Molecular Genetics

Front 1

Nucleotides

Back 1

made up of polymers of either DNA or RNA

Front 2

Nucleotide Monomer

Back 2

consists of a nitrogen base, a sugar, and a phosphate

Front 3

DNA

Back 3

sugar-deoxyribose; adenine, thymine, guanine, cytosine, constains herditary information, double helix

Front 4

RNA

Back 4

ribosel; adenine, uracil, guanine, cytosine

Front 5

mRNA

Back 5

provides the instructions for assembling amino acids into a polypeptide chain, linear

Front 6

tRNA

Back 6

delivers amino acids to a ribosome for their addition into a growing polypeptide chain, "clover leaf" shaped

Front 7

rRNA

Back 7

combines with proteins to form ribosomes- globular

Front 8

DNA Replication

Back 8

during interphase when a second chromatid containing a copy of the DNA moleucle is assembled and it involves separating (unzipping) the DNA molecule into two strands, each of which is a templace for a complementary strand

Front 9

Semiconservative Replication

Back 9

because each of the two double-stranded molecules of DNA consists of a single strand of old DNA (the template stand) and a single strand of new, replicated DNA (the complementary strand)

Front 10

helicase

Back 10

enzyme that unwinds the DNA helix

Front 11

replicase fork

Back 11

the y-shaped end after helicase unwinds the DNA

Front 12

Single-Stranded DNA binding proteins

Back 12

these attach to each strand of the uncoiled DNA to keep them separate

Front 13

toipoisomerases

Back 13

a group of enzymes that break and rejoin the double helix allowing the twists in front of the helicase to unravel and preventing the formation of knots

Front 14

DNA polymerase

Back 14

moves in the 3'-> 5' direction along each template strand and the new complement strand grows in the antiparallel 5' -> 3' direction

Front 15

leading strand

Back 15

the complementary strand that occurs readily as the DNA polymerase follows the replication fork assembling a 5' -> 3' stand on the 3'->5' template strand

Front 16

Okazaki Segments

Back 16

short segments of complementary DNA that develop along the 5'->3' template strand

Front 17

DNA Ligase

Back 17

connects Ozaki Segments producing a single complement strand

Front 18

Lagging Strand

Back 18

name for the complementary strand of the 5'->3' template strand because it requires more time to assemble than the leading strand

Front 19

RNA primase

Back 19

initiates the first nucleotides of the leading strand and each Okasaki fragment, it initiates each complementary segment with RNA nucleotides

Front 20

RNA Primer

Back 20

the RNA nucleotides on the complementary segment that append succeednig DNA nucleotides, later the RNA nucleotides are replaced with DNA nucleotides

Front 21

Step 1 of DNA replication

Back 21

Helicase unwinds the DNA, producing a replication fork. Single-stranded DNA binding proteins prevent the single strands of DNA from recombining. Topoisomerase removes twists and knots in the double stranded templatre as a result of the unwinding induced by helicase

Front 22

Step 2 of DNA replication

Back 22

RNA primase initiates DNA replication at special nucleotide sequences (called origins of replication) with short segments of RNA nucleotides (Called RNA primers)

Front 23

Step 3 of DNA replication

Back 23

DNA polymerase attaches to the RNA primers and begins elongation, the adding of DNA nucleotides to the complement strand

Front 24

step 4 of DNA replication

Back 24

the leading complementary strand is assembled continuously as the double-helix DNA uncoils

Front 25

step 5 of DNA replication

Back 25

the lagging complementary strand is assembled in short Okazaki fragments, which are subsequently joined by DNA ligase

Front 26

step 6 of DNA replication

Back 26

the RNA primers are replaced by DNA nucleotides

Front 27

energy for elongation

Back 27

provided by the two additional phosphates that are attached to each new nucleotide, making a total of three phosphates attached to the nitrogen base. Breaking the bonds holding the two extra phosphates provides teh chemical energy for the process

Front 28

proof-reads

Back 28

what the DNA polymerase does in bacteria

Front 29

Thymine Dimer

Back 29

originates when two adjacent thymine nucleotides in the same strand base-pair with eachotehr instead of with the adenine bases in the complementary strand, these can be fixed by excision repair

Front 30

Excision Repair

Back 30

enzymes that splice out the error and use the complementary strand as a pattern, or template, for replacing the excised nucleotides

Front 31

mutation

Back 31

if a DNA error is not repaired (normally caused by raditation).. it is any sequence of nucleotides in a DNA molecule that does not exactly match the original DNA molecule from which it was copied

