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Biology (NCERT) - Class XII > XII Chap 6 Molecular Inheritance > Flashcards

XII Chap 6 Molecular Inheritance Flashcards

1
Q

Adenine pairs with?

A

Thymine

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2
Q

Guanine pairs with?

A

Cytosine

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3
Q

DNA is a long polymer of _______________

A

deoxyribonucleotides

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4
Q

Length of DNA is defined as:

A

number of base pairs (pairs of nucleotides)

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5
Q

What are the 3 components of nucleotides?

A
  1. Nitrogenous base
  2. Pentose (5-carbon) sugar
  3. Phosphate group
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6
Q

Two types of nitrogenous bases?

A

Purines (Adenine and Guanine) - 2 rings

Pyrimidines (Cytosine, Thymine and Uracil) - 1 ring

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7
Q

How long is the haploid content of human DNA?

A

3.3 x 10^9

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8
Q

______ (nitrogenous base) is only present in DNA and ______ only in RNA

A

Thymine in DNA

Uracil in RNA

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9
Q

DNA was first identified by ?

A

Friedrich Meischer in 1869 - “acidic substance in nucleus”

Named it Nuclein

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10
Q

What is a nucleoside?

A

Sugar attached to nitrogenous base;

nitrogenous base is linked to OH of 1’ C pentose sugar through an N-glycosidic linkage

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11
Q

Examples of nucleosides

A 
Adenosine or deoxyadenosine
Guanosine or deoxyguanosine
Cytidine or deoxycytidine
Uridine or
Deoxythymidine
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12
Q

How is nucleotide formed from nucleoside?

A

Phosphate group is linked to OH of 5’ C of a nucleoside through phosphoester linkage

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13
Q

What is a dinucleotide?

A

Two nucleotides linked through 3’ - 5’ C phosphodiester linkage to form a dinucleotide

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14
Q

What are at the 2 ends of a polymer?

A

One end a free phosphate moeity at 5’ end of sugar

One end a free OH of 3’ C group

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15
Q

Backbone of polynucleotide chain is formed due to _____ and ______

A

sugar and phosphates

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16
Q

The _________ linked to sugar moiety project from the backbone

A

nitrogenous bases

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17
Q

In RNA, every nucleotide residue has an additional ________ present at the ______ position in the ribose

A

-OH group;

2’-position

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18
Q

__________ is another chemical name for thymine

A

5-methyl uracil

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19
Q

In ________ Watson and Crick suggested the _________ model based on the X-ray diffraction data produced by __________

A

1953;
Double Helix;
Rosalind Franklin + Maurice Wilkins

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20
Q

___________ observed that for a double stranded DNA the ratios of Adenine:Thymine:Guanine:Cytosine are constant and equals one

A

Erwin Chargaff

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21
Q

What are the 5 salient features of the Double-helix structure of DNA?

A
  1. Made of 2 polynucleotide chains, sugar-phosphate backbone and bases project inside
  2. Two chains have anti-parallel polarity
  3. Bases in 2 strands are paired through hydrogen bonds forming base pairs; purine always opposite to a pyrimidine => uniform distance between the 2 strands of helix
  4. Two chains are coiled in right-handed fashion; helix pitch is 3.4 nm; 10 bp in each turn; distance between bps is 0.34 nm
  5. Stacking of bp planes and H-bonds => stable helix structure
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22
Q

1 Nanometer = ____ meters

A

1 billionth => 1 / 10^9

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23
Q

What is anti-parallel polarity?

A

One chain has polarity 5’ -> 3’ then the other has 3’ -> 5’

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24
Q

Adenine and Thymine form how many hydrogen bonds? Same Q for Cytosine and Guanine?

A

AT - 2 bonds

CG - 3 bonds

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25
Q

What is the Central Dogma? Who proposed it?

A

Francis Crick;

genetic information flows from DNA to RNA (transcription) to Protein (translation)

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26
Q

In some viruses, flow of information is reversed from RNA to DNA. This is called?

A

Reverse transcription

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27
Q

What is the distance between 2 consecutive base pairs?

A

0.34 nm

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28
Q

If length of human DNA is calculated it comes out to be ____ metres

A

2.2

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29
Q

How is DNA arranged in prokaryotes?

A

No nucleus

Large loops of DNA (negatively charged) - proteins (positively charged) - ‘nucleoid’ region

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30
Q

How is DNA arranged in eukaryotes?

A

Nucleosomes (negatively charged DNA wrapped around 8 molecules of positively charged protein => histone octamer) in chromatin (repeating structure) like ‘beads-on-string’ structure

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31
Q

What is a histone?

