Red Booklet Flashcards
1
Q
what is the structure of dna
A
Phosphate, deoxyribose sugar, nitrogenous bases
2
Q
How many hydrogen bases are there between a and T
A
2
3
Q
how many hydrogen bases are there between c and g
A
3
4
Q
Gene definition
A
Section of dna on a chromosome coding for one or more polynucleotides
5
Q
How does stable structure help dnas role of carrying genetic information
A
It can pass through generations without significant change making most mutations repair themselves so persistant mutations are rare
6
Q
Why are hydrogen bonds helpful for dna in carrying genetic information
A
Easy to break during dna replication
7
Q
Is dna a large molecule
A
Yes so it carries lots of genetic information
8
Q
Why does it help dna to have nitrogenous bases on the inside of the molecule
A
Protects them from external chemicals
9
Q
What does base pairing allow dna to do
A
Allows dna to replicate and transfer info into mRNA
10
Q
describe how genetic code is turned into primary structure of a protein
A
- three nucleotides code for a triplet
- each triplet codes for a specific amino acid
- order of amino acids determines primary structure of a protein
11
Q
Mutation definition
A
A change in the genetic material of the cell
12
Q
What can mutations during mitosis cause
A
Can be one cell that is effected- could be a cell of no use and die, could cause a tumour in some cases
13
Q
What can mutations during meiosis cause
A
Produces mutated gametes
- all subsequent cells contain the mutation causing ranging effects- can be the cause of downsyndrome
14
Q
What is a silent mutation
A
Due to degenerate code mutation doesn’t effect the gene
15
Q
Nonsense mutation meaning
A
Premature terminator due to change in stop codon
16
Q
Missense mutation meaning
A
Changed amino acid
17
Q
What can insertion or deletion cause
A
Framshift
18
Q
What does a frame shift cause for the protein
A
- one or more nucleotides inserted or deleted
- causing all the triplets after the inserted or deleted to be different
- likely to have a far greater effect of the protein
19
Q
What will happen if one single base is duplicated in the code
A
Frameshift will occur
20
Q
What will the duplication of three bases cause
A
Add another amino acid but subsequent codons remain the same
21
Q
What will inversion of bases cause ( a group of bases separate and rejoin in the same position but code runs in opposite directions)
A
Change of codons for inserted section and then back to the origional
22
Q
What would happen if a translocation of bases to another chromosome happens
A
- same genes but significant effect on gene expression
- whether the protein is and made and how much
- can cause abnormal phenotype
23
Q
What does translocation of bases to another chromosome cause (phenotype)
A
- forms of downsyndrome
Reduced fertility
Increased risk of cancer
24
Q
What is spontaneous mutation
A
- during dna replication with no outside cause
- typically 1 or two per 100,000 genes per generation
25
What name is given to a factor that increases the basic mutation rate
Mutogenic agents
26
How does nitrous acid change dna (chemical)
Can remove an NH2 group from cytosine in dna changing it to uracil
27
What does benzopyrene change dna (chemical)
Adds a large group to guanine that makes it unable to pair with cytosine
- dna polymerase then inserts any of the other bases
28
How can ionising radiation such as x rays change dna
Produce highly reactive reagents called free radicals
- these alter the shape of bases so dna polymerase can no longer act on them
29
How can uv radiation change dna
Affect thymine causing it to form bonds with nucleotides on either side of it (disrupts dna replication)
30
In what ways can gene expression be stopped
Switching off genes either at transcription or translation
31
What can stem cells do
Differentiate into many kinds of specialised cells
32
What are cells said to be in the early stages of embryo development
Pluripotent and can become any of the different kinds of cells in the human body
33
What is the nucleus to cytoplasm ratio like in stem cells
Large nucleus to cytoplasm ratio
- it can divide repeatedly by mitosis to make large numbers of new cells
34
Totipotent stem cells definition
Can divide to form a whole organism
For example a fertalised egg
35
Pluripotent stem cells definition
Can form any type of cell but not a whole organism
- early embryonic cells
36
Multipotent stem cells definition
Can divide to form several but not any type of cell
37
Unipotent stem cells definition
Only differentiate to one single cell type such as skin dermis
38
Examples of diseases that could be treated by iPS cell therapy in the future
Parkinson’s, diabetes, bone marrow
39
What medical treatments already use multipotent stem cells
Bone marrow transplants, replacing damaged treatments, drug testing before use on animals or humans
40
Arguments against human embryonic tissue being used in development of new treatments for disease
- human rights of the doner or embryo
- concerns of source and fate of embryo
- contrary to religious belief
- embryonic stem cells could be considered the same as destroying a human life
- may cause immune response
- may transmit infection
- may cause tumours
41
What name is given to tissue made up of plant stem cells
Meristem
42
Describe how we can use plant stem cells to produce multiple clones (micro propagation)
1- meristem removed
2- tissue placed in growth medium and separates into single totipotent cells which undergo mitosis
3- plant hormones/growth factors are added to stimulate differentiation into root stems and leaves
4- small plants are transferred to soil
5- plants are planted out
43
What is a transcription factor?
