Biology Exam 2 Definitions

Front 1

Ligand

Back 1

Signaling molecule

Front 2

Receptor protein

Back 2

Molecule to which a ligand binds

Front 3

Paracrine Signals

Back 3

Signals with short-lived, local effects

Front 4

Hormones

Back 4

Longer-lived signal molecules that may affect cells very distant from the releasing cell

Front 5

Endocrine Signaling

Back 5

Type of intercellular communication that uses hormones

Front 6

Neurotransmitters

Back 6

The signal molecules of the nervous system cells

Front 7

Chemical Synapse

Back 7

The association of a neuron and its target cell

Front 8

Synaptic Signaling

Back 8

The type of intercellular communication between a neuron and its target cell

Front 9

Signal Transduction

Back 9

The events that occur within the cell on receipt of a signal

Front 10

Phosphorylation/Dephosphorylation

Back 10

The addition or removal of phosphate groups

Front 11

Phosphatases

Back 11

A class of enzymes that removes phosphate group, reversing the action of kinases

Front 12

Protein Kinases

Back 12

Enzymes that add phosphate groups to proteins

Front 13

G Protein

Back 13

A class of cell surface receptors that act indirectly on enzymes or ion channels in the plasma membrane with the aid of assisting protein

Front 14

Second Messangers

Back 14

Small molecules or ions that alter the behavior of cellular proteins by binding to them and changing their shape

Front 15

Cyclic Adenosine Monophosphate (cyclic AMP) or Calcium Ions

Back 15

A common second messenger

Front 16

Nuclear Receptors

Back 16

The ligand-receptor complex of steroid hormones

Front 17

Coactivators

Back 17

Act in concert with receptors, controlling a cell's response to signal

Front 18

Receptor Tyrosine Kinases (RTKs)

Back 18

Type of receptor that influences the cell cycle, cell migration, cell metabolism, and cell proliferation

Front 19

Adapter Proteins

Back 19

Class of proteins that can also bind to phosphotyrosines and act as a link between the receptor and protein

Front 20

Mitogen-Activated Protein (MAP) Kinases

Back 20

Class of cytoplasmic kinases that stimulates cell division by activating the normal pathways that control division

Front 21

Kinase Cascade

Back 21

The signaling module that activates MAP kinases

Front 22

Ras

Back 22

A small GTP-binding protein, this is the link between the RTK and the MAP kinase cascade

Front 23

Adenylyl Cyclase

Back 23

The enzyme that GPCR uses as an effector to create a large amount of cAMP

Front 24

Diacylglycerol (DAG) and Inositol-1,4,5-trisphosphate (IP3)

Back 24

The products when PIP2 is cleaved by an inositol phospholipid

Front 25

Binary Fission

Back 25

The duplication and segregation of genetic information into daughter cells, and the division of cellular contents in bacteria

Front 26

Septum

Back 26

The barrier that grows between two dividing bacteria cells

Front 27

Septation

Back 27

The process of creating a septum in bacterial reproduction

Front 28

Mitosis

Back 28

The phase of the cell cycle in which the spindle apparatus assembles, binds to the chromosomes, and moves the sister chromatids apart

Front 29

Chromatin

Back 29

What chromosomes are composed of

Front 30

Heterochromatin

Back 30

Domains of chromatin that are not expressed

Front 31

Euchromatin

Back 31

Domains of chromatin that are expressed

Front 32

Histone Proteins

Back 32

Proteins that the DNA duplex winds around in the chromosome structure

Front 33

Nucleosome

Back 33

The complex of DNA and histone proteins

Front 34

Karyotype

Back 34

The particular array of chromosomes in an individual organism

Front 35

Haploid (n)

Back 35

Number of different chromosomes in a species

Front 36

Diploid (2n)

Back 36

The total number of chromosomes in a cell

Front 37

Homologous

Back 37

The maternal and paternal chromosomes

Front 38

Homologue

Back 38

One chromosome of a homologous pair

Front 39

Cohesins

Back 39

Complex of proteins that holds chromosomes together

Front 40

Sister Chromatids

Back 40

What composes one condensed chromosome of two strands held together around the centromere

Front 41

G1 (Gap Phase 1)

Back 41

Primary growth phases of the cill, fills the gap between cytokinesis and DNA synthesis, and is the longest phase

