3C Differentiation and Variation Flashcards
(53 cards)
1
Q
stem cell
A
undifferentiated cell with potential to continue to DIVIDE to become specialised cells with one function
2
Q
differentiated cell
A
cell with one purpose -> cannot become multiple cells
3
Q
totipotent
A
stem cells that can become ALL cells
- embryonic stem cells that can differentiate into any cell type in embryo
- … and extra-embryonic cells (cells that make up placenta and umbilical cord)
“i can totally be pregnant” -> embryonic cells
4
Q
pluripotent
A
stem cells that can become MOST cells
- embryonic stem cells that can differentiate into any cell type found in an embryo
- but NOT able to differentiate into cells forming placenta and umbilical cord
5
Q
(multipotent)
A
stem cells that can become SOME cells
adult stem cells that have LOST SOME OF POTENCY associated with embryonic stem cells and are no longer pluripotent
6
Q
explain why some cells do not remain totipotent
A
during fertilisation and cell division -> become specialised for a purpose
7
Q
state 3 examples of multipotent stem cells in humans
A
- nerve cells
- muscle cells
- bone marrow
8
Q
explain how “potency” of plant and animal cells differ
A
animal cells: once specialised, it is usually permanent
plant cells: become specialised and unspecialised throughout lifetime
9
Q
describe potential uses of stem cells in medicine
A
- used to regrow limbs, organs
- cure degenerative diseases
v useful as no chance of rejection (unlike donor organs)
10
Q
explain why PLURIPOTENT EMBRYONIC stem cells could be considered more useful than ADULT MULTIPOTENT stem cells
A
- embryonic stem cells -> can turn into more types of cells than body cells
11
Q
discuss the ethical views on the use of embryonic stem cells
A
obtaining stem cells from embryos created via IVF raise ethical issues as procedure destroys viable embryo
FOR:
- embryos will be destroyed anyway
- advancing science with hope of saving lives
AGAINST:
- mothers pressured into donating eggs
- murder? -> on religious grounds
- ppl believe that at moment of fertilisation: genetically unique individual created -> has a right to life
12
Q
why aren’t stem cells rejected by body?
A
DNA is from YOU -> not recognised as foreign
13
Q
what are the dangers of stem cell therapy?
A
- stem cells becoming cancerous
- body may reject stem cells
- when injecting stem cells -> risk of introducing INFECTION
14
Q
activators
A
factors that increase rate of transcription
- help RNA polymerase bind to DNA and begin transcription
15
Q
repressors
A
factors that decrease rate of transcription
- prevent RNA polymerase binding to DNA and stopping transcription
16
Q
where do transcription factors bind to in EUKARYOTES (animals and plants)?
A
specific DNA sites near START of TARGET GENES (genes they control expression of)
17
Q
where do transcription factors bind to in PROKARYOTES?
A
OPERONS
18
Q
operon
A
section of DNA that includes…
- cluster of structural genes that are transcribed together (these code for useful proteins e.g. enzymes)
-
control elements -> including a PROMOTER REGION (a DNA sequence that RNA polymerase initially binds to)
-> OPERATOR REGION (where transcription factors bind)
19
Q
lac operon
A
controls production of enzyme LACTASE and 2 other structural proteins
where genes that produce enzymes needed to respire lactose are found
20
Q
promoter
A
DNA sequence located BEFORE structural genes that RNA POLYMERASE binds to
21
Q
operator
A
DNA sequence that TRANSCRIPTION FACTORS bind to
22
Q
E. coli
A
bacterium that respires glucose BUT will use lactose if glucose isn’t available
23
Q
name lac operons structural genes
A
- lacZ
- lacY
- lacA
they produce proteins that help bacteria digest lactose
24
Q
potency
A
ability of stem cells to differentiate into more specialised cell types
25
how are epigenetic changes to a cell's gene expression passed on?
- when a **cell ÷** and **replicates** ...
