the control of gene expression Flashcards
1
Q
What is a mutation?
A
Any change in the quantity or structure of DNA of an organism.
2
Q
What is a gene mutation?
A
Any change to the base (nucleotide) sequence of the DNA.
3
Q
When do mutations likely occur?
A
During DNA replication in interphase of the cell cycle.
4
Q
List the types of gene mutations.
A
- Addition
- Deletion
- Substitution
- Inversion
- Duplication
- Translocation of bases
5
Q
What is a substitution mutation?
A
A nucleotide in a section of a DNA molecule is replaced by another nucleotide with a different base.
6
Q
What is the effect of a non-sense mutation?
A
It creates a stop codon, leading to premature termination of polypeptide production.
7
Q
What is the effect of a mis-sense mutation?
A
It results in a different amino acid, potentially altering the protein’s function.
8
Q
What is the effect of a silent mutation?
A
There is no effect as it codes for the same amino acid, or occurs in an intron.
9
Q
What occurs during a deletion mutation?
A
The loss of a nucleotide base from a DNA sequence, causing a frame shift.
10
Q
What happens when bases are added to a DNA sequence?
A
It usually causes a frame shift to the right, altering the downstream sequence.
11
Q
What is a duplication mutation?
A
One or more bases are repeated in the base sequence, causing a frame shift.
12
Q
Describe an inversion mutation.
A
A section of bases becomes separated and rejoined in the inverse order.
13
Q
What is translocation of bases?
A
A section of bases is moved from one location in the genome to another.
14
Q
What are mutagenic agents?
A
Factors that increase the mutation rate, such as ionising radiation, ultraviolet radiation, and certain chemicals.
15
Q
What is the role of stem cells?
A
Stem cells are undifferentiated cells that can continually divide and become specialised.
16
Q
What is differentiation?
A
The process by which stem cells become specialised to perform specific functions.
17
Q
How do stem cells contribute to multicellular organisms?
A
All specialised cells originate from stem cells, which adapt to perform specific roles.
18
Q
What are the different types of stem cells?
A
- Totipotent
- Pluripotent
- Multipotent
- Unipotent
19
Q
What are totipotent stem cells?
A
Stem cells that can mature into any type of body cell.
20
Q
What are pluripotent stem cells?
A
Stem cells that can develop into almost any type of body cell except for placenta cells.
21
Q
What are multipotent stem cells?
A
Stem cells that can differentiate into a few different types of cells.
22
Q
What are unipotent stem cells?
A
Stem cells that can divide and differentiate into one type of cell.
23
Q
Where are embryonic stem cells sourced from?
A
Embryos in the early stages of development.
24
Q
What are induced pluripotent stem cells (iPS cells)?
A
Pluripotent stem cells produced from adult somatic cells that have been genetically altered.
25
How do iPS cells retain genetic information?
They can reactivate genes that were switched off in adult cells.
26
What are the benefits of using stem cells in medicine?
* Replace damaged cells
* Treat various diseases
* Grow organs for transplants
27
What ethical issues are associated with stem cell use?
Destruction of embryos and the belief that life begins at fertilisation.
28
What is the role of transcriptional factors?
Proteins that switch genes on or off, controlling transcription.
29
What are the two types of transcriptional factors?
* Activators
* Repressors
30
What is the role of oestrogen in transcription?
It binds to a receptor on an inactive transcriptional factor, activating it.
31
What is epigenetics?
Heritable changes in gene function without changes to the DNA base sequence.
32
What is the role of the complex formed by proteins and DNA in transcription?
Acts as an activator and stimulates transcription of genes by helping RNA polymerase to bind.
33
What are oestrogen receptors and their significance?
Some cells do not have oestrogen receptors, so some cells are not affected by oestrogen.
34
Define epigenetics.
Heritable changes in gene function, without changes to the base sequence of DNA.
35
What influences can affect genetic inheritance according to epigenetics?