A

Set of positively charged basic proteins;
rich in basic amino acid residues lysine and arginine;
amino acid residues carry positive charges

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32
Q

What is a histone octamer?

A

8 units of histomes (o.e. positively charged proteins)

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33
Q

Typical nucleosome contains _______ base pairs of DNA

A

200

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34
Q

How are chromosomes formed in eukaryotes?

A

Beads-on-string structure in chromatin is packaged to form chromatin fibers, coiled and condensed at metaphase stage of cell division to form chromosomes

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35
Q

What are NHC proteins?

A

Additional set of proteins to pack chromatin at higher level - Non-histone Chromosomal protein

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36
Q

What is euchromatin?

A

Region of chromatin that is loosely packed, stains light and transcriptionally active

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37
Q

What is heterochromatin?

A

Region of chromatin that is tightly packed, stains dark and transcriptionally inactive

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38
Q

Explain Griffith’s Transforming Principle

A

Some genetic material was transferred from heat-killed S strain bacteria to R bacteria that allowed R bacteria (previously benign) to develop a smooth polysaccharide coat and kill the mice

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39
Q

When did Griffith conduct his experiments to yield the transforming principle? What was his experiment

A

1928,

Mice were infected with 2 different strains of bacteria Streptococcus pneumoniae (pneumococcus). One killed mice (S strain) and the other (R strain) was benign. A mixture of heat-killed S strain and benign R strain showed some kind of ‘transformation’ because R strain was now able to kill the mice.

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40
Q

What contribution did Avery, MacLeod and McCarty make to the study of DNA?

A

They determined the biochemical nature of Griffith’s transforming principle

Previously genetic material was though to be a protein. They purified proteins, RNA, DNA, etc. and discovered that DNA alone transformed R bacteria.

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41
Q

In Avery, MacLeod and McCarty’s experiment, digestion with ____ and _____ did not inhibit transformation but digestion with _______ did.

A

Protease or RNase did not inhibit;

DNase did => DNA caused the transformation

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42
Q

What are protein-digesting enzymes called?

A

Proteases

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43
Q

What are RNA-digesting enzymes called?

A

RNase

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44
Q

________ experiment proved unequivocally that DNA was the genetic material

A

Hershey-Chase experiment involving viruses (bacteriophages) and E. coli bacteria

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45
Q

Describe the Hershey-Chase experiment

A

bacteriophages - DNA made radioactive with phosphorus - protein made radioactive with sulfur - infection => blending to separate viral coat => centrifugation to separate virus from bacteria

bacteria with radioactive DNA => radioactive;
bacteria with radioactive protein => not radioactive

Therefore, DNA is the genetic material passed from virus to bacteria

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46
Q

When does RNA act as genetic material?

A

In some viruses e.g. Tobacco Mosaic, QB bacteriophage

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47
Q

Criteria of a molecule that can act as genetic material?

A
  1. Replication
  2. Stability (chemical and structural)
  3. Scope for Mutation
  4. Express itself in ‘Mendelian Characters’
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48
Q

______ molecules fail to fulfill the first criteria (replication) itself

A

Protein

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49
Q

_____ present at every nucleotide in RNA make it ______ and _______

A

2’-OH group;

labile/unstable and easily degradable

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50
Q

RNA is known to be ______ and hence reactive

A

catalytic

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51
Q

Both RNA and DNA are able to mutate. T or F?

A

True

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52
Q

_________ can directly for the synthesis of proteins. RNA or DNA?

A

RNA

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53
Q

_______ is better for storage of genetic material whereas _________ is better for transmission of genetic material

A

DNA - storage

RNA - transmission

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54
Q

Compare the characteristics of RNA and DNA as genetic material

A

DNA - more stable, less reactive, better for storage

RNA - mutates and evolves faster, can directly code for protein synthesis, better for transmission

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55
Q

______ was the first genetic material

A

RNA

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56
Q

Some important biochemical reactions in living systems are catalyzed by ________ instead of protein enzymes.

A

RNA catalysts

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57
Q

DNA has evolved a process of _________

A

repair

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58
Q

What is the semiconservative DNA replication model? Who is credited with it?

A

Credit - Watson and Crick

Two strands of DNA separate, act as template for new complementary strands;
after replication each DNA molecule will have one parental strand and one newly synthesized strand

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59
Q

Who & which experiment proved that DNA replicates semiconservatively?

