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Genetic > Genetic Expression > Flashcards

Genetic Expression Flashcards

1
Q

What is the building block of DNA?

A

Nucleotides

Ribose sugar+ nitrogenous base and phosphate group

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2
Q

Nucleotides are linked together by ——- bond

A

5’-3’ phosphodiester bond

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3
Q

——— and ——— outside structure and ——- stay inside

A

Sugar and phosphate ——> outside

Nitrogenous base

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4
Q

Adenine and thymine pairs with ——— bond
Guanine and cytosine with ———

A

Two hydrogen bonds

Three hydrogen bonds

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5
Q

How does packaging of DNA in eukaryotes and prokaryotes take place ?

A

Eukaryotes - histone-DNA complex ( nucleosides )+ linker DNA between the nucleosomes

Prokaryotes - supercoiling the DNA

1 turn of the helix- normal 10 base pairs

Prokaryotes may underwound- more than 10 base pairs in 1 turn of helix

Prokaryotes may overwound- less than 10 base pairs in 1 turn of helix

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6
Q

In the ——phase, DNA is the most compact

A

Metaphase

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7
Q

Euchromatin and heterochromatin

A

Euchromatin- less dense regions on the chromosomes

Heterochromatin- more dense regions such as centrosomes and telomere

Euchromatin allows the transcription processes from DNA to mRNA

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8
Q

DNA replicate in ——- manner

A

Semiconservative

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9
Q

DNA replication stages

A

1 helicase breaks the DNA strand
2. SSB proteins keep the stands separated
3. To poison erase prevents overcoiling
4. Primase adds to the DNA strand to direct DNA polymerase
5. DNA polymerase constructs the DNA in 5’ to 3’ direction. So 3’—-> 5’ strand is the leading strand. 5’—>3’ strand is the lagging strand
6. Lagging strands require many primase enzymes to initiate the replication again and again——> result DNA fragments called Okazaki fragments are obtained.
7. Ligand enzyme filling the gaps between the Okazaki fragments

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10
Q

Every nitrogenous base contains———

A

Nitrogen. The more common one is 14N which is slightly lighter than the 15N

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11
Q

In prokaryotic replication, how many DNA polymerase are there ?

A

Two

Polymerase 3——> adds nucleotide to the growing strand
Polymerase 1- ——> replace the RNA primer with the DNA segments

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12
Q

Prokaryotic DNA replication starts at ———

A

Replication origin , proceeds in bidirectional

1 strand 3’——> 5 ‘ leading strand

Another direction ———> 5’ to 3’ ——-> lagging strand

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13
Q

Prokaryotes have multiple replication origin. T or F

A

False single only

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14
Q

What is the function of topoisomerase in the prokaryotic division?

A

Prevent the supercoiling of DNA ahead of the replication.

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15
Q

DNA polymerase 1 and ligase have the same func. T or F

A

False. DNA polymerase 1 ——> removes primers and replace it with DNA

Ligase——> Okazaki fragments on the lagging strands——. Filled with DNA

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16
Q

What is the func of sliding camp. Their shape?

A

Present on both leading and lagging strands. They hold DNA polymerase 3 as they are replicating . Keeps DNA polymerase from floating off. Sliding camp are the ring shaped proteins

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17
Q

Eukaryotes have multiple replicating origins. What are the differences compared to prokaryotes?

A

Prokaryotes —-> single circular chromosome
Eukaryotes —> multiple linear chromosome so can have multiple replicating origin

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18
Q

Why do telomere shorten as we age?

A

Telomerase enzymes are present only in germ cells and adult stem cells but not in somatic cells. So, there is a loss of DNA sequences in some regions as the cell divides

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19
Q

How many DNA polymerase enzymes are present in eukaryotes and prokaryotes

A

Eu- 14
Pol alpha, beta, gamma, delta and epsilon ko tone tl

Pro- 5

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20
Q

Are telomerase present in both prokaryotes and eukaryotes?

A

No , present only in eukaryotes

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21
Q

RNA primer removal is carried out by ? In pro and eu

A

Eu-RNAase
pro-polymerase 1

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22
Q

Major enzyme of DNA replication in eu and pro

A

Eu-leading - pol delta Lagging - pol epsilon
Pro- polymerase 3

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23
Q

Sliding camp is present only in prokaryotes

A

True, in eu an enz called PCNA is present

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24
Q

Nucleoside is

A

The same structure with nucleotide but without phosphate group

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25
Q

When DNA is replicated , how is it made sure to avoid mistakes to prevent from mutation?

