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IB HL Biology I > Unit 10 > Flashcards

Unit 10 Flashcards

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1
Q

How do you go from DNA to a protein?

A

DNA –> RNA –> protein

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2
Q

Transcription

A

DNA sequence is rewritten as message RNA (mRNA)

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3
Q

Translation

A

mRNA is used to build a polypeptide (protein) from amino acids at a ribosome

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4
Q

Where is DNA transcribed in a prokaryote?

A

cytoplasm

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5
Q

Why does a prokaryote transcribe DNA in the cytoplasm

A

it has no nucleus

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6
Q

Where is DNA transcribed in a eukaryote?

A

nucleus

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7
Q

How many steps are there for transcription?

A

3

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8
Q

What are the steps of transcription? (3)

A
  1. Initiation
  2. Elongation
  3. Termination
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9
Q

Initiation (Transcription)

A

RNA polymerase recognizes a starting sequence on a gene (promoter) and unzips DNA

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10
Q

RNA polymerase

A

enzyme that catalyzes the reactions of transcription

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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
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12
Q

Elongation (Transcription)

A

RNA polymerase reads DNA coding region and uses ribonuclease to make a complementary strand of mRNA

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13
Q

What is the direction of elongation?

A

5’ to 3’

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14
Q

Termination (Transcription)

A

mRNA and RNA polymerase detach at termination DNA sequence

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15
Q

What is RNA that has been transcribed called?

A

messenger RNA (mRNA)

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16
Q

Which DNA strand is transcribed?

A

antisense strand

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17
Q

antisense strand

A

template for transcription (transcribed)

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18
Q

sense strand

A

coding DNA/gene (not transcribed)

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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)
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20
Q

What must happen in eukaryotes before translation?

A

mRNA must be processed/modified

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21
Q

RNA processing is… (3)

A

1) addition fo 5’ end cap
2) Addition of 3’ end poly (A) tail
3) Splicing

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22
Q

Splicing

A

removed from DNA regions that don’t codes for protein

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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

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24
Q

intron

A

DNA or RNA that doesn’t code for protein

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25
Q

extron

A

DNA or RNA base sequence that directly codes for proteins

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26
Q

alternative splicing

A

producing multiple RNA transcripts by joining different splice/cut sites

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27
Q

What is the result of splicing mRNA? (2)

A
  • it increases the number of different proteins an organism can produce
  • in eukaryotes, alternative splicing is more efficient because information can be stored economically
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28
Q

pre-mRNA

A

exons and introns

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29
Q

mature mRNA

A

exons only

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30
Q

ribonucleotides

A

RNA nucleotides with ribose

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31
Q

Why is transcription regulated?

A

so cells can only make protein they need

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32
Q

What are characteristics of genes in transcription? (2)

A
  • types of proteins determines a cell’s characteristics
  • most genes in a cell are turned off at any one time
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33
Q

gene expression (2)

A
  • using a gene to make protein
  • requires making specific mRNA and using mRNA to build polypeptides/proteins
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34
Q

What are factors that can impact gene expression? (2)

A
  • temperature
  • hormones
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35
Q

How do factors regulate gene expression?

A

regulating transcription

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36
Q

What does regulation of transcription orchestrate?

A

cells differentiation and development in multicellular organisms

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37
Q

What are factors that regulate transcription in eukaryotes? (3)

A

1) Transcription factors and non-coding DNA Sequences
2) DNA methylation
3) histone-protein modification

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38
Q

transcription factors (3)

A
  • 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
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39
Q

What transcription factors don’t bind the promoter? (2)

A
  • activator proteins
  • repressor proteins
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40
Q

activator proteins

A

bind to enhancer sequences (↑ rate of transcription)

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41
Q

repressor proteins

A

bind to silence sequences (↓ rate of transcription)

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42
Q

Where are enhancer and silencer sequences not located? (2)

A
  • in a gene
  • in non-coding DNA
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43
Q

What happens when a transcription factor binds to a promoter?

A

transcription at moderate levels

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44
Q

What happens when transcription factors bind to promoter and activators bind to enhancers?

