Chapter 4: Molecular Biology Flashcards

Question

How many base pairs does the human genome have vs the bacterial genome?

Answer 1

humans have 10^9 bacterial have 10^6

Answer 2

An enzyme that requires ATP to twist the circular DNA in prokaryotes Breaks the DNA and twists the two sides of the circle around each other, resulting in a twisted circle that is composed of dsDNA Creation of supercoils

Answer 3

Globular proteins where DNA is wrapped around it

Answer 4

Made up of an octamer of histones with DNA wrapped around it

Answer 5

The string-like DNA between nucleosomes that is bound by a single linker histone

Answer 6

Fully packed DNA that is composed of closely stacked nucleosomes When staining, it is the darker region that is more dense and rich in repeats When staining, it is the lighter region that is less dense and therefore has higher transcription rates and higher gene activity because the looser packing makes DNA accessible to enzymes and proteins

Answer 7

The region of the chromosome that spindle fibers attach to during cell division Made of heterochromatin and repetitive DNA sequences

Answer 8

Multiprotein complexes that act as anchor attachment sites for spindle fibers

Answer 9

short arm (p) long arm (q) 1. Metacentric - p and q are equal 2. Submetacentric - q is slightly longer than p 3. Acrocentric - q is a stalk while p is bulb-like 4. Telocentric - there is only one arm because the centromere is at the end of the chromosome

Answer 10

The ends of linear chromosomes that have repeated nucleotide sequences (about 50-several hundred times) Can be single or double stranded DNA about 300 BP long Acts as a disposable buff that blocks the ends of chromosomes to prevent deterioration and also prevents fusion with neighboring chromosomes

Answer 11

6-8 BP long repeated unit Guanine rich

Answer 12

3.2 billion BP

Answer 13

Non-coding DNA Can direct assembly of specific chromatin and can contribute to regulation of nearby genes Intergenic regions includes tandem repeats and transposons

Answer 14

Single Nucleotide Polymorphisms which are single nucleotide changes/ mutations that mostly occur in the non-coding regions of the genome. However, some SNPs lead to specific traits and phenotypes. Occurs once in every 1,000 BP

Answer 15

3 mill base pairs are human SNPS Since SNPs happen once every 1000 BPs 3 billion BP / 1000 BP = 3 mill human SNPs

Answer 16

Misalignment of repetitive DNA sequences during synapsis of homologous chromosomes in meiosis leads to different copies of DNA.

Answer 17

10^3 to 10^6 BP

Answer 18

0.4% of the genome Associated with cancer and other diseases Immune system function Brain development and activity

Answer 19

short sequences of nucleotides repeated (3-100 times) one after the other

Answer 20

When the repeating unit is short (di- or tri-nucleotides) or when the repeat itself is very long Unstable tandem repeats can lead to chromosome break and disease

Answer 21

Reading DNA and writing the information as RNA Can make a final gene product (all non-coding RNA) Can make a messenger molecule

Answer 22

The synthesis of proteins using mRNA as a template Ribosome is the massive enzyme that is composed of many proteins and rRNA

Answer 23

1) DNA 2) protein

Answer 24

Inherited information used to create enzymes and structural proteins DNA --> RNA --> proteins

Answer 25

The language used by DNA and mRNA A,G,T,C

Answer 26

A 3 letter nucleotide sequence that codes for a particular amino acid.

Answer 27

64 codons (enough to specify 20 unique amino acids) 4 nucleotides 3 nucleotides per codon 4^3 = 64 different combinations

Answer 28

This is because RNA is the nucleic acid that encodes protein during translation. RNA has a U instead of a T.

Answer 29

G =C T= A G= C The RNA codon was transcribed from DNA as CAC coding for histidine.

Answer 30

Does not code for a specific amino acid, but instead notifies the ribosome that the protein is complete. Causes it to stop reading the mRNA Also called nonsense codons

Answer 31

No since CUN codes for leucine, regardless of what N is. Notice that switching the third nucleotide in the majority of codons will have no effect.

Answer 32

Synonyms are when two or more codons code for the same amino acid The genetic code is degenerate because of this

Answer 33

Retroviruses make DNA from RNA using the enzyme reverse transcriptase. Info can be transferred in other ways such as DNA methylation and post-translational modification of proteins that can alter gene expression and convey information, even though they are not directly included in the Central Dogma. Lastly, many final products are not proteins but rather RNA instead.

