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biology > protein synthesis (7.1, 7.2, 7.3) > Flashcards

protein synthesis (7.1, 7.2, 7.3) Flashcards

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1
Q

what is one-gene-one-protein

A

each gene is unique and encodes for specific proteins by specifying the amino acid sequence

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2
Q

what is the connection between DNA, RNA, and protein

A

central dogma — the fundamental principle of molecular genetics, it states that genetic information flows from DNA to RNA proteins

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3
Q

what is transcription?

A

a mechanism where the information encoded in RNA is copied into amino acids of proteins into the cytoplasm

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4
Q

what is translation

A

a mechanism where the information encoded in RNA is copied into amino acids of proteins into the cytoplasm

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5
Q

what are properties of DNA

A
  • double stranded
  • adenine + thymine
  • guanine + cytosine
  • deoxyribose sugar
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6
Q

what are properties of RNA

A
  • single stranded
  • adenine + uracil
  • guanine + cytosine
  • deoxyribose sugar
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7
Q

what types of RNA are there

A
  1. messenger RNA (mRNA)
  2. transfer RNA (tRNA)
  3. ribosomal RNA (rRNA)
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8
Q

what is messenger RNA (mRNA)

A

— the end product of the transcription of a gene
— translated by ribosomes into a protein
— is the RNA version of the gene

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9
Q

what is transfer RNA (tRNA)

A

— a carrier molecule that binds to a specific amino acid and adds to the growing polypeptide chain

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10
Q

what is ribosomal RNA (rRNA)

A

— an RNA molecule within the ribosome that bonds the correct amino acid to the polypeptide chain

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11
Q

list the steps of transcription and translation

A
  1. first step of protein synthesis is transcription
  2. then, RNA polymerase creates an RNA molecule with a base sequence complementary to the template DNA strand, this creates pre mRNA
  3. after pre-mRNA is modified, it leaves the nucleus and translation occurs in the ribosomes
  4. the ribosome moves along mRNA, and the amino acids are delivered by tRNA and joined by forming a polypeptide chain
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12
Q

what are codons

A

a group of three base pairs coding for an individual amino acid

— there are 64 possible codons (n^r = 4^3)
— 61 of which code for amino acids
— 3 of which code for a stop

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13
Q

list the three types of codons

A
  1. initiation codons
  2. termination codons
  3. anticodons
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14
Q

what are initiation codons

A

signals the beginning of a protein
— methionine is an initiation codon (AUG)

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15
Q

what are termination codons

A

signals the end of a protein (UAA, UAG, UGA)

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16
Q

what are anticodons

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A

three nucleotides at one end of a tRNA that determine which amino acids the tRNA will pick up and transport

17
Q

what is transcription

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A

the mechanism where information in DNA is transcribed into a complementary RNA copy.

— information in DNA is copied onto RNA

18
Q

what are the three steps of transcription?

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A
  1. initiation
  2. elongation
  3. termination
19
Q

what occurs in initiation

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A
  1. RNA polymerase binds to DNA at a promoter region
  2. RNA polymerase moves until it finds the first three nucleotides that need to be transcribed
  3. DNA is unwound, exposing the template strand to be copied
20
Q

what occurs in elongation

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A
  1. once DNA is unwound, ribonucleotides are added in 5’ to 3’ direction, using RNA polymerase
  2. the DNA strand not being copied is called the coding strand, and contains same sequence of bases as the RNA strand
21
Q

what occurs in termination

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A
  1. enzymes encounter a termination sequence of a specific nucleotide
  2. the transcribed molecule is released and the core enzyme dissociates itself from the DNA
22
Q

where does the post-transcriptional model occur

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A

in the nucleus before RNA enters the cytoplasm

23
Q

how does post-transcriptional modification protect pre-mRNA

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A

poly (A) tail (adenine), is added to the 3’ end of the pre-mRNA to protect it from enzymatic destruction in the cytosol

24
Q

what are DNA coding regions of eukaryotic genes called

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A

exons and introns

25
what are exons?
a sequence of DNA or RNA that codes for part of a gene
26
what are introns
a non-coding sequence of DNA or RNA in eukaryotes only
27
what removes introns and why?
— precursor mRNA needs to remove the introns — if they are left in the mRNA, introns would alter the amino acids sequence and prevent proper folding of the protein, thus altering its function
28
what is splicing
splicing cuts out introns and joins the exons together by enzyme splicosome
29
what are splicosomes
splicosomes are complexes of pre-mRNA and small ribonucleioproteins (snRNPs)
30
what are the two steps of translation — nucleic acid to polypeptide
— transcription: DNA coded message to mRNA — translation: translate the information in mRNA to a protein - the encoded message is read by ribosome and assembles one amino acid at a time into polypeptide chain
31
what is tRNA
transfer RNA molecules (tRNAs) are small RNA molecules with four double helical segments forming a clover-leaf pattern — at the tip of one of the double helical segments is the anti-codon (the sequence of base pairs corresponding to the codon on mRNA)
32
what is aminoacylation
the process of adding amino acids to tRNA
33
what helps form peptide bonds during translation
energy in the aminoacyl-tRNA helps form the peptide bonds that links amino acid during translation
34
what do ribosomes do?
ribosomes carry out protein synthesis by translating mRNA into chains of amino acids
35
what are main functions of ribosomes
— carries out protein synthesis — translates mRNA into chains of amino acids at 5’ end — ribosomes have two parts made of ribosomal proteins: large (60s) and small (40s)
36
what are the ribosome sites that bring mRNA together
1. A (aminoacyl) site 2. P (peptidyl) site 3. E (exit) site
37
what occurs during initiation
1. methionine-tRNA (met-tRNA) forms with the small ribosomal subunit 2. the complex binds to 5’ end and scans mRNA until it reaches codon (AUG) 3. the large ribosomal (60S) subunit binds to complete ribosome
38
what occurs in elongation
1. the next charged tRNA binds to the a-site 2. peptide bond forms 3. the ribosome moves (translocation) to the next codon and brings tRNA with the next growing polypeptide to the p-site and moves the empty tRNA to the e-site
39
what occurs in termination?
— a-site arrives at stop codon (UAA, UAG, UGA) — protein release factor binds at the a-site instead of aminoacytl-tRNA and detached from ribosome — ribosomal subunits separate and detach

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