Unit 10 Flashcards
(128 cards)
1
Q
How do you go from DNA to a protein?
A
DNA –> RNA –> protein
2
Q
Transcription
A
DNA sequence is rewritten as message RNA (mRNA)
3
Q
Translation
A
mRNA is used to build a polypeptide (protein) from amino acids at a ribosome
4
Q
Where is DNA transcribed in a prokaryote?
A
cytoplasm
5
Q
Why does a prokaryote transcribe DNA in the cytoplasm
A
it has no nucleus
6
Q
Where is DNA transcribed in a eukaryote?
A
nucleus
7
Q
How many steps are there for transcription?
A
3
8
Q
What are the steps of transcription? (3)
A
- Initiation
- Elongation
- Termination
9
Q
Initiation (Transcription)
A
RNA polymerase recognizes a starting sequence on a gene (promoter) and unzips DNA
10
Q
RNA polymerase
A
enzyme that catalyzes the reactions of transcription
11
Q
promoter sequence (2)
A
- is a DNA sequence that defines where transcription begins
- defines the direction of transcription and indicated which DNA strand and gene will be transcribed
12
Q
Elongation (Transcription)
A
RNA polymerase reads DNA coding region and uses ribonuclease to make a complementary strand of mRNA
13
Q
What is the direction of elongation?
A
5’ to 3’
14
Q
Termination (Transcription)
A
mRNA and RNA polymerase detach at termination DNA sequence
15
Q
What is RNA that has been transcribed called?
A
messenger RNA (mRNA)
16
Q
Which DNA strand is transcribed?
A
antisense strand
17
Q
antisense strand
A
template for transcription (transcribed)
18
Q
sense strand
A
coding DNA/gene (not transcribed)
19
Q
How is the antisense strand transcribed? (2)
A
- using complementary base pairing
- base sequence of mRNA is the same as the sense strand (U replaces T)
20
Q
What must happen in eukaryotes before translation?
A
mRNA must be processed/modified
21
Q
RNA processing is… (3)
A
1) addition fo 5’ end cap
2) Addition of 3’ end poly (A) tail
3) Splicing
22
Q
Splicing
A
removed from DNA regions that don’t codes for protein
23
Q
What happens in the step of splicing?
A
introns are cut out of mRNA and exons are joined together to form a coding sequence
24
Q
intron
A
DNA or RNA that doesn’t code for protein
25
extron
DNA or RNA base sequence that directly codes for proteins
26
alternative splicing
producing multiple RNA transcripts by joining different splice/cut sites
27
What is the result of splicing mRNA? (2)
- it increases the number of different proteins an organism can produce
- in eukaryotes, alternative splicing is more efficient because information can be stored economically
28
pre-mRNA
exons and introns
29
mature mRNA
exons only
30
ribonucleotides
RNA nucleotides with ribose
31
Why is transcription regulated?
so cells can only make protein they need
32
What are characteristics of genes in transcription? (2)
- types of proteins determines a cell's characteristics
- most genes in a cell are turned off at any one time
33
gene expression (2)
- using a gene to make protein
- requires making specific mRNA and using mRNA to build polypeptides/proteins
34
What are factors that can impact gene expression? (2)
- temperature
- hormones
35
How do factors regulate gene expression?
regulating transcription
36
What does regulation of transcription orchestrate?
cells differentiation and development in multicellular organisms
37
What are factors that regulate transcription in eukaryotes? (3)
1) Transcription factors and non-coding DNA Sequences
2) DNA methylation
3) histone-protein modification
38
transcription factors (3)
- proteins that ↑ or ↓ decrease transcription rate by regulating binding of RNA polymerase to promoter
- some factors bind to promoter directly
- transcription can't be initiated without certain factors
39
What transcription factors don't bind the promoter? (2)
- activator proteins
- repressor proteins
40
activator proteins
bind to enhancer sequences (↑ rate of transcription)
41
repressor proteins
bind to silence sequences (↓ rate of transcription)
42
Where are enhancer and silencer sequences not located? (2)
- in a gene
- in non-coding DNA
43
What happens when a transcription factor binds to a promoter?
transcription at moderate levels
44
What happens when transcription factors bind to promoter and activators bind to enhancers?
the gene is transcribed at higher rates
45
What happens when transcription factors bind to promoter and repressors bind to silencer?
gene is transcribed at lower rates
46
DNA methylation
methyl groups (CH3) are added to DNA
47
What does methylation do?