- **epigenetic** changes to its **gene expression** **passed on** to daughter cells
- certain genes that are **activated / deactivated** in **o.g cell** will **also** be activated / deactivated in **daughter** cells
- so **daughter cells equipped to deal with changed env** in **same way** as o.g cell was
26
differentiation
proccess by which a cell becomes specialised
27
where are totipotent stem cells present?
first few cell ÷ of an embryo
28
how do stem cells become specialised?
(1 mark)
**different genes** in their DNA become **active** and get expressed
29
how are stem cells specialised in animals and plants?
- when **chemical stimulus present** -> some **genes activated** / others **inactivated** (differential gene expression)
- **transcription** occurs at **active** genes
- **active mRNA** from active genes **translated** on **ribosome** to synthesise **proteins**
- protein **modifies cell** and **determines structure and functions**
- **changes** to cell produced by these proteins **cause cell to become specialised**
30
discuss the way **society uses scientific knowledge** to make **decisions** about the use of stem cells in medical therapies
(6 marks)
- looking at ***proposals of research*** and deciding if they should be allowed -> **ethical issues into account**
-> ensures research isn't **unnecessarily repeated by diff groups**
- ***licensing and monitoring centres*** -> ensures only fully trained staff carry out research
-> staff won't waste **precious resources eg. embryos**
-> helps **avoid unregulated research**
- ***guidelines / codes of practice*** -> all scientists working in similar manner
-> ensures scientists using **acceptable source of stem cells** and **method** to extract cells are controlled (includes **max. age** of embryo that can be used)
- ***monitoring developments***
-> ensures changes in field regulated appropriately and all **guidelines up to date**
- providing ***info / advice to governments / professionals***
-> helps promote science involved in embryonic research
-> helps **society understand** what's involved / why it's important
31
adult stem cells can only develop into a limited range of cells whereas embryonic stem cells can develop into all types of specialised cells.
suggest why **adult** stem cells might be used **instead** of embryonic stem cells
if patient needs stem cell transplant and own stem cells can be used -> **less risk of rejection**
as cells are not foreign ('self') and **doesn't initiate immune system response**
32
describe how stem cells can be used to treat a range of diseases
- stem cells can differentiate into any cell type -> so can be used to **replace damaged tissue** in range of diseases
- eg. **leukemia (cancer of bone marrow)** kills **bone marrow stem cells** -> so bone **marrow** transplants given to **replace** them
33
what conditions are scientists researching for stem cell treatment?
- **spinal cord injuries**
-> stem cells could be used to **repair** damaged **nerve** tissue
- **heart disease** and damage caused by **heart attacks**
-> **replace** damaged **heart** tissue
34
explain one benefit of **using embryonic** stem cells instead of adult stem cells
embryonic stem cells **can develop into all types of specialised cell**
whereas adult stem cells can **only develop** into a **limited range of cells**
35
state 2 reasons why some ppl are opposed to using embryonic stem cells
- believe embryos have a **right to life** from **moment of fertilisation**
- believe its wrong to **destroy viable** embryos
36
RBCs contain lots of **haemoglobin** and have **no nucleus** (to make room for more haemoglobin).
they are produced from a type of stem cell in the **bone marrow**.
describe how a red blood cell becomes specialised
1. stem cell in bone marrow produces **new cell** where **genes** for **haemoglobin production activated**
2. other genes (eg. those involved in **removing nucleus**) **activated too**
3. many other genes **activated / inactivated** -> leads to specialised RBC
37
what is the variation in **phenotype** influenced by?