Environmental influences such as diet, stress, toxins, etc.
36
What is the epigenome?
A layer of chemical tags on the DNA that impacts gene expression.
37
What determines whether DNA is tightly wound or unwound?
Chemical tags on the epigenome.
38
What is a nucleosome?
DNA wrapped around proteins called histones.
39
What effect does increased methylation of DNA have on gene transcription?
Inhibits transcription by preventing the binding of transcriptional factors.
40
Fill in the blank: Methylation is the addition of a ______ group to a molecule.
methyl
41
What is the consequence of decreased acetylation of DNA?
Increases the positive charges on histones, making DNA less accessible to transcription factors.
42
True or False: Epigenetic marks alter the base sequence of DNA.
False
43
What is the role of histone deacetylase (HDAC) enzymes?
Remove acetyl groups from histones.
44
What is the relationship between epigenetic changes and cancer?
Epigenetic changes can lead to abnormal activation of oncogenes or silencing of tumor suppressor genes.
45
What are the two main types of genes that control cell division?
* Proto-oncogenes
* Tumor suppressor genes
46
What are benign tumors characterized by?
Well differentiated, grow slowly, and often encapsulated.
47
What distinguishes malignant tumors from benign tumors?
Malignant tumors grow rapidly, invade other tissues, and are not encapsulated.
48
What is the primary treatment for benign tumors?
Surgery
49
What is the effect of increased DNA methylation on gene activity in cancer patients?
Higher than normal gene activity - more genes are turned on.
50
What are the characteristics of malignant tumors?
* Grow rapidly
* Metastasize
* Not encapsulated
* Life-threatening
51
What is RNA interference (RNAi)?
A mechanism that inhibits translation of mRNA, leading to silenced genes.
52
What are the two types of RNA involved in RNAi?
* Micro-RNA (miRNA)
* Small interfering RNA (siRNA)
53
Fill in the blank: Cancer is caused by damage to the genes that regulate ______ and the cell cycle.
mitosis
54
What is the impact of environmental factors on the epigenome?
They can activate or inhibit specific sets of genes.
55
What happens to the mRNA molecule during RNAi?
It is destroyed before it is translated.
56
What does the term 'epigenetic silencing' refer to?
When a gene is switched off and not expressed due to epigenetic marks.
57
What is the significance of the Dicer enzyme in RNAi?
It cleaves double-stranded RNA into smaller sections (siRNA).
58
What is the role of the RISC complex in RNAi?
It guides the enzyme to the target mRNA for degradation.
59
What is metastasis?
Grows projections into surrounding tissues
60
What defines a primary tumor?
Tumor in original location
61
What defines a secondary tumor?
Tumor that arises after metastasis
62
What are the localized effects of tumors?
Can disrupt functioning of a vital organ
63
What are the systematic effects of tumors?
Fatigue, weight loss
64
Which type of tumor is less likely to be life-threatening?
Primary tumor
65
How are primary tumors typically treated?
Easier to treat, often removable by surgery alone
66
How are secondary tumors typically treated?
Removed by radiotherapy, chemotherapy, and surgery
67
Which type of tumor more frequently recurs after treatment?
Secondary tumor
68
What are some similarities between primary and secondary tumors?
* Can grow to large size
* Cause blockages
* Cause organ damage
* Put pressure on other organs
69
What is a key identifying feature of tumor cells?
The nucleus is larger and darker than normal cells
70
What can indicate the presence of tumor cells?
More than one nucleus may be present
71
What is the typical shape of tumor cells?
Irregular shape
72
How do tumor cells differ in protein production?
They don’t produce all the proteins they need to function properly
73
What type of gene mutation is involved in tumor development?
Mutation in tumor suppressor genes and/or oncogenes
74
What is hypermethylation and its effect on tumor suppressor genes?
Increases methyl groups, silences genes, leads to increased cell division
75
What is the role of proto-oncogenes?
