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MCAT Biology (Mine) > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

Nucleotides are built from what 3 things?

A
  1. A sugar (Deoxyribose for DNA & ribose for RNA)
  2. An aromatic base (nitrogenous base)
  3. 1-3 phosphate grouo
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2
Q

G & A are what?

A

Purines

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3
Q

C, T, & U are what?

A

Pyrimidines

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4
Q

Nucleosides contain what?

A

A sugar & a base (purines or pyrimidines)

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5
Q

Nucleotides contain what?

A

A sugar, base (purine or pyrimidine), & 1-3 phosphate groups where if it has 3 its called nucleoside triphosphate (NTP where N is a purine or pyrimidine)

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6
Q

The __________ & __________ make up the backbone of DNA

A

Sugar & phosphate

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7
Q

Nucleotides in DNA chain are covalently lined by _____________ bonds between the 3’ hydroxyl group of one dexoribose and the 5’ phosphate group of the next dexoribose

A

Phosphodiester bonds

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8
Q

In a polynucleotide, the end of the chain with a free 5’ phosphate group is written _______ with other nucleotides written in the 5’ to 3’ direction

A

First

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9
Q

In DNA H-bonded pair always consist of a __________ plus a _________

A

Purine, pyrimidine so we can actually calculate the # of purines if we know the # of pyrimidines (A+G = T+ C)

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10
Q

Annealing (hybridization)

A

The binding of two complementary strand of DNA into a double-stranded structure

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11
Q

Denaturation (melting)

A

The separation of strands

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12
Q

DNA strand are always antiparallel & the _____ end is always written first

A

5’

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13
Q

___________ is used to stabilize prokaryotes chromosomes

A

DNA gyrase

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14
Q

What is the telomere sequence that is found at the end of DNA?

A

5’-TTAGGG-3’

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15
Q

Intergenic DNA

A

Are composed of noncoding DNA

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16
Q

Single nucleotide polymorphisms (SNPS)

A

Are essentially mutations, they are single nucleotide changes (predicted that there is one for every 1,000 base pair) & usually occur in noncoding regions of the genome)

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17
Q

Single nucleotide polymorphisms (SNPS)

A

Are essentially mutations, they are single nucleotide changes (predicted that there is one for every 1,000 base pair) & usually occur in noncoding regions of the genome) & they can lead to specific traits & phenotypes like how some ppl can’t taste PTC & others can

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18
Q

Copy number variations (CNVs)

A

Are structural variations in the genome that lead to different copies of DNA sections

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19
Q

Tandem repeats

A

Where short sequences of nucleotides are repeated one right after the other from as little as 3 to over 100 times

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20
Q

Synonyms

A

Two or more codons coding for the same amino acids & are degenerate (each codon only specifies one amino acid)

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21
Q

Is DNA replicat onserative, semiconservative, or disperative?

A

Semi-conservative (The old strand is used to make the new strand)

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22
Q

Helicase enzyme uses the energy of ______- hydrolysis to break the DNA strand for replication

A

ATP

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23
Q

Polymerization occurs in the __________ direction

A

5’ to 3’

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24
Q

DNA polymerase requires a __________ to make a copy strand (daughter strand)

A

Template

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25
Q

DNA polymerase requires a _______ to start replication

A

Primer

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26
Q

Replication forks grow away from the ________ in both directions & each fork contains a leading strand & a lagging strand

A

Origin

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27
Q

Replication of the leading strand is ___________ and leads into the replication fork while replication of the lagging strand is ___________ resulting in Okazaki fragments

A

Continuous, discontinuous

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28
Q

Eventually, all RNA primers are replaced by DNA & the fragments are joined by an enzyme called ________ ligase

A

DNA ligase

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29
Q

DNA polymerase 3

A

Is responsible for the super fast accurate elongation of the leading strand & also has proofreading functions

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30
Q

Exonuclease

A

“cutting a nucleic acid chain at the end”

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31
Q

Endonuclease

A

Will cut a polypeptide acid chain in the middle of the chain, usually at a particular sequence

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32
Q

What are the two types of endonucleases?

