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Genetics > Genetics Test 3 > Flashcards

Genetics Test 3 Flashcards

1
Q

What are the two specific steps in the expression of genetic information?

A

Transcription and Translation

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2
Q

How many RNA molecules are found in a ribosome?

A

3-5 molecules + 50-90 proteins

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3
Q

What are the RNA molecules that are translated on ribosomes?

A

mRNA or messenger RNA

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4
Q

What is the primary transcript in eukaryotes? (the product of transcription)

A

The primary transcript is usually equivalent to the mRNA molecule.
Therefore, mRNA

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5
Q

What is the primary transcript in eukaryotes? (the product of transcription)

A

pre-mRNA

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6
Q

What is an exon?

A

the expressed sequence of a gene

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6
Q

What are introns?

A

non coding sequences that separate the expressed sequences or “exons” of a gene

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7
Q

What are spliceosomes and what is their job?

A

They are a macromolecular structure which removes introns though a splicing reaction

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7
Q

What are the 5 types of RNA molecules?

A

tRNA (transfer RNA)
rRNA (ribosomal RNA)
snRNA (small nuclear RNA)
miRNA (micro RNA)
mRNA (messenger RNA)

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8
Q

What do mRNA do?

A

They carry genetic information from DNA to the ribosomes where proteins are synthesised.

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9
Q

What are tRNA and what do they do?

A

They are small RNA molecules that function as adaptors between amino acids and codons in mRNA during translation

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10
Q

What are snRNA and what do they do?

A

They are structural components of spliceosomes

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10
Q

What are rRNA and what do they do?

A

They are structural and catalytic components of ribosomes
They are the intricate machines that translate nucleotide sequences of mRNAs into amino acid sequences of polypeptides

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11
Q

What are miRNA and what do they do?

A

They are short single stranded RNAs that block the expression of complementary or partially complementary mRNAs by either causing their degredation or repressing their translation.

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12
Q

When are all of the different RNAs made?

A

Transcription

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13
Q

What are the final products of the RNAs

A

mRNA specifies for nucleotides
They other RNAs produce RNA molecules

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14
Q

Which of the RNA molecules are not translated?

A

tRNA
rRNA
snRNA
miRNA

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15
Q

What does the central dogma explain?

A

Genetic information flows from DNA to DNA during chromosome replication
From DNA to RNA during transcription
RNA to protein during translation

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16
Q

What happens during transcription

A

the synthesis of an RNA transcript complementary to one strand of DNA of a gene

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17
Q

What happens during translation

A

the conversion of information stored in the sequence of nucleotides in the RNA transcript into the sequence of amino acids in the polypeptide gene product

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18
Q

RNA synthesis is the same as DNA however, what are the 3 differences

A
  1. Ribonuclease Triphosphate in stead of Deoxtribonucleoside Triphosphates
  2. Only 1 strand of DNA is used as a template

3.RNA strands can be initiated de novo (no primer needed)

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19
Q

How will the RNA molecule that is produced during RNA synthesis be compared to the DNA template strand?

A

complementary and antiparallel

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20
Q

How will the RNA molecule that is produced during RNA synthesis be compared to the DNA nontemplate strand?

A

Identical except for the U replacing the T

21
Q

What is mRNA and what is another name for it

A

A coding strands of RNA
Also known as sense strands

22
Q

What is a sense strand

A

the strand of sense RNA where the nucleotide sequences specify the sequences of amino acids in the protein gene

23
Q

What is the antisense RNA

A

an RNA molecule that is complementary to an mRNA

24
Q

Where does RNA synthesis takes place?

A

Takes place within a locally unwound segment of DNA, sometimes called a transcription bubble

24
Q

In what direction does the synthesis of RNA occur

A

5’ to 3’ with the addition of ribonucleotides to the 3’ OH at the end of the chain

25
Q

What produces a transcription bubble?

A

RNA polymerase

26
Q

In eukaryotes, where are genes found?

A

The nucleus

27
Q

In eukaryotes, where are polypeptides synthesized.

A

The cytoplasm

28
Q

What is the job of mRNA?

A

Messenger RNA molecules function as intermediaries that carry genetic information from DNA to the ribosomes, where proteins are synthesized.

29
Q

In RNA synthesis, how many strands of DNA are used as a template for RNA synthesis?

A

Only one strand of DNA functions as a template for RNA synthesis

30
Q

What is a transcription unit?

A

A segment of DNA that is transcribed to produce one RNA molecule

31
Q

The complete RNA polymerase molecule, the holoenzyme, has the composition α2ββ′σ, what do each represent/do?