Answer 34

Semiconservative replication - One strand of the DNA is parental while the other strand is the daughter strand Conservative replication - the parental dsDNA stays as is while an entirely new ds genome is created as the daughter Dispersive replication - both copies of the genomes were composed of scattered pieces of new and old DNA

Answer 35

semiconservative Individual strands of the double-stranded parent are pulled apart and then a new daughter strand is synthesized using the parental DNA as a template to copy from. Each new daughter chain is perfectly complementary to its template or parent.

Answer 36

An enzyme that requires ATP to break the hydrogen bonds and separate the dsDNA at the origin of replication

Answer 37

Prok: DnaA protein finds the ORI Euk: three proteins cooperate to find the ORI 2 of the proteins are synthesized during M and G1 phase and destroyed in the S phase. These link DNA replication to the cell cycle to ensure DNA replication doesn't initiate during other phases of the cell cycle

Answer 38

An enzyme that cuts one or both of the strands and unwraps the hel

Answer 39

Single stranded binding protein that protects the DNA that has been unpackaged in preparation for replication and to help keep the strands separated

Answer 40

Where the strands are separated during DNA replication

Answer 41

An RNA polymerase that is part of the primosome. It synthesizes an RNA primer for each template strand during DNA replication

Answer 42

A set of proteins that help to synthesize an RNA primer for each template strand during DNA replication

Answer 43

8-12 nucleotides long

Answer 44

Elongates the primer on the daughter strand by adding dNTP's to its 3' end 3' OH group acts as a nucleophile in the polymerization reaction to displace 5' pyrophosphate from the dNTP to be added.

Answer 45

3' to 5' because the daughter strand is made in the 5' to 3' direction and the two strands have to be antiparallel

Answer 46

A large complex of proteins that help DNA polymerase polymerize the DNA quickly

Answer 47

13 components 27 components because it must also unwind the DNA from the histones

Answer 48

Removal and hydrolysis of pyrophosphate (P2O7 4-) from each dNTP added to the chain

Answer 49

5' to 3' direction without exception This means the existing chain is always lengthened by the addition of a nucleotide to the 3' end of the chain. There is never 3' to 5' polymerase activity.

Answer 50

A template and a primer It cannot make a DNA chain from scratch but must copy an old chain. This makes sense b/c it would be useless if DNA pol just made a strand of DNA randomly without copying a template. Needs a primer since it cannot start a new nucleotide chain

Answer 51

No. The DNA strands are antiparallel meaning that the upper strand would have to be extended in a 3' to 5' direction which is impossible. (excess nucleotide is an extraneous phrase, typical MCAT smokescreen)

Answer 52

The area where the parental double helix continues to unwind during DNA replication

Answer 53

1) 3' to 5' 2) 5' to 3'

Answer 54

Elongating continuously Needs RNA primers constantly as the replication fork widens

Answer 55

Small chunks of DNA on the lagging strand

Answer 56

1) away 2) leading strand 3) lagging strand

Answer 57

continuous and leads into the replication fork

Answer 58

discontinuous resulting in Okazaki fragments

Answer 59

DNA ligase, an enzyme

Answer 60

Because it can rapidly build DNA and is able to add tens of thousands of nucleotides before falling off the template

Answer 61

Prokaryotes I: Slow processivity allows it to start adding nucleotides onto the RNA primer, but DNAPIII takes over about 400 BP downstream. This means it has 5' to 3' polymerase activity. Also has 3' to 5' exonuclease proofreading activity. In addition, 5' to 3' exonuclease activity that removes the RNA primer and replaces it with DNA in a 5' to 3' polymerase activity. Lastly, it is important for excision repair II: Used as a back up for DNAPIII so it has 5' to 3' polymerase activity as well as 3' to 5' exonuclease proofreading activity, and is involved in DNA repairing pathways III: High processivity means that there is fast and accurate 5' to 3' polymerase activity. Known as a replicative enzyme because it has no known function in repair. Has 3' to 5' exonuclease proofreading activity IV and V: Error prone in 5' to 3' proofreading activity, but functions to stall other polymerase enzymes at replication forks when DNA repair pathways have been activated

Answer 62

The enzyme moves backwards to chop off the nucleotide it just added, if it was incorrect Proofreading function

Answer 63

Exonuc: cutting a nucleic acid chain at the end Endonuc: cutting a polynucleotide acid chain in the middle of the chain, usually a particular sequence

Answer 64

Yes, The 3' to 5' exonuclease activity is the polymerase's way of editing its work. Without this editing function, many more point mutations would occur due to the incorporation of wrong nucleotides. The normal polymerase is remarkably adept at sensing correct base paring and removing bases that don't belong.