Stimulate cell division by producing growth factors
76
What happens when a proto-oncogene mutates into an oncogene?
Cell division becomes permanently activated
77
What is the 'two hit' hypothesis in cancer?
Two mutations needed to inactivate tumor suppressor genes; one mutation activates proto-oncogenes
78
What is the role of estrogen in breast cancer development?
Increased exposure leads to higher risk; stimulates cell division
79
What are common environmental risk factors for cancer?
* Radiation exposure
* Lifestyle choices
* Smoking
* Alcohol
* High-fat diet
80
What is the relationship between smoking and cancer risk?
Smokers are at a significantly higher risk for lung cancer
81
How does obesity affect cancer risk?
Being overweight increases the risk of cancer
82
What is the purpose of cancer screening?
Identify mutations early for preventative measures
83
What is recombinant DNA technology?
Transfer of DNA fragments from one organism to another
84
What does the Human Genome Project aim to achieve?
Determine the sequence of bases in the human genome
85
What are SNPs?
Single nucleotide polymorphisms associated with diseases
86
What is the proteome?
All proteins produced by a cell or organism at a given time
87
What are the challenges in sequencing complex organisms' genomes?
Presence of non-coding DNA and complex regulatory genes
88
What is the significance of BRCA1 and BRCA2 mutations?
Linked to increased risk of breast and ovarian cancer
89
What is the effect of hypomethylation in oncogenes?
Decreases methyl groups, leading to activation of oncogenes
90
Fill in the blank: A _______ is anything that increases the chance of getting a disease.
risk factor
91
True or False: A correlation between two variables indicates a causal relationship.
False
92
What is the current estimate of the number of genes in humans?
25,000 genes
## Footnote
This number is constantly being revised down as techniques for identifying genes improve.
93
What is recombinant DNA technology?
Involves the transfer of fragments of DNA from one organism to another.
94
What is a transgenic organism?
An organism that contains DNA from another species, often referred to as a genetically modified organism (GMO).
95
Why can the DNA of one organism function normally in a different species?
The genetic code is universal and mechanisms of transcription and translation are essentially the same in all living organisms.
96
List the stages involved in making a protein using DNA technology.
* Isolation of DNA fragments
* Using reverse transcriptase
* Using restriction endonuclease enzymes
* Using a gene machine
* Insertion of the DNA fragment into a vector
* Transformation into suitable host cells
* Identification of successful host cells
* Amplification/cloning of the population of host cells.
97
What does reverse transcriptase do?
Catalyses the production of complementary DNA (cDNA) from mRNA.
98
What is the purpose of using restriction endonuclease enzymes?
To cut DNA at specific recognition sequences.
99
What are sticky ends?
Single-stranded ends of DNA that can bind to other DNA pieces with complementary base pairs.
100
What is a gene machine?
A computerized device that synthesizes DNA fragments from scratch without a pre-existing template.
101
What is the polymerase chain reaction (PCR)?
A method used to amplify DNA fragments, creating numerous copies.
102
What are the two methods of cloning DNA fragments?
* In vivo - copies made inside a living organism
* In vitro - copies made outside the living organism.
103
What is a benefit of in vivo cloning?
It is useful for introducing a gene into another organism with minimal contamination risk.
104
What is plant pharming?
The process of transforming plants to produce specific substances, such as drugs.
105
What are the benefits of GM crops?
* Higher yields
* More nutritious
* Disease resistance.
106
What is gene therapy?
A therapeutic strategy using genetic engineering techniques to treat diseases.
107
What distinguishes somatic gene therapy from germ line therapy?
Somatic gene therapy alters alleles in body cells and does not affect offspring, while germ line therapy alters alleles in sex cells affecting all offspring.
108
What is SCID?
Severe combined immunodeficiency, a genetic disorder that affects the immune system.
109
True or False: Gene therapy can be used to replace defective genes in humans.
True.
110
What are potential issues with recombinant DNA technology?
