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Ch 17 Flashcards

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1
Q

tRNA activation process

A

tRNA activation involves an enzyme binding to ATP and a specific amino acid, forming an amino acid-AMP complex. This complex recruits a tRNA molecule, which binds to the amino acid, releasing AMP and producing ‘charged’ tRNA.

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2
Q

Gene Expression

A

If a gene is being expressed, it is being transcribed and translated.

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3
Q

mRNA Codons

A

A codon is a group of 3 mRNA nucleotides.

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4
Q

Molecules of tRNA are specific for only one amino acid.

A

One end of tRNA attaches to a specific amino acid, while the other end, called the anticodon, hydrogen bonds to the mRNA codon by base pairing.

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5
Q

Redundancy in genetic coding

A

Codons GAA and GAG both specify glutamic acid, demonstrating redundancy. This is also known as “degeneracy.”

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6
Q

tRNA anticodon

A

A sequence of 3 bases on tRNA that pairs with the mRNA codon.

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7
Q

Bound ribosome

A

Ribosome is bound to rough ER; Protein made will be secreted, become part of the membrane, or will be inside lysosomes.

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8
Q

Termination step of translation

A

Termination occurs when a “STOP” codon is reached, and there isn’t a complementary tRNA. A “release factor” binds to the “A” site, causing the addition of a water molecule to the polypeptide, which hydrolyzes the completed polypeptide from the tRNA.

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9
Q

Describe chemical reaction of forming a peptide bond

A

Reaction is a condensation reaction/ dehydration synthesis reactions, a water is removed, a covalent bond is formed called a peptide bond, performed by the ribosome

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10
Q

Structure of tRNA

A

tRNA molecules help decode mRNA sequences into proteins by carrying amino acids to the ribosome. They hydrogen bond with themselves to form the unique tRNA shape, bind an amino acid at its 3’end, and have 3 exposed bases that point outward called the anticodon.

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11
Q

Free ribosome

A

free floating ribosome in cytosol; Protein made is used in the cytosol.

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12
Q

Cell Responsibility in Gene Expression

A

Certain cells express specific genes, while others express different genes. For example, skin cells don’t produce insulin or antibodies.

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13
Q

Elongation Phase of Translation

A

Incoming tRNA binds in A site, ribosome forms peptide bond between amino acid chain in P site to amino acid in A site, passing the chain to the A site.

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14
Q

tRNA activation process (Charging up tRNAs)

A

Each amino acid has an enzyme that binds it to the correct tRNA on the 3’ end (CCA) using ATP.
Occurs in the cytosol/cytoplasm. The enzyme may recognize multiple tRNA molecules due to redundancy/degeneracy.

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15
Q
A
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16
Q

Initiator tRNA

A

Brings the first amino acid to start codon (AUG): Methionine (Met).

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17
Q

Initiation of Translation

A

mRNA binds to small ribosomal subunit, initiator tRNA bonds to start codon (AUG), large ribosomal subunit binds, placing initiator tRNA in P site.

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18
Q

tRNA Binding Sites

A

Ribosomes have three tRNA binding sites: A, P, and E.

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19
Q

Redundancy of the code

A

Refers to multiple codons coding for the same amino acid, providing a buffer against mutations.

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20
Q

High vs Low Level of gene Expression

A

High level: A lot of protein is made. Low level: Not much protein is made.

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21
Q

Translocation process in ribosomes

A

Translocation process in ribosomes involves moving tRNA from the “A” site to the “P” site, and tRNA from the “P” site to “E” site where it will exit the ribosome. Ribosome moves 5’ to 3’

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22
Q

Steps of Translation

A

Translation includes 4 processes: initiation, elongation, translocation, and termination.
elongation and translocation repeat many times

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23
Q

Gene Copies in Cells

A

Every cell has a copy of every gene, but not all genes are in the “on” position.

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24
Q

No ambiguity in genetic coding

A

Neither GAA nor GAG specifies any other amino acid, indicating no ambiguity.

