DNA and Proteins Flashcards
(129 cards)
1
Q
What is DNA?
A
DNA, or deoxyribonucleic acid is the genetic material found mostly in the nucleus of a cell, that directs or controls the activities of the cell.
2
Q
Function of DNA
A
Stores and transmits genetic information.
3
Q
What is a chromosome?
A
A chromosome is an organised structure consisting of a singular piece of coiled DNA together with a protein and containing many genes.
4
Q
Which two organelles have DNA resembling that of Prokaryotes?
A
Mitochondria and Chloroplasts.
5
Q
What is the structure of DNA?
A
DNA is a double-stranded helical molecule composed of nucleotides. Each nucleotide contains a phosphate group, a sugar (deoxyribose), and a nitrogenous base (adenine, thymine, cytosine, or guanine). The two strands are antiparallel and held together by hydrogen bonds between complementary base pairs (A with T and C with G).
6
Q
What is the shape of eukaryotic chromosomes?
A
Linear.
7
Q
Where are eukaryotic chromosomes located?
A
In the nucleus.
8
Q
What are eukaryotic chromosomes associated with?
A
Histone proteins.
9
Q
What is the chromosome in Prokaryotes?
A
One single circular chromosome that floats freely in the cytosol (no protein attached).
10
Q
What is a gene?
A
A gene is a segment of DNA on a chromosome that contains the complete sequence of bases required to direct the manufacture of a polypeptide or RNA molecule.
11
Q
What is a protein?
A
A protein is a macromolecule composed of long chains of amino acids folded into unique shapes that give cells their structure and functions.
12
Q
What is an exon?
A
Coding segment of DNA. Sequences that are translated (expressed) into a protein.
13
Q
Introns
A
Non-coding segments of DNA. Sequences that are transcribed but then cut out of the mRNA, not being translated.
14
Q
What are the three components of a DNA nucleotide?
A
A phosphate group, deoxyribose sugar, and a nitrogenous base (adenine, thymine, cytosine, or guanine).
15
Q
What are the base-pairing rules in DNA?
A
Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).
16
Q
What type of bonds hold the two strands of DNA together, and why are they important for replication?
A
Hydrogen bonds; they are weak enough to allow the strands to separate during replication.
17
Q
Why is complementary base pairing (A-T and C-G) important in DNA replication?
A
It ensures accurate copying of genetic information, as each base on a template strand guides the addition of the correct complementary base on the new strand.
18
Q
What does “semi-conservative” mean in DNA replication?
A
Each new DNA molecule consists of one original (parent) strand and one newly synthesized strand.
19
Q
What enzyme unwinds the DNA double helix at the start of replication?
A
Helicase.
20
Q
Which enzyme adds new nucleotides to form a complementary strand during DNA replication?
A
DNA polymerase.
21
Q
How does the semi-conservative model of DNA replication help maintain genetic stability?
A
By conserving one original strand in each new DNA molecule, it ensures accurate transmission of genetic information to new cells.
22
Q
Which enzyme joins the sugar-phosphate backbone of the free nucleotides?
A
DNA ligase.
23
Q
What are enzymes?
A
Enzymes are proteins that speed up or slow down chemical reactions.
24
Q
What are exons in eukaryotic genes?
A
Exons are the coding segments of a gene that contain sequences coding for amino acids and are translated into proteins.
25
What are introns in eukaryotic genes?
Introns are non-coding segments of a gene that do not code for amino acids and are removed during mRNA processing.
26
Are both exons and introns transcribed into RNA?
Yes, both exons and introns are transcribed into pre-mRNA.
27
What happens to introns during mRNA processing?
Introns are removed from the pre-mRNA through a process called splicing, leaving only exons in the mature mRNA.
28
How is RNA different to DNA?
The sugar is Ribose
It is single stranded
It uses Uracil instead of Thymine.
It is not confined to the nucleus.
29
What is gene expression?
The process where the genetic code, stored on the DNA is used to make gene products (proteins).
30
What is transcription?
The production of messenger RNA (mRNA).
31
What is translation?
Translation is the synthesis of a polypeptide using the genetic information on mRNA.
32
What is the role of DNA in protein synthesis?
DNA acts as the template for transcription, providing the genetic code that is transcribed into mRNA.
33
What is mRNA and its function in protein synthesis?
mRNA (messenger RNA) carries the genetic information from DNA to the ribosome, where it is translated into a protein.
34
What is tRNA and its role in translation?
tRNA (transfer RNA) brings amino acids to the ribosome and matches its anticodon with the mRNA codon to ensure correct amino acid sequencing.