A

α = subunits participate in the assembly of the tetrameric core (α2ββ′) of RNA polymerase.

Β = subunit contains the ribonucleoside triphosphate binding site

β′ = subunit harbors the DNA template-binding region

σ = is involved only in the initiation of transcription; it plays no role in chain elongation

32
Q

What is the function of sigma?

A

To recognize and bind RNA polymerase to the transcription initiation or promoter sites in DNA.

33
Q

What is the difference in function between the core enzyme and the holoenzyme?

A

The core enzyme (with no σ) will catalyze RNA synthesis from DNA templates, and it will initiate RNA chains at random sites on both strands of DNA.

The holoenzyme (σ present) initiates RNA chains in vitro only at sites used in vivo.

34
Q

The initiation of RNA chains in prokaryote transcription occur in what three steps?

A
  1. Binding of the RNA polymerase holoenzyme to a promoter region in DNA
  2. The localized unwinding of the two strands of DNA by RNA polymerase, providing a template strand free to base-pair with incoming ribonucleotides.
  3. The formation of phosphodiester bonds between the first few ribonucleotides in the nascent RNA chain
35
Q

During the initiation process, what does the holoenzyme do and what transition occurs halfway through the process?

A

The holoenzyme remains bound at the promoter region during the synthesis of the first eight or nine bonds; then the sigma factor is released, and the core enzyme begins the elongation phase of RNA synthesis.

36
Q

What happens to nucleotides in the initiation process in prokaryotes? When does it stop?

A

During initiation, short chains of two to nine ribonucleotides are synthesized and released.

This abortive synthesis stops once chains of 10 or more ribonucleotides have been synthesized and RNA polymerase has begun to move downstream from the promoter.

37
Q

What nucleotides are given a (+1)

A

The nucleotide pair corresponding to the first (5′) nucleotide of the RNA transcript.

38
Q

What base pairs are given a (-) prefix?

A

Base pairs preceding the initiation site.

39
Q

What base pairs are given a (+) prefix?

A

Those following the initiation site are given plus (+) prefixes.
(relative to the direction of transcription)

40
Q

What is the difference between upstream sequences and downstream sequences?

A

Nucleotide sequences preceding the initiation site are referred to as upstream sequences.

Those following the initiation site are called downstream sequences.

41
Q

What is considered the midpoint in prokaryotic transcription? (HINT: nucleotide base pairs)

A

At about 10 and 35 nucleotide pairs before the transcription initiation site.

42
Q

What makes up the recognition sequence in prokaryotic transcription (initiation)?

A

The sigma subunit initially recognizes and binds to the −35 sequence

43
Q

The elongation of RNA chains in prokaryotic transcription is sped up when?

A

Elongation of RNA chains is catalyzed by the RNA polymerase core enzyme, after the release of the σ subunit.

44
Q

Where does the covalent extension of RNA chains take place in prokaryotic transcription?

A

The covalent extension of RNA chains takes place within the transcription bubble, a locally unwound segment of DNA.

45
Q

What is RNA polymerase capable of doing in prokaryotic transcription?

A

Contains both DNA unwinding and DNA rewinding activities.

46
Q

How is the stability of the transcription complex maintained in prokaryotic transcription?

A

Primarily by the binding of the DNA and the growing RNA chain to RNA polymerase

47
Q

How is the termination of RNA chains reached in prokaryotic transcription?

A

Termination of RNA chains occurs when RNA polymerase encounters a termination signal. (six A’s)

48
Q

Where is RNA synthesized in eukaryotes?

A

RNA is synthesized in the nucleus, and most RNAs that encode proteins must be transported to the cytoplasm for translation on ribosomes.

49
Q

In eukaryotes, the majority of the primary transcripts of genes that encode polypeptides undergo three major modifications prior to their transport to the cytoplasm for translation, what are they?

A
  1. 7-Methyl guanosine caps are added to the 5′ ends 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.
50
Q

What is the 5′ cap on most eukaryotic mRNAs?

A

A 7-methyl guanosine molecule joined to the initial nucleoside of the transcript by a 5′-5′ phosphate linkage.

51
Q

What do all eukaryotic RNA polymerases require in order to initiate the synthesis of RNA chains?

A

Proteins called transcription factors. A protein that regulates the transcription of genes.

52
Q

What transcribes the vast majority of eukaryotic genes?

A

RNA polymerase II

53
Q

How is each basal transcription factor denoted?

A

TFIIX (Transcription Factor X for RNA polymerase II, where X is a letter identifying the individual factor).

Genetics (9 decks)

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