unit 6 test (6.5-6.8)

Question 1

operons

Answer 1

group of genes that can be turned on or off

have three parts
-promotor
-operator
-gener

Question 2

promotor of an operon

Answer 2

where RNA p. can attach

Question 3

operator of an operon

Answer 3

on/off switch

Question 4

genes of an operon

Answer 4

code for related enzymes in pathway

Question 5

operons can be — or —

Answer 5

repressible; inducible

Question 6

repressible operons

Answer 6

(on to off)
transcription is usually on, but can be repressed (stopped)

ex: trp operon

Question 7

inducible operons

Answer 7

(off to on)
transcription is usually off, but can be induced (started)

ex: lac operon

Question 8

regulatory gene

Answer 8

produces a repressor protein that binds to the operator to block RNA p. from transcribing the gene
-always expressed, but at low levels
-binding of a repressor to a operator is reversible

Question 9

allosteric activator

Answer 9

substrate binds to the allosteric site and stabilizes the shape of the enzyme so that the active sites remain open

Question 10

allosteric inhibitor

Answer 10

substrate binds to allosteric sire and stabilizes the enzyme shape so that the active sites are closed (inactive form)

Question 11

trp operon

Answer 11

-in bacteria, controls the synthesis of tryptophan
-since its repressible, transcription is active
–it can be switched off by a trp repressor
—allosteric enzyme that is only active when tryptophan binds to it

Question 12

when too much tryptophan builds up in the bacteria, tryptophan is — likely to bind to the — turning it —, which will then temporarily — — transcription for tryptophan.

Answer 12

more; repressor; active; shut off

Question 13

the lac operon

Answer 13

-controls the synthesis of lactase, an enzyme that digests lactose (milk sugar)
-since it is inducible, transcription is usually off
–a lac repressor is bound to the operator (allosterically active)
-the inducer for the lac repressor is allolactose
–when present it will bind to the lac repressor and turn it off (allosterically inactive)
—genes can now be transcribed

Question 14

eukaryotic gene expression is regulated at 5 different stages

Answer 14

chromatin structure, epigenic inheritance, transcription initiation, rna processing, translation initiation

Question 15

chromatin structure:

if dna is tightly wound, it is — accessible for transcription. how can it be modified?

Answer 15

less;
histone acetylation & dna methylation

Question 16

histone acetylation

Answer 16

adds acetyl groups to histones, which loosens the DNA

Question 17

DNA methylation

Answer 17

adds methyl groups to dna, which cause chromatin to condense

Question 18

epigenic inheritance

chromatin modifs dont alter the — sequence of the dna, but they can be — to future generations. modifs can be — unlike mutations. explains why one — twin may inherit a disease while the other doesnt

Answer 18

nucleotide; heritable; reversed; identical

Question 19

transcription initiation

once chromatin modifs allow the dna to be more accessible, specific transcription factors bind to — —. sections of non-coding dna that serve as binding sites. — — can be increased/decreased by binding of activators or — to control elements

Answer 19

control elements; gene expression; repressors

Question 20

rna processing

Answer 20

alternative splicing of a pre-mrna

Question 21

translation initiation

Answer 21

-translation can be activate/repressed by initiation factors
-micro rna’s and small interfering rna’s can bind to mrna and degrade it or block translation

Question 22

during embryonic development, cell — and cell — occurs

Answer 22

division; differentiation
-cells become specialized in their structure and function
-morphogenesis: physical process that gives an organism its shape

Question 23

how do cells differentiate during early development?

Answer 23

cytoplasmic determinants and induction

Question 24

cytoplasmic determinants

Answer 24

substances in the maternal egg that influence cells

Question 25

induction

Answer 25

cell to cell signals that can cause a change in gene expression

Question 26

both cytoplasmic determinants and induction influence

Answer 26

pattern formation
-a “body plan” for the organism
–homeostatic genes: map out the body structures

Question 27

as cells differentiate, — plays a critical role

Answer 27

apoptosis

ex: if this didnt happen during devel, humans would have webbed feet and hands.

Question 28

mutation

Answer 28

change in genetic material of a cell, which can alter phenotypes

Question 29

mutations are the primary source of

Answer 29

genetic variation
-normal function and production of cellular products is essential
–any disruption can cause new phenotypes

Question 30

mutations or changes can be — — or — —

Answer 30

large scale; small scale

Question 31

large scale mutations

Answer 31

chromosomal changes

Question 32

small scale mutations

Answer 32

nucleotide substitutions, insertions, or deletions

ex: point mutations, frameshift mutations

Question 33

point mutations (small scale mutation)

Answer 33

change a single nucleotide pair of a gene
-substitution: replacement of one nucleotide and its partner with another pair of nucleotides
-types:
–silent
–missense
–nonsense

Question 34

silent point mutation (small scale mutation)

Answer 34

change still codes for same AA (redundancy)

Question 35

missense point mutation (small scale mutation)

Answer 35

change results in a diff AA
-conservative: keeps same grouping of AA

Question 36

nonsense point mutation (small scale mutation)

Answer 36

change results in a stop codon

Question 37

frameshift mutation (small scale mutation)

Answer 37

when the reading frame of genetic info is altered
-disastrous effects to resulting proteins
–insertion: nucleotide is inserted
–deletion: nucleotide is deleted

Question 38

large scale mutations

Answer 38

mutations that affect chromosomes
-types:
–nondisjunction
–translocation
–inversions
–duplications
–deletions

Question 39

nondisjunction (large scale mutation)

Answer 39

when chromosomes dont separate properly in meiosis
-results in the incorrect number of chromosomes
–trisomy 21

Question 40

translocation (large scale mutation)

Answer 40

segment of one chromosome moves to another

Question 41

inversions (large scale mutation)

Answer 41

segment is reversed

Question 42

duplications (large scale mutation)

Answer 42

segment is repeated

Question 43

deletions (large scale mutation)

Answer 43

segment is lost

Question 44

any time mutations occur, they are subject to — —

Answer 44

natural selection

Question 45

genetic changes can sometimes — the survival and reproduction (fitness) of an organism

Answer 45

enhance

Question 46

prokaryotes can exchange genetic material through

Answer 46

horizontal gene transfer

Question 47

if there is a mutation that is beneficial to the survival and reproduction of that prokaryote, then it can be

Answer 47

transferred from one prokaryote to another
-types:
–transformations
–transductions
–conjugations
–transpositions

Question 48

transformations

Answer 48

up taking of dna from a nearby cell

Question 49

transduction

Answer 49

viral transmission of genetic material

Question 50

conjugation

Answer 50

cell to cell transfer of dna

Question 51

transposition

Answer 51

movement of dna segments within and between dna molecules

Question 52

pcr

Answer 52

polymerase chain reaction: method used in molecular bio to make several copies of a specific dna segment
-segments of dna are amplified
-results can be analyzed using gel electrophoresis