A

the gene is transcribed at higher rates

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45
Q

What happens when transcription factors bind to promoter and repressors bind to silencer?

A

gene is transcribed at lower rates

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46
Q

DNA methylation

A

methyl groups (CH3) are added to DNA

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47
Q

What does methylation do?

A
  • inhibits the binding of transcription factors and activators and decrease transcription/gene expression
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48
Q

nucleosomes

A

DNA wrapped around histone proteins for packing

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49
Q

Why do nucleosomes regulate transcription?

A
  • DNA is inaccessible to transcription factors and RNA polymerase
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50
Q

In what case can binding occur with nucleosomes?

A

chemically modifying the histones forces nucleosome unwinding and allows binding

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51
Q

Epigenetics (2)

A
  • study of changes to DNA that alter gene expression without changing DNA sequence
  • some epigenetic changes can be inherited
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52
Q

What are some examples of epigenetics?

A

methylation and histone modification

53
Q

What does translation build?

A

a primary structure

54
Q

primary structure

A

amino aid sequence of a protein

55
Q

What is an example of a product of translation?

A

enzymes that are used to speed up the process of transcription and translation

56
Q

polypeptide

A

a sequence of amino acids

57
Q

How does genetic information flow from mRNA to protein? (2)

A
  • triplet code
  • codon
58
Q

Triplet code

A

groups of 3 bases

59
Q

codon (2)

A
  • a group of 3 base that does for one amino acid in a protein
  • code for the same amino acids
60
Q

The genetic code is… (2)

A
  • universal
  • degenerate
61
Q

universal

A

living thing use the same bases, codons and amino acids

62
Q

degenerate

A

same amino acid may be coded for by more than one codon, reduces impact of mutation

63
Q

How do you read mRNA to determine the amino acid sequence? (3)

A

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
Q

What is the start codon?

A

AUG

65
Q

How many stop codons are there?

A

3

66
Q

transfer RNA (tRNA)

A

read codons on mRNA and bring amino acid to the ribosome

67
Q

What is on tRNA? (4)

A
  • attached amino acid
  • anticodon
  • hydrogen bonds
  • tRNA activating enzyme
68
Q

attached amino acid to tRNA

A

specified by bound codon

69
Q

anticodon on tRNA

A

is nucleotides that bind to mRNA codon using complementary base pairing

70
Q

hydrogen bonding on tRNA

A

holds strands together/provide structure

71
Q

tRNA activating enzyme (2)

A
  • uses ATP to attach new amino acid to tRNA
  • there are 20 of these enzymes that correspond to the 20 amino acids
72
Q

What does a ribosome compose of? (4)

A
  • large subunit
  • small subunit
  • ribosomal RNA (rRNA)
  • proteins
73
Q

Where is the mRNA binding site?

A

the small subunit

74
Q

What holds the tRNA and mRNA together during translation?

A

the ribosomal subunits

75
Q

At how many sites does a ribosome bind to mRNA?

A

3

76
Q

What are the three binding sites on DNA?

A
  • A-site
  • P-site
  • E-site
77
Q

A-site

A

where incoming tRNA anticodon binds mRNA codon

78
Q

P-site

A

where tRNA sits with the growing polypeptide chain

79
Q

E-site

A

where tRNA without amino acid
resides before being released

80
Q

How many types of ribosomes are there?

A

3

81
Q

What are the types of ribosomes? (3)

A
  • bound ribosomes
  • polysomes
  • free ribosomes
82
Q

Bound ribosomes (2)

A
  • on Rough ER
  • make protein for export
83
Q

Polysomes

A

many free ribosomes working on the same mRNA to complete translation more efficiently

84
Q

Free ribosomes

A

make proteins for the cell

85
Q

What are the steps of translation? (3)

A

1) Initiation
2) Elongation
3) Termination

86
Q

Initiation (Translation) (2)

A

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
Q

Elongation (Translation) (5)

A

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
Q

Termination (Translation) (3)

A

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
Q

What is the direction of translation?