* Reduced biodiversity due to monoculture
* Creation of superweeds
* Unpredictable ecological consequences.
111
What is the role of DNA probes in DNA amplification?
To identify the fragment containing the required gene.
112
What is the significance of using mRNA to create DNA fragments?
More mRNA is available in cells than DNA, and introns are removed during splicing.
113
What are the advantages of using a gene machine?
* Any sequence of nucleotides can be produced
* Very short production time
* Great accuracy.
114
What is the disadvantage of in vitro cloning?
PCR can amplify contaminating DNA, requiring very pure samples.
115
How can transformed bacteria be utilized in medicine?
To produce proteins for commercial or medical use, such as insulin.
116
What are the ethical concerns regarding gene therapy?
Potential for eugenics and the implications of altering human genetics.
117
What is the importance of promoter regions in transformed organisms?
They control where and when proteins are produced in the organism.
118
What is somatic gene therapy?
Altering alleles in body cells
## Footnote
Does not affect offspring as does not affect sex cells.
119
What is germ line therapy?
Altering alleles in sex cells
## Footnote
Every offspring is affected by the gene therapy so they won’t suffer from the disorder. This is illegal in humans.
120
What is SCID?
Severe combined immunodeficiency, a rare inherited disorder where individuals do not show a cell-mediated immune response or produce antibodies.
121
What defect causes SCID?
A defect in the gene that codes for the enzyme adenosine deaminase (ADA).
122
What is the role of the ADA enzyme?
Destroys toxins that would otherwise kill white blood cells.
123
What are common treatments for SCID?
Bone marrow transplants and/or injections of ADA.
124
What causes cystic fibrosis?
A deletion mutation on a recessive allele affecting the cystic fibrosis transmembrane conductance regulator (cftr).
125
What is the effect of the defective cftr gene?
Less chloride ions are transported out of the cell, leading to thick mucus production.
126
What are symptoms of cystic fibrosis?
* Mucus congestion in lungs
* Thick mucus in pancreatic ducts
* Infertility due to mucus in sperm ducts
127
What is a DNA probe?
A short, single-stranded length of DNA with an attached label that makes it identifiable.
128
What are the two types of labelled DNA probes?
* Radioactively labelled probes
* Fluorescently labelled probes
129
What happens during DNA hybridisation?
DNA strands are mixed with a DNA probe, which binds to the complementary base sequence.
130
What is the purpose of DNA sequencing in locating alleles?
To determine the sequence of nucleotide bases of the mutant allele.
131
What is a microarray?
A glass slide with microscopic spots of different DNA probes attached in rows.
132
What is the function of a microarray in genetic screening?
To screen many genes at the same time.
133
How can DNA probes help identify inherited conditions?
By identifying gene mutations that cause genetic disorders.
134
What is personalized medicine?
Medicines tailored to the DNA of the individual.
135
What is genetic counselling?
A type of social work giving advice and information following disease screening using alleles.
136
What is genetic fingerprinting?
A technique to compare two DNA samples through analysis of VNTR DNA fragments.
137
What are VNTRs?
Variable number tandem repeats, repetitive non-coding DNA sequences that vary among individuals.
138
What is the method of genetic fingerprinting?
* Collection / extraction
* Digestion
* Separation
* Hybridisation
* Development
* Analysis
139
What does gel electrophoresis measure?
The size of DNA fragments based on their length.
140
How is genetic fingerprinting used in forensic science?
To establish whether a person was likely present at a crime scene based on DNA evidence.
141
What is the significance of the probability calculation in forensic DNA matching?
It estimates the likelihood that someone else's DNA may match that of the suspect.
142
What is the role of genetic fingerprinting in medical diagnosis?
To diagnose genetic disorders or cancer when specific mutations are unknown.
143
How can genetic fingerprinting be used in breeding programs?
To prevent undesirable inbreeding and identify individuals with desirable alleles.
