes, transcription if target genes can be stimulated or inhibited when specific transcriptional factors move from cytoplasm into the nucleus
this can turn on/off genes so only certain proteins are produced in a particular cell
turning on/off particular genes in a cell is what enables them to become specialised

Answer 17

A

Transcription of a gene will only occur when a molecule from cytoplasm enters the nucleus and binds to the DNA in the nucleus
these molecules are proteins called transcription factors - each one can bind to different base sequences on DNA, and therefore initiate transcription of genes
once bound transcription begins creating mRNA molecule for that gene which can be translated in cytoplasm to create the protein
without binding of transcription factor, the gene is inactive and protein won’t be made

Answer 18

A

Steroid hormone that can initiate transcription - binds to receptor site on transcriptional factors
when it binds to transcriptional factor is causes it to change shape slightly - makes it complementary and able to bind to the DNA to initiate transcription

Answer 19

A

In eukaryotic organisms, another way gene expression (protein synthesis) is controlled is by epigenetics

Answer 20

A

Heritable change in gene function, without changing the DNA base sequence
these changes are caused by changes in the environment and can inhibit transcription

Answer 21

A

increased methylation of DNA inhibits transcription
when methyl groups are added to DNA, they attach to the cytosine base - prevents transcriptional factors from binding and attracts proteins that condense the DNA-histone complex. In this way, methylation prevents a section of DNA from being transcribed

Answer 22

A

decreased acetylation of associated histones proteins on DNA inhibits transcription
if Acetyl groups are removed from DNA then histones become more positive and are attracted to the phosphate group on DNA - this makes DNA and histones more strongly associated and hard for the transcription factors to bind

Answer 23

A

In eukaryotes and some prokaryotes, translation of mRNA produced from target genes can can inhibit led by RNAi
this is when an mRNA that has already been transcribed gets destroyed before it is translated to create a polypeptide chain
small interfering RNA (siRNA)

Answer 24

A

an enzyme can cut the mRNA into siRNA
One strand of the siRNA then combines with another enzyme
this siRNA-enzyme complex will behind via complementary base pairing to another mRNA molecule
once bound, the enzyme will cut up the mRNA so it cannot be translated