A

The ribosome moves along the mRNA strand in the 5’ to 3’ direction

90
Q

gene transfer (2)

A
  • placement of new genes into an organism’s genome
  • possible because the genetic code is universal
91
Q

What is the result of inserting new genes?

A

making new proteins

92
Q

How many steps are there of gene transfer?

A

4

93
Q

What are the steps of gene transfer? (5)

A

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
Q

plasmid (2)

A
  • 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
Q

restriction endonuclease

A

break covalent bonds between nucleotides at specific recognition sequences

96
Q

sticky ends

A

single-stranded complementary ends

97
Q

What is the same restriction endonuclease used for?

A

to cut the target gene out of the organism’s genome

98
Q

What does using the same restriction endonuclease result in?

A

complementary sticky ends

99
Q

What can complementary sticky ends do?

A

hydrogen bond to make recombinant DNA

100
Q

recombinant DNA

A

DNA with a different combination of genes than it had originally

101
Q

DNA ligase

A

enzyme that covalently bonds DNA strands together (phosphodiester bond)

102
Q

What typically is the host cell? (2)

A
  • bacterium
  • yeast
103
Q

What will the host cell do after the gene transfer is completed?

A

The host cell will transcribe and then translate the gene of interest to make the desired protein

104
Q

Why is gene transfer possible?

A

due to universality of genetic code

105
Q

antibiotic selection

A

placing antibiotic resistance gene in plasmids to identify which cells have recombinant DNA

106
Q

making human insulin

A

gene transfer is used to insert the human gene for insulin into bacteria

107
Q

What happens when insulin is successfully transferred into a bacteria cell?

A

Bacteria produce insulin protein and the insulin is extracted from the cells

108
Q

gene therapy

A

inserting genes into cells to treat hereditary diseases by replacing defective alleles/genes

109
Q

How does gene therapy work? (2)

A
  • 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
Q

What is an example of gene therapy in humans? (2)

A
  • 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
Q

What are some applications of gene transfer within the filed of genetic engineering? (4)

A

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
Q

genetic modification

A

DNA of an organism is artificially changed such that some characteristic of the organism is changed

113
Q

What are the benefits of GM crops for human health? (3)

A
  • 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
Q

What are the risks of GM crops for human health? (3)

A
  • 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
Q

What is an example of a GM crop meant to improve human health?

A

golden rice: enriched with beta-carotene which is converted into vitamin A to prevent blindness

116
Q

What are the benefits of GM crops for economics? (3)

A
  • 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
Q

What are the risks of GM crops for economics? (3)

A
  • 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
Q

What are some examples of a GM crop that comes with economic benefits? (2)

A
  • insecticide sweet corn
  • salt-resistant tomatoes
119
Q

What are the benefits of GM crops for the environment? (2)

A
  • pest-resistant crops result in less spraying of insecticides/pesticides
  • include genes to increase variety of growing locations / can grow in threatened conditions
120
Q

What are the risks of GM crops for the environment? (2)

A
  • non-target organisms can be affected
  • genes transferred to crop plants to make them herbicide resistant could spread to wild
121
Q

What is a named example of a GM crop that comes with environmental benefits?

A

Bt potatoes

122
Q

Bt corn (3)

A
  • 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
Q

What is the concern of Bt corn?

A

monarch butterflies eating Bt corn pollen could be harmed/die

124
Q

What was the outcome of the study on Bt corn?

A

no significant increase in mortality when monarch larva were placed in or near an actual Bt corn field

125
Q

What are the benefits of Bt corn? (2)

A
  • corn borer/insect pest is killed by Bt toxin increasing crop production
  • less pesticides/fertilizers/chemicals needed so better for environment
126
Q

What are the harmful effects of Bt corn?

A

non-target insects may be killed as well

127
Q

transgenic animal (2)

A
  • gene transfer is used to deliberately modify the genome of an animal
  • Recombinant DNA must be inserted into all cells including germ cells
128
Q

germ cells

A

cells that give rise to gametes

IB HL Biology I (10 decks)

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