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Anatomy 203 > RNA and protein > Flashcards

RNA and protein Flashcards

1
Q

What is the central dogma of biology?

A

*Central dogma is a process of molecular biology that transfers genetic information from DNA to RNA and produces a functional protein product.

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2
Q

What does the central dogma process explain?

A

The central dogma process explains the transformation of the genetic information called DNA replication, RNA encoding by transcription, and encoding for protein through translation.

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3
Q

What is a ribonucleic acid? State how different it is from DNA.

A

Ribonucleic acid (RNA) is a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself.

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4
Q

RNA structure : What does each nucleotide in RNA contain?

A

Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1’ through 5’.

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5
Q

RNA structure : What is a base attached to?

A

A base is attached to the 1’ position, in general, adenine (A), cytosine (C), guanine (G), or uracil (U).

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6
Q

RNA structure :

State which bases are purines and pyrimidines.

A

Purines (A and G) and pyrimidines (C and U).

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7
Q

RNA structure : What is a phosphate group attached to?

A

A phosphate group is attached to the 3’ position of one ribose and the 5’ position of the next.

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8
Q

RNA structure : When do the phosphate groups have a negative charge?

A

Phosphate groups have a negative charge at physiological pH, making RNA a charged molecule (polyanion).

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9
Q

RNA structure : How is RNA distinguished from DNA?

A

RNA is distinguished from DNA due presence of a hydroxyl group at the 2’ position of the ribose sugar.

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10
Q

RNA structure : What does the presence of the hydroxyl group cause?

A

The presence of this functional group causes the RNA helix to adopt the A-form geometry rather than the B-form most commonly observed in DNA.

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11
Q

RNA structure : What is the second consequence of the presence of the hydroxyl group?

A

A second consequence of the presence of the 2’-hydroxyl group that is not involved in formation of a double helix can chemically attack the adjacent phosphodiester bond to cleave the backbone.

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12
Q

Types of RNA molecules : What is Messenger RNA[mRNA]?

A

Messenger RNA (mRNA) is the RNA that carries genetic information from DNA to the ribosome, the site of protein synthesis (translation), in the cytoplasm.

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13
Q

Types of RNA molecules : What is the coding sequence of the mRNA?

A

*The coding sequence of the mRNA determines the amino acid sequence in the protein molecule that is produced.

However, many RNAs do not code for protein, about 97% of the transcriptional output is non-protein-coding in eukaryotes.

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14
Q

Types of RNA molecules : What are these so-called non-coding RNAs encoded by?

A

These so-called non-coding RNAs (ncRNA) can be encoded by their own genes (RNA genes), but can also be derived from mRNA introns.

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15
Q

Types of RNA molecules : What is the most prominent examples of non-coding RNAs?

A

The most prominent examples of non-coding RNAs are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation.

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16
Q

Types of RNA molecules : What non-coding RNAs also involved in?

A

There are also non-coding RNAs involved in gene regulation, RNA processing and other roles.

17
Q

Types of RNA molecules : What are certain RNAs capable of?

A

Certain RNAs are capable to act as enzymes; these are known as ribozymes.

18
Q

Transcription occurs in 3 steps :

A

Initiation, Elongation and Termination

19
Q

Transcription - Initiation[1-2] :

A
  1. RNA polymerase binds to the promoter region of DNA near beginning of each gene, separate the double helix near the promoter.
  2. RNA polymerase is the enzyme responsible for making mRNA copies of genes. DNA unzips at the site of the gene that is needed.
20
Q

Transcription - Elongation[1-3] :

A
  1. RNA polymerase travels along the DNA template strand, catalyzing the addition of ribose nucleotide into an RNA molecule.
  2. RNA nucleotide into an RNA are complementary to the template strand of the DNA.
  3. RNA polymerase matches bases in the sense strand with RNA bases, building a strand of mRNA that carries the information encoded in the DNA.
21
Q

Transcription - Termination[1-3] :