Answer 65

Repair enzymes remove chemically damaged DNA from the chain Restriction enzymes are found in bacteria and they destroy the DNA of infecting viruses, thereby restricting the host range of the virus

Answer 66

Replication that occurs in prokaryotes because it only has one circular chromosome and one origin, so a partially duplicated genome looks like the Greek letter theta

Answer 67

Many have many origins because having only one would be too slow aka replication bubbles

Answer 68

Disposable repeats at the end of chromosomes that are consumed and shorted during cell division (becomes between 50-200 BP shorter)

Answer 69

Enters a senescent state where the cell is alive but no longer dividing Activates DNA repair pathways Activates apoptosis, or pre-programmed cell death

Answer 70

The number of times a normal human cell type can divide until telomere length stops cell division

Answer 71

An enzyme that adds repetitive nucleotide sequences to the ends of chromosomes and lengthens telomeres. A ribonucleoprotein complex that contains RNA primer and reverse transcriptase that reads RNA templates and generates DNA Only expressed in the germ line, embryonic stem cells, or some white blood cells in most organisms Cancer cells can also express telomerase, which helps the cancer cells to immortalize

Answer 72

A mutation that can be passed onto offspring since it occurs in the germ cells which give rise to gametes

Answer 73

A mutation that is not passed onto offspring since it occurs in somatic/ non-gametic cells

Answer 74

Environmental or chemical factor as well as occurring spontaneously

Answer 75

X-ray, alpha particles, gamma rays Causes DNA breaks

Answer 76

Causes a photochemical damage to DNA Pyrimidine dimer formation when two pyrimidines (2 C's or 2 T's) are close to each other and covalently linked to each other, which causes a distortion in the DNA backbone that can cause mutations during DNA replication if it isn't repaired

Answer 77

Any compound that can cause mutations

Answer 78

Compounds that look like purines and pyrimidines with large flat aromatic ring structures that cause mutations by inserting themselves between base pairs Ethidium Bromide

Answer 79

Viruses that insert into the genome of the host cell and disrupt genetic function

Answer 80

1) Point mutations 2) Insertions 3) Deletions 4) Inversions 5) Amplifications 6) Translocations and rearrangements 7) Loss of heterozygosity

Answer 81

1) Missense - One amino acid is replaced with a different amino acid. If the amino acids are similar it may not be serious 2) Nonsense - A stop codon replaces a regular codon and prematurely shortens the protein 3) Silent - A codon is changed into a new codon for the same amino acid, so there is not change in the protein's amino acid sequence

Answer 82

For example, substitution a small hydrophobe (valine) for another small hydrophobe (leucine) will cause little disruption of the protein structure. They cause changes in primary structure but do not affect secondary, tertiary, or quaternary structure

Answer 83

Mutations that cause a change in the reading frame Insertions and deletions can result in a frameshift mutation where there is the addition or deletion of nucleotides to or from the DNA sequence

Answer 84

No because if a whole codon is inserted or deleted then an amino acid is added or deleted without changing the reading frame

Answer 85

A type of mutation where a segment of a chromosome is reversed end to end. The chromosome undergoes breakage and rearrangement within itself.

Answer 86

substitution of a pyrimidine for another pyrimidine

Answer 87

Substitution of a purine for a pyrimidine

Answer 88

A type of mutation where the segments of a chromosome are duplicated

Answer 89

A type of mutation that occurs when recombination happens between non-homologous chromosomes that can create a gene fusion, where a new gene product is made from parts of two genes that were not previously connected

Answer 90

Where no genetic information is lost Where genetic information is lost or gained

Answer 91

A mobile genetic element Can cause inversions, deletions, and rearrangements

Answer 92

Degenerate retroviruses

Answer 93

1) IS elements are composed of a transposase gene flanked by inverted repeat sequences 2) Complex transposons are transposons that contain genes like antibiotic resistance 3) Composite transposons are two similar or identical IS elements with central region in between

Answer 94

A protein that is coded for by transposons, and has cut-and-paste activity where it catalyzes mobilization of the transposon. Acts as the scissors

