XII: Chapter 6- Molecular basis of inheritance Flashcards
1
Q
What is the haploid content of human DNA?
A
3.3 x 10^9 bp
2
Q
What type of chemical compound is deoxyguanosine?
A
Nucleoside
3
Q
What type of chemical compound in deoxycytidine?
A
Nucleoside
4
Q
What type of chemical compound is uridine?
A
Nucleoside
5
Q
DNA was first identified by
A
Friedrich Meischer
6
Q
When was DNA first identified?
A
1869
7
Q
What did Friedrich Meischer name DNA?
A
Nuclein
8
Q
How is uniform distance maintained between the two strands of DNA?
A
A purine always pairs with a pyrimidine, which maintains a uniform distance between them.
9
Q
In which direction are the two chains of DNA coiled?
A
RIght handed
10
Q
Histones are rich in which amino acids?
A
Lysine and arginine
11
Q
What is the length of DNA wrapped around a histone octamer?
A
200 bp
12
Q
While working with which bacteria did Griffith give his transforming principle?
A
Streptococcus pneumoniae
13
Q
Why do the S strain Streptococcus pneumoniae produce smooth and shiny colonies?
A
Because they have a mucous (polysaccharide) coating
14
Q
Which scientists described the biochemical nature of Griffith’s transforming principle?
A
Avery, MacLeod and McCarty
15
Q
The unequivocal proof that DNA is the genetic material came from
A
Hershey-Chase experiments
16
Q
Which scientists proved that DNA replicates semi-conservatively?
A
Meselson and Stahl
17
Q
How could the heavy DNA in Meselson Stahl experiment be distinguished from normal DNA?
A
By centrifugation in a cesium chloride density gradient
18
Q
Which experiment was performed by Taylor et al to prove the semiconservative nature of DNA?
A
Radioactive thymidine was used to detect distribution of newly synthesised DNA in the chromosomes of Vicia faba
19
Q
Which phosphates of deoxynucleoside triphosphates are high energy phosphates?
A
Two terminal phosphates
20
Q
In which direction can DNA dependent DNA polymerase catalyse polymerisation?
A
5’ -> 3’
21
Q
Which strand of DNA is known as the template strand?
A
strand with 3’ -> 5’ polarity
22
Q
Which strand of DNA is known as the coding strand?
A
strand with 5’ -> 3’ polarity
23
Q
Towards which ends of DNA are promoter and terminator flanked?
A
Promoter= 5' end of coding strand Terminator= 3' end of coding strand
24
Q
What is a segment of DNA which codes for a polypeptide called?
A
Cistron
25
Monocistronic genes are found in
Eukaryotes
26
Polycistronic genes are found in
Prokaryotes
27
How many DNA dependent RNA polymerase catalyse the transcription of RNA in bacteria?
one
28
How many DNA dependent RNA polymerase catalyse the transcription of RNA in eukaryotes?
At least 3
29
RNA polymerase I polymerises the transcription of
rRNAs (28s, 18s, 5.8s)
30
RNA polymerase III polymerises the transcription of
tRNA, 5s rRNA and snRNAs
31
RNA polymerase II polymerises the transcription of
hnRNA (precursor of mRNA)
32
In capping, which molecule is added to the hnRNA? Towards which end of RNA is it added?
Methyl guanosine triphosphosphate, 5' end
33
In tailing what is added to the hnRNA?. Towards which end of RNA is it added?
Adenylate residues (200-300), 3' end
34
Which physicist suggested that in order to code for 20 amino acids, the code should be made of 3 nucleotides?
George Gamow
35
Which scientist developed the cell free system using which the genetic code was deciphered?
Marshall Nirenberg
36
What is Severo Ochoa enzyme?
Polynucleotide phosphorylase
37
The genetic code is nearly universal, exception to this are
mitochondrial codons, some protozoans
38
Three stop codons exist in the genetic code. How many tRNA exist for these stop codons?
Zero
39
Which letter does the tRNA resemble?
Inverted L
40
What happens in the first phase of translation?