**variation in genotype (genes)** and the **env**
(phenotype produced by **interactions** of env and genotype)
38
locus
location of genes on chromosome
39
**explain the type of variation shown by human blood groups**
(3 marks)
## Footnote
check this
**discontinuous variation**
-> blood groups: A, B, AB, O
**monogenic characteristics** (controlled by **one gene**) so blood groups show this type of variation
- blood groups **only influenced by genotype** (not env)
40
discontinous variation
- when **2 or more distinct** categories
- each individ. falls into **only 1 category**
41
mono**gen**ic characteristics
controlled by **one gene**
usually show **discontinous variation**
eg. blood group
42
polygenic characteristics
| polygenic inheritance
controlled by **no. of genes at diff loci**
usually show **continuous variation**
eg. height
43
continous variation
when individ. in pop **vary within a range** -> **no** distinct categories
Eg.
- height
- mass
- skin colour
44
height is a phenotype influenced by both genotype and env.
describe how the env affects the height of an individ.
- height is **polygenic** (controlled by no. of genes at diff loci)
- and affected by env factors eg. **nutrition**
- tall parents **usually** produce tall children (polygenic inheritance)
- BUT if child **undernourished**: won't grow to **max.** height (as **protein required for growth**)
45
MAOA is enzyme that breaks down monoamines (chemical) in humans.
describe how the env affects the MAOA of an individ.
- **low levels** of MAOA linked to **mental health problems**
- MAOA production controlled by single gene **(monogenic)**
- BUT taking **anti-depressants / smoking** can **reduce** amount produced
46
risk of cancer is influenced by genotypes and the env.
suggest what env factors influence the risk of cancer
cancer: **uncontrolled ÷ of cells** -> leads to lumps of cells (tumours) forming
- risk **affected by genes**
- BUT env factors eg. **diet** can also influence risk
47
some arctic animals have dark hair in summer but white hair in winter.
describe how the env interacts with the animals' genotype to produce this phenotype
- animal hair colour is **polygenic**
- BUT env plays part in some animals
- env factors eg. **decreasing temp** **trigger** this **change** BUT **couldn't happen** if animal **didn't have genes for it**
48
describe how changes to the env can cause changes in gene expression
(4 marks)
in eukaryotes, epigenetic control can determine if certain genes expressed -> altering phenotype
- epigenetic control **doesn't alter base seq DNA**
-> works by **attaching / removing chemical groups** to / from **DNA** ...
- ... altering how easy it is for **enzymes** (and other proteins needed for transcription) to **interact** with and **transcribe genes**
- epigenetic changes are **independent** -> modification in 1 area **not linked** to modification in another
- epigenetic changes to gene expression play role in lots of cellular processes
-> also occur in response to changes to env (pollution, availability of food)
49
one method of epigenetic control is **methylation of DNA**.
describe this process
- when **methyl group** (-CH₃) is **added to DNA coding for gene**
- group always **attaches at a CpG site** -> where a **cytosine** and **guanine** base are **next to each other** in **DNA**
- increased methylation **changes DNA structure** ...
- ... so **proteins** and **enzymes** needed for **transcription** (transcription factors) **cannot bind to gene**
- so gene **not expressed** (inactivated)
50
one method of epigenetic control is the **modification of histones**.
explain why this is the case
histones: proteins that DNA wraps around to form chromatin -> which makes up chromosomes
- adding/removing **acetyl** groups to chromatin make it **highly condensed / less condensed**
- how condensed it is **affects accessibility of DNA** and if proteins and enzymes needed for transcription can **bind** to it
- so modification of histones affects gene expression
51
describe the epigenetic modifications of histones
include addition / removal of **acetyl groups** (COCH₃)
1. when histones **acetylated** -> chromatin **less condensed**
-> so **proteins** involved in **transcription** **can bind to DNA**
-> so genes **can** be **transcribed** (activated)
2. when acetyl groups **removed** from histones
-> chromatin **highly condensed**
-> **genes** in DNA **cannot** be **transcribed**
-> as transcription proteins **cannot bind** to them
-> so **genes repressed**
3. modification of histones **REVERSIBLE** -> can be diff in diff cell types + **varies with age**
52
histone
**protein** that **DNA wraps around** to form **chromatin** (which **makes up chromosomes**)
53
epigenome
all epigenetic tags in an organism