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25
1 Codon Codes for ___ Amino Acid (how many?)
Each codon corresponds to one amino acid.
26
Ribosome structure
Ribosomes are the cellular structures where protein synthesis occurs, composed of rRNA and proteins. 2 subunits: Small: has binding site for mRNA Large: has 3 binding sites for tRNAs
27
Why can’t a codon be 2 mRNA nucleotides? Why 3?
A codon is 3 nucleotides long to provide enough combinations to code for all 20 amino acids.
28
Base-pair substitution
Replacement of one base pair with another; most common type of mutation.
29
Importance of Amino acid properties in base-pair substitution
The new amino acid may have similar properties to the one it replaces, or it may be in a part of the protein where the exact amino acid sequence is not essential to its activity.
30
Effects Insertions/Deletions have on proteins
Can result in Frameshift mutations, which will lead to extensive missense mutations or nonsense mutations.
31
Mutations
Random, permanent changes in DNA that can involve large chromosomal regions or a single nucleotide pair.
32
Base pair substitution mutations can be silent/same sense.
No change occurs; the same amino acid is placed.
33
Base pair deletion
The deletion of one nucleotide pair from a gene. It can also involve more than one nucleotide base pair, altering the reading frame of the genetic message. Usually results in a frameshift mutation.
34
Frameshift mutation
a frameshift is caused by base-pair insertion or deletion; can lead to a nonfunctional protein due to extensive missense or nonsense mutation.
35
Types of Point Mutations
1) Base-pair substitution 2) Base pair insertion 3) Base pair deletion
36
Causes of mutations
1) Mutagens (can be chemical or physical) 2) Mistakes in DNA copying during S phase of Interphase. Only mutations to germ cells (cells that lead to eggs or sperm) are passed onto offspring, not mutations in body cells (somatic cells).
37
Describe the diagram showing normal and sickle cell hemoglobin and their effects on red blood cells and blood vessels.
Normal hemoglobin results in round, free-flowing red blood cells, while sickle cell hemoglobin causes sickle-shaped cells that can block blood vessels.
38
SNP
Single nucleotide polymorphism, pronounced "snip." Caused by substations; most common differences amongst DNA in individuals.
39
Reason for minimal effect of base-pair substitution
Due to degeneracy (redundancy) in the genetic code; a base pair change may transform one codon into another that codes for the same amino acid.
40
Base pair substitution mutations can be missense.
A different amino acid is placed, which can alter the shape and function of the protein. More serious if amino acid properties are very different.
41
Point Mutation
A mutation limited to one base pair in a single gene.
42
Base pair substitution mutations can be nonsense.
Results in a premature stop codon. The earlier the new stop codon, the more harmful the mutation will likely be.
43
Example of a condition caused by base pair substitution.
Sickle cell anemia.
44
describe mutation in sickle cell anemia.
A base-pair substitution leads to a missense mutation where glutamic acid has been substituted with Valine. These amino acids have different properties. In low O2 conditions, valine will cause the hemoglobin proteins to bind together, forming sickled red blood cells.
45
Effect of base-pair substitution on proteins
Possible to result in little or no change in the protein encoded by the mutated gene. Mutation can be silent, or lead to missense or nonsense mutations in proteins.
46
Base pair insertion
The insertion of one nucleotide pair into a gene. It is possible to insert more than one nucleotide pair, but it wouldn’t be a “point mutation” (just insertion). Usually results in frameshift mutation.
47
Chromosomal Mutations
mutations that affect larger chromosomal regions
48
Mutagens
High energy or chemical agents that interact with DNA to cause mutations. Chemical: pollutants, pesticides, cigarette smoke Energy/physical: X-rays, UV radiation
49
Can Base pair substitutions lead to significant changes in protein activity?
Yes. Some base pair substitutions result in detectable changes in proteins that may significantly alter protein activity.
50
Effects substitution mutations have on proteins
Can result in Silent, Missense, or Nonsense mutations.
51
Termination of transcription in eukaryotes
In eukaryotes, the mechanism for cleaving pre-mRNA from DNA is more complicated and not completely understood. Transcription ends when RNA polymerase "falls off" the DNA.
52
The role of the messenger in transcription.
The messenger carries the blueprints from the nucleus to the ribosomes.
53
Exons
Exons are coding regions of DNA; they are eventually expressed and turned into a protein.
54
RNA processing in eukaryotes (post-transcriptional modifications)
RNA processing is an extra step between transcription and translation that does not occur in prokaryotes. 1) both ends are altered (5' guanine cap added, 3' poly-A tail added) 2) RNA splicing
55
The messenger in transcription.
The messenger is messenger RNA (mRNA).
56
Protein synthesis in prokaryotes
In bacteria, transcription and translation happen in the same location (cytosol) and often occur simultaneously (at the same time).