35
What is rRNA and its role in translation?
rRNA (ribosomal RNA) forms the core structure of ribosomes, catalyzing the assembly of amino acids into a polypeptide chain.
36
What is a codon?
A codon is a three-nucleotide sequence on mRNA that codes for a specific amino acid.
37
What is an anticodon, and where is it found?
An anticodon is a three-nucleotide sequence on tRNA that pairs with the complementary codon on mRNA during translation.
38
What is the main purpose of transcription?
To copy DNA’s genetic code into mRNA, which will later be used to make proteins.
39
What enzyme is responsible for building the mRNA strand during transcription?
RNA polymerase.
40
What is the pre-mRNA?
The initial RNA strand produced from transcription, which includes both coding (exons) and non-coding (introns) regions.
41
What happens to introns during mRNA processing?
Introns are removed, and exons are joined together in a process called splicing.
42
Where does the mature mRNA go after processing?
It exits the nucleus and travels to the ribosome for translation.
43
What is the purpose of translation?
To use the mRNA sequence to build a protein.
44
Where does translation take place in the cell?
At the ribosome in the cytoplasm.
45
What is the start codon, and what does it signal?
The start codon (usually AUG) signals the ribosome to begin translation.
46
What is the role of tRNA in translation?
tRNA brings amino acids to the ribosome and matches its anticodon with mRNA codons.
47
How does the ribosome know which amino acid to add next?
Each mRNA codon pairs with a matching tRNA anticodon, which carries the correct amino acid.
48
What happens when the ribosome reaches a stop codon?
Translation ends, and the ribosome releases the completed protein.
49
What is a polypeptide chain?
A chain of amino acids linked together, which folds to become a functional protein.
50
What determines the way a protein will form?
The sequence of amino acids.
51
What are the four levels of protein structure?
Primary, secondary, tertiary and quaternary.
52
What is primary structure?
The chain of amino acids.
53
What is secondary structure?
The coiling and folding of the polypeptide chain due to bonding between molecules.
54
What is tertiary structure?
The overall 3D shape of the entire polypeptide chain.
55
What is quaternary structure?
If the protein consists of two or more peptide chains, then this complex structure arises from them.
56
How does a protein's shape allow it to bind to specific molecules?
A protein’s 3D structure forms binding sites that match the shape and charge of specific target molecules.
57
What role does shape play in enzyme function?
Enzymes have active sites shaped to bind specific substrates, allowing them to catalyze reactions accurately.
58
How do receptor proteins use their shape?
Receptors have specific shapes to bind only certain signaling molecules, enabling precise cell communication.
59
Why is shape important for structural proteins like collagen?
Structural proteins have shapes that provide physical support and stability to cells and tissues.
60
Why is the three-dimensional shape of a protein critical?
It determines the proteins function.
61
What would happen if a proteins shape is altered?
It may lose its ability to function properly.
62
Why does the shape of a protein matter so much?
Specificity for binding
Proper interaction with other molecules
Structural support
Regulation of biological activity.
63
How does the induced-fit model lower activation energy?
It lowers activation energy by positioning the substrate for a reaction and straining specific bonds within the substrate.
64
What happens after the reaction is complete in the induced-fit model?
The product is released, and the enzyme returns to its original shape, ready to bind to another substrate.
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Why is the induced-fit model important for enzyme specificity?
The shape change ensures that enzymes bind only to specific substrates, preventing unwanted reactions and increasing efficiency.
66
What factors affect enzymes function?
Temperature
pH
Presence of chemical inhibitors.
67
What can changes in the enzyme’s optimum conditions do?
It can change the shape of the active site (denature), which means the substrate can no longer bind.
68
How do low temperatures affect enzymes?
At low temperatures, molecules move slower, therefore less successful collisions between enzyme and substrate molecules occur per unit time. Thus the rate of enzyme-catalysed reaction is reduced at lower temperatures.
69
How do high temperatures affect enzymes?
As the temperature increases, so too does the enzyme activity until the point where the temperature is high enough to destroy chemical bonds in the active site, thus changing its shape and function.
At this point the enzyme ceases to function and the enzyme is denatured.
70
How can a change in pH affect enzymes?
A change in pH can alter the charge on amino acids in the protein, affecting the affinity (or force of attraction) of the active site for the substrate.
71
What are enzyme inhibitors?
Enzyme inhibitors are chemicals that bind to enzymes and decrease their activity. Some poisons and heavy metals act as inhibitors.
