Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biology > gene expression is controlled by a number of factors > Flashcards

gene expression is controlled by a number of factors Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

define a stem cell

A

an undifferentiated cell that can divide indefinitely and turn into other specific cell types

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the 3 types of stem cells?

A
  1. totipotent
  2. pluripotent
  3. multipotent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are totipotent stem cells

A
  • can develop into any body cell type including the placenta and embryo
  • all genes in the nucleus must be activated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

explain what happens to totipotent cells during embryonic development?

A
  • certain parts of the DNA are selectively translated so that only some genes are switched on
  • in order to differentiate the cell into a specific type and form the tissues that make up the foetus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

explain how stem cells become specialised via differentiation

A
  • not all of the genes are transcribed and translated
  • under the right conditions, some genes are expressed and others are switched off
  • mRNA is transcribed from specific genes
  • the mRNA is translated into proteins
  • these proteins modify the cell, they determine the cell structure and control cell processes
  • changes to the cell produced by the protein cause the cell to become specialised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are pluripotent stem cells

A
  • can develop into any cell type including the 3 germ layers (any tissue in the body) excluding the placenta and embryo
  • majority of the genes are still able to be activated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are multi-potent stem cells

A
  • can divide to form different cell types with a limited range (closely related cell types)
  • some genes have been switched off but they have the genes for some different cels still available
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are unipotent stem cells

A
  • cells that can only form one other type of cell
  • they can self-renew
  • lots of genes have been switched off via regulation of translation factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a unique feature of pluripotent cells and the use of this feature

A

they can divide in unlimited numbers, and can therefore be used to repair or replace damaged tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is an example of a unipotent cell?

A

cardiomyocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how does our heart recover from a myocardial infraction

A
  • unipotent stem cells differentiate into new cardiomyocyte cells
  • so cardiomyocytes are generated and replace the old damaged cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

which types of stem cells are found in embryos

A
  • totipotent and pluripotent
  • multi-potent and unipotent cells are only found in mature mammals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are some uses of stem cells

A
  1. medical therapies for example bone marrow transplants
  2. drug testing on artificially grown tissues
  3. research on formation of organs and embryos
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

evaluate the use of stem cells in medicine

A
  1. unused IVF embryos can be donated to research facilities instead of being destroyed, some people object to this as it is the destruction of a potential foetus
  2. egg cells frozen from IVF which have not been fertilised can be stimulated to divide, causes less objection as they would not survive after a few days if implanted into a womb and would not create a foetus
  3. it is possible to use adult stem cells for some treatments which people feel is more ethical, however they cannot develop into all the specialised cell types that embryonic stem cells can
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

explain how are induced pluripotent stem cells produced

A
  • from mature, fully specialised (somatic cells)
  • that are reprogrammed into specialised adult body cells to become pluripotent
  • the cell regains the capacity to differentiate (express genes) through the use of transcription factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

explain how transcription factors can be introduced to the iPS cells

A
  • infecting the iPS cells with a specially-modified virus
  • the virus has genes coding for the transcription factor within its DNA
  • when it infects the adult cell, these genes are passed into the iPS cell so the cell is able to produce the transpiration factors
17
Q

what are the advantages of using iPS cells over stem cells?

A
  • iPS cells do not require the destruction of an embryo, unlike stem cells, so they are more ethical
  • iPS cells can be obtained from adult tissue unlike stem cells which are obtained from the foetus’ so more ethical
  • iPS cells can be made from the patient’s own cells so they are genetically identical to the patient’s cells and the body would not reject them since the immune system doesn’t recognise the antigens as foreign
18
Q

what is a transcription factor?

