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Genetics Essentials
Chapter 99
taking a chance
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1

you want to design a repressor protein mutant. which protein domain is the best target for preventing binding of the corepressor?

allosteric domain

2

Physical separation of a segment of a large population by a physical barrier that prevents gene flow can lead to

Allopatric speciation

3

In the lac operon, what acts as the inducer?

allolactose

4

Which of the following prezygotic reproductive isolating mechanisms best explains why salamanders that live in trees do not successfully mate with salamanders that live in soil by rivers?

Ecological isolation

5

The length of a branch on a phylogenetic tree can be indicative of

The evolutionary distance

6

In the absence of glucose, the CAP protein binds to a DNA sequence adjacent to the promoter of the lac operon. Binding of CAP helps RNA polymerase to bind to the promoter and allows for a high level of transcription of the lac operon. Regulation of the lac operon by the CAP protein is an example of

positive regulation

7

Given the DNA sequence 5'TAC AAA ATA CAG CGG-3', which of these sequences represents a frameshift mutation?

5';-TAC AAA TAC AGC GGG-3'

8

Most genes in prokaryotes and eukaryotes are regulated primarily at which level of expression

Transcription

9

In Burkitt lymphoma patients, despite translocation, the oncogene c-MYC remains intact in its new location. Yet c-MYC isbelieved to be responsible for the lymphoma because

the c-MYC gene is placed under the control of B-cell-specific gene regulatory sequences

10

Which position of a codon evolves at the highest rate?

third position

11

In catabolite repression (response to glucose levels) of the lac operon, glucose affects most directly

level of cAMP

12

Which of the following is an example of a postzygotic mechanism for reproductive isolation?

hybrid sterility

13

A mutant E. coli strain grown under conditions that normally induce the lac operon, does not produce functional b-galactosidase. What is a possible genotype of the cells?

lacI+lacP-lacO+lacZ+lacY+lacA+

14

Which type of mutation converts a nucleotide to an alternative structure with the same composition but slightly different placement of hydrogen bonds with a rare, less stable form that causes base-pair mismatch?

Tautomeric shift

15

you have conducted an Ames test on a given compound; which of the following would be classified as a positive result on the Ames test?

His- strain grows on an his- plate&nbsp

16

When populations share a single habitat but are isolated by genetic or postzygotic mechanisms that prevent gene flow, what process can cause populations to diverge?

sympatric speciation

17

Which of these haploid strains produce beta;-galactosidase constitutively but do not produce permease?

I- P+ O+ Z+ Y-&nbsp

18

During the attenuation of the trp operon, which stem loop leads to polycistronic mRNA synthesis during tryptophan starvation?

2-3 (antitermination) stem loop

19

An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operon. The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule.

Negative repressible

20

In lamda; phage, which protein, the product of the cI gene, blocks the transcription required to initiate the lytic cycle?

lambda repressor

21

Cancer is often the result of activation of ____ to ____ and the inactivation of ____ genes.

proto-oncogenes, oncogenes, tumor-suppressor genes

22

About 50% of all human cancers may involve an abnormal or missing

p53

23

Inherited retinoblastoma requires ____ mutation(s) or deletion(s).

two

24

What is a constitutive gene?

A constitutive gene is not regulated and is expressed continually.

25

Why is transcription a particularly important level of gene regulation in both bacteria and eukaryotes?

Transcription is the first step in the process of information transfer from DNA to protein. For cellular efficiency, gene expression is often regulated early in the process of protein production.

26

how does the binding of regulatory proteins to enhancers affect transcription at genes that are thousands of base pairs away?

The DNA between the enhancer and the promoter loops out, so that transcription activators bound to the enhancer are able to interact directly with the basal transcription apparatus.

27

how does the poly(a) tail affect mrNa stability?

The poly(A) tail stabilizes the 5' cap, which must be removed before the mRNA molecule can be degraded from the 5' end

28

How does a suppressor mutation differ from a reverse mutation?

A reverse mutation restores the original phenotype by changing the DNA sequence back to the wild type. A suppressor mutation restores the phenotype by causing an additional change in the DNA at a site that is different from that of the original mutation

29

how are flanking direct repeats created in transposition?

In transposition, staggered cuts are made in DNA and the transposable element inserts into the cut. Later, replication WORKED PROBLEM of the single-stranded pieces of DNA creates short repeats on either side of the inserted transposable element.

30

Why are defects in DNA repair often associated with increases in cancer?

Changes in DNA structure may not undergo repair in people with defects in DNA-repair mechanisms. Conse- quently, increased numbers of mutations occur at all genes, including those that predispose to cancer. This observation indicates that cancer arises from mutations in DNA.

31

Base substitution

Changes a single DNA nucleotide

32

transition

Base substitution in which a purine replaces a purine or a pyrimidine replaces a pyrimidine

33

transversion

Base substitution in which a purine replaces a pyrimidine or a pyrimidine replaces a purine

34

Insertion

Addition of one or more nucleotides

35

Deletion

Deletion of one or more nucleotides

36

Frameshift mutation

Insertion or deletion that alters the reading frame of a gene

37

In-frame deletion or insertion

Deletion or insertion of a multiple of three nucleotides that does not alter the reading frame

38

Expanding nucleotide repeats

Increases the number of copies of a set of nucleotides

39

Forward mutation

Changes the wild-type phenotype to a mutant phenotype

40

reverse mutation

Changes a mutant phenotype back to the wild-type phenotype

41

Missense mutation

Changes a sense codon into a different sense codon, resulting in the incorporation of a different amino acid in the protein

42

Nonsense mutation

Changes a sense codon into a nonsense (stop) codon, causing premature termination of translation

43

Silent mutation

Changes a sense codon into a synonymous codon, leaving the amino acid sequence of the protein unchanged

44

Neutral mutation

Changes the amino acid sequence of a protein without altering its ability to function

45

Loss-of-function mutation

Causes a complete or partial loss of function

46

Gain-of-function mutation

Causes the appearance of a new trait or function or causes the appearance of a trait in inappropriate tissue or at an inappropriate time

47

Lethal mutation

Causes premature death

48

Intragenic suppressor mutation

Suppresses the effect of an earlier mutation within the same gene

49

Intergenic suppressor mutation

Suppresses the effect of an earlier mutation in another gene

50

Suppressor mutation

Suppresses the effect of an earlier mutation at a different site

51

What role does genetic drift play in allopatric speciation?