Front 42

Cell Cycle

Back 42

The duplication of the genome, its accurate segregation, and the division of cellular contents

Front 43

S (Synthesis)

Back 43

The phase in which the cell synthesizes a replica of genome

Front 44

G2 (Gap Phase 2)

Back 44

The second growth phase, and preparation for separation of the newly replicated genome, during this phase microtubules begin to reorganize to form a spindle

Front 45

Interphase

Back 45

G1, S, and G2, the portion of the cell cycle between cell divisions

Front 46

Cytokinesis

Back 46

The phase of the cell cycle when the cytoplasm divides, creating two daughter cells- in animal cells, the microtubule spindle helps position a contracting ring of actin that constricts like a drawstring to pinch the cell in two

Front 47

G0 Phase

Back 47

A resting state in the cell cycle , generally before G1 (before DNA replication)

Front 48

Centromere

Back 48

The point of constriction on the chromosome containing repeated DNA sequences that bind specific proteins

Front 49

Kinetochore

Back 49

The proteins from the centromere that make up a dislike structure

Front 50

Tubulin

Back 50

The protein that forms microtubules

Front 51

Prophase

Back 51

The first stage of mitosis, when the chromosome condensation initiated in G2 phase reaches the point at which individual condensed chromosomes first become visible with the light microscope

Front 52

Spindle Apparatus

Back 52

The assembly that will later separate the sister chromatids during prophase

Front 53

Aster

Back 53

The arrangement of microtubules where the centrioles extend a radial array of microtubules toward the nearby plasma membrane when they reach the poles of the cell

Front 54

Prometaphase

Back 54

The condensed chromosomes become attached to the spindle by their kinetochores- each chromosome possesses two kinetochores, one attached to the centromere region of each sister chromatid

Front 55

Metaphase

Back 55

The alignment of the chromosomes in the center of the cell

Front 56

Anaphase

Back 56

The shortest stage of Mitosis, begins when the proteins holding sister chromatids together at the centromere are removed. Then comes the simultaneous removal of these proteins from all of the chromosomes. Finally, the sister chromatids are pulled rapidly toward the poles to which their kinetochores are attached

Front 57

Cytokinesis

Back 57

The phase of the cell cycle when the cell actually divides

Front 58

Telophase

Back 58

Phase where the spindle apparatus disassemble as the microtubules are broken down and a nuclear envelope forms around each set of sister chromatids

Front 59

Cleavage Furrow

Back 59

A pinching belt around the cell's circumference created by actin filaments

Front 60

Cyclins

Back 60

Proteins that are produced in synchrony with the cell cycle

Front 61

Cyclin-Dependent Kinase (Cdk)

Back 61

A protein kinase enzyme that is only active when complexed with cyclin

Front 62

G1/S Checkpoint

Back 62

The primary checkpoint at which the cell "decides" whether or not to divide, the phase during which growth factors affect the cycle and also the phase that links cell division to cell growth and nutrition

Front 63

G2/M Checkpoint/M Phase-Promoting Factor (MPF)

Back 63

Complex checkpoint which represents the commitment to mitosis, assessing the success of DNA replication and can stall the cell cycle if DNA has not been accurately replicated

Front 64

Spindle Checkpoint

Back 64

Checkpoint that ensures that all of the chromosomes are attached to the spindle in preparation for anaphase

Front 65

Anaphase-Promoting Complex

Back 65

The signal that tells the cell it can pass by the spindle checkpoint is transmitted through this

Front 66

Platelet-Derived Growth Factor (PDGF)

Back 66

One of the first growth factors to be identified, is a receptor tyrosine kinase that initiates a MAP kinase cascade to stimulate cell division

Front 67

Cancer

Back 67

The unrestrained, uncontrolled growth of cells

Front 68

p53

Back 68

The gene that plays a key role in the G1 checkpoint, monitoring the integrity of DNA, and halting cell division, stimulating the activity of special enzymes to repair the damage

Front 69

Tumor-suppressor Gene

Back 69

Genes that prevent the development of many mutated cells

Front 70

Oncogenes

Back 70

Genes that can, when introduced into a cell, cause it to become a cancer cell

Front 71

Proto-oncogenes

Back 71

Normal cellular genes that become oncogenes when mutated

Front 72

Retinoblastoma Susceptibility Gene (Rb)

Back 72

The first tumor-suppressor gene identified which predisposes individuals for a rare form of cancer that affects the retina of the eye

