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Biology > Unit Ei > Flashcards

Unit Ei Flashcards

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1
Q

What is a gene mutation?

A

A change in the base sequence of DNA

Can arise spontaneously during DNA replication (interphase)

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2
Q

What is a mutagenic agent?

A

A factor that increases the rate of mutation, e.g., ultraviolet (UV) light or alpha particles

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3
Q

Explain how a gene mutation can lead to the production of a non-functional protein or enzyme.

A
  1. Changes sequence of base triplets in DNA so changes sequence of codons on mRNA
  2. Changes sequence of amino acids in the encoded polypeptide
  3. Changes position of hydrogen / ionic / disulphide bonds (between amino acids)
  4. Changes tertiary structure (shape) of protein
  5. Active site changes shape so substrate can’t bind
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4
Q

Describe the different types of gene mutations.

A
  • Substitution: A base/nucleotide is replaced by a different base/nucleotide
  • Addition: 1 or more bases/nucleotides are added to the DNA base sequence
  • Deletion: 1 or more bases/nucleotides are lost from the DNA base sequence
  • Duplication: A sequence of DNA bases/nucleotides is repeated/copying
  • Inversion: A sequence of bases/nucleotides detaches and rejoins in reverse order
  • Translocation: A sequence of bases/nucleotides detaches and is inserted at a different location
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5
Q

Why do not all gene mutations affect the order of amino acids?

A
  1. Some substitutions change only 1 triplet code/codon which could still code for the same amino acid
  2. Some occur in introns which do not code for amino acids
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6
Q

Explain why a change in amino acid sequence is not always harmful.

A
  1. May not change tertiary structure of protein
  2. May positively change the properties of the protein, giving the organism a selective advantage
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7
Q

What is a frameshift?

A

A frameshift occurs when gene mutations change the number of nucleotides/bases by any number not divisible by 3

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8
Q

What happens if a multiple of 3 bases is added or removed?

A

There won’t be a frameshift, but extra/less triplets will result in extra/less amino acids in the encoded polypeptide

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9
Q

What is the significance of a frameshift?

A

It can lead to the production of a stop codon, resulting in a shorter polypeptide

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10
Q

What are stem cells?

A

Undifferentiated/unspecialised cells capable of:
* Dividing (by mitosis) to replace themselves indefinitely
* Differentiating into other types of (specialised) cells

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11
Q

Describe how stem cells become specialised during development.

A

Stimuli lead to activation of some genes (due to transcription factors), somRNA is transcribed only from these genes and then translated to form proteins that modify cells permanently

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12
Q

What are totipotent cells?

A

Cells that can divide AND differentiate into any type of body cell (including extra-embryonic cells) for a limited time in early mammalian embryos

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13
Q

What are pluripotent cells?

A

Cells found in mammalian embryos that can divide AND differentiate into most cell types (every cell type in the body but not placental cells)

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14
Q

What are multipotent cells?

A

Cells found in mature mammals that can divide AND differentiate into a limited number of cell types, e.g., multipotent cells in bone marrow

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15
Q

What are unipotent cells? Provide an example.

A

Cells found in mature mammals that can divide AND differentiate into just one cell type, e.g., unipotent cells in the heart can differentiate into cardiomyocytes

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16
Q

How can stem cells be used in the treatment of human disorders?

A

Transplanted into patients to divide in unlimited numbers and differentiate into required healthy cells

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17
Q

What is the process to produce induced pluripotent stem (iPS) cells?

A
  1. Obtain adult somatic cells
  2. Add specific protein transcription factors to reprogram the cells
  3. Culture cells to allow them to divide by mitosis
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18
Q

Evaluate the use of stem cells in treating human disorders.

A

For: Can relieve human suffering, embryos left over from IVF can be used, iPS cells unlikely to be rejected
Against: Ethical issues with embryonic stem cells, risk of immune rejection, potential for tumor formation

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19
Q

What are transcription factors?

A

Proteins which regulate (stimulate or inhibit) transcription of specific target genes in eukaryotes

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20
Q

How is transcription regulated using transcription factors?

A

Transcription factors move to the nucleus, bind to DNA at a promoter region, and stimulate or inhibit transcription

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21
Q

How does oestrogen affect transcription?

A

Oestrogen binds to its receptor, forming an active transcription factor that stimulates transcription of target genes

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22
Q

What is epigenetics?

A

Heritable changes in gene function/expression without changes to the base sequence of DNA

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23
Q

What is the epigenome?

