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SBI 4U Biology > Molecular Genetics > Flashcards

Molecular Genetics Flashcards

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1
Q

What are the three components of DNA?

A

Phosphate, Deoxyribose, Nitrogenous Base

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2
Q

What are the bonds in DNA called?

A

Phosphodiester bond, Glycosidic Bond, Hydrogen Bonds

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3
Q

What two bases are Purines?

A

Adenine & Guanine

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4
Q

What bases (in both DNA & RNA) are Pyrimidines?

A

Thymine (or Uracil) & Cytosine

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5
Q

What is the difference between Purines and Pyrimidines?

A

Purines have a double ring structure and pyrimidines only have one.

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6
Q

What do 5’ and 3’ mean?

A

They indicate the carbon numbers in the sugar backbone. The 5’ end has a phosphate group and the 3’ end has a hydroxyl group. The two strands of DNA are antiparallel.

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7
Q

What is the difference between Prokaryotes and Eukaryotes in terms of DNA structure?

A

Prokaryotes: DNA is stored in the cytosol, typically have one chromosome, are circular and double-stranded, usually haploid

Eukaryotes: DNA is stored in the nucleus, multiple types of chromosomes, and typically diploid

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8
Q

What does Semi-Conservative mean?

A

Half of the helix is new and the other half is original; some of the original parent material is still present.

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9
Q

What does Helicase do?

A

Breaks down hydrogen bonds.

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10
Q

What do Single Stranded Binding Proteins do?

A

Prevent annealing after the strands are broken apart.

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11
Q

What does Gyrase do?

A

Relieves the tension that was created during the unwinding process.

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12
Q

What is the Replication Fork?

A

The point where two strands of DNA are still attached.

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13
Q

What does DNA Polymerase III do?

A

Adds nucleotides at the 3’ end and checks for errors along the strand.

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14
Q

What does RNA Primer do?

A

Acts as the starting strand for DNA polymerase.

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15
Q

What does Primase do?

A

Places RNA primers on the template strand.

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16
Q

What is the Leading Strand?

A

Replicates continuously and towards the replication fork.

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17
Q

What is the Lagging Strand?

A

Replicates sections away from the replication fork.

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18
Q

What are Okazaki Fragments?

A

Built away from the replication fork (lagging strand).

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19
Q

What does DNA Ligase do?

A

Joins the Okazaki Fragments together.

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20
Q

What is a gene?

A

A sequence of nucleotides in DNA that performs a specific function such as coding for a particular protein.

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21
Q

What is the “One Gene-One Polypeptide” Hypothesis?

A

Each gene is responsible for the synthesis of a single polypeptide. It was originally the ‘One Gene-One Enzyme Hypothesis’, but was modified upon the discovery that genes also coded for non-enzyme material. This hypothesis is NOT TRUE.

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22
Q

Why must DNA remain in the nucleus?

A

There are enzymes within the cytosol that could break it down. DNA is also a very large molecule, and is negatively charged.

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23
Q

What is the Central Dogma of Molecular Genetics?

A

Transcription & Translation

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24
Q

How does DNA make proteins?

A

DNA stores the codes to make proteins. Proteins are synthesized outside of the nucleus on the ribosomes.

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25
Q

How does DNA get to the ribosomes?

A

DNA is transcribed into a complementary RNA message (mRNA), which carries the code to the ribosomes. The ribosomes then translate into a polypeptide chain, which is then processed into proteins.

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26
Q

What are proteins?

A

Complex molecules composed of one or more polypeptide chains made of amino acids and folded into three-dimensional shapes that determine protein function.

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27
Q

What is Transcription?

A

The way that DNA information is copied into mRNA.

28
Q

What is translation?

A

The process that ribosomes use mRNA information to synthesize proteins.

29
Q

How do DNA and RNA differ?

A

DNA: contains genetic info, contains deoxyribose, contains thymine, is double-stranded

RNA: a carrier of genetic info, contains ribose, contains uracil instead of thymine, is single-stranded

30
Q

What are the three major classes of RNA?

A

mRNA: transcription of DNA
tRNA: transfers amino acids to the ribosome for protein synthesis
rRNA: structural component of ribosome

31
Q

How does DNA compare to RNA? (Hint: sugar, strands, bases, and area)

A

DNA: Deoxyribose, 2 strands, AT & GC, nucleus

RNA: Ribose, 1 strand, AU & CG, can be in the nucleus or free in the cytosol

32
Q

What does transcription mean?

A

Making a copy

33
Q

What does a triplet code for?

A

One amino acid

34
Q

What does a gene code for?

A

Polypeptides, proteins

35
Q

What does a transcription unit code for?

A

A gene

36
Q

What does translation mean?

A

Writing in a different language

37
Q

What is the promoter region?

A

The region of DNA that initiates the transcription of a particular gene.

38
Q

How does RNA polymerase recognize the promoter region?

A

The TATA region; an abundance of adenine and thymine bases.

39
Q

What does RNA polymerase do during Transcription?

A

RNA polymerase attaches to the DNA template strand and begins assembling a new chain of nucleotides to produce a complementary RNA strand.

40
Q

Which direction does RNA polymerase work in?

A

From the 5’ to the 3’ end.

41
Q

What is the strand of DNA called that will be copied by RNA polymerase?

A

The template strand.

42
Q

What are the three modifications that must be made to mRNA before it leaves the nucleus?