Front 32

Substitution

Back 32

type of mutation when there is an incorrect nucleotide

Front 33

deletion

Back 33

type of mutation when there is a missing nucleotide

Front 34

insertion

Back 34

type of mutation when there is an additional nucleotide not present in the orignal DNA molecule

Front 35

frameshift mutation

Back 35

when an insert mutation occurs, it causes all the subsequent nucleoties to be displaced one position

Front 36

mutagens

Back 36

radiation or chemicals that cause mutations

Front 37

carcinogens

Back 37

mutagenst that activate uncontrolled cell growth (cancer)

Front 38

traits

Back 38

end products of metabolic processes regulated by enzymes

Front 39

one-gene-one-enzyme hypothesis

Back 39

that the gene is defined as the segment of DNA that codes for a particular enzyme

Front 40

one-gene-one-polypeptide hypthesis

Back 40

Since many genes code for polypeptides that are not enzymes, genes have been redefined as the DNA segment that codes for a particular polpeptide

Front 41

protein synthesis

Back 41

process that describes how enzymes and other proteins are made from DNA

Front 42

three steps in protein synthesis

Back 42

transcription, RNA processing, and gtranslation

Front 43

Messenger RNA

Back 43

a single strand of RNA that provides the template used for sequencing amino acids. A codon codes for one specific amino acids.

Front 44

Codon

Back 44

in mRNA, a triplet group of three adjacnt nucleotides that code for one specific amino acid. There are 64 possible codons but only 20 amino acids.

Front 45

Genetic Code

Back 45

provides the "decoding" for each codon, and it identifies the amino acid specified y each o the possible 64 codon combinations

Front 46

Transfer RNA

Back 46

short RNA molecule (80 nucleotides) that is used for transporting amino acids to their proper place on the mRNA template.

Front 47

anticodon

Back 47

portion of tRNA specified by a triplet comibination of nucletides, that pairs with the codon of the mRNA.

Front 48

CCA

Back 48

end of the 3' end of tRNA that attcaches to an amino acid

Front 49

wobble

Back 49

fact that there does not need to be an exact base-paring between the third nucleotide of the tRNA anticodon and the third nucleotide of the mRNA codn, which allows the codon of some tRNA's to base pair with more than one kind of codon, therefore about 45 different tRNA's base-pair with the 64 different codons

Front 50

Ribosomal RNA

Back 50

molecules that are the building blocks of ribosomes. The nucleolus is an assemblage of DNA actively being transcribed into this. These are large and small ribosome subunits which form a polypeptide chain.

Front 51

Transcription

Back 51

when RNA molecules are created by using the DNA molecules s a template

Front 52

initiation

Back 52

first step of transcription in which the RNA polymerase attaches to promoter regions on the DNA and begins to unzip the DNA into two strands. A promoter region for mRNA transcriptopns contains the sequence T-A-T-A

Front 53

TATA box

Back 53

Promoter region for mRNA transcriptions

Front 54

Elongation

Back 54

2nd step of transcription, occurs as the RNA polymerase unzips the DNA and assembles RNA nucleotides using one strand of the DNA as a template. As in DNA replication, elongation of the RNA molecule occurs in the 5'->3' direction. In contrase, new nucleotides are RNA nucleotides and only one DNA strand is transcribed

Front 55

Termination

Back 55

last step of transcription- occurs when the RNA polymerase reaches a special sequence of nucleotides that serve as a termination point. In eukaryotes it is usually AAAAAAAAA

Front 56

RNA Processing

Back 56

after transcription, this modifies the RNA molecule with deletions and additions

Front 57

translation

Back 57

the processed RNA molecules are used to assemble amino acids into a polypeptide

Front 58

steps of RNA processing

Back 58

before the mRNA leaves the nucleus, a 5' cap is addedand a poly-A tail, also some mRNA segments are removed

Front 59

5' Cap

Back 59

GTP added to 5'end (PPPG'5') which provides stability to the mRNA and a point of attachment for the small subunit of the ribosome

Front 60

poly-A tail

Back 60

a sequence of 150-200 adenine nucleotides added to the 3' end to provide stability and control the movement of mRNA across the nuclear envelop, may serve to regulate gene expression

Front 61

exons

Back 61

sequences of mRNA that EXpress a code for a polypeptide

Front 62

introns

Back 62

INtervening sequences that are noncoding in mRNA

Front 63

heterogenous nuclear RNA

Back 63

original unprocessed mRNA molecule that contains both the coding and the noncoding sequences