A

a protein that controls the rate of transcription of genes so only certain parts of the DNA are expressed

19
Q

outline how transcription factors work

A
  1. transcription factors move from the cytoplasm into the nucleus
  2. in the nucleus they bind to specific DNA sites (the promoter region) near the start of their target genes
  3. makes it easier/more difficult for RNA polymerase to bind to a gene, this increases/decreases the rate of transcription
20
Q

what are activators

A

transcription factors that stimulate or increase the rate of transcription by helping RNA polymerase to bind to the start of the target gene and activate transcription

21
Q

what are repressors

A

transcription factors that inhibit or decrease the rate of transcription by binding to the promoter region of the target gene, preventing RNA polymerase from binding which stops transcription

22
Q

give an example of a hormone that affects transcription and explain how it works

A
  • steroid hormone oestrogen binds to an oestrogen receptor, forming an oestrogen-oestrogen receptor complex
  • the complex moves from the cytoplasm into the nucleus where it binds to promoter regions near the start of the target gene
  • the complex can act as an activator of transcription which helps RNA polymerase to bind to the start of the target gene
23
Q

what is RNAi

A
  • small double stranded RNA molecule that stops target genes from being translated into proteins
  • found in eukaryotes
24
Q

explain how siRNA and miRNA work in plants

A
  • once transcribed mRNA leaves the nucleus for the cytoplasm
  • double-stranded siRNA associates with several proteins and unwinds
  • a single strand binds to the target mRNA
  • base sequence of the siRNA is complementary to the base sequence is sections of the target mRNA
  • the proteins associated with the siRNA cut mRNA into fragments so it can no longer be translated
  • fragments move into a processing body
25
Q

explain how miRNA work in mammals

A
  • miRNA isn’t fully complementary to the target mRNA, so it can target more than 1 mRNA molecule
  • it associates with proteins and binds to target mRNA in the cytoplasm
  • miRNA-protein complex physically blocks the translation of the target mRNA
  • mRNA is moved into a processing body where it can be stored or degraded
  • when it’s stored it can be returned and translated at another time
26
Q

what is meant by epigenetics?

A

a heritable change in gene function without change to the base sequence of DNA

27
Q

how does increased methylation of DNA affect gene transcription

A
  • involves addiction of CH3 group to cytosine bases which are next to guanine
  • causes DNA to be more tightly coiled around histone protein
  • prevents transcription factors from binding
  • therefore gene transcription is supressed
28
Q

how does decreased acytelation of histones affect gene transcription

A
  • positively charged histones bind to negatively charged DNA
  • decreasing acytelation increases positive charge of histones
  • binding becomes too tight and prevents transcription factors from accessing the DNA
  • therefore gene transcription is suppressed
29
Q

how might epigenetic changes affect humans

A

they can cause disease, either by over activating a gene’s function or by suppressing it

30
Q

give an application of epigenetics

A
  • treatments of various diseases
  • development of ways to reverse epigenetic changes
31
Q

describe the process of RNA interference, including the organism in which it occurs

A
  • rna molecules act to inhibit gene expression
  • usually by destroying mrna so that it cannot be translated
  • occurs in eukaryotes and some prokaryotes
32
Q

give some characteristics of benign tumours

A
  • slow growth
  • defined by a clear boundry due to the cell adhesion molecules
  • cells retain function and normal shape
  • don’t spread easily
  • easy to treat
33
Q

give some characteristics of malignant tumours

A
  • rapid, uncontrollable growth
  • ill-defined boundary with finger like projections
  • cells do not retain function and often die
  • spreads quickly and easily via metastasis
  • difficult to treat
34
Q

describe the role of tumour-suppressor genes

A
  • code for proteins that control cell division
  • stop the cell cycle when damage is detected
  • involved in programming apoptosis (self-destruction) of the cell
35
Q

explain how tumour-suppressor genes can be involved in developing cancer

A
  • a mutation in the gene could code for a non-functional protein
  • increased methylation of decreased acetylation could prevent transcription
  • cells will divide uncontrollably resulting in a tumour
36
Q

describe the role of proto-oncogenes

A
  • control cell division
  • code for protein that stimulate cell division
37
Q

explain how proto-oncogenes can be involved in developing cancer

A
  • mutation in the gene could turn it into a permanently activated oncogene
  • decreased methylation or increased acetylation could cause excess transcription
  • this results in uncontrolled cell division and formation of a tumour
38
Q

explain how abnormal methylation of genes can cause cancer

A
  • hyper-methylation of tumour supressor genes or oncogenes can impact their function
  • and cause the cell to divide uncontrollably

biology (46 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions