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BIOL 2050 (Genetics) > Genetic Exams Review > Flashcards

Genetic Exams Review Flashcards

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1
Q

What are the three basic stages of transcription

A

1) Initiation
2) Elongation
3) Termination

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2
Q

Describe what takes place in Initiation

A

Initiation is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter

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3
Q

Describe what takes place in Elongation

A

The DNA is threaded through RNA polymerase, and the polymerase unwinds the DNA and adds new nucleotides, one at a time, to the 3’ end of the growing RNA strand

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4
Q

Describe what takes place in Termination

A

is the ending of transcription, and occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA.

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5
Q

How are transcription and replication similar?

A

Both involve in the generation of a new copy of the DNA in a cell.

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6
Q

What does DNA transcription replicate DNA into?

A

RNA

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7
Q

What does DNA replication DNA into?

A

Another copy of DNA

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8
Q

How are transcription and replication different?

A
  • DNA replication is the process of making two daughter strand where each daughter strand contains half of the original DNA double helix.
  • Transcription is the process of synthesis of RNA using DNA as a template.
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9
Q

Where is the 5’ cap added and what does it do?

A

The 5’ cap is added to the first nucleotide in the transcript during transcription. The cap is a modified guanine (G) nucleotide, and it protects the transcript from being broken down. It also helps the ribosome attach to the mRNA and start reading it to make a protein.

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10
Q

What are the three main modifications to the eukaryotic mRNA?

A

1) 5’ cap
2) poly (A) Tail
3) RNA Splicing

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11
Q

Where is the poly (A) tail added and what is it function?

A

It attaches to the 3’ end and it makes the RNA molecule more stable and prevents its degradation. Additionally, the poly-A tail allows the mature messenger RNA molecule to be exported from the nucleus and translated into a protein by ribosomes in the cytoplasm.

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12
Q

What similarity’s do the 5’ cap and poly (A) tail share?

A

Both the cap and the tail protect the transcript and help it get exported from the nucleus and translated on the ribosomes (protein-making “machines”)

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13
Q

What is the function of the spliceosome?

A

The spliceosome removes introns from a transcribed pre-mRNA, a type of primary transcript.

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14
Q

What is a spliceosome and how is it assembled?

A

a large and complex molecular machine found primarily within the nucleus of eukaryotic cells. The spliceosome is assembled from small nuclear RNAs and approximately 80 proteins.

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15
Q

What is alternative splicing?

A

Alternative splicing is the process of selecting different combinations of splice sites within a messenger RNA precursor (pre-mRNA) to produce variably spliced mRNAs.

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16
Q

How does alternative splicing lead to the production of multiple proteins from a single gene?

A

In splicing, some sections of the RNA transcript (introns) are removed, and the remaining sections (exons) are stuck back together.
Some genes can be alternatively spliced, leading to the production of different mature mRNA molecules from the same initial transcript.

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17
Q

Summary: different types of processing that can take place in pre-mRNA

A
  • Addition of the 5′ cap to the 5′end of the pre-mRNA
  • cleavage of the 3′ end of a site downstream of the AAUAAA consensus sequence of the last exon
  • addition of the poly(A) tail to the 3′ end of the mRNA immediately after cleavage
  • removal of the introns (splicing)
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18
Q

Describe the structure of tRNA?

A
  • a distinctive folded structure with three hairpin loops that form the shape of a three-leafed clover.
  • One of these hairpin loops contains a sequence called the anticodon, which can recognize and decode an mRNA codon.
  • Each tRNA has its corresponding amino acid attached to its end.
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19
Q

What is the E site?

A
  • The E site is where a tRNA goes after it is empty, meaning that is has transferred its polypeptide to another tRNA (which now occupies the P site)
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20
Q

What is the P site?

A
  • The P site holds a tRNA that carries a growing polypeptide (the first amino acid added is methionine-Met)
21
Q

What is the A site?

A
  • The A site accepts incoming tRNA bound to an amino acid
22
Q

What is a missense mutation?

A

A genetic alteration in which a single base pair substitution alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position.

23
Q

What is a nonsense mutation?

A

the substitution of a single base pair that leads to the appearance of a stop codon where previously there was a codon specifying an amino acid.

24
Q

What is the difference between a missense mutation and a nonsense mutation?

A
  • Nonsense mutation: changes an amino acid to a STOP codon, resulting in premature termination of translation.
  • Missense mutation: changes an amino acid to another amino acid.
25
Q

what is a silent mutation?

A

its a mutation that does not cause a significant change in the amino acid. As a result, the protein is still functional because the changes are regarded as though they are evolutionarily neutral.

26
Q

What is a neutral mutation?