A
  1. 5’ cap, is used for protection
  2. Poly-A tail, also used for protection (RNA followed by a long strand of non-coding adenines)
  3. Introns are removed by spliceosomes
43
Q

What are the three steps involved in Transcription?

A
  1. Initiation –> RNA polymerase binds to the promoter region
  2. Elongation –> RNA polymerase builds the mRNA
  3. Termination –> RNA polymerase reaches the stop codon
44
Q

What is an Intron?

A

Non-coding DNA (“junk DNA”)

45
Q

What is an Exon?

A

Coding DNA

  • -> Before leaving the nucleus: All the introns are removed by spliceosomes
  • -> After leaving the nucleus: 5’ cap forms, followed by exons and the poly-A tail
46
Q

What is the difference between Prokaryotes and Eukaryotes in terms of transcription?

A

Prokaryotic: Coupled transcription-translation, occurs in the cytoplasm, doesn’t occur in a definite phase of the cell, only one RNA polymerase, transcriptional unit has one or more genes
Eukaryotic: Coupled translation is not possible, occurs in the nucleus, takes place in the G1 and G2 phases of the cell cycle, RNA polymers I, II, & III are used, initiation of transcription requires the proteins known as Transcription Factors (which recognize the TATA box)

47
Q

How do ribosomes recognize the beginning of the sequence of mRNA to be translated? (Translation)

A

There will be a start codon, which is AUG (or Methionine)

48
Q

What is the reading frame?

A

One of three possible ways of reading a nucleotide sequence.

49
Q

What is the job of tRNA in Translation?

A

To carry an amino acid into the ribosome, and contain an anti-codon that will match with a codon on the mRNA strand (and cause it to release the amino acid onto a polypeptide chain)

50
Q

How do ribosomes know when to stop translating the mRNA?

A

When it encounters a stop codon.

51
Q

What is the difference between prokaryotes and eukaryotes in terms of translation?

A

Prokaryotic: Paired with transcription, faster process (mRNA is unstable), requires three release factors, whole thing occurs in the cytoplasm

Eukaryotic: Separate from transcription, occurs in the cytoplasm, slower process (mRNA is stable), requires nine initiation factors

52
Q

What are housekeeping genes?

A

Genes that are switched on all the time because they are need for the vital life functions of an organism.

53
Q

Compare and contrast DNA replication and transcription.

A

DNA Replication:
–> Differences: all of the DNA is copied (at multiple locations), contains multiple enzymes (helicase, gyrase, etc.), double stranded, remains in the nucleus
Transcription:
–> Differences: transcribes one gene at a time, only one enzyme (RNA polymerase; does multiple jobs), small portion of mRNA is produced, leaves the nucleus

–> Similarities:
Occur in the nucleus, use enzymes, DNA needs to be uncoiled and unzipped, proceeds from the 5’ end to the 3’ end

54
Q

What are transcription factors?

A

Proteins that switch on genes by binding to DNA and helping the RNA Polymerase to bind (in humans)

55
Q

Explain the Lac Operon System.

A

Only prokaryotes use operons to control genes. Lactose is the signal-molecule; when it is present, it binds to the Lactl protein, changes its’ form, and removes it from the promoter region (mRNA can be made). There are three genes the deal with lactose: the lacZ, lacY, and lacA genes. The regulatory sequence is called the promotor (where RNA polymerase grabs on) as well as an operator, which is similar to an on/off switch. It regulates if the genes are turned on or not. Occurs in transcription.

56
Q

Explain the Trp Operon system.

A

Only occurs in Prokatyotes. Tryptophan is an amino acid that is used by E.coli for the production of proteins. If not present, the cell can make its’ own, and the Trp Operon is repressed when there are high levels of tryptophan. Instead of three genes, it has five. The promoter and operator are the same as in the Lac Operon system, and this also occurs during Transcription.

57
Q

What is a mutation?

A

An error that is made in the DNA sequence that in inherited. Some are harmful, some have no effect, and some are positive.

58
Q

What is a silent mutation?

A

A mutation that does not cause a change in the amino acid coded for, and therefore does not cause a phenotypic change.

59
Q

What is a missence mutation?

A

A mutation that results in a single substitution of one amino acid in the resulting polypeptide.

60
Q

What is a nonsense mutation?

A

A mutation that converts a codon for an amino acid into a stop codon.

61
Q

What is a frameshift mutation?

A

A mutation that causes the reading frame of codons to change, resulting in different amino acids being incorporated into the polypeptide.

62
Q

What is a point mutation?

A

A mutation that occurs at a specific base pair in the genome (ex. Silent, Nonsense, & Missence)

63
Q

What are three examples of mutagenic substances?

A
  1. Methane (Chemical Mutagen)
  2. UV Ray (Physics Mutagen)
  3. Bacteria (Bio Mutagen)
64
Q

What is biotechnology?

A

The use of living organisms, or substances from living organisms, to develop a useful product or process.
(Ex. alcohol fermentation, using DNA as evidence, etc.)

65
Q

What is recombinant DNA?

A

A fragment of DNA composed of sequences that originate from at least two different sources.

66
Q

Explain the applications of PCR, Gel electrophoresis.

A

Can be used for analytical purposes; PCR amplifies DNA. Can also be used for DNA sequencing. The gel electrophoresis separates the macromolecules according to their size by being pushed through an electrical field.

SBI 4U Biology (2 decks)

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