Amino acids are activated in the presence of ATP and linked to the cognate tRNA
41
Charging of tRNA is also known as
Aminoacylation of tRNA
42
Which unit of ribosome encounters mRNA?
Smaller subunit
43
How many sites are present in the larger subunit of ribosome for the amino acids to bind to?
2
44
A transational unit in mRNA codes for
Polypeptide
45
The untranslated regions in mRNA have no function. True/false?
False. The UTRs are required for efficient translation process.
46
WHat binds to stop codon for terminalisation of translation?
Release factor
47
Which is the predominant site for regulation of gene expression in prokaryotes?
Control of the rate of transcriptional initiation
48
What regulate the ability of RNA polymerase to recognise start sites for transcription?
Accessory proteins
49
Which scientists elucidated the lac operon?
Monod and Jacob
50
Does the lac operon have a polycistronic or a monoscistronic structural gene?
Polycistronic structural gene
51
In the i gene of lac operon, 'i' refers to
Inhibitor
52
Which protein does the z gene of lac operon code for? What is its function?
z gene codes for β-galactosidase which hydrolyses lactose to form galactose and glucose.
53
Which protein does the y gene of lac operon code for? What is its function?
y gene codes for permease which increases permeability of the cell to β-galactosidase.
54
Which protein does the a-gene of lac operon code for?
a-gene codes for transacetylase.
55
The human genome project was closely associated with the rapid development of a new area in biology called
Bioinformatics
56
How many genes are present in Human DNA?
30,000
57
Expand ELSI.
Ethical, legal and social issues (implications)
58
How long did the Human Genome Project take?
13 years
59
Name a free living non pathogenic nematode whose complete DNA has been sequenced?
Caenorhabditis elegans
60
Which plants were completely sequenced in the Human Genome Project?
Arabidopsis and rice
61
What are expressed sequence tags?
Expressed sequence tags (ESTs) are fragments of mRNA sequences
62
What was the sequence annotation method used in human genome project?
Sequencing the whole set of genome and then assigning different regions in the sequence with functions.
63
Which were the commonly used hosts and vectors in human genome project?
The commonly used hosts were bacteria and yeast and the vectors were called as bacterial artificial chromosomes (BAC) and yeast artificial chromosomes (YAC).
64
DNA sequencers used in human genome project worked on the principle of a method developed by
Frederick Sanger
65
WHo developed the method for determination of amino acid sequences in proteins?
Frederick Sanger.
66
Which was the last chromosome to be completely sequenced? When was it completely sequenced?
Chromosome 1, 2006
67
How were genetic and physical maps on the genome developed?
Using the information of polymorphism of restriction endonuclease recognition sites and some repetitive DNA sequences known as microsatellites.
68
How many bases are present in the average gene?
3000 bases
69
Which is the largest gene? How many base pairs does it have?
Dystrophin, 2.4 million bases
70
What percent of the genome codes for proteins?
< 2%
71
Which chromosomes have the maximum and the minimum number of genes? How many genes are present on them?
Max- chromosome 1, 2968
| Min- chromosome y- 231
72
How many locations have been identified by scientists where single base DNA differences occur?
1.4 million
73
The bulk genomic DNA form a __1___ peak while the satellite DNA form the __2___ peak.
1 and 2 refer to
1- major
| 2-minor
74
DNA can be classified into many categories such as mini satellite, micro satellite,etc based on
Base composition (A:T rich or G:C rich)
Length segment
Number of repetitive segments
75
Allelic sequence variations have been described as DNA polymorphism if more than one variant at a locus occurs in human population with a frequency
> 0.01%
76
Who developed the technique of DNA fingerprinting?
Alec Jeffreys
77
Alec Jeffreys initially developed the technique of DNA fingerprinting using a satellite DNA that shows a very high degree of polymorphism, as a probe which was called
Variable Number of Tandem Repeats
78
Which blotting technique is used in DNA fingerprinting?