Answer 95

completely excised duplicated Inverted repeats

Answer 96

.... it inserts into a relatively unimportant part of the genome .... they jump into an important part of the genome

Answer 97

... turns of gene expression ..... disrupts/ mutates the sequence ..... ramps up gene expression at a nearby site

Answer 98

When they work in pairs

Answer 99

Chromosomal segment between the two transposons loop around in order for the transposons to line up parallel to each other. Recombination happens and deletion of the DNA between the transposons happens. The DNA that is lost takes one transposon with it, meaning it can jump back into the genome somewhere else, causing chromosome rearrangement Chromosomal segment between the two transposons form a hairpin like structure so that the transposons can line up parallel to each other. Recombination happens and the DNA between the two transposons ends up inverted

Answer 100

A type of mutation where a deletion removes the normal copy of the gene and the only remaining copy is the mutated version. Makes the locus hemizygous, meaning there is only one gene copy in the diploid organism

Answer 101

Only having one gene copy in the diploid organism

Answer 102

Greater effect because autosomes are present in double copies so a mutation can be easily repaired if the other copy is normal

Answer 103

Increases the activity of a certain gene product, or changes it so that it gains a new and abnormal function

Answer 104

Results in the gene product having less or no function

Answer 105

When a diploid organism has a single functional copy of a gene and it's not enough to support a normal state

Answer 106

Sickle-cell Anemia is when deoxygenated hemoglobin dimerizes and form long chains that cause the RBC to sickle, then are prematurely destroyed, and leads to anemia. People who carry this gene are more resistant to malaria and that's why it's beneficial 35 BP are missing from the CCR5 gene. HIV resistance is given to homozygotes and delays AIDS onset in heterozygotes

Answer 107

A huge group of genetic diseases that involve disorders of metabolism. Cause: Single mutation in a single gene that codes for some sort of metabolic enzyme Symptom: Build-up of a toxic compound that can't be broken down OR by defeciency of an essential molecule that can't be synthesized, as well as many other symptoms regarding their respective metabolic pathway that the mutation affects

Answer 108

Mutation accumulation

Answer 109

Can be inherited or caused by carcinogen exposure

Answer 110

A mutagen that is directly involved in causing cancer

Answer 111

oncogenes Tumor suppressors

Answer 112

Genes that can cause cancer when it's mutated or expressed at high levels

Answer 113

If they are deleted or expressed at low levels, it can cause cancer

Answer 114

Involved in direct reversal in DNA repair when an enzyme uses visible light to repair UV-induced pyrimidine photodimers. Commonly performed by bacteria and many plants

Answer 115

A type of repair that is dependent upon the DNA characteristic that DNA is double-stranded and complementary 1) Excision repair is repair that happens before DNA replication. It removes defective bases or nucleotides and replaces them. If it doesn't, then replication machinery can't pair them properly 2) Post-replication repair is repair that happens during and after DNA replication

Answer 116

Mismatch repair pathway (MMR) that targets mismatched Watson-Crick BP that weren't repaired by DNA polymerase proofreading during replication. To figure out which base is the correct one in bacteria, it uses methylation on the parental template strand. In other prokaryotes and most eukaryotes, the newly synthesized strand is recognized by the free 3' terminus on the leading strand, or by the presence of gaps between Okazaki fragments on the lagging strand

Answer 117

1) Reactive oxygen species 2) Ionizing radiation 3) UV light 4) Chemical agents

Answer 118

1) Homologous recombination happens when the DSB is identified and nuclease trims at 5' ends and breaks the phosphodiester bonds, then the helicase unwinds the DNA to generate ssDNA, and many proteins bind to the ends to search for a sister chromatid region that's complementary 2) Non-homologous end-joining is for cells that aren't actively growing or cycling through the cell cycle because it doesn't have the option of using sister chromatids to repair the DSB in and error-free way. It does not require specificity; the broken ends are stabilized and processed, and then DNA ligase connects the fragments. This can result in BP's being lost or chromosomes being connected in an abnormal way.