Front 73

Gametes

Back 73

The egg and sperm cells, each containing two chromosomes

Front 74

Somatic Cells

Back 74

All of the nonreproductive cells of embryos and mature individuals, which contain four chromosomes

Front 75

Zygote

Back 75

The cell created with the fusion of an egg and a sperm cell

Front 76

Fertilization/Syngamy

Back 76

The fusion of gametes to form a new cell

Front 77

Meiosis

Back 77

Occurs during gamete formation, producing cells with half the normal number of chromosomes

Front 78

Sexual Reproduction

Back 78

Reproduction that involves the alternation of meiosis and fertilization

Front 79

Germ-line Cells

Back 79

The cells that will eventually undergo meiosis to produce gametes

Front 80

Meiosis I/II

Back 80

The two rounds of division in Meiosis that each have a prophase, metaphase, anaphase, and telophase stage

Front 81

Synapsis

Back 81

A process during Prophase I of meiosis when homologous chromosomes find each other and become closely associated

Front 82

Synaptonemal Complex

Back 82

An elaborate structure that helps homologous chromosomes find their proper partners during Prophase I

Front 83

Recombination/Crossing Over

Back 83

Process that allows homologues to exchange chromosomal material

Front 84

Chiasmata

Back 84

The sites where crossing over or recombination occurs

Front 85

Independent Assortment

Back 85

The genes in Meiosis I result in the __________ of maternal and paternal chromosomes into gametes

Front 86

Achiasmate Segregation

Back 86

Alternative mechanism for joining homologues and then allowing their segregation during Anaphase I (without chiasmata)

Front 87

Prophase II

Back 87

Phase of Meiosis II where the nuclear envelope breaks down as a new spindle forms at the two poles of the cell

Front 88

Metaphase II

Back 88

Phase of Meiosis II where spindle fibers from opposite poles bind to kinetochores of each sister chromatid, allowing each chromosome to migrate to the metaphase plate as a result of tension on the chromosomes from polar microtubules pulling on sister centromeres

Front 89

Anaphase II

Back 89

Phase of Meiosis II where the spindle fibers contract, and the cohesion complex joining the centromeres of sister chromatids is finally destroyed, allowing sister chromatids to be pulled to opposite poles

Front 90

Telophase II

Back 90

Phase of Meiosis II where the nuclear envelope re-forms around the four sets of daughter chromosomes

Front 91

Aneuploid Gametes

Back 91

Gametes with an improper number of chromosomes

Front 92

Hybridizations

Back 92

Cross-fertilization of different strains to obtain fertile offspring

Front 93

True-breeding

Back 93

Offspring produced from self-fertilization remains uniform from one generation to the next

Front 94

Segregating

Back 94

Some offspring exhibits one form of a trait, and other offspring from the same mating exhibits a different form

Front 95

Self-fertilization

Back 95

Both male and female sexual organs are enclosed in organism, and gametes produced by the parts of the same organism can fuse to form viable offspring

Front 96

Reciprocal Crosses

Back 96

Using sperm from one organism to fertilize another, and vice-versa (such as from white to purple flowers and purple to white flowers)

Front 97

First Filial Generation/F1

Back 97

The first generation ofter a cross-breeding

Front 98

Dominant

Back 98

The trait that is expressed in the F1 generation

Front 99

Recessive

Back 99

The trait that is not expressed in the F1 generation

Front 100

Second Filial Generation/F2

Back 100

The second generation after cross-breeding, contains a 3:1 phenotypic ratio and 1:2:1 genotypic ratio

Front 101

Mendelian Ratio

Back 101

3:1 segregation of phenotypic characteristics for a monohybrid cross

Front 102

Alleles

Back 102

Alternative forms of genes

Front 103

Homozygous

Back 103

When two haploid gametes contain the same allele fuse during fertilization

Front 104

Heterozygous

Back 104

When two haploid gametes contain a different allele fuse during fertilization

Front 105

Genotype

Back 105

The total set of alleles that an individual contains

Front 106

Phenotype

Back 106

The physical appearance of an individual which results from an allele's expression

Front 107

Principle of Segregation

Back 107

States: The two alleles for a gene segregate during gamete formation and are rejoined at random, one from each parent, during fertilization

Front 108

Punnett Square

Back 108

A simple diagram that allows the visualization of the possibilities of the F2 generation

