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General Biology I > Chapter 10: Gene expression > Flashcards

Chapter 10: Gene expression Flashcards

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1
Q

Gene expression is the process by which ____(1).

A

(1) DNA is transformed into protein

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2
Q

One gene encodes _____(1).

A

(1) one polypeptide

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3
Q

What is the central dogma of molecular biology?

A

The central dogma of molecular biology explains the flow of genetic information, from DNA to RNA, to make a functional product, a protein

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4
Q

Sickle cell anemia is caused by ___(1) in the gene coding for hemoglobin proteins.

A

(1) a mutation

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5
Q

Not all genes code for polypeptides. What else might they code for?

A

tRNA, mRNA, rRNA

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6
Q

Genes are expressed in two steps. What are these two steps in simple words

A
  1. Transcription: Information from a. DNA sequence is copied to a. complementrary RNA sequence
  2. Translation: Converts the RNA sequence to an amino acid sequence
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7
Q

Where does transcription, mRNA processing, and translation occur in a eukaryotic cell? What about in a prokaryote?

A

Eukaryote:
- Transcription and mRNA processing occur in the nucleus.
-Translation occurs in the cytosol

Prokaryotes:
- Transcription and translation occur at the same time in the cytosol
- THERE IS NO MRNA PROCESSING OR PRE MRNA in prokaryotes.

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8
Q

What does mRNA processing involve? To go from pre-mRNA to mature mRNA?

A

Introns spliced out of pre-mRNA; 5’ cap an 3’ poly A tail added to mRNA

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9
Q

What is the difference between introns and exons?

A

Exons are termed nucleic acid coding sequences, which are present in mRNA. Introns are the non-coding sequences present in the hnRNA, which are removed by RNA splicing before translation.

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10
Q

What is the purpose of the 5’ cap and poly A tail?

A

A 5’ cap(G cap) is added to the 5’ end. It facilitates binding to a ribosome and prevents digestion by ribonuclease(stabilizes mRNA).

A poly A tail is added to the 3’ end. It assists in export from the nucleus and contributes to the stability of the mRNA. It helps move mRNA from the nucleus to the cytoplasm

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11
Q

The mRNA that is produced from transcription looks most like the coding strand or the template strand?

A

It looks most like the coding strand, except that the T’s are replaced with U’s

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12
Q

Transcription of DNA in prokaryotes and eukaryotes produces ___(1).

A

(1) a single-stranded RNA molecule

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13
Q

When is DNA polymerase used vs RNA polymerase?

A

DNA polymerase is sued for DNA replication, while RNA polymerase is sued during transcription.

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14
Q

Transcription is DNA-Directed RNA synthesis. What does this mean?

A

DNA = template

RNA = product

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15
Q

What are the three steps that happen in transcription?

A
  1. Intiation: RNA polymerase binds to the promoter and starts unwind the DNA strands.
  2. Elongation: RNA polymerase moves along the DNA template strand from 3’ to 5’(so that it can be synthesized in the 5’ to 3’ direction). It produces the RNA transcript by adding nucleotides to the 3’ end of the growing RNA.
  3. Termnation: When RNA polymerase reaches the termination site, the RNA transcript is set free from the template.
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16
Q

what and where is the promoter?

A

The promoter is a region on the DNA where RNA polymerase binds. The promoter will not be transcribed as it is right in from of the area that is transcribed.

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17
Q

In DNA replication, a helices unwinds the DNA. What unwinds DNA in transcription?

A

RNA polymerase

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18
Q

Is energy required for transcription

A

Yes. When the nucleotides are added to the chain, 2 phosphate groups are added

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19
Q

The genetic code is universal except for a few exceptions. What are those exceptions?

A

Mitochondria, chloroplasts, and some protists

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20
Q

What is a missense mutation?

A
  • A point mutation
  • results in a codon that codes for a different amino acid
  • It is nonsynonymous
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21
Q

What is a silent mutation?

A
  • A point mutation that doesn’t lead to an amino acid change in the protein product
22
Q

What is a nonsense mutation?

A

A premature stop

23
Q

What is a frameshift mutation?

A

All amino acids changed beyond the point of insertion

24
Q

How does translation work?