A

All chemical modifications of DNA and histone proteins

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24
Q

Summarise the epigenetic control of gene expression in eukaryotes.

A

Methylation of DNA inhibits transcription, while acetylation of histones allows transcription

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25
How do methylation and acetylation inhibit transcription?
Increased methylation prevents binding of transcription factors and RNA polymerase; decreased acetylation causes tighter binding of histones to DNA
26
What is RNA interference (RNAi)?
Inhibition of translation of mRNA produced from target genes, by RNA molecules such as siRNA or miRNA
27
Describe the regulation of translation by RNA interference.
1. siRNA or miRNA binds to a protein forming RISC 2. RISC binds to target mRNA 3. Leads to hydrolysis of mRNA or prevents ribosome binding
28
How do tumours and cancers form?
Mutations in DNA/genes controlling mitosis can lead to uncontrolled cell division, forming a mass of abnormal cells
29
What is a malignant tumour?
A cancerous tumour that can spread by metastasis
30
What are the two types of small RNA that bind to target mRNA molecules?
siRNA and miRNA ## Footnote siRNA (small interfering RNA) and miRNA (microRNA) bind to mRNA to prevent translation.
31
What can mutations in DNA or genes controlling mitosis lead to?
Uncontrolled cell division ## Footnote This can result in the formation of tumours.
32
What characterizes a malignant tumour?
Cancerous, can spread by metastasis ## Footnote Malignant tumours invade surrounding tissues.
33
What is the difference in growth rate between benign and malignant tumours?
Benign tumours grow slowly, malignant tumours grow faster ## Footnote Cells in benign tumours divide less often than those in malignant tumours.
34
How do tumour suppressor genes function?
Inhibit/slows cell cycle or cause apoptosis of potential tumour cells ## Footnote They act as a control mechanism for cell division.
35
What happens when a tumour suppressor gene is mutated?
Leads to production of non-functional protein ## Footnote This can result in uncontrolled cell division.
36
What do proto-oncogenes code for?
Proteins that stimulate cell division ## Footnote They play a role in signaling pathways related to growth factors.
37
What is an oncogene?
A mutated or abnormally expressed proto-oncogene ## Footnote It causes overproduction or permanent activation of proteins that stimulate cell division.
38
Why do tumours require mutations in both alleles of a tumour suppressor gene?
One functional allele can control cell division ## Footnote This means that at least one functional gene is needed to inhibit tumour growth.
39
What is the role of epigenetics in cancer treatment?
Reversing epigenetic changes that cause cancer ## Footnote This can prevent uncontrolled cell division.
40
What role do increased oestrogen concentrations play in breast cancer?
Stimulates cell division in oestrogen receptor-positive breast cancer cells ## Footnote Oestrogen binds to receptors, activating transcription factors.
41
What does genome sequencing involve?
Identifying the DNA base sequence of an organism’s genome ## Footnote It allows for the determination of amino acid sequences of proteins.
42
What is the proteome?
The full range of proteins that a cell can produce ## Footnote It is coded for by the cell's DNA/genome.
43
What are potential applications of genome sequencing projects?
* Identification of genes associated with diseases * Development of targeted drugs * Early prevention screening * Identification of species and evolutionary relationships ## Footnote These applications can revolutionize personalized medicine.
44
What is recombinant DNA technology?
Transfer of DNA fragments from one organism to another ## Footnote This technology is used to create transgenic organisms.
45
How can DNA fragments be produced using restriction enzymes?
By cutting DNA at specific recognition sequences ## Footnote This often results in 'sticky ends' that facilitate the joining of DNA fragments.
46
What is the advantage of obtaining genes from mRNA?
* More mRNA available than DNA for extraction * Introns removed during splicing ## Footnote This makes mRNA easier to use for protein synthesis in prokaryotes.
47
What is the purpose of PCR (polymerase chain reaction)?
To amplify DNA fragments ## Footnote This process results in exponential increases in DNA quantity.
48
What role do primers play in PCR?
Short DNA fragments that allow DNA polymerase to bind and start synthesis ## Footnote Two different primers are needed for amplification.
49
What are the steps involved in amplifying DNA fragments in vivo?
* Add promoter and terminator regions * Insert DNA fragments into vectors * Transform host cells * Detect genetically modified cells * Culture transformed cells ## Footnote This process allows for cloning and protein production.
50
Why are marker genes inserted into vectors?
To allow detection of genetically modified cells ## Footnote This ensures only transformed cells are identified.
51