Southern blot
79
VNTR belongs to a class of satellite DNA referred to as
Mini satellite
80
The size of VNTR varies from
0.1 to 20 kb
81
What is base ratio?
A+T
-------
G+C
82
Base ratio in organisms of the same species can vary. True/False.
False. Base ratio is constant for any species
83
What is the base ratio for humans?
1.55
84
WHat are the non histone proteins found in prkaryotes which bind DNA called?
Polyamines
85
Which has more DNA content as compared to RNA content- heterochromatin or euchromatin?
euchromatin
86
What is the base ratio of eukaryotes?
>1
87
What is the base ratio of prokaryotes?
<1
88
80% of all RNAs are
rRNAs
89
5% of all RNAs are
mRNAs
90
15% of all RNAs are
tRNAs
91
Which are the smallest RNAs?
tRNAs
92
Which are the longest RNAs?
mRNAs
93
rRNAs are synthesised in
Nucleolus
94
mRNAs are synthesised in
Nucleoplasm
95
tRNAs are synthesised in
Nucleoplasm
96
Which type of RNA is the most stable?
rRNA
97
Which type of RNA is the least stable?
mRNA
98
Insoluble RNA is also known as
rRNA
99
Soluble RNA is also known as
tRNA
100
What do the P site, A site and E site in ribosome stand for?
Peptidyl site
Aminoacyl site
Exit site
101
How many loops does the clover leaf model of tRNA have?
3
102
How many arms does the clover leaf model of tRNA have?
5
103
Which is the largest loop of clover leaf model of tRNA?
DHU loop
104
What is the function of DHU loop of clover leaf model of tRNA?
Binding aminoacyl tRNA synthetase
105
How many N-bases are present in DHU loop of clover leaf model of tRNA?
8to 10
106
How many N-bases are present in TΨC loop of clover leaf model of tRNA?
7 N bases
107
WHat is the function of TΨC loop of clover leaf model of tRNA?
Helps in binding two ribosomal subunits during photosynthesis
108
Is the short variable arm present in all tRNA?
No
109
Where is the CCA sequence present in tRNA?
On amino acid attachment site's 3' end.
110
WHere does the amino acid bind in tRNA?
The amino acid loaded onto the tRNA by aminoacyl tRNA synthetases, to form aminoacyl-tRNA, is covalently bonded to the 3'-hydroxyl group on the CCA tail.
111
If recombination occurs in a cistron it is called
Recon
112
If mutation occus in a cistron it is called
Muton
113
Double stranded RNA is found in which viruses?
Reovirus, wound tumour virus
114
What is the function of small nuclear RNA?
Splicing
115
How many ori do prokaryotes have?
One
116
Eukaryotes have many ori in their DNA. True/false?
True
117
Which enzyme opens the DNA to form a replication fork?
Helicase
118
What prevent the replication fork of DNA from closing?
Single stranded binding proteins
119
Which enzyme is called DNA gyrase in prokaryotes?
Topoisomerase
120
Which enzyme removes the coiling tension created by Helicase enzyme in DNA?
Topoisomerase
121
What is the function of RNA primase in DNA replication?
It synthesises a small stretch of RNA at the free 3' end of the DNA strand
122
What happens to the RNA primer synthesised by RNA primase during DNA replication?
It is converted into DNA by DNA polymerase II
123
Which DNA polymerase synthesises the new DNA strand in 5' to 3' direction?
DNA polymerase III
124
Which are the major and minor repair enzymes in DNA replication?
DNA Polymerase III
| DNA polymerase II
125
What are the fragments of DNA formed during DNA replication from lagging strand called?
Okazaki fragments
126
What is the core subunit of RNA polymerase made of?
two alpha (2α), one beta (β), one beta prime (β') and one omega (ω)
127
What is TATA box?
Sequence that is recognised by sigma factor (σ) during transcirption of DNA.
128
What is the TATA box called in eukaryotes? WHat is its sequence?
Hogness box
| TATAAAA...
129
What is the homologue of TATA box in prokaryotes? What is its sequence?
Pribnow box
| TATAAT...