Front 64

small nuclear ribonucleoproteins

Back 64

snRNPs whcih delete out the introns and splice the exons together before the RNA moves to the cytoplasm

Front 65

Cytoplasm

Back 65

where translation occurs

Front 66

aminoacyl-tRNA

Back 66

in the cytoplasm, amino acids attach to the 3'end of the tRNA's forming this, requires the energy from one ATP

Front 67

Ribosomes

Back 67

actually assembles proteins, has a spot for mRNA, tRNA, and then one for a second tRNA that delivers the next amino acid

Front 68

GTP

Back 68

molecules that provide the energy for translation

Front 69

First step of Translation

Back 69

Initiation begins when the small ribosomal unit attaches to a speicl region near the 5' end of the mRNA, then a tRNA (with anticodon UAC) carrying methionnie attaches to the mRNA (at the start codon AUG) with hydrogen bonds, then a large ribosmal subunit attaches to the mRNA forming a complete ribosome with the tRNA occuping the P site

Front 70

Second step of Translation

Back 70

Elongation begins when the next tRNA binds to the A site of the ribosome, and then methionine is removed from the 1st tRNA and attached to the amino acid on the newly arrived tRNA. The 1st tRNA is relaeased and then binds with another amino acid (repeated deliveries), the remaining tRNA moved from the A site to the P site and a new tRNA enters the A site. then the tRNA in the P site is released and the steps repeat

Front 71

last step of translation

Back 71

termination occurs when the ribosome encounters one of the three "stop" codons and the completed polypeptide, the last tRNA, and the two ribosomal subunits are released. the ribosomal subunits can now attach to the same of another mRNA and repeat the process

Front 72

histone

Back 72

proteins that from DNA-histone complexes called nucleosomes

Front 73

nucleosomes

Back 73

DNA-histome complexes that appear like beads on a string

Front 74

Euchromatin

Back 74

describes regions where DNA is loosely bound to nucleosomes. DNA in these regions is actively being transcribed

Front 75

heterochromatin

Back 75

represents areas where the nucleocomes are more tightly compacted and where DNA is inactive. Because of its condensed arrangement, it stains darker than euchromatin

Front 76

transposons

Back 76

jumping genes that are DNA segments that can move to new locations on the same or different chromosome. Some only consist only of DNA that codes for an enzyme that enables it to be transported. Otheres contain genes that invoke replication of th transpoon. After relication, a new transposon copy is transported to the new location. Wherever they are inserted, they have the effect of a mutation. They can change the expression of a gene, turn it on or off, or have no effect

Front 77

Bacteriophages

Back 77

or phages, these only attack bacteria

Front 78

Virus parts

Back 78

nucleic acid surrounded by a protein coat

Front 79

capsid

Back 79

protein coat surrounding a virus

Front 80

capsid

Back 80

protein coat surrounding a virus

Front 81

envelop

Back 81

parts of some capsides that assists them in penetrating their hosts. THese incorporate phospholips and proteins obtained from the cell membrane of the host

Front 82

lytic cycle

Back 82

when a virus pentrates the cell membrance of the host, uses its enzymes to replicate viral DNA, transcribes viral DNA into RNA, and translates the RNA into proteins. The proteins and DNA are then assembled into new viruses which subsequently erupt from the host cell, destroying the cell in the process. The new viruses then infect other cells and the process repeats

Front 83

lysogenic cycle

Back 83

the viral DNA is temprarily incorporated into the DNA of the host cell and remins incactive until some trigger, usually an external enviroment stimulas, causes the virus to begin the lytic cycle

Front 84

provirus

Back 84

or a a prophage if it is a bacteriophahe, that is in the dormant stage of the lysogenic cycle

Front 85

retroviruses

Back 85

uses REVERSE TRANSCRIPTASE to make a DNA complement of their RNA

Front 86

binary fission

Back 86

reproduction of a bacterial cell- the chromsome replicates and the cell divides into two cells, each one bearing one chromosome. There are no spindle apparatus, microtubules, nor centrioles

Front 87

plasmids

Back 87

short circular DNA molecules outside the chromosome in bacteria that carry genes which are benificial but not normally essential to the survival of the bacterium. they replicate independently of the chromosome

Front 88

episomes

Back 88

plasmids which become incorporated into the bacterial chromosome

Front 89

Conjugation

Back 89

the process of DNA exchange between bacteria. A donor bacterium produces a tube that connects to a recipient bacterium which sends chromosomal or plasmid DNA to teh recipient

Front 90

pilus

Back 90

tube that is extended in conjugation, it sends plasmid or chromosomal DNA to the recipient