Answer 119

The process where information contained in genes begins to have effects in the cell

Answer 120

RNA is : single stranded, except in some viruses contains uracil instead of thymine the pentose ring in RNA is ribose rather than 2' deoxyribose

Answer 121

The 5' UTR or untranslated region that is not translated into protein The ORF or open reading frame that codes for a protein and starts at the start codon and ends at a stop codon The 3' region after the stop codon that isn't translated into protein but contains regulatory regions that influence post-transcriptional gene expression

Answer 122

mRNA that has only one ORF that codes for one polypeptide, and thus one protein. Follows the "one gene, one protein" principle. Found in Eukaryotes

Answer 123

mRNA that codes for more than one polypeptide, and has more than one ORF. The different ORFs are generally related in function fond in Prokaryotes

Answer 124

Between ORFs Termination information helps finish the PREVIOUS peptide chain Initiation helps start translation of the NEXT ORF on the transcript

Answer 125

Heterogeneous nuclear RNA is the RNA transcribed from DNA that is immature and is a precursor to mRNA. ONLY found in eukaryotes because prokaryotes don't go through processing events

Answer 126

when hnRNA goes through splicing, and addition of the methyl cap and the poly A tail, it then becomes mature and ready to be translated

Answer 127

Non-coding RNA that isn't translated into a protein but is still functional

Answer 128

1) Transfer RNA (tRNA) carries the amino acid from the cytoplasm to the ribosome to be added to a growing protein 2) Ribosomal RNA (rRNA) is the major component of the ribosome. Humans only have four types of rRNA (18S,5.8S,28S, and 5S) but almost all RNA made in a given cell is rRNA. Serves as components of the ribosome.

Answer 129

between 20-61 tRNAs

Answer 130

catalytic RNAs, they are capable of performing specific biochemical reactions similar to protein enzymes.

Answer 131

molecules (150 nucleotides) associate with proteins to form sRNP (small nuclear ribonucleic particles) complexes in the splicesome.

Answer 132

function in RNA interference (RNAi) a form of post-transcriptional regulation of gene expression. Both can bind to specific mRNA molecules to increase or decrease translation.

Answer 133

Are single-stranded and short (typically between 21 and 31 nucleotides in length). They work with a class of regulatory proteins called PIWI proteins to prevent transposons from mobilizing.

Answer 134

are longer than 200 nucleotides. They help control basal transcription levels in a cell by regulating initiation complex assembly on promoters. They also help contribute to many types of post-transcriptional regulation by controlling splicing and translation and they function in imprinting and X-chromosome inactivation.

Answer 135

the synthesis of RNA (mRNA, tRNA, or rRNA) using DNA as the template. Information is transferred from one polynucleotide to another.

Answer 136

complementary

Answer 137

The driving force for both processes is hte removal and subsequent hydrolysis of pyrophosphate from each nucleotide added to the chain with the existing chain acting as a nucleophile. Transcription can only occur in the 5' to 3' direction Begins at a specific spot on the chromosome.

Answer 138

RNA pol does not require a primer. RNA pol can't remove mismatched nucleotides (no exonuclease activity) so it can't correct its errors. Lower fidelity process than replication. DNA replication begins at the origin RNA transcription begins at the start site.

Answer 139

complimentary not identical

Answer 140

template, non-coding, transcribed, antisense strand. Its complimentary to the transcript

Answer 141

Coding or sense strand (has same sequence as transcript except the T is a U).

Answer 142

Downstream: toward the 3' end of the coding strand and transcript (+ #s) Upstream: towards the 5' end of the coding strand, beyond the 5' end of the transcript (-#s)

Answer 143

All types of RNA are made by the same RNA polymerase. 5 subunits: 2 alpha, 1 beta, 1 beta', 1 omega. Omega is the core enzyme responsible for rapid elongation of the transcript but needs sigma factor to make a holoenzyme that helps with initiation.

Answer 144

Initiation: RNA pol holoenzyme binds to the promoter (two primary sequences Pribnow box at -10 and -35 sequences). Holoenzyme scans along the chromosome like a train on a railroad track until it recognizes a promoter and then stops, forming a closed complex. The RNA pol must unwind a portion of the DNA double helix before it can begin to synthesize RNA. The RNA pol bound at the promoter with a region of a single-stranded DNA is termed the open complex. Once the open complex forms, transcription can begin. Elongation: The core enzyme elongates the RNA chain processively with one polymerase and complex synthesizing an entire RNA molecule. As the core enzyme elongates the RNA, it moves along the DNA downstream in a transcription bubble in which a region of the DNA double helix is unwound to allow the polymerase to access the complementary DNA template. Termination: When the termination signal is detected (with the help of rho) the polymerase falls off the DNA, releases the RNA and the transcription bubble closes.