Front 109

Pedigree

Back 109

A consistent graphical representation of matings and offspring over multiple generations for a particular trait

Front 110

Dihybrid Cross

Back 110

The following of behavior of two different traits in a single cross-breed

Front 111

Principle of Independent Assortment

Back 111

States: In a dihybrid cross, the alleles of each gene assort independently

Front 112

Testcross

Back 112

A procedure where an individual with unknown genotype is crossed with a homozygous recessive genotype to reveal what the unknown genotypes are

Front 113

Polygenic Inheritance

Back 113

A mode of inheritance where more than one gene affects the phenotype

Front 114

Continuous Variation

Back 114

The gradation that arises when genes segregate independently and more than one gene affects the phenotype

Front 115

Quantitative Traits

Back 115

The traits that form from continuous variation

Front 116

Pleiotropic

Back 116

An allele that has more than one effect on a phenotype

Front 117

Incomplete Dominance

Back 117

The heterozygote is intermediate in appearance between the two homozygotes

Front 118

Codominant

Back 118

The heterozygote shows some aspect of the phenotype of both homozygotes

Front 119

ABO Blood Groups

Back 119

Four different cell-surface phenotypes that are a good example of codominant alleles

Front 120

Epistasis

Back 120

The type of gene interaction in which one gene can interfere with the expression of another

Front 121

Chromosomal Theory of Inheritance

Back 121

Theory that similar chromosomes pair with one another during Meiosis

Front 122

X Chromosome

Back 122

The sex of an individual is determined by the number of copies of the ___ chromosome

Front 123

Y Chromosome

Back 123

The chromosome the X Chromosome pairs with in Meiosis

Front 124

Sex Chromosomes

Back 124

The X and Y Chromosomes

Front 125

Sex-linked

Back 125

A trait determined by a gene on the X Chromosome

Front 126

Autosomes

Back 126

The twenty-two pairs of perfectly matched chromosomes

Front 127

Dosage Compensation

Back 127

The inactivation of one of the X Chromosomes in females so that there is an equal level of expression from the sex chromosome

Front 128

Genetic Mosaics

Back 128

Individual cells may express different alleles, depending on which chromosome is inactivated

Front 129

Maternal Inheritance

Back 129

The mode of uniparental inheritance from the mother

Front 130

Linked

Back 130

When genes are close together and the number of recombinant progeny is much lower than the number of parental progeny

Front 131

Recombination Frequency

Back 131

The number of recombinant progeny divided by the total progeny

Front 132

Map Unit

Back 132

Each 1% of recombination

Front 133

Anonymous Markers

Back 133

Genetic markers that can be detected using molecular techniques, but that do not cause a detectable phenotype

Front 134

Single-Nucleotide Polymorphisms (SNPs)

Back 134

Polymorphisms affecting a single base of a gene locus

Front 135

Nondisjunction

Back 135

The failure of homologues or sister chromatids to separate properly during meiosis

Front 136

Aneuploidy

Back 136

The gain or loss of a chromosome

Front 137

Monosomics

Back 137

Humans who have lost one copy of an autosome

Front 138

Trisomics

Back 138

Humans who have gained one copy of an autosome

Front 139

X Chromosome Nondisjunction

Back 139

When the X Chromosomes fail to separate during Meiosis

Front 140

Y Chromosome Nondisjunction

Back 140

When the Y Chromosomes fail to separate during Meiosis

Front 141

Genomic Imprinting

Back 141

The phenotype caused by a specific allele is exhibited when the allele comes from one parent, but not from the other

Front 142

Epigenetic Inheritance

Back 142

A stably heritable phenotype resulting from changes in a chromosome without alteration in the DNA sequence

Front 143

Amniocentesis

Back 143

A procedure that permits the prenatal diagnosis of many genetic disorders

Front 144

Chorionic Villi Sampling (CVS)

Back 144

A less invasive procedure for genetic screening than amniocentesis

Front 145

Transformation

Back 145

The transfer of virulence from one cell to another

Front 146

Bacteriophages/Phages

Back 146

Viruses that infect bacteria

Front 147

Purine

Back 147

Adenine or Guanine nitrogenous base in DNA

Front 148

Pyrimidine

Back 148

Thymine or Cytosine nitrogenous base in DNA (or Uracil instead of Thymine in RNA)

