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BIO 1010 > Lecture 5- How genes work > Flashcards

Lecture 5- How genes work Flashcards

1
Q

Genes

A

provide the instructions for making specific proteins

-does not build a protein directly

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2
Q

Gene expression

A

-the process by which DNA directs the synthesis of proteins

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3
Q

one gene- one enzyme hypothesis

A

hypothesis that a gene dictates the production of a specific enzyme

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4
Q

What is the link between genotype and phenotype

A

proteins

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5
Q

Metabolic pathways

A
  • cells synthesize and degrade organic molecules via metabolic pathways
  • each chemical reaction in a sequence is catalyzed by a specific enzyme
  • such metabolic pathways lead to the synthesis of pigments that determine an organism’s colour
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6
Q

one gene- one enzyme hypothesis

A

states that the function of a gene is to dictate the production of a specific enzyme

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7
Q

What is the bridge between DNA and protein synthesis

A

RNA

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8
Q

transcription

A

is the synthesis of any RNA using information in DNA.

-making RNA from DNA

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9
Q

mRNA

A
  • messenger RNA

- carries a genetic message from DNA to ribosome

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10
Q

translation

A
  • the synthesis of a polypeptide using the information in mRNA
  • making a protein by reading mRNA
  • change in language
  • cell translates the nucleotide sequence of an mRNA molecule into the amino acid sequence of a protein
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11
Q

what organisms does transcription and translation occur

A
  • all organisms

- eukaryotes and prokaryotes

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12
Q

ribosomes

A
  • the site of translation

- link amino acids into polypeptide chains

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13
Q

primary transcript

A
  • the initial RNA transcript from any gene

- including those specifying RNA that is not translated into protein

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14
Q

Transcription in eukaryotes

A

-occurs in the nucleus

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15
Q

Transcription in prokaryotes

A
  • lacks a nucleus, so occurs in the cytoplasm
  • DNA is not separated
  • mRNA produced by transcription is immediately translated without additional processing
  • lack of compartmentalization allows translation of mRNA to begin while its transcription is still in progress
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16
Q

pre mRNA

A

-the original RNA transcript

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17
Q

Central dogma

A

1) DNA in nucleus replicates
2) Transcription in nucleus. RNA polymerase moves along DNA and synthesizes corresponding mRNA
3) mRNA move out of nucleus through pore into cytosol,
binds to ribosome where it is translated and protein is synthesized

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18
Q

How many amino acids are there

A

20

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19
Q

Why can’t the genetic code be read like chinese?

A
  • only 4 nucleotide bases
  • one nucleotide does not equal one amino acid
  • 2 nucleotide combinations would only specify 4^2= 16 amino acids
  • 3 nucleotide combinations specify 4^3=64 amino acids
  • triplets of nucleotide bases is the smallest units that can code for all of the amino acids
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20
Q

Triplet code

A

the genetic instructions for making a protein are written in the DNA as a series of 3 nucleotide words
-the series of words in a gene is transcribed into a complementary series of non-overlapping, three nucleotide words in mRNA, which is then translated into a chain of amino acids

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21
Q

The genetic code

A

consists of nucleotide bases that are read linearly, three a time, the sequence of each codon specifying an amino acid
-there is redundancy, but no ambiguity

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22
Q

Start codon

A

AUG

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23
Q

Stop codon

A

UAA, UAG, UGA

24
Q

codons

A

nucleotide triplet

25
Q

During transcription, the gene determines the

A

sequence of nucleotide bases along the mRNA that is being synthesized

26
Q

Template strand

A

the strand that is being read to make mRNA

  • only one of the two DNA strands
  • is determined by the orientation of the enzyme that transcribes the genes, which depends on the DNA associated with a given gene
27
Q

synthesizing mRNA

A
  • mRNA is complementary rather than identical to its DNA template strand
  • U’s instead of T’s
  • synthesized in anti-parallel direction, 5’ to 3’
28
Q

