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Genetics > Chapter 14 (Test 2 Study) > Flashcards

Chapter 14 (Test 2 Study) Flashcards

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Biology 101 flashcards
1
Q

What percentage of our genes is non-coding?

A

50%

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2
Q

What type of RNA codes for amino acids?

A

mRNA

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3
Q

What codes for a continuous sequence?

A

polypeptide chain

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4
Q

The number of nucleotides in the gene is proportional to the number of amino acids in the protein describes ______.

A

collinearity

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5
Q

Is the coding sequence in a gene always continuous?

A

No, coding sequences in a gene may be interrupted by noncoding regions.

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6
Q

An experiment was conducted when DNA and complementary RNA was mixed and then heated to separate the DNA strands. The mixture is then cooled and complementary sequences pair. From this, DNA may reanneal with its complementary strand or with RNA. The noncoding regions can be found in the loops of RNA.

What does this experiment determine?

A

It determines that coding sequences in a gene may be interrupted by noncoding regions.

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7
Q

Does the flow of genetic information follow the principle of collinearity?

A

No, not all mRNA sequences code for amino acids. Collinearity means all is coded.

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8
Q

Which gene structures are more complex: Eukaryotes or prokaryotes?

A

eukaryotes

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9
Q

How are introns removed from RNA after transcription?

A

splicing

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10
Q

At what point are introns removed?

A

After transcription during pre-mRNA and before translation.

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11
Q

Where are introns uncommonly found?

A

bacteria

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12
Q

Does the size of introns vary?

A

Yes, from gene to gene.

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13
Q

What type of genes do introns contain?

A

non-coding genes

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14
Q

Which processes occur in the nucleus and which occur in the cytoplasm?

A

nucleus: [DNA > translation > pre-mRNA > splicing]; cytoplasm: [mature RNA > translation > amino acids]

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15
Q

What are the major types of introns? Which type of organisms are each of these intron genes found in?

A

Group I (genes in bacteria, bacteriophages, and eukaryotes)
Group II (genes in bacteria, archaea, and eukaryotes)
Nuclear pre-mRNA (protein-encoding genes, nucleus of eukaryotes)
tRNA (genes in bacteria, archaea, and eukaryotes)

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16
Q

Which splicing mechanism corresponds to each major type of introns?

A

Group I: self-splicing (no-splicing mechanism)
Group II: self-splicing (no-splicing mechanism)
Nuclear pre-mRNA: spliceosomal
tRNA: enzymatic

** A RNA molecule speeding up own splicing would be considered enzyme activity **

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17
Q

True or False: Genes include DNA sequences that code for all exons and introns.

A

True

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18
Q

Which sequences of RNA are not translated into a protein? What is considered the entire transcription unit?

A

The beginning and end of the RNA

promoter, RNA coding sequence, and terminator

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19
Q

Which regions protect the coding region from degradation?

A

The 5’ UTR and 3’ UTR (untranslated region)

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20
Q

In (eukaryotic/prokaryotic) the _____________ sequence is where the ribosome starts. Where is this found in relation to mRNA protein-coding region?

A

prokaryotic; Shine-Dalgarno

It is found a few sequences upstream of the protein coding region—to the left of the start codon.

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21
Q

Which part of mRNA initiates the first amino acid assembly?

A

the start codon

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22
Q

Even though the 5’ and 3’ UTR do not encode any amino acids, what other important information do they contain?

A

RNA stability and regulation of translation

23
Q

In pre-mRNA, certain modification will be made. What are the four main modifications? Provide a short description of each of their functions?

A

Addition of 5’ cap: a G (guanine) that helps the binding of ribosome to 5’ end, prevents degredations, adds stability. AKA 7mG.

3’ cleavage and addition of ploy(A) tail: a string of adenines “poly(A)”, length can increase and decrease, helps binding of ribosome to mRNA.

RNA splicing: removes introns from pre-mRNA, exports mRNA to cytoplasm.

RNA editing: alters nucleotide sequence of mRNA.

24
Q

Most eukaryotic mRNAs have a 5’ cap. The cap consists of a nucleotide with ____________ attached to the pre-mRNA by a unique __-__ bond.

A

7-methylguanine; 5’-5’ bond

25
Q

Describe the process of 5’ capping in eukaryotic messages. At the end, study the figure.

A
  1. One of the three phosphate groups at the 5’ end of the mRNA is removed.
  2. Then, a guanine nucleotide (w/ its phosphate group) is added.
  3. Methyl groups are added to position 7 at the base of the terminal guanine nucleotide.
  4. Methyl groups are also added to the 2’ position of the sugar in the 2nd and 3rd nucleotides.
  5. The base on the initial nucleotide also may be methylated.
26
Q

Which eukaryotic RNA polymerase is involved in mRNA synthesis/transcription?