Front 149

Phosphodiester Bond

Back 149

The linkage from the 5' phosphate and 3' hydroxyl groups that allow DNA and RNA to form long chains of nucleotides

Front 150

Base-pairs

Back 150

Adenine and Thymine (or Uracil) OR Cytosine and Guanine

Front 151

Semiconservative Model

Back 151

One strand of the parental duplex remains intact in daughter strands

Front 152

DNA Polymerase

Back 152

The enzyme that matches the existing DNA bases with complementary nucleotides and then links the nucleotides together

Front 153

Replicon

Back 153

The DNA controlled by the origin

Front 154

DNA Polymerase I (Pol I)

Back 154

Enzyme that acts on the lagging strand to remove primers and replace them with DNA

Front 155

DNA Polymerase II (Pol II)

Back 155

Enzyme that does not appear to play a role in replication, but is involved in DNA repair processes

Front 156

DNA Polymerase III (Pol III)

Back 156

The main replication enzyme

Front 157

Endonucleases

Back 157

Nucleases that cut DNA internally

Front 158

Exonucleases

Back 158

Nucleases that chew away at an end of DNA

Front 159

Helicases

Back 159

Enzymes that use energy from ATP to unwind the DNA templates

Front 160

Supercoiling

Back 160

When the unwinding of two strands of DNA introduce torsional strain

Front 161

Topoisomerases

Back 161

Enzymes that can alter the topological state of DNA

Front 162

DNA Gyrase

Back 162

A topoisomerase that is involved in DNA replication by relieving supercoiling

Front 163

Leading Strand

Back 163

The DNA strand that is replicated continuously

Front 164

Lagging Strand

Back 164

The DNA strand that is replicated discontinuously

Front 165

Okazaki Fragments

Back 165

DNA fragments synthesized on the lagging strand

Front 166

Replication Fork

Back 166

The partial opening of a DNA helix to form two single strands

Front 167

DNA Ligase

Back 167

An enzyme which seals the "nick," joining the Okazaki fragments into complete strands

Front 168

Replisome

Back 168

The enzymes involved in DNA replication form a macromolecular assembly called the ___________

Front 169

Telomeres

Back 169

The specialized structures found on the ends of eukaryotic chromosomes

Front 170

Telomerase

Back 170

The enzyme that creates the sequence of telomeres

Front 171

Mutagen

Back 171

An agent that increases the number of mutations above background levels

Front 172

Excision Repair

Back 172

A common form of nonspecific repair where a damaged region is removed and is then replaced by DNA synthesis

Front 173

Nutritional Mutations

Back 173

Mutations in cells where the cells carrying them only grow if the medium is supplemented with additional nutrients

Front 174

One-gene/One-polypeptide Hypothesis

Back 174

Relationship idea that many enzymes contain multiple polypeptide subunits, each encoded by a separate gene

Front 175

Central Dogma of Molecular Biology

Back 175

Information passes in one direction from the gene (DNA) to an RNA copy of the gene, and the RNA copy directs the sequential assembly of a chain of amino acids into a protein

Front 176

Transcription

Back 176

The DNA-to-RNA step of the central dogma of molecular biology

Front 177

Translation

Back 177

The RNA-to-protein step of the central dogma of molecular biology

Front 178

Retroviruses

Back 178

Class of viruses that can convert their RNA genome into a DNA copy

Front 179

Reverse Transcriptase

Back 179

A viral enzyme that is used by retroviruses

Front 180

Template Strand

Back 180

The DNA strand that is copied during transcription

Front 181

Coding Strand

Back 181

The DNA strand that is not copied during transcription

Front 182

Messenger RNA (mRNA)

Back 182

An intermediate form of the information in DNA that can be transported out of the eukaryotic nucleus to the cytoplasm for ribosomal processing

Front 183

Ribosomal RNA (rRNA)

Back 183

The class of RNA found in both ribosomal subunits and is critical to the function of the ribosome

Front 184

Transfer RNA (tRNA)

Back 184

The intermediary adapter molecule between mRNA and amino acids, have amino acids covalently attached to one end and and anticodon that can base-pair with an mRNA codon at the other

Front 185

Small Nuclear RNA (snRNAs)

Back 185

Type of RNA that is involved in nuclear processing of eukaryotic "pre-mRNA"

Front 186

Signal Recognition Particle RNA (SRP RNA)