What is gene therapy?
Introduction of new DNA into cells to replace faulty alleles ## Footnote It aims to treat genetic disorders like cystic fibrosis.
52
What are some issues associated with gene therapy?
* Short-lived effects * Immune response against modified cells * Unknown long-term effects ## Footnote These issues can complicate the efficacy and safety of gene therapy.
53
Why might humanitarians support recombinant DNA technology?
* Increases food production * Potential to cure genetic disorders * Makes medicines more accessible ## Footnote These benefits can help address global health and food security challenges.
54
What are some concerns of environmentalists regarding recombinant DNA technology?
* Risk of creating superweeds * Potential impact on biodiversity * Control of technology by large companies ## Footnote These concerns highlight the potential ecological risks and ethical considerations.
55
What are DNA probes?
Short, single stranded pieces of DNA with a base sequence complementary to part of a target allele, usually labelled with a fluorescent or radioactive tag for identification.
56
Why are DNA probes longer than just a few bases?
A sequence of a few bases would occur at many places throughout the genome; longer sequences are only likely to occur in the target allele.
57
What is DNA hybridisation?
Binding of a single stranded DNA probe to a complementary single strand of DNA, forming hydrogen bonds/base pairs.
58
Explain the process of genetic screening to locate specific alleles of genes.
1. Extract DNA and amplify by PCR 2. Cut DNA at specific base sequences using restriction enzymes 3. Separate DNA fragments using gel electrophoresis 4. Transfer to a nylon membrane and treat to form single strands 5. Add labelled DNA probes which hybridise with target alleles 6. Expose membrane to UV light or use autoradiography to show bound probe.
59
What is gel electrophoresis?
A method used to separate nucleic acid fragments or proteins according to length/mass and charge.
60
How does gel electrophoresis separate DNA fragments?
1. DNA samples loaded into wells in a porous gel and covered in buffer solution 2. Electrical current passed through, causing negatively charged DNA to move towards the positive electrode 3. Shorter DNA fragments travel faster and further.
61
How can data from gel electrophoresis be interpreted?
Run a standard with DNA fragments of known lengths, compare to the position of unknown fragments to estimate their size.
62
What are examples of the use of labelled DNA probes?
* Screening patients for heritable conditions (e.g., cystic fibrosis) * Screening patients for drug responses * Screening patients for health risks (e.g., high blood cholesterol).
63
What is the role of a genetic counsellor?
1. Explain results of genetic screening 2. Discuss treatments available for genetic conditions 3. Discuss lifestyle choices to reduce risk 4. Explain probability of conditions being passed to offspring.
64
What is personalised medicine?
Medicine tailored to an individual's genotype/DNA, increasing effectiveness of treatment.
65
Evaluate the screening of individuals for genetically determined conditions.
For ✓: Enables informed lifestyle choices, decisions about children, and use of personalised medicines. Against 𝖷: May lead to depression, discrimination, or stress.
66
What are variable number tandem repeats (VNTRs)?
Repeating sequences of nucleotides found in non-coding sections of DNA at many sites throughout an organism’s genome.
67
Why are VNTRs useful in genetic fingerprinting?
Probability of two individuals having the same VNTRs is very low; VNTR lengths differ between individuals.
68
Explain how genetic fingerprinting can be used to analyze DNA fragments.
1. Extract DNA and amplify by PCR 2. Cut DNA at specific base sequences using restriction enzymes 3. Separate VNTR fragments using gel electrophoresis 4. Transfer to nylon membrane and treat to form single strands 5. Add labelled DNA probes and wash 6. Expose to UV light or use autoradiography.
69
Compare genetic fingerprinting with genetic screening.
Both use PCR, electrophoresis, and labelled DNA probes; fingerprinting analyzes VNTRs while screening analyzes specific alleles.
70
How can genetic fingerprinting determine genetic relationships?
More closely related organisms have more similar VNTRs; paternity testing shows shared VNTRs/bands.
71
Explain how genetic fingerprinting can show genetic variability within a population.
Differences in VNTRs arise from mutations; more differences indicate greater diversity.
72
What is the use of genetic fingerprinting in forensic science?
Compare genetic fingerprints of suspects to DNA at a crime scene; matching bands suggest presence.
73
What is the use of genetic fingerprinting in medical diagnosis?
Some VNTR patterns are associated with increased risk of certain genetic disorders.
74
What is the use of genetic fingerprinting in animal and plant breeding?
Shows relatedness to avoid inbreeding; breeds pairs with dissimilar genetic fingerprints.

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