Front 91

F plasmid

Back 91

contains the genes that enable a bacterium to produce pili, so when a recipient bacterium recieves this, it can become a donor cell

Front 92

R plasmids

Back 92

a group of plasmids that provide bateria with resistance against antibioticss

Front 93

transduction

Back 93

occurs when new DNA is introduced into bacteria by a virusm and sometimes the bacterial viral DNA can recombine with the resident DNA

Front 94

Transformation

Back 94

occurs when bacteria absorb DNA from their surroundings. Specialized proteins on the cell membrances of some bacteria facilitate this kind of DNA uptake

Front 95

gene regulation

Back 95

the expression of only selected genes

Front 96

operons

Back 96

sequences of SNA that direct particular biosynthetic pathways

Front 97

regulatory gene

Back 97

of an operon, produces a REPRESSOR protein

Front 98

repressor protein

Back 98

a substance produced by a regulatory gene that can prevent gene expression by blocking the action of RNA polymerase

Front 99

promoter

Back 99

region of an operon that is a sequence of DNA to which the RNA polymerace attaches to begin transcription

Front 100

operator

Back 100

region in an operon that can block the action of the RNA polymerase if the region is occupied by a repressor protein

Front 101

structural genes

Back 101

operons that contain DNA sequences that code for several related enzymes that direct the production of some particular end product

Front 102

lac operon

Back 102

in E. Coli, controls the breakdown of lactose. The regulatory gene produces an active repressor that binds to the operatr region so RNA polymerase is unable to ranscribe several structural genes that control the uptake and breakdown of lactose. When lactose is availabel though, it combines with the repssor to make it inactive so then it is able to transcribe for genes to berak down lactose. Lactose is said to be the INDUCIBLE ENZYME

Front 103

inducible enzyme

Back 103

substance that is required to induce (Turn on) the operon, like lactose

Front 104

trp operon

Back 104

in E. Coli, produces enzymes for the synthesis of the amino acid trptophan. The regulatory gene produces an inactive repressor that does not bind to the operator so then the RNA poly. transcribes the structural genes necessary to produce enzymes that synthesize tryptophan. WHen it no longer needs to make its own tryptophan, the rising levels induce some of the trypto. to react with the inactive repressor to make it active. tryptophan acts as a COREPRESSOR, and it prevenets the transcription of more tryptophan. These are called REPRESSIBLE enzymes

Front 105

corepressor

Back 105

when an amino acts to prevent the trasncriptopn of structual genes

Front 106

Repressible enzymes

Back 106

structural genes that stop producing enzymes only in the presence of an active repressor, as in the trp operon

Front 107

Recombinant DNA

Back 107

DNA that contains DNA segments or genes from differnt sources. It can occur through viral tranduction, bacterial conjucation, transposons, or articially through recombin. DNA tech.

Front 108

restriction enzymes

Back 108

in recomn. DNA tech. these cut up DNA and are obtained from bacteria and manufactor these enzymes to combat invading viruses. these are very specific and cut DNA only at specific recognition sequences of nucleotides. The cut is usually staggered producing fragments that have one strand of DNA extending beyond the complementary strand

Front 109

sticky end

Back 109

unpaired extension after a restriction enzyme makes a staggered cut across a DNA

Front 110

tansformation in recombinant DNA tech.

Back 110

matching sticky ends combine and an example of this is how the human gene for insulin has been insertied into E. coli so that it produces insulin which is isolated and used to treat diabetes

Front 111

gel electrophoresis

Back 111

how restriction fragments can be separated and then DNA fragments of different lengths are separated as they diffuse through a gelatinour material under the influence of an electic field. The negalitively charged (phospahte groups) moves toward the postie electrode. The shorter fragments move further. This is ofen used to compare DNA fragments of closely related species in an effort to determine evolutionary relationships

Front 112

restriction fragment length polymorphisms

Back 112

or RFLP's, which cause the fragments to differ in length due to slight differnces in DNA sequences. (in the same species)

Front 113

DNA fingerprinting

Back 113

RFLP's produced from DNA left at a crime scene are compared to RFLPs from the DNA of suspects

Front 114

complementary DNA

Back 114

or cDNA, it is DNA obtained by using reverse transcriptase to make a DNA molecule directly from the mRNA and lacks the introns that suppress transcription

Front 115

polymerase chain reaction

Back 115

or PCR, this uses gragments that can be copied millions of times using DNA polymerase directly instead of yusing bacterium to clone DNA fragments. This uses synthetic primers that initate replication at specific nucleotide sequences