A

Meselson & Stahl (1958);

Grew E. coli in medium containing 15N (heavy nitrogen) for several generations => 15N was incorporated into DNA

Then placed E. Coli with heavy DNA in a medium with normal 14N.

20 minutes => 100% hybrid / intermediate density
40 minutes => 50% hybrid and 50% ‘light’ DNA

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60
Q

Who & which experiment proved that DNA in chromosomes replicate semi-conservatiely?

A

Taylor et al, 1958

radioactive thymidine, Vicia faba (faba beans)

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61
Q

The main enzyme in DNA replication is _________

A

DNA-dependent DNA polymerase

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62
Q

In living cells, the process of replication requires a set of _________

A

catalysts / enzymes

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63
Q

What is DNA polymerase?

A

Enzyme that uses DNA template to catalyze the polymerisation of deoxyribonucleotides; highly efficient; high degree of accuracy

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64
Q

Any mistake during replication would result in _________

A

mutations

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65
Q

What are deoxyribonucleoside triphosphates

A

Act as substrates during replication;

Provide energy for polymerisation reaction

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66
Q

The two terminal phosphates in a deoxynucleoside triphosphates are _____________

A

high-energy phosphates

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67
Q

What is a replication fork?

A

Small opening of the DNA helix where replication occurs (because DNA cannot be separated in its entire length - too much energy required)

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68
Q

DNA polymerases catalyse polymerisation only in one direction: _________

A

5’ -> 3’

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69
Q

On ________ strand the replication is continuous;

on _____ strand discontinuous

A

3’ -> 5’ - continuous

5’ -> 3’ - discontinuous

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70
Q

Discontinuously synthesized fragments in DNA replication are later joined by __________

A

DNA ligase

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71
Q

DNA polymerase can initiate the process of replication on their own. T or F?

A

False

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72
Q

Where does replication begin in DNA?

A

Origin of replication

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73
Q

Why are vectors required in recombinant DNA procedure?

A

Because they provide the origin of replication

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74
Q

In eukaryotes the replication of DNA takes place at ______ phase of cell-cyle

A

S-phase

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75
Q

A failure in cell division after DNA replication can lead to __________

A

polyploidy or chromosomal anomaly

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76
Q

What is transcription?

A

The process of copying genetic information from ONE strand of DNA into RNA

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77
Q

In transcription adenosine forms base pair with _______ instead of _______

A

uracil instead of thymine

78
Q

Difference between replication and transcription

A

Replication: entire DNA gets copied

Transcription: only one of strands and only ONE segment is copied

79
Q

Why are both strands of DNA not copied during transcription?

A
  1. IDK

2. Two RNA molecules would be complimentary and would form double-stranded RNA => cannot be translated into protein

80
Q

What are the 3 regions in a transcription unit?

A
  1. Promoter - regulatory sequence where RNA polymerase attaches
  2. Structural gene - set of genes that control one characteristic or function
  3. Terminator - defines end of transcription
81
Q

Template vs coding strand?

A

Template strand - polarity 3’ -> 5’, acts as a template
Coding strand - 5’ -> 3’, does not code for anything, reference point when defining transcription unit, same sequence as RNA (except U in place of T)

82
Q

_______ and _______ flank the structural gene in a transcription unit

A

Promotor and Terminator

83
Q

Where are promoter and terminator located?

A

Promoter - 5’-end, upstream

Terminator - 3’-end, downstream, end of process of transcription

84
Q

_________ is the functional unit of inheritance

85
Q

The DNA sequence coding for tRNA and rRNA also define a gene. T or F?

86
Q

What is a cistron?

A

segment of DNA coding for a polypeptide/protein

87
Q

Monocistronic vs polycistronic

A

Monocistronic - eukaryotes

Polycistronic - bacteria / prokaryotes

88
Q

What are exons and introns?

A

Exons - coding segments, expressed sequences

Introns - non-coding segments, interruptions / intervening sequences.

89
Q

__________ appear in mature / processed RNA, ______ do not.

A

Exons - appear

Introns - don’t appear

90
Q

Eurokaryotes have ____ genes

91
Q

Regulatory sequences are also called regulatory genes even though they do not code for any RNA or protein. Why?

A

Because regulatory sequences (and promoters) also affect inheritance of a character

92
Q

What are the 3 major types of RNAs?

A

mRNA - messenger - provides template / info to make protein
tRNA - transfer - brings aminoacids and reads the genetic code (adaptor)
rRNA - ribosomal - structural and catalytic role in translation

93
Q

Which RNAs are needed to synthesise a protein in a cell?