Protein molecule that moves from cytoplasm to DNA
- Transcription factor binds to specific genes
- Leads to blocks of pre-mRNA produced
44
Advantages of producing plants using stem cells
No variation and genetically identical to parent plant
- Easy to control or variables
- Can produce large numbers
45
Disadvantages to producing plants using stem cells
No variation and all could
succumb to the same disease
-have to have sterile conditions as it can easily get contaminated
Expensive equipment required
46
Give an example of how plant stem cells can be used in the production of pharmaceutical drugs
Treatment of breast and lung cancer derived from yew trees
47
Describe how transcription factors affect transcription
-Some transcription factor allows RNA polymerase to bind to the DNA allowing transcription
-mRNA can be translated into polypeptide
48
Describe how transcription represses affect transcription
Some transcription factor prevents RNA polymerase from binding to the DNA prevent preventing transcription
49
Why is an inactive transcription factor unable to initiate transcription?
Some transcription factors are inactive meaning they are not complementary to promote a site
- They can be activated by binding with another molecule that causes it to change shape allowing them to bind to the promoter
50
What type of hormones are able to cross the plasma membrane and interact directly with transcription factors in order to activate them
Steroid hormones such as each oestrogen are lipid soluble and can pass through the bilayer
51
Describe what happens when oestrogen enters the cell
1- Oestrogen diffuses through phospholipid bilayer as it is lipid soluble
2- signs to receptor molecule/protein on transcription factor
3- due to complementary shape
4- causes binding site on transcription factor to change shape
5- transcription factor moves into the nucleus and binds to promote a region on DNA
6- RNA polymerase is now able to bind to DNA
7- DNA is transcribed and mRNA is produced
8- mRNA is translated into polypeptide
52
Define Epigenetics
Process by which environmental factors can cause heritable changes in the gene function without changing the basic sequence of DNA
53
Describe how DNA is packaged and explain how this affects gene expression
- dna is super coiled and associated with proteins called histones forming chromatin
- If it is tightly associated it is known as heterochromatin and genes cannot be expressed as DNA polymerase can’t bind
- If it is loosely associated it is known as euchromatin and the genes can be expressed
(Transcription factors need access to the DNA to initiate transcription)
54
Explain why a change in the epigenome is not a mutation
An addition of a chemical tag may change gene expression however the base sequence is not changed so it is not a mutation
55
What is an epigenome
Chemical tags that associate with the DNA and the histones
- Affects how tightly wound the DNA is and therefore what is expressed
56
Why is the epigenome described as a cellular memory?
Due to it sticking to the cell and then mitosis occurring meaning chemical tags are copied
57
What two kinds of factors can result in changes to the epigenome
Environmental factors, such as exposure to chemicals and nutrition
Internal factors such as hormones
58
What is acetylation?
Transfer of an acetal group from acetal coenzyme a
59
What does increased acetylation cause?
Lucy association so transcription factors gain access to DNA and gene expression occurs
60
What does decreased acetylation cause?
Makes the attraction on the phosphate groups to DNA stronger causing tighter association inhibiting gene expression
61
What is methylation?
Addition of methyl groups CH3 to the cytosine bases
62
What does increased methylation cause?
Prevents binding of transcription factors and a attracts proteins that condense DNA histones complex
Inhibits gene expression
63
What happens if pregnant females are exposed to epigenetic factors?
Causes epigenetic changes in the mother, but also in the fetus and the gamete cells of the fetus changing three generations
64
What is a benign cell?
Tumour remains in original tumour location
65
What are malignant tumour cells?
Cells invade surrounding tissues and form secondary tumours in other tissues
66
What is meant by the term tumour
Caused by mutations in genes that regulate mitosis and the cell cycle
-Results in uncontrolled cell division
- Can be benign or malignant
67
Mutations in which two gene types can result in the formation of a tumour
Activation of oncogenes increasing cell division
In activation of Tumour suppressor genes
68
Role of oncogenes in normal cells
Code for growth factors or growth factor receptors
69
Are oncogenes inherited or acquired?
Acquired due to exposure tomutagens
70
Role of tumour suppressor gene in normal cells
Slow down cell division repair faulty DNA and initiate apoptosis
71
Is a mutation to tumour suppressor genes inherited or acquired
Most are acquired, but some are inherited such as BRCA
72
Why are malignant tumours more likely to be life-threatening?
Abnormal tissue replaces normal tissue
73
How would a histologist determine whether a tumour is malignant or benign by looking at the tissue sample under a microscope?
Malignant tumours have larger cell nucleus and the cell nucleus appears darker due to an abundance of DNA
74
The inactivation of gene expression of which gene results in cancer
Tumour suppressor cells
75
Promotion of gene expression in which genes can result in cancer
Oncogenes
76
What is the potential danger of using drugs that inhibit methylation and acetylation?
Must be targeted to cancer cells and could lead to more tumours if change gene expression of normal cells
