Chapter 8 Microbial Genetics

Front 1

Genetics

Back 1

Genetics: The study of what genes are, how they carry information, how information is expressed, and how genes are replicated

Front 2

Gene

Back 2

Gene: A segment of DNA that encodes a functional product, usually a protein

Front 3

Chromosome

Back 3

Chromosome: Structure containing DNA that physically carries hereditary information; the chromosomes contain the genes

Front 4

Genome

Back 4

Genome: All the genetic information in a cell

Front 5

Genomics

Back 5

Genomics: The molecular study of genomes

Front 6

Genotype

Back 6

Genotype: The genes of an organism

Front 7

Phenotype

Back 7

Phenotype: Expression of the genes

Front 8

DNA-Polymer

Back 8

Polymer of nucleotides: Adenine, thymine, cytosine, and guanine

Front 9

What is Double helix of DNA associated with?

Back 9

Double helix associated with proteins

Front 10

What is the back bone of DNA?

Back 10

Backbone" is deoxyribose-phosphate

Front 11

What are the strands of DNA held together with?

Back 11

Strands are held together by hydrogen bonds between AT and CG

Front 12

DNA is copied by?

Back 12

DNA is copied by DNA polymerase

Front 13

Step 1 of DNA replication

Back 13

Topoisomerase relaxes supercoiled DNA.

Front 14

Step 2 of DNA replication

Back 14

Helicase unwinds the double helix by breaking hydrogen bonds between the base pairs.

Front 15

Step 3 of DNA replication

Back 15

Destabilizing Enzymes (SSB) bind to the single strands to keep the strands separated.

Front 16

Step 4 of DNA replication

Back 16

Primase adds RNA primers to initiate DNA synthesis.

Front 17

Step 5 of DNA replication

Back 17

DNA polymerase binds at the RNA primers, DNA polymerase I removes primers and DNA polymerase III synthesizes new DNA in the 5’ to 3’ direction on both the leading and lagging strands.

Front 18

Step 6 of DNA replication

Back 18

Fragments of DNA (Okazaki fragments on the lagging strand) are joined by the enzyme DNA ligase

Front 19

Define Transcription

Back 19

Transcription: RNA is made from the DNA code. The RNA has complementary bases to the DNA.

Front 20

Define Translation

Back 20

Translation: RNA is used as a template to make protein. Amino acids, protein building blocks are coded by the base pairs on the RNA.

Front 21

When does transcription stop?

Back 21

Transcription stops when it reaches theterminator sequence

Front 22

What is the direction of transcription?

Back 22

Transcription proceeds in the 5' to 3' direction

Front 23

When does transcription begin?

Back 23

Transcription begins when RNA polymerase binds to the promoter sequence

Front 24

What does transcribed DNA make?

Back 24

DNA is transcribed to make RNA (mRNA, tRNA, and rRNA)

Front 25

Define degenerate code

Back 25

Degenerate code: most amino acids specified by more than one codon.

Front 26

Define condon

Back 26

Codon: Group of three nucleotides on mRNA that codes for an amino acid.

Front 27

Structure of mRNA Nucleotides

Back 27

The mRNA nucleotides are arranged in 3 nucleotide units called codons. Codons do not overlap.

Front 28

Protein synthesis is based on?

Back 28

Protein is synthesized based on code in mRNA

Front 29

Genetic code structure

Back 29

64 sense codons on mRNA encode the 20 amino acids

Front 30

Translation of mRNA begins at what start codon?

Back 30

Translation of mRNA begins at the start codon: AUG

Front 31

Where does Translation end?

Back 31

Translation ends at nonsense codons: UAA, UAG, UGA

Front 32

What does tRNA carry?

Back 32

tRNA carries the complementary anticodon

Front 33

Name the three types of RNA.

Back 33

messenger RNA
transfer RNA
ribosomal RNA

Front 34

What is messenger RNA?

Back 34

messenger RNA (mRNA) – carries DNA message through complementary copy; message is in triplets called codons

Front 35

What is transfer RNA?

Back 35

transfer RNA (tRNA) – secondary structure creates loops; bottom loop exposes a triplet of nucleotides called anticodon which designates specificity and complements mRNA; carries specific amino acids to ribosomes

Front 36

What is ribosomal RNA?

Back 36

ribosomal RNA (rRNA) – component of ribosomes where protein synthesis occurs

Front 37

Step 1 of Translation

Back 37

Translation of mRNA begins at the start codon: AUG

Front 38

Step 2 of Translation

Back 38

Translation ends at a STOP codon:

Front 39

Step 3 of Translation

Back 39

The large and small ribosomal subunits and tRNA with UAC anticodon and corresponding methonine amino acid assemble at the AUG start codon.

Front 40

Step 4 of Translation

Back 40

The first tRNA moves to P site of the ribosome and the second tRNA with the next amino acid enters A site of the ribosome.

Front 41

Step 5 of Translation

Back 41

The ribosome joins the two amino acids with a peptide bond.