A
  1. Repair enzymes
  2. Restriction enzymes
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33
Q

Repair enzymes

A

Removes chemically damaged DNA from the chian

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34
Q

Restriction enzyme

A

Are endonucleases found in bacteria & are made to destroy the DNA of infecting virus thus restricting the host range of the virus

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35
Q

Telomeres

A

Are disposable repeats at end of chromosomes & are consumed 7 shorten during cell division

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36
Q

Genetic mutations

A

Are any alterations of the DNA sequence of an organism’s genome

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37
Q

Ionizing radiation (such as X-rays, alpha particles, and gamma rays) can cause _______ breaks

A

DNA

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38
Q

Mutagen

A

Any compound that can cause mutations (& biological agents like viruses, transposons, etc can also cause mutations& arent mutagens)

39
Q

What are the type of mutations?

A
  1. Point mutations
  2. Insertions
  3. Deletions
  4. Inversions
  5. Amplifications
  6. Translocation & rearrangements
  7. Loss of heterozygosity
40
Q

Point mutations

A

Are single base pair substitutions (ex. A in place of G)

41
Q

What are the different types of point mutations

A
  1. Transitions
  2. Transversions
42
Q

Transitions

A

Substitution of a pyrimidine for another pyrimidine or substitution of a purine for another purine

43
Q

What are the types of point mutations?

A
  1. Missense mutation
  2. Nonsense mutation
  3. Silent mutation
44
Q

Missense mutation

A

This causes one amino acid to be replaced with a different amino acid

45
Q

Nonsense mutation

A

A stop codon replaces a regular codon & prematurely shortens the protein

46
Q

Silent mutation

A

A codon is changed into a new codon for the same amino acid, so there is no change in the protein’s amino acid sequence

47
Q

Insertion

A

Refers to the addition of one or more extra nucleotides into the DNA sequence

48
Q

Deletion

A

The removal of nucleotides from the sequence

49
Q

What two types of mutations cause a frame shift in the sequence?

A

Insertion & deletion

50
Q

Frameshift mutations

A

Mutations that cause a change in the reading frame

51
Q

An inversion

A

When a segment of a chromosome is reversed end to end (The chromosome undergoes breakage and rearrangement within itself)

52
Q

Insertions, deletions,, & inversion can be caused by _____________

A

Transposons

53
Q

Chromosome amplification

A

When a segment of a chromosome is duplicated

54
Q

Translocations

A

Results when recombination occurs between nonhomologous chromosomes

55
Q

Transposons

A

Mobile genetic elements in the genomes (genetic mobility)

56
Q

Loss of heterozygosity

A

When a deletion occurs in a diploid organism & deletes the normal copy of the gene & the only remaining copy is the mutated version

57
Q

Hemizygous

A

When there is only one gene copy in the diploid organism

58
Q

Haploinsufficiency

A

A diploid organism has only a single - functional copy of a gene and this single copy is not enough to support a normal state

59
Q

Inborn errors of metabolism

A

Are a group of genetic diseases that involve disorders of metabolism

60
Q

What are the different types of DNA repair mechanisms?

A
  1. Direct reversal
  2. Homology- dependent repair
  3. Excisionm repair
  4. Post-replication repair
  5. Double-stranded break repair
  6. Homologous recombination
61
Q

Direct reversal

A

DNA damages that are directly repaired

62
Q

Homology-dependent repair

A

Using the second strand (undamaged strand) of the DNA double-strand to make a complementary repair on the other strand

63
Q

What are the two types of homology-dependent repair?

A
  1. Excision repair
  2. Post-replication repair
64
Q

Excision repair

A

Occurs before DNA replication & removes defective bases or nucleotides & replacing them

65
Q

Post-Replication repair

A

Are repairs that happen before & during DNA replication & use the mismatch repair pathway to target mismatched base pairs that slipped through the DNA proof reading process

66
Q

Double-stranded break repair (DSB)

A

Its caused by reactive oxygen species, ionizing radiation, UV light or chemical agents & its goal is reattach and fuse chromosomes that have come apart because of it

67
Q

What are the two ways that a double-strand repair can work?