A
  1. Encoded in DNA is the sequence know as terminator, that tells RNA polymerase where to stop.
  2. Transcription ends at the end of a gene when RNA polymerase encounters a sequence of DNA called a termination signal.
  3. RNA polymerase detaches from the DNA and releases the RNA molecule.
22
Q

Transcription - Conclusion[1-3] :

A
  1. After termination, the DNA completely rewinds into a double helix.
  2. RNA polymerase may move to another gene and begin transcription.
  3. The newly synthesized mRNA molecule is called pre-mRNA to move from the nucleus to the cytoplasm for protein translation.
23
Q

Transcription and RNA processing in Eukaryotes :

A
  1. 7-Methyl guanosine caps are added to the 5’ end of the primary transcripts.
  2. Poly(A) tails are added to the 3’ ends of the transcripts, which are generated by cleavage rather than by termination of chain extension.
  3. When present, intron sequences are spliced out of transcripts.
    * Following mRNA processing the mRNA is then exported to the cytoplasm for protein synthesis.
24
Q

Translation occurs in 3 steps :

A

Initiation, Elongation and Termination

25
Q

Translation involves three types of RNA, all of which are transcribed from DNA templates:

A
  1. mRNA molecule to provide specifications for each polypeptide.
  2. A total of 3 - 5 ribosomal RNA (rRNA) molecules, which are present as part of the structure of each ribosome.
  3. 40 - 60 small transfer RNA (tRNA) molecules that function as adaptors by mediating the incorporation of the proper amino acids into polypeptides in response to specific nucleotide sequences in mRNA.
26
Q

Components required for protein synthesis : Describe Ribosomes.

A

Ribosomes are approximately half protein and half RNA and composed of two subunits (large and small one)

27
Q

Translation - Initiation[1-2] :

A
  1. Initiation begins with a tRNA bearing methionine (met) amino acid attaching to small ribosomal subunit, forming an initiation complex.
  2. The codon for methionine is a universal “start” codon for “reading” the mRNA strand.
28
Q

Translation - Initiation[3-4] :

A
  1. The initiation complex binds to an mRNA molecule where the codon for met is located (AUG).
  2. The Methionine (Met) tRNA anticodon (UAC) base pair with the “start” codon (AUG) on mRNA.
29
Q

Translation - Initiation[5-7] :

A
  1. The larger ribosomal subunit now binds to the smaller unit, forming a ribosomal complex.
  2. The Methionine tRNA binds to the first tRNA active (binding) site on the ribosome.
  3. Translation may now begin.
30
Q

Translation - Elongation[1-2] :

A
  1. The second codon in mRNA (GUU) matches the anticodon of a tRNA carrying the amino acid Valine (CAA).
  2. The second tRNA binds to the second active site on the larger subunit.
31
Q

Translation - Elongation[3-4] :

A
  1. A catalytic site on the larger subunit catalyzes the formation of a peptide bond linking the amino acids Methionine and Valine.
  2. The two amino acids are now attached to the tRNA in the second binding position.
32
Q

Translation - Elongation[5-6] :

A
  1. The first tRNA now detaches and goes of to find another met in the cytoplasm.
  2. The mRNA chain shifts over one codon, placing the third codon (CAU) over the second active site.
33
Q

Translation - Elongation[7-8] :

A
  1. The third codon of mRNA (CAU) base-pairs with the anticodon carrying the amino acid histidine (His).
  2. This tRNA enters the second tRNA binding site on the large subunit.
34
Q

Translation - Elongation[9-11] :

A
  1. A new peptide bond forms between Val and His on the catalytic site.
  2. The tRNA that carried val will detach and find another Val in the cytoplasm.
  3. The mRNA strand will then shift over one more codon.
35
Q

Translation - Termination[1-2] :

A
  1. The process continues until the ribosome finds a “stop” codon.
  2. The subunits detach from one another, the mRNA is released,

Anatomy 203 (6 decks)

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