Answer 145

Help the polymerase find promoters by: 1) Increasing the ability of RNA polymerase to recognize promoters. 2) Decrease the nonspecific affinity of holoenzyme for DNA. Once open complex and several phosphodiester bonds are formed, the sigma factor isn't needed and it leaves the RNA pol complex

Answer 146

Prokaryotic: -before the kernel/karyon (nucleus) b/c they have no nucleus so transcription occurs free in the cytoplasm, the same area where translation occurs meaning both can happen simultaneously. -The primary transcript in prokaryotes is mRNA. Eukaryotic: -Must transcribe their mRNA in the nucleus, modify it, and then transport it across the nuclear membrane to the cytoplasm where it can be translated. Transcription and translation DO NOT occur simultaneously. - Eukaryotic primary transcript hRNA made by RNA pol II is modified a ton before translation.

Answer 147

These are intervening sequences in the RNA. Avg size is about 2000 nucelotides

Answer 148

Protein coding regions of the RNA because they get expressed.

Answer 149

1) removed 2) joined together 3) splicing

Answer 150

A complex containing over 100 proteins and 5 small nuclear RNA (sRNA) molecules and snRNPs. It assembles around the introns that need to be removed.

Answer 151

To catalyze the splicing reaction, snRNPs recognize and hydrogen bond to conserved nucelotides in the intron: usually GU at the 5' end, AG at the 3' end, and adenine 15-45 bases upstream of 3' splice site. This aligns the hnRNA so that splicing can take place. Two splicing reactions are catalyzed by splicesome. First rxn attaches one end of intron to conserved adenine causing it to make a loop, then the second rnx joins two exons and releases the loop. The five conserved nucleotides needed for this rxn are found in all eukaryotic species.

Answer 152

GU, A, and AG are found in all genes and across all eukaryotic species.

Answer 153

Alternative splicing is a cellular process in which exons from the same gene are joined in different combinations, leading to different, but related, mRNA transcripts. These mRNAs can be translated to produce different proteins with distinct structures and functions — all from a single gene.

Answer 154

methylated guanine nucleotide stuck on the 5' end. Also prevents the digestion of mRNA by exonucleases that are free in the cell.

Answer 155

string of several hundred adenine nucleotides. Essential for translation and also prevents the digestion of mRNA by exonucleases that are free in the cell.

Answer 156

RNA poly I transcribes most rRNA RNA poly II transcribes hnRNA (mRNA), most snRNA, and some miRNA RNA pol III trascribes tRNA, long ncRNA, siRNA, and some miRNA and a subset of rRNA

Answer 157

This is the synthesis of polypeptides according to the amino acid sequence dictated by the sequence of codons in the mRNA. 1) An mRNA molecule attaches to a ribosome at a specific codon, and the appropriate amino acid is delivered by a tRNA molecule. Then the second amino acid is delivered by another tRNA molecule. Then the ribosome binds the two amino acids together creating a dipeptide. This is repeated until the polypeptide is complete at which point the ribosome drops the mRNA and the new polypeptide departs.

Answer 158

It is a sequence of 3 ribonucleotides which are complementary to the mRNA codon the tRNA translates.

Answer 159

The specific base paring between the tRNA anticodon and the mRNA codon.

Answer 160

This is where the amino acid is attached to the tRNA. Key point: There is a tRNA for each codon so each tRNA is specific for one amino acid. Meanwhile, each amino acid may have several tRNAs.

Answer 161

Most organisms have fewer than 45 different types of tRNAs meaning some anticodons must pair with more than one codon. The hypothesis explains that the first two codon-anticodon pairs obey normal base pairing rules but the third position is more flexible, allowing for non-tradiational pairing, and explains why a smaller number of tRNAs are possible.

Answer 162

A modified inosine base (I) at the 5' end of the anticodon, it can bond to 3 different codon bases including A,U, or C.

Answer 163

G-U, I-U, I-A, I-C.