Front 42

Step 6 of Translation

Back 42

The first tRNA molecule leaves the ribosome and the second tRNA moves into P site while the third tRNA and its amino acid enters A site.

Front 43

Step 7 of Translation

Back 43

This process proceeds down the mRNA and amino acid chain is formed.

Front 44

Step 8 of Translation

Back 44

Translation ends when one of three nonsense (stop codons) UAA, UAG, UGA is reached and the ribosome subunits separate from the mRNA and release the polypeptide chain, tRNA.

Front 45

What genes are expressed at a fixed rate?

Back 45

Constitutive genes are expressed at a fixed rate

Front 46

What other genes are expressed only when needed?

Back 46

Repressible genes
Inducible genes
Catabolite repression

Front 47

What are normally turned off, but can be tured on?

Back 47

Inducible Operons

Front 48

When lactose is present what else is present?

Back 48

when lactose is present, allolactose is present which turns on b-galactosidase to process the lactose

Front 49

What does Allolactose induce?

Back 49

Allolactose induces the transcription of b-galactosidase.

Front 50

What happens to media when lactose is present?

Back 50

When lactose is present in the media it is converted by the cell to allolactose.

Front 51

What happens when no lactose is present in the media?

Back 51

When no lactose is present in the media, E. coli do not make b-galactosidase.

Front 52

What breaks down lactose into glucose?

Back 52

b-galactosidase breaks down lactose into glucose and galactose.

Front 53

What is required for lactose metabolism in E. coli?

Back 53

inducible genes

Front 54

Lac operon

Back 54

Genes required for tryptophan synthesis are normally transcribed.

Front 55

When excess tryptophan is present, it can act as a corepressor.

Back 55

Lac Operon Tryptophan Operon

Front 56

Normally on, can be turned off.

Back 56

Lac Operon Tryptophan Operon

Front 57

Define Spontaneous mutations.

Back 57

Spontaneous mutations: Occur in the absence of a mutagen

Front 58

Define Mutagen.

Back 58

Mutagen: Agent that causes mutations

Front 59

Describe Mutaion.

Back 59

A change in the genetic material
Mutations may be neutral, beneficial, or harmful

Front 60

Base substitution

Back 60

Change in one base

Front 61

Missense substitution

Back 61

Result in change in amino acid

Front 62

Result in change in amino acid

Back 62

Insertion or deletion of one or more nucleotide pairs

Front 63

Frequency of Mutagens

Back 63

Mutagens increase to 10–5 or 10–3 per replicated gene

Front 64

Frequency of spontaneous mutation

Back 64

Spontaneous mutation rate = 1 in 109 replicated base pairs or 1 in 106 replicated genes

Front 65

Define Ionizing radiation

Back 65

Ionizing radiation (X rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone

Front 66

What does radiation cause?

Back 66

UV radiation causes thymine dimers

Front 67

Radiation repair

Back 67

Photolyases separate thymine dimers
Nucleotide excision repair

Front 68

Horizontal Gene Transfer

Back 68

Horizontal gene transfer: The transfer of genes between cells of the same generation.

Front 69

Vericle Gene Transfer

Back 69

Vertical gene transfer: Occurs during reproduction between generations of cells.

Front 70

The Genetic recombination in bacteria are?

Back 70

Conjugation
Transformation
Transduction

Front 71

when does crossing over occur?

Back 71

Crossing over occurs when two chromosomes break and rejoin

Front 72

Define transformation.

Back 72

Transformation – chromosome fragments from a lysed cell are accepted by a recipient cell

Front 73

Explain Griffith’s Transformation Experiment.

Back 73

injected mice with bateria, encapsuled, non encapsuled, heat fixed encapsuled, and non heat encapsuled to see if they would live or die.

Front 74

Define Conjugation.

Back 74

Conjugation – transfer of a plasmid or chromosomal fragment from a donor cell to a recipient cell via a direct connection

Front 75

Define high-frequency recombination.

Back 75

High-frequency recombination – donor’s fertility plasmid has been integrated into the bacterial chromosome

Front 76

Gram-negative cell donor has whas what type of fertility?

Back 76

Gram-negative cell donor has a fertility plasmid (F plasmid, F′ factor) that allows the synthesis of a conjugation (sex) pilus

Front 77

Define transduction.

Back 77

Transduction – bacteriophage serves as a carrier of DNA from a donor cell to a recipient cell

Front 78

what are the types of Transduction by a Bacteriophage?

Back 78

Generalized
Specialized

Front 79

function of Complex transposons

Back 79

Carry other genes

Front 80

Transpons contain?

Back 80

Contain insertion sequences for cutting and resealing DNA (transposase)

Front 81

Transpons mobility

Back 81

Segments of DNA that can move from one region of DNA to another

Front 82

Genes and evolution

Back 82

Fittest organisms for an environment are selected by natural selection

Front 83

What do mutation and recombination provide?

Back 83

Mutations and recombination provide diversity