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BIOLOGY - Cliff > Molecular Genetics > Flashcards

Molecular Genetics Flashcards

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1
Q

What is the central dogma of molecular biology?

A

DNA –> RNA –> Proteins/enzymes –>Traits, metabolism, homeostasis

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2
Q

A nucleotide monomer is made up of….?

A

A nitrogenous base, a sugar, and a phosphate (DNA sugar: deoxyribose; RNA sugar: ribose)

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3
Q

RNA Nitrogenous bases

A

AUGC - Uracil instead of Thymine in DNA

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4
Q

DNA Nitrogenous bases

A

ATGC - Thymine instead of Uracil in RNA

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5
Q

What is the function of DNA?

A

Molecules of DNA contain chromosomes which bear the genetic information that is passed from parents to offspring

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6
Q

Who is credited for determining the structure of DNA?

A

Watson, Crick, Wilkins and Franklin

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7
Q

What did Hershey and Chase establish in their experiments?

A

DNA was the genetic material of phages (viruses that infect bacteria)

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8
Q

What did Microbiologist Frederick Griffith discover?

A

Essentially: Transformation (That genetic information can be transferred from dead bacteria to living bacteria)

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9
Q

DNA polymerase synthesizes in which direction?

A

From 5’ to 3’ on both leading and lagging strands. On lagging strand, moving away from overall direction of replication.

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10
Q

Describe 2 functions of DNA polymerase

A

Elongation & Proofreading

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11
Q

What is the function of DNA gyrase?

A

Also known as topoisomerase, break and rejoin the double helix, allowing the twists to unravel and preventing the formation of knots as helices unwinds the double helix

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12
Q

How do prokaryotic and eukaryotic chromosomes differ?

A

Prokaryotic chromosomes are circular, whereas eukaryotic chromosomes are linear with ends called telomeres

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13
Q

When replication reaches the end of the DNA strand, what are two problems that can occur?

A
  1. not enough template strand to which primate can attach
  2. empty space previously occupied by RNA primer will remain unfilled if no Okazaki fragment for DNA polymerase attachment
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14
Q

How are the problems at DNA replication alleviated and the loss of DNA prevented?

A

The enzyme telomerase extends the end of the template strand by adding repeating nucleotide sequences.

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15
Q

What is the purpose of tRNA’s anticodon?

A

The anti-codon of tRNA base pairs with the codon of mRNA during translation.

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16
Q

What is wobble pairing?

A

A relaxed base-pairing requirement that characterizes the relationship between the third nucleotide of tRNA’s anticodon, with the third nucleotide of mRNA’s codon. This allows allows the anticodon of some tRNAs to base pair with more than one kind of codon.

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17
Q

What does wobble pairing result in?

A

It results in 45 tRNA’s that are able to base pair with 61 codons that code for amino acids.

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18
Q

How are the activities of mRNA and tRNA coordinated?

A

By ribosomes, which have 2 subunits that are joined in the cytoplasm, but synthesized in the nucleolus.

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19
Q

How are ribosomes made?

A

rRNA is transcribed in the nucleolus, then proteins are imported from the cytoplasm to form a large and small subunit.

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20
Q

Mnemonic device for ribosomal subunits un eukaryotic and prokaryotic cells:

A

“You-cary b4 8, then PROceed at 5:37”
Eukaryotes: 60S, 40S, 80S
Prokaryotes: 50S, 30S, 70S

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21
Q

How does translation begin?

A

The first step is initiation in which RNA polymerase attaches to a promoter region on DNA and begins to unzip the double helix - this promoter region is usually referred to as the TATA box

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22
Q

Describe some similarities between RNA polymerase and DNA polymerase

A

Both participate in elongation ALONG the DNA template strand. For both enzymes, they elongate in the 5’ to 3’ direction.

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23
Q

What occurs after termination of transcription?

A

mRNA is processed before it leaves the nucleus. A 5’ cap is added (GTP) and this serves as an attachment point to the small subunit of the ribosome.

A poly-A tail (200 A nucleotides) is attached to the 3’ end of mRNA to provide stability and control movement across the nuclear envelope

24
Q

Describe RNA splicing that happens after termination of transcription

A

This is the process in which snRNP delete introns (intervening, noncoding sequences of transcribed DNA (or immature mRNA)…and splice exons

25
Q

How can different mRNA’s be generated from the same RNA transcript?

A

Alternative splicing allows selectively removing different parts of an RNA transcript, resulting in different mRNAs, which code for different protein products

26
Q

Briefly describe translation

A
  1. mRNA, tRNA, ribosomal subunits are transported across the nuclear envelope and into the cytoplasm
  2. tRNA brings an amino acid to the ribosome (that corresponds with its anticodon and the codon of the mRNA)
  3. Peptide bonds are formed between each AA as new ones are brought in by tRNA then tRNA is released
  4. This continues until a stop codon on the mRNA is reached then polypeptide is released
27
Q

What fuels the required energy for translation?

A

GTP

28
Q

What are the 3 ribosomal binding sites?

A 
A Site (acceptor, first binding site for tRNA)
P Site (Polypeptide site, second binding site, holds the tRNA with growing chain of AA)
E Site (exit, third binding site which holds the tRNA after it gives up its AA)
29
Q

What are common structures that make up a virus?

A

Nucleic Acid, Capsid/Protein coat, envelope*

*surrounds the capsid of SOME viruses

30
Q

How are viruses replicated?