- inhibits the binding of transcription factors and activators and decrease transcription/gene expression
48
nucleosomes
DNA wrapped around histone proteins for packing
49
Why do nucleosomes regulate transcription?
- DNA is inaccessible to transcription factors and RNA polymerase
50
In what case can binding occur with nucleosomes?
chemically modifying the histones forces nucleosome unwinding and allows binding
51
Epigenetics (2)
- study of changes to DNA that alter gene expression without changing DNA sequence
- some epigenetic changes can be inherited
52
What are some examples of epigenetics?
methylation and histone modification
53
What does translation build?
a primary structure
54
primary structure
amino aid sequence of a protein
55
What is an example of a product of translation?
enzymes that are used to speed up the process of transcription and translation
56
polypeptide
a sequence of amino acids
57
How does genetic information flow from mRNA to protein? (2)
- triplet code
- codon
58
Triplet code
groups of 3 bases
59
codon (2)
- a group of 3 base that does for one amino acid in a protein
- code for the same amino acids
60
The genetic code is... (2)
- universal
- degenerate
61
universal
living thing use the same bases, codons and amino acids
62
degenerate
same amino acid may be coded for by more than one codon, reduces impact of mutation
63
How do you read mRNA to determine the amino acid sequence? (3)
1) Scan the mRNA to find the START CODON
2) Continue reading codons and adding amino acids
3) Continue adding amino acids until you reach the STOP CODON
64
What is the start codon?
AUG
65
How many stop codons are there?
3
66
transfer RNA (tRNA)
read codons on mRNA and bring amino acid to the ribosome
67
What is on tRNA? (4)
- attached amino acid
- anticodon
- hydrogen bonds
- tRNA activating enzyme
68
attached amino acid to tRNA
specified by bound codon
69
anticodon on tRNA
is nucleotides that bind to mRNA codon using complementary base pairing
70
hydrogen bonding on tRNA
holds strands together/provide structure
71
tRNA activating enzyme (2)
- uses ATP to attach new amino acid to tRNA
- there are 20 of these enzymes that correspond to the 20 amino acids
72
What does a ribosome compose of? (4)
- large subunit
- small subunit
- ribosomal RNA (rRNA)
- proteins
73
Where is the mRNA binding site?
the small subunit
74
What holds the tRNA and mRNA together during translation?
the ribosomal subunits
75
At how many sites does a ribosome bind to mRNA?
3
76
What are the three binding sites on DNA?
- A-site
- P-site
- E-site
77
A-site
where incoming tRNA anticodon binds mRNA codon
78
P-site
where tRNA sits with the growing polypeptide chain
79
E-site
where tRNA without amino acid
resides before being released
80
How many types of ribosomes are there?
3
81
What are the types of ribosomes? (3)
- bound ribosomes
- polysomes
- free ribosomes
82
Bound ribosomes (2)
- on Rough ER
- make protein for export
83
Polysomes
many free ribosomes working on the same mRNA to complete translation more efficiently
84
Free ribosomes
make proteins for the cell
85
What are the steps of translation? (3)
1) Initiation
2) Elongation
3) Termination
86
Initiation (Translation) (2)
1) mRNA binds to small subunit and methionine tRNA binds to start codon
2) Large subunit binds with start tRNA in the P site. The A-site is aligned with 2nd mRNA codon.
87
Elongation (Translation) (5)
1) A site holds tRNA with next amino acid to be added
2) peptide bond is formed between the amino acid of the A site and polypeptide at the P site
3) polypeptide is transferred to the tRNA in the A site
4) Ribosome moves so the tRNA with the polypeptide in the A site moves to the P site
5) The tRNA without an amino acid moves to E site and leaves the ribosome
88
Termination (Translation) (3)
1) Ribosome reaches stop codon
2) A release factor binds in the A site causing the disassembly of the ribosome subunits
3) Polypeptide is released
89
What is the direction of translation?
The ribosome moves along the mRNA strand in the 5’ to 3’ direction
90
gene transfer (2)
- placement of new genes into an organism’s genome
- possible because the genetic code is universal
91
What is the result of inserting new genes?
making new proteins
92
How many steps are there of gene transfer?
