Chapter 4 - Protein Synthesis Flashcards

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1
Q

What is the genetic code?

A
  • The specific order of nitrogen bases
  • It is read by the cell and produces structural and functional proteins for use by the cell or the organism
  • organised into genes and codes for a specific protein
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2
Q

What is gene expression?

A

Reading one gene at a time. It is the process of using one genetic code to synthesise specific proteins.

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3
Q

How are genes bundled together in prokaryotic cells and eukaryotic cells?

A

Prokaryotic cells - single circular chromosome
Eukaryotic cell - multiple linear chromosome

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4
Q

What are the 3 stages of gene expression/protein synthesis?

A
  • Transcription
  • mRNA processing
  • Translation
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5
Q

What is transcription?

A

the process of synthesising a strand of mRNA that is complementary to the DNA base sequence of the gene being read

(makes a copy of a specific gene)

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6
Q

Where does trandcription occur?

A

inside the nucleus before the mRNA leaves the nucleus

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7
Q

What is the promoter region?

A
  • Indicates the location on chromosome where gene starts
  • not transcribed
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8
Q

What is the template strand?

A
  • Strand of the DNA that is transcribed
  • All thymine bases will be replaced with uracil
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9
Q

What are the 3 stages of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination
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10
Q

What is transcription initiation?

A
  • Transcription factors (proteins) bind to the promoter region. This helps RNA polymerase bind to the DNA
  • RNA polymerase unwinds the DNA by breaking hydrogen bonds
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11
Q

What is transcription elongation?

A
  • RNA polymerase adds complementary nucleotides to the DNA
  • Occurs from 5’ to 3’ direction
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12
Q

What is transcription termination?

A
  • RNA polymerase is released
  • 2 strands of the DNA reanneal
  • Single strand of the RNA peels off the DNA
  • the RNA becomes the primary RNA transcript
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13
Q

What is mRNA processing?

A

The primary RNA transcript is processed in the nucleus. It is modified in three ways before it leaves the nucleus.

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14
Q

What are the 3 ways the RNA is modified in?

A
  1. Caps and Tails
  2. Splicing the gene
  3. Reading the genetic code
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15
Q

What is caps and tails?

A

5’ cap - a modified guanine nucleotide is added to 5’ end.

Poly-A tail - once the whole transcript has peeled f=off the DNA, 50-250 adenine nucleotides are added to 3’ end of RNA

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16
Q

What types of sequence is the gene made up from?

A

Introns and exons

17
Q

What are introns?

A

non-coding regions that do not contribute to building proteins

18
Q

What are exons?

A

it is made up of coding sequences. genetic code within exons builds polypeptide.

19
Q

What is splicing the gene?

A

A complex of proteins and RNA molecules cut out all introns and stick the exons back together into a single mRNA sequence

20
Q

What is the reading the genetic code?

A
  • reading the gene in sets of three bases.
    Triplet codes - codons (codes for a specific amino acid)
21
Q

What are stop codons?

A

Found at the end of the mRNA sequence
UAA, UAG, UGA

22
Q

What are start codons?

A

AUG - codes for methionin (MET)

23
Q

What happens before translation?

A

Mature mRNA moves out of the nucleus and into the cytoplasm

24
Q

What is translation?

A

The process of building a polypeptide chain using the mRNA as instructions

24
Q

Where does translation occur?

A

Occurs in the ribosome

25
Q

What are ribosomes made from

A

small and large subunit made from proteins and rRNA

26
Q

What are the 3 stages of translation?

A
  1. Initiation
  2. Elongation
  3. Termination
27
Q

What is translation initiation?

A
  • Small ribosomal subunit binds to 5’ of mRNA and moves to start codon
  • A tRNA binds to mRNA
  • Large ribosomal subunit attaches to the complex
28
Q

What is translation elongation?

A
  • A tRNA molecules with an inticodon complementary to the next mRNA codon enters ribosome
  • Each tRNA carries the amino acid coded for by the codon
  • The two amino acids bond together and the first tRNA molecule is released to fetch more amino acid molecules
  • mRNA moves through ribosome
29
Q

What is translation termination?

A
  • Elongation continues until the stop codon moves through the chromosome
  • The polypeptide chain is released from the ribosome since the tRNA has a complementary anticodon
30
Q

What is an anticodon?

A

The triplet code found on tRNA that is complementary to mRNA sequence

31
Q

What is the coding region?

A

The section of the gene that is used to build the polypeptide chain

32
Q

What is a codon?

A

Three RNA bases in a row that code for a specific amino acid