72
What are the two types of inhibitors?
Competitive inhibitors
Non-competitive inhibitors.
73
What are competitive inhibitors?
Competitive inhibitors have a complementary shape to the active site on the enzyme (or similar to the shape of the substrate).
They bind to the active site preventing the substrate from binding.
74
What are non-competitive inhibitors?
Non-competitive inhibitors bind to another part of the enzyme causing a change in shape of the active site.
The substrate will no longer have a complementary shape to the active site and is then no longer able to bind effectively.
75
What happens as the substrate concentration increases?
Increasing substrate concentration results in an increase in the rate of enzyme controlled reaction, as there will be more collisions between substrates and active sites on the enzyme per unit time.
However, at a certain substrate concentration, all active sites on the enzymes will be occupied, resulting in no further increase in the rate of reaction.
76
What happens as enzyme concentration increases?
Increasing enzyme concentration results in an increase in the rate of an enzyme controlled reaction, as there will be more collisions between substrates and active sites on the enzyme per unit time.
However, at a certain enzyme concentration, all substrate particles will be converted to products, resulting in no further increase in the rate of reaction.
77
What does phenotypic expression of genes depend on?
It depends on factors controlling transcription and translation, including transcription factors, products of other genes, and environmental influences.
78
What are transcription factors?
Transcription factors are proteins that bind to specific DNA sequences to help start or stop transcription of certain genes, influencing phenotype.
79
How do products of other genes affect gene expression?
Proteins from other genes can interact with or modify the activity of other gene products, impacting overall gene expression and phenotype.
80
How can environmental factors influence gene expression?
Environmental factors like temperature, nutrients, or toxins can alter transcription or translation, affecting gene expression and phenotype.
81
What is the phenotype?
The physical characteristics.
82
What is the genotype?
The genetic expression.
83
What is differentiation?
Differentiation is the changing or specialising of cells into different roles.
84
What is responsible for the differentiation of cells?
The switching on or off of genes.
85
What is epigenetics caused by?
Epigenetics is caused by environmental factors.
86
What regulates gene expression?
Methylation.
87
What nucleotide is methylated?
Cytosine.
88
What happens when DNA is methylated?
Transcription factors and enzymes can't read the DNA so the gene isn't transcribed. This results in the protein not being produced, and the effect of the gene isn't expressed.
89
What does demethylation lead to?
More expression of the gene.
90
What does methylation of histones do?
It causes them to stick together, reducing the expression of genes.
91
What does acetylation of histones do?
It results in a looser packing of histones, making it easier for transcription to occur, and therefore more expression of genes.
92
What happens if methylation occurs and suppressor genes are switched off?
The gene will not be transcribed and the suppressor proteins will not be available to control cell division, leading to cancer.
93
What are mutations?
Changes in the DNA sequence.
94
What can mutations be caused by?
Errors in DNA replication
Errors in cell division
Damage by physical or chemical factors in the environment.
95
What can increase mutation rate?
Ionising radiation
Mutagenic chemicals
Viruses
96
What happens if mutations affect germ cells?
It may be passed onto subsequent generations.
96
What happens if mutations occur in somatic cells?
Generally, they will only affect the individual organism.
97
What does Polymerase Chain Reaction (PCR) do?
It multiplies pieces of DNA by several orders of magnitude.
98
What are primers?
Short single-stranded DNA sequences that are complementary to the target DNA region's start and end points.
99
What are primers role in PCR?
Primers bind to the specific locations on each DNA strand, guiding the DNA polymerase enzyme to the correct site for starting DNA synthesis. This ensures that only the target segment of DNA is amplified.
100
What is the DNA polymerase role in PCR?
Taq polymerase adds free nucleotides to the primers, creating new DNA strands. Its heat resistance allows it to function during the repeated heating and cooling cycles without denaturing.
101
What is the PCR process?
Denaturation: Heat to separate DNA strands.
Annealing: Cool so primers can attach to the target DNA regions.
Extension: Taq polymerase adds nucleotides to the primers, creating new DNA strands.
102
What is denaturation in PCR?
DNA is heated. It disrupts the hydrogen bonds and separates the two strands of DNA.
103
What is annealing in PCR?
Reaction temperature is lowered. Primers attach to the complementary nucleotides, highlighting where the DNA needs to be copied.
104
What is extension/elongation in PCR?
The mixture is heated again. DNA polymerase creates a new complementary structure by adding free nucleotides.
105
What is electrophoresis?
