Chapter 14.2, Problem 26AQP

a.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that the gene contains three exons, also to identify,$5^{\prime }\text{untranslated}\text{region}$.

Introduction:

The typical eukaryotic gene consists of an exon, intron, promoter sequence, a terminator sequence, upstream sequence, downstream sequence, enhancer,and silencer. A eukaryotic gene transcribes in the m-RNA followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig.1: $5^{\prime }\text{untranslated}\text{region}$

RNA containsan $5^{\prime }\text{untranslated}\text{region}$ at whichnucleotide sequence does not get translated into amino acids or protein and an $3^{\prime }$ untranslated region at whichnucleotide sequence does not get translated into amino acids or protein

In the figure $5^{\prime }\text{untranslated}\text{region}$ present before the exon 1 in $\text{mRNA}$

b.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that the gene contains threeexons, also to identify, promoter.

Introduction:

The typical eukaryotic gene consists of an exon, intron, promoter sequence, a terminator sequence, upstream sequence, downstream sequence, enhancer,and silencer. A eukaryotic gene transcribes in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 2: Promoter.

DNA contains a promoter region in the transcription unite on which RNA polymerase binds in order to start the transcription. It is present upstream to the structural gene, and next to the transcription start site.

In the figure promoter present before the exon 1 on the DNA strand.

c.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that the genecontains threeexons, also to identify, promoter,$AAUAAA\text{consensus}\text{sequence}$

Introduction:

The typical eukaryotic gene consists of an exon, intron, promoter sequence, a terminator sequence, upstream sequence, downstream sequence, enhancer,and silencer. A eukaryotic gene transcribes in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 3:$AAUAAA\text{consensus}\text{sequence}$

In eukaryotic $\text{mRNA}$, the consensus sequence is a nucleotidesequence ($AAUAAA$) which is present on ${\text{3}}^{\prime }\text{-untranslated}\text{region}$. Consensus sequence provides a site for the cleavage and generates an $3^{\prime }$ end which is polyadenylated.

In the figure $AAUAAA\text{consensus}\text{sequence}$present within the exon 3on $\text{pre-mRNA}$ the strand.

d.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that gene contains threeexons, also to identify,transcription start site

Introduction:

The typical eukaryotic gene consists of an exon, intron, promoter sequence, a terminator sequence, upstream sequence, downstream sequence, enhancer,and silencer. A eukaryotic gene transcribes in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 4: Transcription start site

The actual site from where the transcription initiation occurs on the DNA template, is termed as transcription start site.

In figure transcription start site present within the starting of exon 1 on DNA strand.

e.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that gene containsthree exons, also to identify, $3^{\prime }\text{untranslated}\text{region}$

Introduction:

The typical eukaryotic gene consists of an exon, intron, promoter sequence, a terminator sequence, upstream sequence, downstream sequence, enhancer,and silencer. A eukaryotic gene transcribes in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 5: $3^{\prime }\text{untranslated}\text{region}$

The $3^{\prime }\text{untranslated}\text{region}$ is responsible to maintain the stability of $\text{mRNA}$ and regulates protein synthesis from the protein coding region.

In the figure $3^{\prime }\text{untranslated}\text{region}$is present after exon 3 on $\text{pre-mRNA}$the strand.

f.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that the gene contains three exons, also to identify, introns.

Introduction:

The typical eukaryotic gene consists of an exon, intron, promoter sequence, a terminator sequence, upstream sequence, downstream sequence, enhancer,and silencer. A eukaryotic gene transcribes in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 6: Introns

DNA contains a particular sequence of nucleotide which codes for a particular protein, termed agene. Gene containssome regions which do not code any protein is termed as an intron.

Introns are present in-between the coding sequence (gene) of DNA. Introns are transcribed and produce, but during the splicing process of RNA transcript, the intron segment is eliminated, hence do not code proteins.

In the figure, one intronsis present exon1 and exon2, and second introns are present in between exon 2 and exon 3, on DNA and $\text{pre-mRNA}$strand.

g.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that the genecontains threeexon, also to identify, exon.

Introduction:

The typical eukaryotic gene consists of exon, intron, promoter sequence, terminator sequence, upstream sequence, downstream sequence, enhancer and silencer. A eukaryotic gene transcribe in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 7: Exons.

DNA contains a particular sequence of nucleotide which codes for a particular protein, termed as gene. Gene contains the coding regions which codes a particular functional protein is termed as exon.

In the figure, coding sequences marked as exon1, exon 2 , and exon 3, on DNA $\text{pre-mRNA}$ and $\text{mRNA}$strand.

h.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that gene contains three exon, also to identify, poly (A) tail.

Introduction:

The typical eukaryotic gene consists of exon, intron, promoter sequence, terminator sequence, upstream sequence, downstream sequence, enhancer and silencer. A eukaryotic gene transcribe in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 8: Poly (A) tail

Eukaryotic $\text{mRNA}$ contain a $3^{\prime }$ poly (A) tail which contain almost $\text{50-250}\text{adenine}$ nucleotides. The $3^{\prime } \text{poly }\left(\text{A}\right)\text{ tail}$ stabilize the $\text{mRNA}$, and also helps in translation.

In the figure, poly (A) tail present on the $3^{\prime }$end of the $\text{mRNA}$strand.

i.

Summary Introduction

To determine:

The typical eukaryotic gene and the $\text{pre-mRNA}$ and $\text{mRNA}$ derive from it; assuming that gene contains three exon, also to identify,$5^{\prime }\text{cap}$.

Introduction:

The typical eukaryotic gene consists of exon, intron, promoter sequence, terminator sequence, upstream sequence, downstream sequence, enhancer and silencer. A eukaryotic gene transcribe in $\text{mRNA}$ followed by protein synthesis.

Explanation of Solution

Pictorial representation:

Fig. 9: $5^{\prime }\text{cap}$

Eukaryotic $\text{mRNA}$ contain a $5^{\prime }$ made-up of $7-\text{methyl}\text{guanosine}$ liked to the $5^{\prime }\text{terminal}$ of the $\text{mRNA}$ by an $5^{\prime },5^{\prime }-\text{triphosphate}\text{linkage}$. This $5^{\prime }\text{cap}$ help initiation of translation as translation initiation factor bind to it. $5^{\prime }\text{cap}$ in addition with poly A tail provide stability to $\text{mRNA}$.

In the figure,$5^{\prime }\text{cap}$present inthe $5^{\prime }\text{untranslated}\text{region}$ of the $\text{mRNA}$strand.