Back 186

Type of RNA that mediates the synthesis of proteins on the rough endoplasmic reticulum

Front 187

Small RNAs (mi-RNA or siRNA)

Back 187

Class of RNA that includes both micro-RNA (miRNA) and small interfering RNA (siRNA)

Front 188

Codons

Back 188

A series of blocks of information, each corresponding to an amino acid in the encoded protein

Front 189

Reading Frame

Back 189

The genetic code is read in increments of three nucleotides (triplet code) without punctuation so the ________ is extremely important

Front 190

Frameshift Mutations

Back 190

Mutations that alter the reading frame of the genetic message

Front 191

Stop Codons

Back 191

Three codons, UAA, UGA, and UAG, that signals "stop"

Front 192

Start Codon

Back 192

One codon, AUG, that signals "start"

Front 193

Degenerate

Back 193

Word that describes the fact that some amino acids are specified by more than one codon

Front 194

Promoter

Back 194

DNA site that forms a recognition and binding site for the RNA polymerase

Front 195

Start Site

Back 195

DNA site where the RNA polymerase begins transcription

Front 196

Terminator

Back 196

DNA site where the RNA polymerase is signaled to end transcription

Front 197

Transcription Unit

Back 197

The region on the DNA strand from the promoter to the terminator

Front 198

Transcription Bubble

Back 198

The region that contains the RNA polymerase, the DNA template, and the growing RNA transcript

Front 199

Operon

Back 199

The grouping of functionally related genes

Front 200

RNA Polymerase I

Back 200

The enzyme that transcribes rRNA

Front 201

RNA Polymerase II

Back 201

The enzyme that transcribes mRNA and some small nuclear RNAs

Front 202

RNA Polymerase III

Back 202

The enzyme that transcribes tRNA and some small nuclear RNAs

Front 203

TATA Box

Back 203

Part of the "core promoter" that RNA Polymerase II binds to

Front 204

Transcription Factors

Back 204

Factors that allow for promoter recognition

Front 205

Primary Transcript

Back 205

The RNA synthesized by RNA Polymerase II

Front 206

Mature mRNA

Back 206

The RNA produced from the primary transcript after undergoing caps, tails, and splicing

Front 207

5' Cap/Methyl-G Cap

Back 207

The modified primary transcript by the addition of GTP to the 5' PO4 group

Front 208

3' Poly-A Tail

Back 208

A series of adenine residues added to the 3' end of the primary transcript

Front 209

Spliceosome

Back 209

An organelle that splices the pre-mRNA so that noncoding sequences are removed

Front 210

Introns

Back 210

The noncoding DNA that interrupts the sequence of the gene

Front 211

Exons

Back 211

The coding sequences of DNA

Front 212

Pre-mRNA Splicing

Back 212

The process of the primary transcript being cut and put back together

Front 213

Small Nuclear Ribonucleoprotein Particles (snRNPs)

Back 213

Complexes composed of snRNA and protein that cluster together to form a spliceosome

Front 214

Alternative Splicing

Back 214

A process where a single primary transcript can be spliced into different mRNAs by the inclusion of different sets of exons

Front 215

Aminoacyl-tRNA Synthetases

Back 215

This enzyme activates the covalent attachment of an amino acid to the correct tRNA for protein synthesis

Front 216

Acceptor Stem

Back 216

The end of the tRNA that allows amino acids to be attached

Front 217

Anticodon Loop

Back 217

The part of the tRNA that contains the anticodon sequence so it can base-pair with codons in the mRNA

Front 218

Charging Reaction

Back 218

The reaction where an amino acid joins to a tRNA

Front 219

P Site (Peptidyl)

Back 219

Ribosomal site that binds to the tRNA attached to the growing peptide chain

Front 220

A Site (Aminoacyl)

Back 220

Ribosomal site that binds to the tRNA carrying the next amino acid to be added

Front 221

E Site (Exit)

Back 221

Ribosomal site that binds to the tRNA that carried the previous amino acid added

Front 222

Peptidyl Transferase

Back 222

This enzyme is required for the formation of peptide bonds within the ribosome

Front 223

Initiation Complex

Back 223

The complex that includes the small subunit, mRNA, tRNA (fMet), and some other initiation factors

Front 224

Initiator tRNA

Back 224

A special tRNA molecule that is charge with a chemically modified methionine

Front 225

Ribosome-Binding Sequence (RBS)