A

Neutral mutations are changes in DNA sequence that are neither beneficial nor detrimental to the ability of an organism to survive and reproduce.

27
Q

What is the difference between neutral mutation and silent mutation?

A

silent mutation is a specific type of neutral mutation that does not have an observable effect on the organism’s phenotype while neutral mutation is a change in the DNA sequence that is neither beneficial nor harmful to the ability of an organism to survive and reproduce.

28
Q

What is the wobble hypothesis?

A

A wobble base pair is a pairing between two nucleotides in RNA molecules that does not follow Watson-Crick base pair rules.

29
Q

What is a operon?

A

an operon is a segment of DNA containing adjacent genes including structural genes, an operator gene, and a regulatory gene. An operon is thus a functional unit of transcription and genetic regulation.

30
Q

What are the three broad levels of regulating gene expressions?

A
  • transcriptional control (whether and how much a gene is transcribed into mRNA)
  • translational control (whether and how much an mRNA is translated into protein)
  • post-translational control (whether the protein is in an active or inactive form, and whether the protein is stable or degraded)
31
Q

What are the three structural genes?

A

1) Lac Z
2) Lac Y
3) Lac A

32
Q

What does Lac Z do?

A

codes for β-galactosidase, which acts to cleave lactose into galactose and glucose

33
Q

What does Lac Y do?

A

Codes for lac permease, which is a transmembrane protein necessary for lactose uptake

34
Q

What does Lac A do?

A

Codes for a transacetylase that transfers an acetyl group from coenzyme A (CoA) to the hydroxyl group of galactosidase.

35
Q

What happens in the presence of lactose?

A

When lactose is present, the lac repressor loses its DNA-binding ability. This clears the way for RNA polymerase to bind to the promoter and transcribe the lac operon.

36
Q

What happens in the absences of lactose

A

When lactose is absent, the lac repressor binds tightly to the operator. It gets in RNA polymerase’s way, preventing transcription.

37
Q

What happens when mutations occur?

A

When a gene mutation occurs, the nucleotides are in the wrong order which means the coded instructions are wrong and faulty proteins are made or control switches are changed.

38
Q

Gel electrophoresis what is it used for?

A

a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size.

39
Q

Where does the DNA fragment migrate when the electric current is applied? What happens if the strands are short?

A
  • DNA is negatively charged, therefore, when an electric current is applied to the gel, DNA will migrate towards the positively charged electrode.
  • Shorter strands of DNA move more quickly through the gel than longer strands resulting in the fragments being arranged in order of size.
40
Q

What is PCR used for?

A

the polymerase chain reaction (PCR) is a fast and inexpensive technique used to “amplify” - copy - small segments of DNA.

41
Q

What are the three steps of PCR?

A

(1) denaturation of the template into single strands
(2) annealing of primers to each original strand for new strand synthesis
(3) extension of the new DNA strands from the primers.

42
Q

What is CRISPR-CAS9 used for?

A

unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.

43
Q

What are the problems associated with CRISPR DNA Editing?

A

There are certain problems with CRISPR such as unwanted off-target mutations. It works by cutting the double-stranded DNA at precise locations in the genome. When the cell’s natural repair process takes over, it can cause damage

44
Q

What are the differences between Purines and Pyrimidines?

A
  • purines in DNA are adenine and guanine, the same as in RNA.
  • The pyrimidines in DNA are cytosine and thymine; in RNA, they are cytosine and uracil.
  • Purines are larger than pyrimidines because they have a two-ring structure while pyrimidines only have a single ring.
45
Q

What are the two major differences between DNA and RNA?

A
  • The major difference between DNA and RNA is that DNA is double-stranded and RNA is single-stranded.
  • DNA is responsible for genetic information transmission, whereas RNA transmits genetic codes that are necessary for protein creation.
46
Q

What are the three main classes of RNA?

A

1) mRNA
2) tRNA
3) rRNA

47
Q

What is the function of mRNA?

A

carries genetic code from DNA in a cell’s nucleus to ribosomes,

48
Q

What are the functions of rRNA and tRNA? What are additional RNA’s involved in?

A
  • rRNA and tRNA are involved in protein synthesis.

- Additional RNAs are involved in gene regulation and mRNA degradation.

49
Q

What are the enzymes associated with initiation, unwinding, elongation and termination + a brief description of their function?

A
  • Helicase (unwinds the DNA double helix)
  • Gyrase (relieves the buildup of torque during unwinding)
  • Primase (lays down RNA primers)
  • DNA polymerase III (main DNA synthesis enzyme)
  • DNA polymerase I (replaces RNA primers with DNA)
    Ligase (fills in the gaps)

BIOL 2050 (Genetics) (4 decks)

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