A laboratory technique used to separate DNA fragments based on size. DNA samples are placed in a gel, and an electric current is applied.
106
How does electrophoresis work?
DNA fragments are negatively charged due to their phosphate backbone, so they move toward the positive end of the gel. Smaller DNA fragments move faster and travel farther through the gel, while larger fragments move more slowly and stay closer to the starting point.
107
What is an electropherogram?
An electropherogram is a graphical representation of DNA fragment sizes, showing peaks that correspond to specific DNA bases or fragment lengths.
108
How are DNA sequences interpreted on an electropherogram?
Each peak represents a specific nucleotide (A, T, C, or G) in the DNA sequence, with the order of peaks showing the base sequence.
109
What is DNA profiling?
DNA profiling identifies unique genetic patterns of individuals by comparing DNA fragment lengths at specific loci, useful in forensics and kinship testing.
110
Why is DNA profiling valuable in wildlife conservation?
DNA profiling helps track endangered species populations, study genetic diversity, and manage breeding programs for conservation efforts.
111
What are some ethical issues relation to the collection of genetic information?
Privacy: DNA profiles contain sensitive genetic information. Collecting and storing this data can raise privacy concerns, especially if used without consent.
Genetic Discrimination: Individuals may face discrimination in employment or insurance based on genetic information that suggests disease predispositions.
Informed Consent: Individuals should have the right to know and consent to how their genetic data is used, stored, or shared.
112
What are some economic issues relation to the collection of genetic information?
Cost of Testing: Advanced DNA sequencing and profiling techniques are expensive, making them inaccessible to some. Lowering costs could increase accessibility, but could also lead to privacy concerns if data is widely shared.
Impact on Healthcare: Genetic profiling can help personalize medical care, but it also poses economic burdens on healthcare systems if widely adopted.
113
What are some cultural issues relation to the collection of genetic information?
Varying Beliefs: Cultural attitudes toward genetic testing vary. Some groups may oppose DNA collection due to beliefs about bodily integrity, privacy, or distrust in scientific institutions.
Identity and Ancestry: DNA profiling can impact cultural identity, especially in ancestry testing. Some communities view genetic profiling with skepticism or see it as a potential disruption to traditional notions of kinship and heritage.
114
What are restriction enzymes?
Proteins that come from bacteria and cut DNA at highly specific regions.
115
What is the restriction site?
The sequence of bases recognised by the restriction enzyme. It is usually 4-6 nucleotides long.
116
What are blunt ends?
When the restriction enzyme cuts straight across the double helix.
117
What are sticky ends?
When the restriction enzymes cut diagonally (more common) leaving a few nucleotides from each strand exposed.
118
What is a probe?
Probes are short, single-stranded DNA or RNA sequences that are complementary to a specific target sequence of interest in a genome. They can be labeled with fluorescent or radioactive markers to facilitate detection.
119
What is Bacterial Transformation?
Bacterial transformation is a method used to introduce foreign DNA into a bacterial cell, allowing it to express new genes. This is commonly used in genetic engineering and cloning.
120
What is Electroporation?
Electroporation is a technique that uses electrical pulses to create temporary pores in the cell membrane, allowing foreign DNA to enter the cell.
121
What is Microinjection?
Microinjection is a technique that involves directly injecting foreign DNA into the nucleus or cytoplasm of a cell using a fine glass micropipette.
122
What is transgenics?
Transgenics refers to the process of introducing a gene or genes from one organism into the genome of another organism, resulting in a transgenic organism. This technique is commonly used in genetic engineering and biotechnology to create organisms with new traits or characteristics
123
What is CRISPR-Cas9?
A revolutionary tool for gene editing. It allows scientists to precisely cut and modify specific sequences of DNA in living cells, including those of plants, animals, and humans.
124
What is Protein Design?
Protein design involves creating novel proteins with specific structures and functions. Scientists use knowledge of amino acid sequences, protein folding, and 3D modeling to design proteins for targeted purposes.
125
What is the first step in the CRISPR-Cas9 process?
Identifying the target DNA sequence that scientists want to edit.
126
What is a guide RNA in CRISPR-Cas9?
A short RNA sequence designed to match the target DNA, guiding Cas9 to the specific spot in the genome.
127
What is the role of Cas9 in the CRISPR-Cas9 process?
Cas9 is an enzyme that acts as "molecular scissors" to cut the DNA at the target site.
128
What is the purpose of CRISPR-Cas9 in research and medicine?
To precisely edit genes, enabling studies on gene function, disease treatment, and genetic modifications.