A
  1. Homologous recombination
  2. Nonhomologous recombination
68
Q

Homologous recombination

A

Process where one sister chromatid can help repair a DSB in the other

69
Q

Nonhomologous end joining

A

Process of just reconnecting the broken chromosomes at the end

70
Q

mRNA (coding RNA)

A

Carries genetic information to the ribosome where it can be translated into proteins each unique polypeptide is created based on the codon on the mRNA

71
Q

Transfer RNA (tRNA) (non-coding RNA)

A

Is responsible for translating the genetic code & carries amino acids from the cytoplasm to the ribosome to be added to a growing protein

72
Q

Ribosomal RNA (rRNA) (non-coding RNA)

A

Are the major components of the ribosome

73
Q

RNA polymerase 1 transcribes most _______

A

rRNA

74
Q

RNA polymerase 2 transcribe ___________

A

hnRNA (which results in mRNA), most snRNA, & some miRNA

75
Q

RNA polymerase 3 transcribe ________

A

tRNA, long ncRNA, siRNA, some miRNA, & some rRNA

76
Q

Translation

A

Is the synthesis of polypeptides according to the amino acid sequence dictated by the sequence of codons in mRNA

77
Q

Wobble Hypothesis

A

States that the first two codon-anticodon pairs obey normal base pairing rules, but the 3rd position is more flexible which is why there is smaller numbers in tRNA

78
Q

What are the most common wobble base pairs?

A
  1. G-U
  2. I-U
  3. I-A
  4. I-C
79
Q

Amino acid activation (tRNA loading)

A

A process where two high energy phosphate bonds are hydrolyzed to provide the energy to attach an amino acid to its tRNA molecule

80
Q

What are the 3 steps in the amino acid activation process?

A
  1. An amino acid is attached to AMP to form aminoacyl AMP
  2. The pyrophosphate leaving group is hydrolyzed to 2 orthophosphate
  3. tRNA loading, an unfavorable reaction is driven forward by the destruction of the high energy aminoacyl - AMP bond created in step 1
81
Q

Aminoacyl-tRNA synthetase enzymes

A

Are used to attach the appropriate amino acid to each tRNA molecule

82
Q

What are the two main functions that amino acid activation serves?

A
  1. Specific & accurate amino acid delivery
  2. Thermodynamic activation of the amino acid
83
Q

What are the binding site in the ribsome?

A
  1. A site - where each new tRNA delivers its amino acid
  2. P site- where the growing polypeptide chain is located during translation
  3. E site- where a now empty tRNA sits prior to its release from the ribosome
84
Q

What are the binding site in the ribsome?

A
  1. A site - where each new tRNA delivers its amino acid
  2. P site- where the growing polypeptide chain is located during translation
  3. E site- where a now empty tRNA sits prior to its release from the ribosome

A —> P —> E

85
Q

What are the main differences between eukaryotic & prokaryotic translation?

A

The ribosome is larger & has different components than the prokaryotic ribosome, the mRNA must be processed before it can be translated, & the N-terminal amino acid is different

86
Q

Cap independent translation

A

A eukaryote starting translation in the middle of an mRNA molecule (without the requirement of the 5’ cap of the mRNA)

87
Q

Regulation of gene expression occurs where?

A

In transcription

88
Q

What are the 3 most commonly used way to regulate gene expression?

A

DNA methylation, chromatin remodeling, & RNA interference

89
Q

What are the two ways the DNA methylation turns off eukaryotic gene expression?

A
  1. Methylation physically blocks the gene from transcriptional proteins
  2. Certain proteins bind methylated Cp5 groups & recuit chromatin remodeling proteins that change the winding of DNA around histones
90
Q

Gene imprinting

A

When only one allele of a gene is expressed

91
Q

Regulation of _____________ is the primary method of regulation of gene expression in prokaryotes

A

Transcription

92
Q

Anabolic enzymes whose transcription is inhibited in the presence of an excess amount of products are __________

A

Repressible

93
Q

Catabolic enzymes whose transcription can be stimulated b the abundance of a substrate are called ___________

A

Inducible enzymes

94
Q

The Lac Operon is __________ since the enzymes it codes for are part of lactose catabolism

A

Inducible

MCAT Biology (Mine) (5 decks)

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