chapter 8: microbial genetics

Question 1

gene

Answer 1

segments of DNA (usually proteins)

Question 2

chromosome

Answer 2

structures with DNA that contain genes & carry hereditary info; string of DNA wrapped around proteins that give the nucleic acid bases structure

Question 3

DNA

Answer 3

deoxyribose nucleic acid; macromolecule that carries genetic information; typically double stranded

Question 4

how are genes encoded?

Answer 4

by three codons which code as a specific amino acid

Question 5

what do genes encode?

Answer 5

the synthesis of a gene product, either RNA or protein

Question 6

gene expression

Answer 6

controlled by operons; process by which the information encoded in a gene is used to direct the assembly of a protein molecule

Question 7

constitutive gene expression

Answer 7

gene transcribed at a constant level; expressed at a fixed rate

Question 8

regulated gene expression

Answer 8

some switch to turn gene on or off (repressor / transcription factors)

Question 9

central dogma

Answer 9

DNA transcribed → RNA translated→ protein

Question 10

what makes retroviruses different?

Answer 10

they reverse transcribe RNA → DNA

Question 11

“semiconservative nature of DNA replication”

Answer 11

DNA is half old and half new when it is replicated

Question 12

vertical gene transfer

Answer 12

genes from parents; flow of genetic info from one generation to the next

Question 13

horizontal gene transfer

Answer 13

organisms can pick up genetic traits from sources other than parents
ex) virus picks up your genes and gives it to another host “transduction”; tree “tumors”; important for evolution

Question 14

bacterial operon

Answer 14

group of genes turned on by single promoter

Question 15

promoter

Answer 15

binds RNA polymerase + DNA

Question 16

operator

Answer 16

genetic sequences recognized by oppressor; allows proteins responsible for transcription (operons) to attach to the DNA sequence

Question 17

repressible operon

Answer 17

sticks to DNA and prevents gene from being expressed; blocks transcription; default position is on

Question 18

inducible operon

Answer 18

requires an inducer; default position is off

Question 19

phenotype

Answer 19

“physical” expression of genes

Question 20

genotype

Answer 20

genetic makeup of an organism

Question 21

base substitution / point mutation

Answer 21

change in one base in DNA; single DNA base pair is altered

Question 22

frameshift mutation

Answer 22

insertion / deletion of one or more nucleotide pairs; shifts the translational “reading frame”

Question 23

missense mutation

Answer 23

base substitution results in change in an amino acid; the meaning of the genetic material gets changed

Question 24

nonsense mutation

Answer 24

base substitution results in nonsense (stop) codon

Question 25

nucleotide excision repair

Answer 25

cut out the nonmethylated strand where there is damage and then use the methylated strand to write in a complementary copy

Question 26

photolyases

Answer 26

DNA repair enzyme that uses visible light to break thymine dimers (abnormal chemical bond of thymine bases in DNA) apart; mostly used for repairing damage from ultraviolet radiation

Question 27

non-homologous end joining (NHEJ)

Answer 27

mechanism for repairing double-strand breaks in the sugar-phosphate backbone of DNA; “non-homologous” =does not use a template to place broken piece back on

Question 28

homologous recombination (HR)

Answer 28

mechanism for repairing double-strand breaks in the sugar-phosphate backbone of DNA which uses a homologous / sister chromosome as a template to know where to piece the broken pieces of the DNA back together

Question 29

positive (direct) selection

Answer 29

killing off everything that does not match what you want to keep; mutant cells grow / appear different that unmutated cells

Question 30

negative (indirect) selection

Answer 30

killing off cells that you want; mutant cells that cannot grow or perform a certain function

Question 31

selective media

Answer 31

allows certain organisms to grow while inhibiting the growth of other organisms

Question 32

replica plating

Answer 32

technique in which one or more secondary petri dishes containing different selective growth media are inoculated with the same colonies of microorganisms from a primary plate by stamping
ex) in selective, colony will die; in nonselective, colony will live

Question 33

ames test

Answer 33

tests for carcinogenicity by growing bacteria that require histidine without histidine

Question 34

transformation (horizontal gene transfer)

Answer 34

genes transferred from one bacterium to another as “naked” DNA

Question 35

transduction (horizontal gene transfer)

Answer 35

DNA is transferred from a donor cell to a recipient via a bacteriophage (virus)

Question 36

conjugation (horizontal gene transfer)

Answer 36

plasmids transferred from one bacterium to another; requires cell-to-cell contact via pili

Question 37

plasmid

Answer 37

circle of DNA that have an origin of replication; code for proteins that enhance pathogenicity of a bacterium

Question 38

transposon

Answer 38

section of DNA that can cut and paste itself from one region to another; “jumping genes”; contains insertion sequences (IS) that codes for transposae that cuts and reseals DNA