Genetic drift can bring about changes in the allelic frequencies of populations and lead to genetic differences among populations. Genetic differentiation is the cause of postzygotic and prezygotic reproductive isolation between populations that leads to speciation

52

Helix-turn-helix

Location:bacterial regulatory proteins related motif in eukaryotic proteins Characteristics: two alpha helices , Binding site:Major groove.

53

helix-loop-helix

Location: eukaryotic proteins Characteristics: two alpha helices by a loop of amino acids , Binding site:Major groove.

54

zinc finger

Location: eukaryotic regulatory and other protiens Characteristics: Loop of amino acids with zinc at base , Binding site:Major groove.

55

leucine-zipper

Location: eukaryotic transcription factors Characteristics: helix of leucine resides and a basic arm two leucines residues interdigate , Binding site: two adjacent Major grooves

56

Constitutive

always on at constant level

57

Inducible

-normally off, but can turn on when
needed. change environment, gene turns on

58

Repressible--

normally on, but can be turned off
when needed change environment, gene turns off

59

operon

is a group of bacterial genes transcribed together aka coordinate expression

60

Negative-->

repressor

61

Positive-->

active regulator

62

Cis-

acting Same DNA molecule

63

Trans-acting

Can act on another DNA molecule

64

lactose

is an example of positive control when lactose is present. The transcription for lactase will be made to get rid of the extra lactose. So lactose is inducible or force to turn on

65

tryptophan

is a negative control when tryptophan present then the system will turn off and stop making tyrptophan. so tryphtophan is reducible forced to turn off.

66

merodiploids

which will create a single bacteria with two different
copies of a gene. by using F’ plasmids, Such as a Z+ and Z- gene?

67

What attenuation is terminates TRP transcription?

The secondary structures or TRP codons 1+2 and 3+4

68

What attenuation is allows TRP transcription?

2+3 trp operons unless their is no charged rna then will act as a secondary brake.

69

src

Normal function: protein tyrosine kinase Cancer in which gene is mutated: many types of cancer

70

sis

Normal function: growth factor Cancer in which gene is mutated: giloblasomas and other cancers

71

ras

Normal function: GTP binding GTPase Cancer in which gene is mutated: many types of cancer

72

myc

Normal function: transcription factore Cancer in which gene is mutated: Lympomas, leukemias neuroblastoma

73

jun

Normal function: Transcription factor cell cycle control Cancer in which gene is mutated: lung cancer breast cancer

74

fos

Normal function: transcription factor Cancer in which gene is mutated: Osteosarcoma and endometrial carcinoma

75

erbB

Normal function: part of growth factor receptor Cancer in which gene is mutated: Many types of cancer

76

Riboswitches

are mRNAs which contain regulatory elements which alter their
translatability or stability after transcription.

77

how do ribosomes find the binding site?

shine dalgarno sequence

78

in the binary decision for transcription of lamba bacterial phages.

Transcription will processes will proceed to the left

79

in the binary decision for lysogeny of lamba bacterial phages.

Transcription will processes will proceed to the right

80

What does expanding trinucleotide repeat produce and what does it do.?

It cause strand slippage that causes one strand to pair with the extra repeat. This causes a loop to form with could be excised. Which causes a frame shift mutation that can lead to nasty diseases. It is also usually sex determined.

81

Deamination

is the removal of an amine group from a molecule. can be repaired by a specific repair process which detects uracil, not normally present in DNA; otherwise the U will cause A to be inserted opposite it and cause a C:G to T:A transition when the DNA is replicated.

82

Depurination

in DNA is a chemical reaction of purine deoxyribonucleosides, deoxyadenosine and deoxyguanosine, in which the β-N-glycosidic bond is hydrolytically cleaved releasing a nucleic base, adenine or guanine

83

overdominance

Selection in which the heterozygote has higher fitness than either homozygote; also called heterozygote advantage.

84

underdominance

Selection in which the heterozygote has lower fitness than either homozygote.

85

directional selection

Selection in which one trait or allele is favored over another.

86

Anagenesis:

evolution taking place in a single group
(a lineage) with the passage of time

87

Cladogenesis:

splitting of one lineage into two; new
species arise

88

parsimony

is the principle that the simplest explanation that can explain the data is to be preferred

89

examples of cellular oncogenes that are activators

ras, src, abl,

90

examples of cellular genes that are tumor suppressors

Rb, p53, BRCA

91

In colon cancer what does acetylation and methylation due?

Acetylation will increase access and methylation will decrease access.

92

hypermethylation leads to gene silencing and genomic instability this ultimately effects?

apotoisis, dna repair, and cell cycle control.

93

negative inducible

active repressor= transcription is normaly off

94

positive inducible

inactive activator= transcription is normaly off

95

negative repressible

inactive repressor= transcription is normaly on

96

positive repressible

active activator= transctipion is normaly on