A
  1. Each tRNA is loaded with the corresponding amino acid
  2. The ribosome attaches to an mRNA at its start codon
  3. The tRNAs deliver the correct amino acids in the correct order
  4. The ribosome reaches the stop codon and detaches from the mRNA
25
Q

Which part of the ribosome actually catalyzes the formation of peptide bonds?

A

Large subunit

26
Q

What causes the release factor to bind to the ribosome? What effect does this have?

A

The stop codon causes the release factor to bind to the ribosome. The whole polypeptide chain dissociates when the release factor binds. After that, the small and large subunit of the ribosome detaches and is reused.

27
Q

What are the three sites for tRNA?

A

tRNAs move through these sites (from A to P to E) as they deliver amino acids during translation

28
Q

Translation can be ramped up using polysomes. What are polysomes?

A

Multiple ribosomes move along a single mRNA

29
Q

Is mRNA short lived or long lived?

A

short lived

30
Q

What two things happen after translation?

A
  • Protein modification
  • Protein shipment
31
Q

What three things can happen in the post translational modification of proteins?

A
  1. Proteolysis: Chop proteins up into multiple proteins
  2. Glycosylation: Addigns sugars to a protein
  3. Phosphorylation: Addition of phosphate groups to a proteins
32
Q

How does the cell know where to send each protein?

A

The amino acid sequence contains an “address label” indicating where in the cell the polypeptide belongs. It gives one of two sets of instructions:

  1. Finish translation and be released to the cytoplasm
  2. Stall translation, go to the ER, and finish synthesis at the ER surface.

proteins produced in the rough ER are processed in the Golgi and then secreted. Proteins needed within the cell are produced but he ribosomes in the cytosol

33
Q

What are the four types of point mutations?

A
  1. Silent
  2. Missense
  3. Nonsense
  4. Frameshift
34
Q

What are the three ways to categorize mutations?

A
  1. Point mutations vs. chromosomal mutations
  2. Neutral, deleterious, and beneficial mutations
  3. Synonymous vs. non synonymous mutations
35
Q

What is a chromosomal mutation?

A

Chromosomal mutations involve changes in the number or structure of chromosomes. These mutations can change the location of genes on chromosomes and can even change the number of copies of some genes
- Involve large REGIONS of the chromosome

36
Q

Are pseudogenes expressed?

A

No

37
Q

What is a gene family?

A

Genes that are all descended from one gene, but all have new but similar functions

38
Q

Some genes have a twin, a second copy of the same gene nearby. Which type of mutation could result in a second copy of an existing gene?

A

Duplication

39
Q

Gene duplications may accumulate mutations and become __(1).

A

(1)pseudogenes

40
Q

What is a pseudogene?

A

Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, such as directly by gene duplication

41
Q

What is a neutral mutation?

A

No effect on phenotype

42
Q

What is a deleterious mutation?

A

Negative effect on phenotype

43
Q

What is a beneficial mutation?

A

Improve phentoype

44
Q

Most mutations are __(1). This is part of the _____(2) which says that a populations evolutionary changes in macromolecules results from __(1) mutations that accumulate through ___(3)

A

(1) neutral
(2) neutral theory of molecular evolution
(3) random genetic drift(the change in the frequency of an existing gene variant in a population due to random chance)

45
Q

Is a missense mutation neutral, deleterious, or beneficial? What about nonsense mutations?

A

Missense mutations can be neutral, beneficial, or deleterious.
Nonsense mutations are most likely to be deleterious

46
Q

What is a synonymous mutation?

A

a silent mutation, and neutral

a change in the DNA sequence that codes for amino acids in a protein sequence, but does not change the encoded amino acid.

47
Q

What is a non synonymous mutation?

A

a nucleotide mutation that alters the amino acid sequence of a protein.

48
Q

Synonymous and nonsynonymous mutations are ways to classify ___(1) mutations.

A

point

49
Q

True or false: nonsynonymous substitutions in the protein-coding sequence of a gene may result in deleterious, beneficial, or neutral mutations.

A

True

50
Q

The less the number of nonsynonymous mutation indicates what?

A

the less the number of nonsynonymous mutation indicates that the codon position is more likely to be critical for the proper functioning of that protein

51
Q

Name two reasons a nonsynonymous substitution in a protein-coding sequence might be a neutral mutation.

A
  1. Might change to a similar amino acid
  2. That amino acid portion might not be critical fro the proper functioning of a protein
52
Q
A

General Biology I (14 decks)

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