130
What is the size of TATA box?
10bp to 30 bp
131
What is the size of CAT box?
40 bp to 70 bp
132
What is CAT box?
Sequence that is recognised by sigma factor (σ) during transcirption of DNA.
133
When RNA polymerase binds on the promoter region, DNA helix unwinds. The opened stretch of DNA is called
Transcription bubble
134
Which is the sense strand of DNA?
The strand running in 5' -> 3' direction
135
Where is mRNA modified post-transcriptionally?
Nucleoplasm
136
Which was the first discovered codon?
UUU- phenylalanine
137
The codon UUC codes for
Phenylalanine
138
The codon CCC codes for
Proline
139
The codon AAA codes for
Lysine
140
The codon GGG codes for
Glycine
141
The codon CUC codes for
Leucine
142
The codon UGG codes for
Tryptophan
143
Which amino acids are not degenerate in reference to the genetic code?
Tryptophan and methionin
144
In yeast, UGA codes for
Tryptophan
145
In the human mitochondria, which is the stop codon?
AGA and AGG
146
What is transversion (point mutation)?
A purine base is replaced by a pyrimidine base and vie versa
147
What is transition (point mutation)?
A purine base is replaced by another purine.
OR
A pyrimidine base is replaced by another pyrimidine base.
148
How do UV rays cause mutations in genetic code?
Affects DNA by forming thymine dimers
149
How do X rays cause mutations?
Deaminating, dehydroxylase nitrogenous bases forming peroxides and oxidise deoxyribose
150
What is the wobble hypothesis? Who proposed it?
According to the wobble hypothesis, an amino acid is identified by the first two nitrogenous bases, and the third nitrogenous base of a codon is a wobble. It was proposed by Francis Crick.
151
How many initiation factors are required in prokaryotes and eukaryotes for the initiation of translation?
Prokaryotes-3
| Eukaryotes- 9
152
What is called translation initiation complex?
rRNA-tRNA-mRNA complex
153
Which enzymes link amino acids to their corresponding tRNA molecules?
Aminoacyl-tRNA synthetases
154
What are the functions of P site and A site of ribosome?
the P site holds the peptide chain and the A site accepts the tRNA.
155
During elongation of peptide chain in translation, which molecule is hydrolysed for energy?
GTP
156
During the charging of tRNA which molecule is hydrolysed as a source of energy?
ATP
157
How many release factors (for translation) are present in prokaryotes and eukaryotes?
Prokaryotes- 2
| Eukaryotes- 1
158
What is an inducible operon?
Substrate has to be added to carry out protein synthesis
159
What is a repressible operon?
In such operon, the substrate is added to stop the protein synthesis.
160
The regulatory gene in inducible and repressible operons are represented by
Inducible- i
| Repressible- r
161
What is the example of repressible operon?
Tryp-operon
162
What is the function of transacetylase enzyme?
Transfer acetyl group to β-galactosidase
163
What is an aporepressor in reference to an operon?
It is a protein molecule that is synthesised by the regulatory gene which may bind to the operator and prevent the transcription.
164
What is a corepressor in reference to an operon?
Non-protein part that attaches to the repressor protein, activates it and stimulates it to bind to the operator region to prevent transcription.
165
Southern blotting is used for blotting which molecule?
DNA
166
Northern blotting is used for blotting which molecule?
RNA
167
Western blotting is used for blotting which molecule?
Proteins
168
Eastern blotting is used for blotting which molecule?
There is nothing like eastern blotting (Different types of blotting include- Northern, Southern and Western blotting)
169
What is the principle of DNA fingerprinting?
RFLP- restriction fragment length polymorphisim
170
What is the length of minisatellite (in DNA)?
11-60 bp repeating upto 100 times
171
What is the length of microsatellite (in DNA)?
5-6 bp repeating upto 10 - 100 times
172
What is the science of matching the prints of fingers, thumbs, toes and skin called?
Dermatoglyphics
173
Which is the smallest gene in human genome?
Testis determining factor on Y-chromosome