57
role of RNA Polymerase in elongation
RNA Polymerase covalently bonds RNA nucleotides during transcription as they base-pair along the DNA template. RNA polymerase forms phosphodiester bonds; it does not form the hydrogen bonds which form spontaneously.
58
importance of RNA being single stranded
RNA can still have a 3-dimensional shape despite being single stranded (tRNA, snRNA, rRNA, etc). It can also remain unfolded such as mRNA so that its code can be read by the ribosome.
59
Proteins are long chains of what?
Proteins are long chains of amino acids.
60
For each gene, only one of the two strands is transcribed. What is this DNA strand called?
Called the ANTISENSE strand, which acts as the template for the message.
61
Function of transport proteins
Transport proteins, such as hemoglobin and membrane channels, help move substances across cell membranes.
62
Comparing RNA and DNA structures
1) RNA is single stranded; DNA is double stranded 2) RNA contains ribose as its sugar; DNA contains deoxyribose 3) RNA contains the base Uracil; DNA contains Thymine instead
63
Functions of the poly-A tail in mRNA.
Inhibits degradation of the mRNA in the cytosol and may facilitate the export of mRNA from the nucleus to the cytoplasm.
64
What happens to the mature mRNA transcript after post-transcriptional modifications?
The mature mRNA will leave the nucleus and enter the cytosol, where it will attach to a ribosome for translation.
65
Importance of amino acid order.
The order/sequence of amino acids is crucial because it determines the protein's structure and function.
66
Gene
A specific sequence of DNA bases that can code for a specific protein.
67
Importance of proteins
Proteins carry out nearly every function of a living thing, including DNA replication, forming structural proteins, transporting molecules, fighting infections, and acting as enzymes.
68
Spliceosomes
Made up of several snRNPS (snurps) which are each made up of snRNA (small nuclear RNA) and protein associated together. The entire spliceosome complex performs splicing which removes non-coding introns and splices coding exons back together.
69
RNA nucleotides are only added to the ___ end.
3' end mRNA is synthesized in the 5’ to 3’ direction.
70
What happens to the mRNA and DNA strands during transcription?
During elongation, mRNA peels away from the DNA strand and the two stands of DNA reunite upstream. RNA polymerase continues to unwind/unzip DNA downstream so transcr
71
Protein synthesis in eukaryotes
In eukaryotic cells, the nuclear envelope separates transcription from translation, providing time for RNA processing.
72
Base pairing in RNA
Instead of thymine (T), RNA contains uracil (U). Base pairing rules: C with G; A with U.
73
Relationship between RNA polymerase and PROMOTERS.
RNA polymerase binds to and separates the 2 DNA strands at regions called PROMOTERS. PROMOTERS are specific sequences of DNA, such as TATA, where transcription begins at the initiation site.
74
How many Different amino acids are there and what makes them different from each other?
There are 20 different amino acids; the R groups makes them different.
75
Proteins help fight infection
Proteins function as antibodies to help fight infections.
76
name the parts of the amino acid
alpha carbon, alpha hydrogen, carboxyl group, amino group, r group (varies between the 20 amino acids)
77
Sugar in RNA
The sugar in RNA is ribose, unlike DNA which has deoxyribose.
78
Introns
Introns are noncoding segments of DNA; they are intervening sequences between the coding segments.
79
Protein Synthesis consists of 2 steps
1) Transcription 2) Translation
80
Role of enzymes in digestion
Enzymes, which are proteins, help digest food through hydrolysis reactions.
81
DNA is called the "code of life." What does this mean?
The information ("code") to make proteins.
82
How does DNA's code relate to a protein?
The DNA nucleotide sequence determines the order of amino acids in a protein chain.
83
Examples of structural proteins
Structural proteins include those found in skin (such as collagen) and muscles (such as actin and myosin).
84
The _____ DNA strand is the strand NOT copied into mRNA.
SENSE; The mRNA has the same base sequence as the sense strand of DNA.
85
Termination of transcription in prokaryotes
In prokaryotes, transcription proceeds until RNA polymerase reaches a termination site on the DNA, causing it to fall off and transcription to end.
86
Post-transcription modification of mRNA in eukaryotes involves RNA splicing.
RNA splicing is the process where introns are removed and exons are joined together to form mature mRNA.
87
Functions of 5' G-cap as a Post-transcription modification of mRNA in eukaryotes
The 5’ end is “capped” with a modified form of guanine (G) to protect mRNA from hydrolytic enzymes in the cytosol and to serve as an “attach here” signal for small ribosomal subunits.
88
Mutations that occur in ______ cells are passed from parents to offspring
germ
89
The primary sequence of a protein refers to the:
order of amino acids
90
On a DNA strand, where is the promoter located?
Upstream to the gene
91
A gene is
The info for making a polypeptide

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