4
93
What are the steps of gene transfer? (5)
1) Plasmids are removed from bacteria
2) Plasmid is cut using restriction endonuclease & the gene for transfer is cut out using the same restriction endonuclease
3) Desired gene is added to opened plasmid
4) DNA ligase covalently bonds DNA fragments
5) Recombinant plasmid is placed into a host cell
94
plasmid (2)
- small, circular DNA molecule in bacteria that doesn’t include essential genes
- used to carry new genes into cells because they can replicate on their own and produce proteins
95
restriction endonuclease
break covalent bonds between nucleotides at specific recognition sequences
96
sticky ends
single-stranded complementary ends
97
What is the same restriction endonuclease used for?
to cut the target gene out of the organism’s genome
98
What does using the same restriction endonuclease result in?
complementary sticky ends
99
What can complementary sticky ends do?
hydrogen bond to make recombinant DNA
100
recombinant DNA
DNA with a different combination of genes than it had originally
101
DNA ligase
enzyme that covalently bonds DNA strands together (phosphodiester bond)
102
What typically is the host cell? (2)
- bacterium
- yeast
103
What will the host cell do after the gene transfer is completed?
The host cell will transcribe and then translate the gene of interest to make the desired protein
104
Why is gene transfer possible?
due to universality of genetic code
105
antibiotic selection
placing antibiotic resistance gene in plasmids to identify which cells have recombinant DNA
106
making human insulin
gene transfer is used to insert the human gene for insulin into bacteria
107
What happens when insulin is successfully transferred into a bacteria cell?
Bacteria produce insulin protein and the insulin is extracted from the cells
108
gene therapy
inserting genes into cells to treat hereditary diseases by replacing defective alleles/genes
109
How does gene therapy work? (2)
- Cells are removed and a virus introduces a functional copy of the defective gene
- Cells are transplanted back that can make the missing protein and restore normal health
110
What is an example of gene therapy in humans? (2)
- treatment of adenosine deaminase (ADA) deficiency
- Individuals who have had gene therapy have shown a steady increase in the levels of ADA in their cells
111
What are some applications of gene transfer within the filed of genetic engineering? (4)
1) industry/medicine: produce large quantities of proteins such as insulin
2) gene therapies: repair faulty genes
3) genetically modified organisms: nutrient rich types
4) transgenic animals for scientific research
112
genetic modification
DNA of an organism is artificially changed such that some characteristic of the organism is changed
113
What are the benefits of GM crops for human health? (3)
- can improve nutritional standards, by incorporating genes for proteins or vitamins
- crops could be produced that lack toxins or allergens
- crops could contain edible vaccines to provide natural disease resistance
114
What are the risks of GM crops for human health? (3)
- Not all GM foods are labelled, making informed decisions difficult for consumers
- antibiotic resistance genes could spread to «pathogenic» bacteria
- transferred genes could cause unexpected problems/allergies
115
What is an example of a GM crop meant to improve human health?
golden rice: enriched with beta-carotene which is converted into vitamin A to prevent blindness
116
What are the benefits of GM crops for economics? (3)
- pest-resistant crops cause less spraying of insecticides/pesticides
- include genes to increase variety of growing locations drought
- genes to slow the rate of spoiling
117
What are the risks of GM crops for economics? (3)
- non-target organisms can be affected
- genes for herbicide resistance could spread to wild
- Patents restrict seed usage and create high prices for use
118
What are some examples of a GM crop that comes with economic benefits? (2)
- insecticide sweet corn
- salt-resistant tomatoes
119
What are the benefits of GM crops for the environment? (2)
- pest-resistant crops result in less spraying of insecticides/pesticides
- include genes to increase variety of growing locations / can grow in threatened conditions
120
What are the risks of GM crops for the environment? (2)
- non-target organisms can be affected
- genes transferred to crop plants to make them herbicide resistant could spread to wild
121
What is a named example of a GM crop that comes with environmental benefits?
Bt potatoes
122
Bt corn (3)
- genetically modified by transferring a gene from a bacterium to corn plants (Bt gene)
- produces a protein (Bt toxin) lethal to insects
- Bt corn is lethal to the European corn borer which eats corn crops
123
What is the concern of Bt corn?
monarch butterflies eating Bt corn pollen could be harmed/die
124
What was the outcome of the study on Bt corn?
no significant increase in mortality when monarch larva were placed in or near an actual Bt corn field
125
What are the benefits of Bt corn? (2)
- corn borer/insect pest is killed by Bt toxin increasing crop production
- less pesticides/fertilizers/chemicals needed so better for environment
126
What are the harmful effects of Bt corn?
non-target insects may be killed as well
127
transgenic animal (2)
- gene transfer is used to deliberately modify the genome of an animal
- Recombinant DNA must be inserted into all cells including germ cells
128
germ cells
cells that give rise to gametes