94
Q

How many DNA dependent RNA polymerases are needed to catalyse transcriptions of the different types of RNA in bacteria?

95
Q

What is initiation?

A

RNA polymerase binds to promoter, initiates transcription by associating transiently with initiation factor (σ sigma)

96
Q

RNA polymerase catalyzes all 3 steps: initiation, elongation and termination while also facilitating the opening of the helix. T or F?

97
Q

What is the termination factor?

98
Q

In bacteria, transcription and translation are decoupled. T or F?

A

False, they are coupled and take place in same compartment (no separation of cytosol and nucleus)

99
Q

In bacteria, many times translation can begin much before mRNA is fully transcribed. How?

A

since mRNA does not require any processing to become active

100
Q

What are the additional complexities of transcription in eukaryotes compared to bacteria?

A
  1. Three different polymerases required to catalyze process

2. Splicing required to remove introns and join exons in defined order (and hnRNA has to be processed into mRNA)

101
Q

What is the division of labor among RNA polymerases in eukaryotes?

A

RNA polymerase I - rRNAs (28S, 18S, 5.8S)
RNA polymerase II - hnRNA
RNA polymerase III - tRNA, 5srRNA, snRNAs

102
Q

What is capping?

A

Met GTP (methyl guanosine triphosphate, which is a nucleotide) added to the 5’-end of hnRNA

103
Q

What is tailing?

A

Adenylate residues (200-300 of them) added at 3’-end in a template independent manner

104
Q

Fully processed hnRNA is called ______ and transported out of the ______ for translation

A

mRNA;

nucleus

105
Q

The presence of _______ is reminiscent of antiquity

A

introns / split-gene arrangements

106
Q

The process of _____ represents the dominance of RNA-world

107
Q

What is translation?

A

transfer of genetic information
from polymer of nucleotides
to synthesize
a polymer of amino acids

OR

polymerisation of amino acids to form a polypeptide

108
Q

________ argued that there would be 64 codons in genetic code

A

George Gamow, physicist

109
Q

Marshall Nirenberg’s ____________ finally helped genetic code be deciphered

A

cell-free system for protein synthesis

110
Q

What was Har Gobind Khorana’s contribution to genetic code?

A

chemical method to synthesize RNA molecules with defined combinations of bases (homopolymers and copolymers)

111
Q

______________ was helpful in polymerising RNA with defined sequences in enzymatic synthesis of RNA (a template independent manner)

A

Severo Ochoa enzyme

112
Q

What are the features of the genetic code?

A
  1. triplet, 61 codons for amino acids, 3 stop codons
  2. Degenerate (some amino acids are coded by more than one codon) & unambiguous (one codon can only code for one amino acid)
  3. no punctuations “comma-free”, codons read in mRNA in contiguous fashion
  4. (nearly) universal (except some mitochondria and protozoans)
  5. AUG has dual function - codes for Methionine and is initiator codon
  6. UAG, UGA, UAA are stop terminator codons
113
Q

Relationships between genes and DNA are best understood by ________ studies

114
Q

What is point mutation vs. frameshift mutation?

A

Point mutation - change of single base pair (nucleotide) in the gene

Frameshift - insertion or deletion of bp that changes reading frame

115
Q

What is tRNA?

A

transfer RNA is an adapter molecule;
an anticodon loop that has bases complementary to code on mRNA;
amino acid acceptor end which binds to amino acids;
clover shape & an inverted L-shape

116
Q

tRNA was called _______ before the genetic code was postulated

A

soluble RNA (sRNA)

117
Q

tRNAs are universal for amino acids. T or F?

A

False, they are specific for each amino acid

118
Q

tRNA has no specific initiator or stop versions. T or F?

A

False;

no tRNA for stop codon BUT there is initiator tRNA

119
Q

Amino acids are joined by a __________ bond

120
Q

Formation of peptide bond requires energy. T or F?

121
Q

What is charging of tRNA? What’s another name for it?

A

Amino acids are activated
in the presence of ATP
linked to their cognate tRNA

another name - aminoacylation of tRNA

122
Q

If two charged tRNAs are brought close enough what happens?

A

Formation of peptide bond, since it is favored energetically

123
Q

What is a ribosome?

A

Cellular factory responsible for protein synthesis;
consists of structural RNAs and 80 different proteins;
large and small subunit

124
Q

How does protein synthesis occur in ribosome?