A

Lytic Cycle (infect host cells to assemble new viruses - host cell is destroyed as new viruses erupt from it)

Lysogenic Cycle (viral DNA is temporary incorporated into DNA of the host cell and remains dormant (provirus or prophage) until some trigger causes the virus to begin lytic cycle

31
Q

How do retroviruses replicate?

A

Retroviruses are ssRNA viruses that use reverse transcriptase to make a DNA complement their RNA transcribed immediately to mRNA for the lytic cycle or can begin the lysogenic cycle.

32
Q

How do prokaryotes replicate?

A

Binary fission: chromosome replicates and the cell divides into two cells, each bearing one chromosome.

33
Q

How does the complexity vary between prokaryotic and eukaryotic replication?

A

Prokaryotic replication is less complex as prokaryotes lack a nucleus and specialized DNA. It also has only a single, circular DNA and no complex proteins.

34
Q

Describe plasmid and its function in a prokaryotic cell

A

Prokaryotes MAY contain plasmids which are short, circular dsDNA molecules OUTSIDE the chromosome. They carry genes that are beneficial but not essential for prokaryote survival (e.g. R plasmids).

35
Q

Do plasmids replicate together with chromosomes?

A

No, they replicate independently, and some plasmids can be incorporated into the chromosomes (episomes)

36
Q

T/F: A single prokaryotic mRNA transcript codes for one specific protein.

A

False. This transcript can contain multiple genes whose enzymes function sequentially as a part of a metabolic pathway.

37
Q

A single prokaryotic mRNA transcript can code for:

A

A closer of genes called operons.

38
Q

How is genetic variation introduced into prokaryotes?

A

Horizontal gene transfer

39
Q

What are the methods of horizontal gene transfer?

A

Transduction (Lytic Cycle)
Transformation (Lysogenic cycle)
Conjugation (Using Pili)

40
Q

Lysogenic Mnemonic

A

“Lyso Lucy” loosens up bacterial chromosome to make room for itself (incorporated by transformation)

41
Q

Transduction Mnemonic

A

“Transduction causes Destruction” as the host cell is used to make new viruses that cause lysis to the host cell as they erupt from it (Lytic Cycle)

42
Q

How is gene expression regulated in prokaryotes?

A

The operator regulates the promoter to prevent or allow transcription, by binding activators or repressors

43
Q

How is Lac Operon regulated (repressor)?

A

Lac Operon is inducible - this cluster of codes for the genes that metabolize Lactose. If lactose is present, it binds to the repressor gene and removes it to allow for transcription. There are low levels of gene expression here.

44
Q

Mnemonic for Lac Operon

A

“I’m Lac, I’ll take it back, like a cat, no cap - let’s break it down” Lactose binds to the repressor gene, taking it back (away) from the operator, allowing for transcription that will eventually break it down

45
Q

How is Trp Operon regulated (repressor)?

A

Trp Operon is repressible - this cluster codes for the genes that SYNTHESIZE Tryptophan. If Trp is present, it binds to the repressor, which bind to the operator to BLOCK transcription.

Note: Without Trp binding to the repressor, transcription proceeds like clockwork

46
Q

Mnemonic for Trp Operon

A

“Trip and get blocked; don’t trip and let’s rock-ana-roll!” The presence of Trp binds to the repressor, which will bind to the operator to block transcription.

47
Q

How is Lac Operon regulated (protein complexes)?

A

When glucose is low, cAMP is high (also meaning Lactose is available). cAMP binds with CAP and they bind to the promoter of Lac Operon. This is when Lac genes are strongly expressed. Lactose must be present

48
Q

How is Trp Operon regulated (attenuation)?

A

Transcription can be stopped by a stem loop when there are high levels of Trp. Alternatively, when Trp levels are low, an alternate stem loop (anti terminator) can form only to stall transcription but still allows it to continue.

49
Q

Briefly summarize the order of DNA organization

A

Chromosome consists of a single strand of DNA (negatively charged) is wrapped around a bundle of 8 histones (positively charged proteins) forming nucleosomes (a chromatin structure)

50
Q

What are specific transcription factors?

A

activators and repressors that are associated with regulating SPECIFIC transcription activities - they bind to enhancers that can be upstream or downstream to the gene (far from the gene it influences). This segment of DNA folds to join the general transcription factors and RNA polymerase on the promoter.

51
Q

What is RNAi?

A

RNA interference involved in gene silencing. mIRNA (from DNA) and sIRNA (from dsRNA outside the cell)

52
Q

How are proteins degraded?

A

Nonfunctinal proteins are marked for destruction by UBIQUITIN

53
Q

Process that fixes a cell’s fate

A

cell determination

54
Q

Order of stem cells

A

Toitipotent > Pluripotent > Multipotent

55
Q

What is recombinant DNA and how are they constructed?

A

DNA from different sources cut up by restriction endonucleases (at the restriction site)in a staggered fashion (sticky end)

56
Q

Define PCR

A

Polymerase chain reaction is a technique that makes large numbers of DNA copies through heating, cooling, then adding polymerases

57
Q

Describe technique of gel electrophoresis

A

This process separates restriction fragments of DNA as they diffuse though a jelly material under an electric field. It is used to compare DNA fragments of closely related species and determine evolutionary relationships (phylogeny)

BIOLOGY - Cliff (12 decks)

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