A
  1. DNA polymerase 3 proofread the complementary synthesized strand every time
  2. Proofreading only after the whole process of replication ——> mix-match repair
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26
Q

Mutation may be ——— or ———

A

Spontaneous- naturally occurring in the body or induced- happens bcuz of the chemicals and external factors and UV light

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27
Q

Three types of mutation

A

Point mutation
Silent mutation
Substitution - transition - purine with purine pyrimidine with pyrimidine replacement

  • tranversion- purine with pyrimidine , pyrimidine with purine
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28
Q

Each amino acid can only represented by one codon

A

False. Each codon can represent one amino acid

But amino acid eg, proline can be encoded by CCU, CCA, CCG, CCC

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29
Q

HIV has ——— enxyme

A

Reverse transcriptase enzyme

RNA ——> DNA ——> mRNA ——> protein

30
Q

Adenine on DNA is read ——— on RNA

A

Uracil

31
Q

Stop codon

A

UGA, UAG , UAA
U gyee ag
U ag gyee
U ag ag

32
Q

Start codon is ——— and A/A is ———

A

AUG ——> methionine

33
Q

Three properties of genetic code

A

1 universal ——> both eu and pro——> same codon= same amino acid

  1. Degenerate or redundancy ——> only 20 A/A . But 64 codons present so, each amino acid can be represented by more than 3 codons
  2. Ambiguous- each codon however can represent only one amino acid
34
Q

Since genetic code is redundant, some amino acid can be represented by the same codon with a change in the last nucleotide ( eg, CCC——> CCG)- still represents proline.

A

True

35
Q

AUG codon is near the ——- end

5’ or 3’

A

5’

36
Q

DNA to mRNA is transcribed by ——— enxyme

A

RNA polymerase.

37
Q

Both DNA replication and transcription of prokaryotes proceed in bidirectional?

A

False

Replication- 2 directions

Transcription - 1 strand of mRNA only used template strand ( 3’—>5’ stand ) bcuz RNA polymerase direction 5’—-> 3’ only

38
Q

———- are the core of the RNA polymerase enz

A

Two alpha, beta and beta prime

All the other subunits are known as holoenxymes

39
Q

Promotor sequence where and what happens in prokaryotes

A

Promoter sequence —-> upstream of initiation start site

They determine whether the transcription is happening all the time, some time or frequently

Various promotor sequences may exist ——> most common are at -35 and 10 regions

-35===> sigma binds and transcription is initiated (TTGACA sequence) -10====> DNA unwinds and mRNA’s phosphodiester bonds are made (TATAAT)

40
Q

Elongation of prokaryotic DNA begins when ———

A

Sigma subunit released

RNA polymerase transcribe the mRNA from DNA in 5’——> 3’ direction 40 nucleotides per second

DNA has to be unwounded for the transcription to take place. This is done by RNA polymerase of prokaryotes .

Base pairing between the template and new RNA strands are not strong enuf. So RNA polymerase acts as a stable linker so that elongation is not interrupted prematurely

41
Q

Termination of prokaryotic transcription

A

2 types: rho dependent and rho independent

Rho dependent——> mRNA encounters long run G nucleotides in the DNA template strand and it stalls the transcription + rho dependent tracks along and meet the former region===> termination

Rho independent

RNA polymerase encounters A-T rich regions on DNA so, it forms C-G rich regions on the new strand, —> as it elongates ——> hair pin like loop ——> stalls the transcription and begins to transcribe A-U rich region. Since A-U rich region weaker-===> it induces the core enz to break away and new strand is obtained

42
Q

After the termination in prokaryotes ——— proceeds

A

mRNA degradation , translation occurs spontaneously bcuz there is no membrane bound nucleus in prokaryotes

43
Q

The number of RNA polymerase and subunits in pro and eu

A

Pro——> one RNA polymerase ——> five subunits 2 alpha beta beta prime and sigma

Eu——>3 RNA polymerase ——> subunits more than 14

Eu require transcription factors to initiate transcription

44
Q

RNA polymerase —— the major transcription enzyme

A

2

They have transcription factors ( D, A, B ,F, E ,H)

45
Q

Each eukaryotic mRNA is ——-, meaning they specify a single protein

A

Monogeni
C

46
Q

Eukaryotes require ——— to bind the RNA polymerase to the promoter region and to initiate transcription

A

Transcriptional factors

47
Q

Promoter sequences are on ———
1 DNA 2 RNA

A

1 DNA

48
Q

Location and role of RNA polymerase 1, 2 and 3

A

RNA polymerase 1
Present in nucleolus
Synthesize rRNA for ribosomes synthesis . They transcribe all the rRNA except 5S rRNA

Polymerase 2
Located in the nucleus ——> responsible for transcribing pre-mRNAs

Polymerase 3
Found in the nucleus ——> responsible for transcribing 5S rRNA, small nuclear RNAs

49
Q

Func of small nuclear RNAs

A

Splicing of the introns fro pre mRNA——> mature mRNA

50
Q

3 RNA polymerase in eukaryotes and their sensitivity to mushroom sensitivity

A

RNA pol 1- insensitive
RNA pol 2- very sensitive
RNA pol 3- moderately sensitive

51
Q

The promoter sequence for eu RNA pol 2

A

TATA box located on the upstream and downstream of transcription start site

52
Q

What are transcription factors and why are they needed?