Back 225

A conserved sequence in the 5' end of the mRNA that helps position the small ribosomal subunit and the mRNA strand correctly

Front 226

Elongation Factor (EF-Tu)

Back 226

A factor that binds to the charged tRNA and to GTP to help bind a second charged tRNA to the empty A site

Front 227

Wobble Pairing

Back 227

The effect of the presence of modified bases with less accurate pairing in the 5' position of the anticodon

Front 228

Signal Sequence

Back 228

A polypeptide that starts with a short series of amino acids

Front 229

Signal Recognition Particle (SRP)

Back 229

A cytoplasmic complex of proteins that specifically recognizes the signal sequence

Front 230

Point Mutation

Back 230

A mutation that alters a single base

Front 231

Base Substitution Mutation

Back 231

The substitution of one base pair for another in DNA

Front 232

Missense Mutation

Back 232

When base substitution changes an amino acid in protein

Front 233

Nonsense Mutations

Back 233

When base substitution changes a transcribed codon to a stop codon

Front 234

Chromosomal Mutations

Back 234

Extensive mutations that alter the structure of the chromosome itself

Front 235

Deletion

Back 235

The loss of a portion of a chromosome

Front 236

Duplication

Back 236

The mutation where the region of a chromosome is replicated and may or may not lead to phenotypic consequences

Front 237

Inversion

Back 237

When a segment of a chromosome is broken in two places, reversed, and put back together

Front 238

Translocation

Back 238

When a piece of one chromosome is broken off and joined to another chromosome

Front 239

Regulatory Proteins

Back 239

Proteins that modulate the ability of RNA polymerase to bind to the promoter

Front 240

Major Groove

Back 240

The deeper groove of the DNA molecule

Front 241

DNA-Binding Motifs

Back 241

Regulatory proteins employ _________ that share the property of interacting with specific sequences of bases

Front 242

Helix-Turn-Helix

Back 242

The most common DNA-binding motif constructed from two alpha-helical segments

Front 243

Homeodomain

Back 243

A special class of helix-turn-helix motifs that play critical roles in development in many eukaryotic organisms

Front 244

Zinc Fingers

Back 244

A DNA-binding motif that uses one or more zinc atoms to coordinate its binding to DNA

Front 245

Leucine Zipper

Back 245

A DNA-binding motif that allows different subunits of a protein to associate with the DNA (an example of a dimerization motif)

Front 246

Positive Control

Back 246

Control that increases the frequency of initiation

Front 247

Negative Control

Back 247

Control that decreases the frequency of initiation

Front 248

Repressors

Back 248

Proteins that mediate negative control

Front 249

Operators

Back 249

The regulatory DNA site that repressors bind to

Front 250

Induction

Back 250

When enzymes for a certain pathway are produced in response to a substrate

Front 251

Repression

Back 251

When enzymes for a certain pathway are non produced

Front 252

Catabolite Activator Protein (CAP)

Back 252

An allosteric protein with cAMP as an effector

Front 253

Derepressed

Back 253

When an operon that has been repressed, stopped being repressed

Front 254

General Transcription Factors

Back 254

Factors necessary to establish productive initiation

Front 255

Specific Transcription Factors

Back 255

Factors that act in a tissue- or time-dependent manner to stimulate higher levels of transcription than the basal level

Front 256

Enhancers

Back 256

The DNA binding sites of specific transcription factors

Front 257

Transcription Complex

Back 257

What all of the specific transcription factors make-up

Front 258

Chromatin-Remodeling Complexes

Back 258

Complexes that alter chromatin structure to regulate gene expression

Front 259

Micro-RNA (miRNA)

Back 259

A type of small RNA directly involved in gene expression

Front 260

Small Interfering RNAs (siRNAs)

Back 260

These use double-stranded RNAs to turn off gene expression

Front 261

RNA-Induced Silencing Complex (RISC)

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The complex of proteins where miRNA eventually is loaded into

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RNA Interference

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The most commonly used term that describes the production of siRNAs

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Translation Repressor Proteins

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Proteins that shut down translation by binding to the beginning of the transcript, so that it cannot attach to the ribosome

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Proteases

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Enzymes that can degrade proteins by breaking peptide bonds, converting a protein into its constituent amino acids

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Proteasome

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The cellular organelle that degrades proteins marked with ubiquitin