Answer 164

3' Base in Codon (mRNA) C (WCB) or U (WB) G U A (WCB) G (WB) A, U, or C (all WB)

Answer 165

2 high-energy phosphate bonds are hydrolyzed to provide the energy to attach an amino acid to its tRNA molecule. Steps: 1) AA attached to AMP to form aminoacyl AMP. Nucleophile = acidic oxygen of AA LG is PPi 2) The pyrophosphate leaving group is hydrolyzed to 2 orthophosphates. Highly favorable rxn G<< 0 3) tRNA loading an unfavorable reaction is driven forward by destruction of the high energy aminoacyl-AMP bond created in Step 1. Eventually, the bond between the AA and tRNA molecule will be broken. This hydrolysis will power the peptide bond formation: the nitrogen of another amino acid will nucelophillically attack the carbonyl carbon of this AA and the tRNA will be the LG Requires: 2 ATP equivalents b/c it uses 2 high-energy bonds. Useful b/c breaking aminoacyl tRNA bond will drive peptide bond formation forward.

Answer 166

These enzymes are specific to each amino acid. They are highly specific and recognize each amino acid-base and tRNA by 3D structure.

Answer 167

Specific and accurate amino acid delivery and the other is thermodynamic activation of amino acid.

Answer 168

Composed of many polypeptides and rRNA chains held together in a big quaternary structure. They float around in the cytoplasm and have a small subunit and a large subunit.

Answer 169

aminoacyl-tRNA is where each new tRNA delivers its amino acid

Answer 170

peptidyl-tRNA site is where the growing polypeptide chain still attached to a tRNA is located during translation.

Answer 171

exit tRNA is where the now empty tRNA sits prior to its release from the ribisome.

Answer 172

A>P>E tRNAs = APE

Answer 173

Translation occurs in the same compartment at the same time as transcription. While the mRNA is being made ribosomes attach and begin translating it.

Answer 174

- The ribosome is larger (80S) with/ different components. - mRNA must be processed before it can be translated (spliced w/ cap and tail added) - N-terminal amino acid is different (Met vs fMet). Eukaryotic mRNA requires transport from nucleus to cytoplasm, thus transcription and translation cannot proceed simultaneously.

Answer 175

In eukaryotic translation, the important role of 5' end mRNA cap recognition as most eukaryotic transcripts were monocistronic and coded for only one polypeptide chain

Answer 176

when eukaryotic translation occurs in the middle of an mRNA molecule. Must have an internal ribosome entry site or IRES. Most code for proteins that help the cell deal with stress.

Answer 177

Changes in gene expression that are not due to mutations, but are long-term and heritable. (DNA methylation, chromatin remodeling, and RNA interference.

Answer 178

DNA methylation is covalent modification through the addition of a methyl group. Bacteria methylate new DNA shortly after synthesis and brief delay is good in mismatch repair pathways. Prokaryotes: control gene expression by promoting or inhibiting transcription. Eukaryotic: controls gene expression (especially in development) and is implicated in several diseases. 1) Methylation physically blocks genes from transcriptional proteins 2) Certain proteins bind methylated CpG groups ad recruit chromatin remodeling proteins that change the winding of DNA around histones.

Answer 179

Anabolic enzymes whose transcription is inhibited in the presence of an excess amount of product are repressible. Catabolic enzymes whose transcription can be stimulated by the abundance of substrates are called inducible enzymes.

Answer 180

Lac operon: inducible since the enzymes it codes for are part of lactose catabolism. trp operon: is repressible since the enzymes it codes for mediate tryptophan biosynthesis or anabolism.

Answer 181

1) coding sequence for enzymes 2) upstream regulatory sequences or control sites. May also include genes for regulatory proteins like repressors or activators but not required.

Answer 182

1)P region: promoter site on DNA to which RNA pol binds to initiate transcription of Y, Z, and A genes. 2) O region: the operator site to which the Lac repressor binds 3) Z gene: codes for enzyme Beta-galactosidase which cleaves lactose into glucose and galactose. 4) Y gene: codes for permease, a protein that transports lactose into the cell. 5) A gene: codes for transacetylase an enzyme which transfers an acetyl group from acetyl-CoA to Beta galactoside.

Answer 183

1) crp gene: located at the distant site, codes for catabolite activator protein (CAP) and helps couple lac operon to glucose levels in the cell. 2) I gene: located at a distant site, gene codes for Lac repressor protein.

Answer 184

Result: Z, Y, and A are not transcribed or translated.

Answer 185

Result: Z,Y, and A are transcribed at low levels.

Answer 186

1) inactivated 2) low

Answer 187

Result: Z, Y, and A are transcribed at high levels

Answer 188

ResultL: trp genes are off in the presence of tryptophan

Chapter 4: Molecular Biology Flashcards

MCAT Mnemonics/Concepts I need to review (216 cards)