A

Regulate the gene transcription

Basal transcription factors func—> assemble the RNA polymerase 2 on the promoter sequence

53
Q

Promoter sequence in RNA pol 1 and 3 TATA as pol 2?

A

No

Pol1 ——> two C- G rich sequences in the -45 to -120 initiate the transcription but sequences from -180 to -105 upstream further enhance initiation

Pol3—> upstream promoter or promoters within the genes transcribe mRNA

54
Q

Termination of transcription in eu

A

Pol 2—> elongation takes place 1000- 2000 nucleotides beyond by the end of the gene being transcribed ——> for pol A tail which is removed during mRNA processing

Pol1——> requires termination signals

Pol 3—> hair pin like loop like rho independent termination

55
Q

After the mRNA is transcribed in eukaryotes, the following process is ———

A

mRNA processing

Transcription ends——> pre-mRNA

RNA processing requires three steps 1. 5’ capping
2. 3’ Poly A tail
3. Splicing

First mRNA is equipped with RNA stablizing proteins to prevent it from breakdown during the processing

56
Q

What is 5’ capping

A

Adding the 7 methyl guanosine to the 5’ end

Func- to initiate the translation and for the ribosomes to recognize translation start site

57
Q

What is pre mRNA splicing ?

A

Pre mRNA after transcription contains introns + exons

Only exons express and encode the functional proteins

Introns must be removed all of them. If one remains——> it will disrupt in the protein synthesis ===> dysfunctional protein

Splicing is carried out by spliceosomes,+ Small nuclear RNAs and complex proteins

58
Q

Splicing occurs after mRNA leaves the nucleus . T or F

A

False. RNA is still in the nucleus

59
Q

TRNA is synthesized in the ———

A

Nucleus

60
Q

Pre rRNA and pre tRNA requires splicing like mRNA?

A

Yes. The only thing difference is that pre mRNA is bound with RNA stablizing proteins. Whereas tRNA and rRNA are bound with methyl group to prevent the breakdown

61
Q

———- starts at AUG sequence

A

Translation

62
Q

Protein synthesis requires energy

A

True

Bcuz apart from water, protein ——> second major composition of the body

63
Q

Ribosomes presence site in both eu and pro

A

Ribosomes can be in the cytoplasm, nucleus ( nucleolus) chloroplast, mitochondria , rough ER

64
Q

Small subunits of pro and eu

A

Eu - 30S+50S = 70S

Pro - 40S + 60S= 80S

65
Q

TRNA needs——— to pair with correct amino acid

A

Aminoacyl tRNA synthase

At least one aminoacyl tRNA synthase is present on the each amino acid

Action of amino acyl tRNA synthase

ATP——-> hydrolysis ——> AMP + P+P

AMP-A/A===> activated amino acid——> tRNA expelled ——> activated amino acid is then transferred to tRNA

66
Q

During the eukaryotic transcription elongation, how are chromosomes unwinded from his tone protein ?

A

FACT

Facilitate chromatin transcription protein pull away the pre mRNA for transcription and reform nucleosomes afterwards

67
Q

How is the translation initiated in bacteria?

A

Bacteria ‘s mRNA presents the Shine Dalgano sequence which the tRNA with the methionine binds and translation begins

Small ribosomal subunit arrives first on the shine dalgano sequence which afterwards the large ribosomal subunit comes bind

Sine dalgano sequence codes the start of each gene sequence , making the right Start codon of each gene

68
Q

How does eukaryotic translation begin?

A

The complex of small rRNA and tRNA recognized the 5’ capping and find the AUG codon on the mRNA. It may not start translation at the first AUG sequence it sees. AUG codon must appear around a gene coding
“ 5’gccRccAUGG” translation starts at the AUG sequence near the similar to that gene coding

69
Q

Elongation of protein synthesis

A

Each 3 codons= 1 amino acid

70
Q

How is the protein elongation terminated?

A

By three codons UGA, UAG, UAA

Stop codons are recognized by proteins called release factors, they add water molecule to the last amino acid in a chain. This reaction separates chain from the tRNA and the newly made protein is released.

71
Q

Post transitional modifications

A

Carboxyl end of amino acid—-> like a train ticket direct the translated proteins to targeted destination. The signalling molecule is usually clipped off after the transport

Genetic (7 decks)

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