A

When small sub-unit encounters mRNA => binds to the start codon (AUG) recognized by the initiator tRNA => translation begins
=> elongation phase => complexes of amino aid linked to tRNA bind to codon in RNA in large subunit,
ribosome moves from codon to codon along mRNA, peptide bonds formed,
at the end, release factor binds to stop codon => terminating translation and releasing polypeptide from ribosome

125
Q

Apart from being a cellular factory, ribosome acts as a _______ in the formation of peptide bond

126
Q

_________ in bacteria is the enzyme ribozyme

127
Q

What are UTRs?

A

Untranslated regions - sequences in mRNA that are not translated; required for efficient translation process;
present before start codon (5’ end) and after stop codon (3’ end)

128
Q

What is a “translational unit” in mRNA?

A

sequence of RNA that codes for polypeptide,

flanked by start codon (AUG) and the stop codon

129
Q

In eukaryotes, regulation can be exerted at which 4 levels?

A
  1. Transcription level (DNA to hnRNA)
  2. Processing level (splicing, hnRNA to mRNA)
  3. Transport of mRNA from nucleus to cytoplasm
  4. Translational level
130
Q

__________ conditions regulate the expression of genes

A

Metabolic, physiological or environmental conditions

131
Q

In prokaryotes, regulation of gene expression occurs at which level?

A

rate of transcriptional initiation

132
Q

Activity of RNA polymerase at a promoter in prokaryotes is regulated by ________

A

accessory/regulatory proteins - could act positively (activators) or negatively (repressors)

133
Q

What are operators?

A

region adjacent to the promoter; regulates the access to promoter by binding to a repressor

134
Q

Each operon has its specific operator and repressor. T or F?

135
Q

What is an operon? Examples?

A

Polycistronic structural gene regulated by a common promoter + regulatory genes (operators)
e.g. lac, trp, ara, his, val

136
Q

Lac operon consists of:

A

One regulatory gene (i gene) - operator

Three structural genes (z, y, a)

137
Q

What do the genes in the lac operon code for?

A

i - repressor
z - beta-galactosidase (β-gal) which is responsible for hydrolysis of disaccharide lactose into monomeric units - galactose + glucose
y - permease, which increases permeability of cell to β-galactosides
a - transacetylase

138
Q

Not all three structural genes in lac operon are required for metabolism of lactose. T or F?

A

False, all are required

139
Q

________ is the substrate for the enzyme beta-galactosidase

140
Q

What is an inducer?

A

Regulates switching on and off of the operon by its presence or absence

141
Q

What happens if lactose is provided in growth medium of bacteria in absence of glucose?

A

lactose is transported into cell through action of permease
=> then lactose induces operon
=> repressor is inactivated
=> RNA polymerase has access to the promoter
=> transcription proceeds

142
Q

Very low level of expression of lac operon is required at all times in the cell. Why?

A

Else lactose cannot enter cell. Inducing lac operon & y-gene only increases permeability, doesn’t stop/start it entirely.

143
Q

________ is the inducer for the lac operon

A

Lactose or allalactose

144
Q

What does the repressor protein in the lac operon do?

A

Prevent RNA polymerase from transcribing the operon

145
Q

Regulation of lac operon can be visualized as regulation of _______

A

enzyme synthesis by its substrate

146
Q

Regulation of lac operon by repressor is referred to positive regulation. T or F?

A

False, negative regulation

147
Q

When was HGP launched and completed?

Who was involved?

A

1990, 2003 (13-year project)

US Dept of Energy, National Institute of Health, Wellcome Trust (UK), Japan, France, Germany, China

148
Q

HGP was closely associated with development of new area in biology called ____________

A

bioinformatics

149
Q

What were the goals of HGP?

A
  1. identify all 20-25k genes in human DNA
  2. determine sequences of 3 billion chemical bps
  3. store info in databases
  4. improve tools for analysis
  5. transfer related tech to other sectors e.g. industry
  6. address ELSI (ethical, legal, social issues)
150
Q

What non-human organisms have also had their DNA sequenced as part of HGP?

A 
bacteria
yeast
Caenorhabditis elegans (free living, non-pathogenic nematode)
Drosophila (fruit fly)
plants like rice and Arabidopsis
151
Q

What were 2 methodologies used in HGP?

A
  1. Expressed Sequence Tags (EST) - Identifying all genes expressed as RNA
  2. Blind approach - sequencing the whole set of genome and later assigning different regions with functions (Sequence Annotation)
152
Q

Commonly used hosts in HGP

A

BAC and YAC

bacterial/yeast artificial chromosomes

153
Q

Fragments of DNA in HGP were sequenced using ________ in a principle / method developed by _______

A

automated DNA sequencers (computer programs);

Frederick Sanger

154
Q

What is Sanger credited with developing?