A

RNA polymerase II

27
Q

During the creation of the 3’ poly(A) tail, after cleavage, what process occurs which is the addition of adenine nucleotides which ultimately generates the 3’ poly(A) tail?

A

polyadenylation (“many A’s”)

28
Q

The protein that adds the 5’ cap is associated with what RNA polymerase?

A

RNA polymerase II, the protein is absent from RNA polymerases I and III which transcribe rRNAs and tRNAs.

29
Q

Where are consensus sequences located?

A

They are found in exon/intron junctions.

30
Q

What is the role of a spliceosome? What components does it consist of?

A

The spliceosome is involved in splicing. It consists of 5 RNA molecules + 300 proteins (massive machine).

31
Q

Which of these starts the 5’ consensus sequence?

CAAG or GU A/G AGU

A

GU A/G AGU

32
Q

Splicing of nuclear pre-mRNA introns is a two step process. What is the first step?

A

The 5’ end of the intron is cleaved from the upstream exon and attached to the branch point to form a lariat.

33
Q

During splicing, what happen after the 5’ end is cleaved and a lariat is formed?

A

The 3’ end of the intron is cleaved from the downstream exon, and the ends of the two exons are spliced together.

34
Q

Where does the splicing process take place within the nucleus?

A

Within the spliceosome

35
Q

What are the names of each RNA molecule that makes up a spliceosome?

A

U1, U2, U4, U5, U6
**No U3

36
Q

Which RNA molecule in a spliceosome attaches to the branch point and which attaches to the 5’ splice site? After a complex joins the spliceosome, which RNA molecules are released?

A

branch point: U2
5’ splice site: U1

molecules released: U1 and U4

37
Q

Complex intron structures help ____ continue reactions?

A

enzymes

38
Q

During alternative splicing and multiple 3’ cleavage sites splicing, there are two different outcomes. What are these two outcomes, each

A

alternative splicing: Either two introns are removed to yield one mRNA or two introns and exon 2 are removed to yield a different mRNA.

multiple 3’ cleavage sites: mRNA products of different lengths are produced after splicing.

39
Q

What part of RNA processing includes the addition, deletion, or alteration of bases?

A

RNA editing

40
Q

What does the guide RNA do?

A

It adds nucleotides to the mRNA that were not encoded by the DNA.

41
Q

When is mature eukaryotic mRNA finally created?

A

When pre-mRNA is transcribed and undergoes several types of processing.

42
Q

What do all tRNAs have in common?

A

a cloverleaf secondary structure

43
Q

What are the two rare modified RNA nucleotide bases?

A

ribothymine and pseudouridine

44
Q

Name some things that tRNA processing may include.

A

splicing, base addition, and base modification

45
Q

What are the two main structures of the ribosome and what are they specified as?

A

The large ribosome subunit: two parts
The small ribosome subunit: RNA-protein complex

46
Q

What is the ribosome size of bacterial cells and eukaryotic cells? What about their respective subunits?

A

Bacterial: 70S (Large 50S, Small 30S)
Eukaryotic: 80S (Large 60S, Small 40S)

47
Q

In bacterial vs eukaryotic ribosomes, what is the respective rRNA component size for each large and small subunit?

A

Bacterial: Large -> 23S rRNA / Small -> 16S rRNA
Eukaryotic: Large -> 28S rRNA / Small -> 18S rRNA

48
Q

What is the name of the complex where one strand of miRNA is combined with proteins? What does this complex further pair with to inhibit translation?

A

RISC complex, RNA-induced Silencing Complex

pairs with an mRNA

49
Q

_______ limits the invasion of foreign genes and censors the expression of their own genes.

A

RNA interference

50
Q

What are the two types of RNA that are produced from double-stranded RNA?

A

small interfering RNAs (siRNA) and microRNA

51
Q

What is the purpose of a dicer in microRNAs?

A

It dices RNA into small chunks to where the RISC can further be created.

52
Q

What is considered the bacterial immune system, is not found in eukaryotes, and protects cells from invasions from bacteriophages and plasmids?

A

crisper RNA (crRNA)

53
Q

True or False: Long non-coding RNAs (lncRNA) are long RNA molecules that do not encode proteins and do not control gene expression.

A

False, even though lncRNA does not encode proteins, it still controls gene expression.

54
Q

True or False: U1-U6 are examples of snRNA.

A

True

Genetics (7 decks)

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