Coding strand

A

the non-template strand

29
Q

The number of nucleotides making up a genetic message is

A

three times the number of amino acids in the protein

100 amino acids long= 3x100=300 nucleotides

30
Q

RNA polymerase

A
  • separates the two strands of DNA apart

- joins together RNA nucleotides complementary to the DNA template strand

31
Q

Similarity between RNA polymerase by DNA polymerase

A

-can assemble polynucleotide in 5’ to 3’ direction

32
Q

Difference between RNA polymerase and DNA polymerase

A

-doesn’t need a primer

33
Q

Promoter

A

the DNA sequence where RNA polymerase attaches and initiates transcription

  • includes start point (the nucleotide where RNA synthesis actually begins)
  • TATA box
34
Q

Terminator

A

the sequence that signals the end of transcription

35
Q

Transcription unit

A

the stretch of DNA downstream from the promoter that is transcribed into an RNA molecule

36
Q

Three stages of Transcription

A

1) Initiation
2) Elongation
3) Termination

37
Q

Initiation of Transcription

A

after RNA polymerase binds to the promoter:

  • DNA strands unwind
  • polymerase initiates RNA synthesis at the start point on the template strand
38
Q

Transcription factors

A
  • collection of proteins that monitor the binding of RNA polymerase and the initiation of transcription
  • after transcription factors bind to promoter, RNA polymerase II binds to it too
39
Q

Transcription initiation complex

A

transcription factor + RNA polymerase II bound to promoter

40
Q

Elongation of Transcription

A
  • RNA polymerase moves down and untwists double helix
  • elongates the RNA in the 5’ to 3’ direction
  • RNA polymerase adds nucleotides to the 3’ end of growing RNA molecule as it moves along DNA
  • new RNA peels away and DNA reforms a double helix
41
Q

Termination of Transcription

A
  • RNA transcript is released

- polymerase detaches from the DNA

42
Q

Three types of RNA transcribed from genes by RNA polymerase

A

1) Messenger RNA
2) Transfer RNA
3) Ribosomal RNA

43
Q

messenger RNA (mRNA)

A

-contain information to be converted into proteins via translation

44
Q

transfer RNA (tRNA)

A
  • transport specific amino acids to a growing polypeptide in the ribosome
  • has an amino acid attachment site
  • anti codon triplet (3’ - 5’)
  • the protein synthesizing complex
45
Q

ribosomal RNA (rRNA)

A

complexed with proteins to form ribosome

  • made in the nucleolus
  • responsible for structure and function of ribosome
46
Q

anticodon direction

A

3’ to 5’

47
Q

codon direction

A

5’ to 3’

48
Q

ribosome

A

the site of protein synthesis

49
Q

P site

A
  • peptidyl-tRNA

- holds the tRNA carrying the growing protein chain

50
Q

A site

A
  • aminoacyl- tRNA

- holds the tRNA carrying the next amino acid to be added to the chain

51
Q

E site

A

exit site

-where the tRNA’s leave

52
Q

Three stages of translation

A

1) Initiation
2) Translocation
3) Termination

53
Q

Initiation of Translation

A
  • small ribosome unit binds to mRNA at the P site
  • tRNA with anti codon UAC base pairs with start codon AUG and carries amino acid Met
  • translation initiation complex= when large subunit arrives, caused by initiation factors
54
Q

one gene- one polypeptide

A
  • one gene dictates the production of one polypeptide
  • not entirely accurate, some proteins like hemoglobin are made of two genes and some genes code for RNA that are translated into proteins
55
Q

Translocation

A
  • a different tRNA base pairs with mRNA at the A site
  • growing polypeptide from P site is attached to amino acid in the A site, leaving P site with empty tRNA
  • ribosome translocates the tRNA from A site to P site. Empty tRNA from P site is moved to E site where it is released
  • this is all using GTP
56
Q

Termination of Transcription

A
  • Ribosome reaches stop codon, A site accepts a “release factor”
  • Release factor promotes hydrolysis/breaking the bond between tRNA in the P site and the last amino acid of the polypeptide chain
  • ribosome completely dissociates, polypeptide is released
57
Q

Is energy required for translation

A

yes, all using GTP. must be carefully monitored

BIO 1010 (2 decks)

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