A
  1. principle used in HGP to sequence fragments

2. method for determination of amino acid sequences in proteins

155
Q

Sequence of Chromosome 1 was the last to be completed in ________ as part of HGP

156
Q

How many chromosomes were sequenced in HGP?

A

24 (22 autosomes + X + Y)

157
Q

Human genome contains ________ bp

A

3164.7 million

158
Q

The total number of genes discovered in HGP were ________

159
Q

Average gene has ______ bases

160
Q

Largest known human gene?

A

Dystrophin at 2.4 million bases

161
Q

What percent of genome codes for protein?

162
Q

________ nucleotide bases are exactly the same in all humans

163
Q

We know the functions of what percent of discovered genes?

164
Q

Repeated sequences that have no direct coding functions make up very large portion of human genome. T or F?

165
Q

Repetitive sequences don’t code directly for functions but they can shed light on ________

A

chromosome structure, dynamics & evolution

166
Q

Which chromosome has the most genes? Least?

A

Chromosome 1 - 2968

Chromosome Y - 231

167
Q

Scientists have identified _______ locations where single-base DNA differences occur. These are called?

A

1.4 million locations;

“snips” - Single Nucleotide Polymorphism (SNP)

168
Q

What is DNA fingerprinting?

A

quick way to compare the DNA sequences of 2 individuals; identifying differences in repetitive DNA

169
Q

Repetitive vs satellite DNA?

A

Repetitive DNA - small stretch of DNA repeated many times

Satellite DNA - small peaks which different from bulk genomic DNA (consists of repetitive DNA)

170
Q

What is polymorphism?

A

variation at genetic level that arises due to mutations;

inheritable mutation that exists in 1% or more of the population (high frequency)

171
Q

New mutations may arise in ____ or ____ cells

A

somatic or germ

172
Q

Who developed DNA fingerprinting?

A

Alec Jeffreys

173
Q

What is VNTR

A

Variable Number of Tandem Repeats is a satellite DNA that shows a high degree of polymorphism. Used as a probe in DNA Fingerprinting

174
Q

What are the steps in DNA Fingerprinting?

A
  1. Isolation of DNA
  2. Digestion of DNA by restriction endonucleases
  3. separation of DNA fragments by gel electrophoresis
  4. transferring/Southern blotting of separated DNA fragments to synthetic membranes
  5. hybridisation using radiolabelled VNTR probe
  6. detection of hybridised DNA fragments by autoradiography
175
Q

VNTR belongs to which class of satellite DNA?

A

mini-satellite

176
Q

_________ varies from chromosome to chromosome in an individual

A

Copy number

177
Q

The size of VNTR varies in size from _____ to ______

A

0.1 to 20 kb

178
Q

The numbers of repeat show very low degree of polymorphism in the DNA sequence used in fingerprinting. T or F?

A

False, HIGH degree of polymorphism

179
Q

Sensitivity of DNA fingerprinting has been increased by use of _________

A

PCR - polymerase chain reaction

180
Q

DNA from a single cell is enough to perform fingerprint analysis. T or F?

181
Q

Applications of DNA fingerprinting?

A
  1. forensic science

2. population and genetic diversities

182
Q

Paternal and maternal alleles of chromosome contain same or different copy numbers of VNTR?

183
Q

Nucleic acids are ________ of nucleotides

A

long polymers

184
Q

Hallmark of double-stranded helix structure is ______ between the bases from opposite strands

A

Hydrogen bonding

185
Q

A segment of DNA that codes for RNA can be referred to simplistically as _______

186
Q

tRNA binds to specific amino acid at one end and pairs through ____-bonding with codes on mRNA through anticodons

187
Q

Translation can also be known as _________

A

protein synthesis

188
Q

_______ acts as a catalyst for peptide bond formation

A

One of the rRNA

189
Q

__________ are energetically expensive processes

A

Transcription and translation

190
Q

Why do transcription and translation have to be regulated?

A

Since they are very expensive energetically

191
Q

Very low level of expression of lac operon is required at all times in the cell. Why?

A

Else lactose cannot enter cell. Inducing lac operon & y-gene only increases permeability, doesn’t stop/start it entirely.

192
Q

The repressors of the lac operon is synthesized all the time from the i gene. What’s another word for “all the time”?

A

Constitutively

Biology (NCERT) - Class XII (18 decks)

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