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AP Biology > DNA, Genes & Protein Synthesis > Flashcards

DNA, Genes & Protein Synthesis Flashcards

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1
Q

RNA

A

 Sugar is ribose
 Uracil is one of the nitrogen bases
 Single stranded

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2
Q

DNA

A

 Sugar is deoxyribose
 Thymine is one of the nitrogen bases
 Double stranded

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3
Q

Transcription (basics)

A

 Completed in nucleus
 Creation of RNA from a DNA template
 mRNA (messenger) carries the genetic message to the cytoplasm

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4
Q

why is an RNA intermediate used instead of DNA for protein synthesis?

A

prevents the degradation of/damage to DNA if it enters cytoplasm
-multiple mRNA molecules can enter cytoplasm to mass produce proteins (ex. antibodies)

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5
Q

Translation (basics)

A

 Completed at a ribosome

 Synthesis of a polypeptide (amino acid sequence) from mRNA

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6
Q

Prokaryotes: protein synthesis

A

 Lack of a nucleus changes protein synthesis

 Translation of mRNA begins while transcription is happening

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7
Q

Eukaryotes: protein synthesis

A

 Transcription occurs in the nucleus
 RNA processing occurs inside the nucleus
 Translation is completed outside the nucleus

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8
Q

Genetic Code

A

 20 different amino acids
 Three DNA nucleotides code for one amino acid (providing 64 options)
 The gene determines the sequence of bases in the mRNA strand, which determines the amino acid

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9
Q

Genetic Code: codons

A

 mRNA triplets that code for one amino acid
 Written & read in the 5’ to 3’ direction
 Begins with the start (initiation) codon & end with a stop codon

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10
Q

Genetic Code: evolutionary significance

A 
nearly universal!
 Results from a common
ancestor shared by all life
 Genes from one species
can be transcribed and
translated from another
(in a laboratory of course)
 medical research
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11
Q

Transcription: initiation

A

 RNA polymerase: enzyme that opens DNA strands
and hooks together RNA nucleotides
 Only works in the 5’ to 3’ direction of the RNA strand
being synthesized (read 3’ to 5’ on the template strand)
 No primer needed
 Transcription factors bind RNA polymerase to the
promoter creating the transcription initiation
complex
 The TATA box (on non-coding strand) will help the transcription factors bind to the promoter (located 25 bases upstream of transcription site)
 RNA polymerase binds to the promoter then
unwinds & opens the DNA strand to begin RNA
synthesis

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12
Q

transcription (initiation): promoter

A

nucleotides that determine where transcription begins & RNA polymerase attaches

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13
Q

transcription (initiation): terminator

A

a nucleotide sequence that signals the end of transcription

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14
Q

transcription (initiation): Transcription unit

A

the portion of DNA that is transcribed into RNA

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15
Q

role of transcription factors in transcription

A

-regulate transcription by determining whether or not RNA polymerase attaches to DNA

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16
Q

Transcription: elongation

A

 RNA polymerase moves downstream (5’ to 3’) along
the DNA template exposing nucleotides as it unwinds
 RNA nucleotides are added to the 3’ end of the RNA strand
 During elongation RNA molecule peels off the DNA
template allowing DNA to reform
 Multiple RNA polymerases can follow each other
allowing one gene to be transcribed several times at
once

17
Q

Transcription: termination (prokaryotes)

A

transcription continues until a terminator sequence is reached which causes the
RNA polymerase to detach

18
Q

Transcription: termination (eukaryotes)

A

the pre-mRNA is cut free while RNA polymerase continues to transcribe
 At the polyadenylation signal (AAUAAA) proteins cut
the pre-mRNA
 RNA polymerase continues transcribing until it
eventually falls off the DNA (what causes this is still
not known)

19
Q

mRNA processing: alteration of ends

A

 Pre-mRNA is modified in the nucleus to help with export, prevent degradation of the genes, assist in attachment to the ribosome
 5’ cap: modified guanine nucleotide is added- helps mRNA exit through nuclear pore and attach to ribosome
 Poly-A tail: 50 to 250 adenine nucleotides are added to the 3’ end- acts as a buffer to prevent mRNA degradation in cytoplasm by enzymes (exonucleases)
-UTR: untranslated region for ribosomal attachment

20
Q

mRNA processing: RNA splicing

A 
the removal of large sections of previously synthesized RNA
 Introns: non-coding
segments of RNA
 Exons: parts of the RNA
sequence that are expressed
 Spliceosomes (small
proteins & RNAs) are able
to recognize the splicing
sites & remove introns
21
Q

mRNA processing: evolutionary significance

A

 Play a role in gene activity
 Alternative RNA splicing:
 Provides extra chances for genetic diversity through
exon shuffling during cross over

22
Q

mRNA processing: Alternative RNA splicing:

A

different polypeptides can
arise from one gene based on which introns and
exons are spliced

23
Q

translation: tRNA

A

transfers amino acids from the cytoplasm to the ribosome (uber driver)
 Uses anticodon on tRNA to bind to the specific codon & deliver correct amino acid
 Reusable
-more tRNA than amino acids because 2 or 4 tRNA molecules will bind to the same amino acid

24
Q

translation: ribosomes

A

 Made up of two subunits (made of rRNA) that
codons and anticodons
 Each ribosome has three binding sites:
P site, A site, E site

25
Q

translation: ribosomes (binding sites)

A

 P site (peptidyl-tRNA): holds the tRNA carrying the
polypeptide chain
 A site (aminoacyl-tRNA): hold the tRNA carrying the
next amino acid
 E site (exit site): releases the tRNA

26
Q

translation: initiation

A

 The small ribosomal unit brings mRNA and an
initiator tRNA (carrying methionine) together at the
start codon
 Then the large ribosomal subunit attaches forming
the translation initiation complex
 The initiator tNRA is moved to the P site & the next tRNA enters the A site as elongation begins

27
Q

translation: elongation

A

 Amino acids are added one by one with the help of
elongation factors
 Occurs in 3 stages:
 Codon recognition:
 Peptide bond formation
 Translocation
-multiple ribosomes can attach to one mRNA strand, synthesizing multiple polypeptide chains from the same strand

28
Q

translation: elongation (codon recognition)

A

the anticodon on the tRNA pairs with the codon on the A site of mRNA

29
Q

translation: elongation (Peptide bond formation)

A

the large subunit creates a peptide bond between the new amino acid in the A site and polypeptide chain in the P site

30
Q

translation: elongation (Translocation)

A

tRNA is moves from the A site to the P site (this moves the tRNA from the P site to the E site)
 mRNA moves long with the tRNA

31
Q

mutations

A

changes in the genetic material of a cell/virus

32
Q

point mutations

A

chemical changes in just one base pair of gene

33
Q

substitutions: base pair

A

replacement of nucleotide and its partners with another pair of nucleotides

34
Q

substitutions: missense

A

altered codon still codes for one amino acid but does not make right sense (codes for different amino acid)

35
Q

substitutions: nonsense

A

change in codon for amino acid to a stop codon, causes translation to be terminated prematurely

36
Q

insertions & deletions

A

additions/losses of nucleotide pairs in a gene

37
Q

mutagens

A

physical and chemical agents that interact with DNA in various ways to cause mutations

38
Q

translation: termination

A

 Elongation continues until the stop codon (mRNA) is
reaches the A site
 Release factors binds the stop codon in the A site
which causes the polypeptide chain to by
hydrolyzed & released from the exit tunnel
 The translation unit comes apart

AP Biology (30 decks)

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