To yeabiruh and others pls try - nija

[ArchivalUser]

The following numbered codons relate to the partial sequence of an mRNA for a protein. Termination codons are UAG, UGA, and UAA; the initiation codon is AUG. The triplets are numbered as shown:


132 133 134 135 136 137 138 139
UUG CUG CCA UAU UUA UGU GUU AAU


Insertion of uridine between the end of codon 135 and the beginning of 136 will result in a protein containing how many amino acids?


A.134
B.135
C.136
D.137
E.138

[ArchivalUser]

The locations of three different nucleotide substitution mutations near the human ?-globin gene are shown by the vertical arrows. Each of these mutations can lead to ? + -thalassemia major. These three nucleotides of the wild-type sequence are most likely to be required for which of the following?


A.Binding eIF4F
B.Binding eIF4G
C.Binding histone acetylase
D.Binding histone deacetylase
E.Binding negative-acting transcription factors
F.Binding positive-acting transcription factors

[ArchivalUser]

A normal peptide has 100 amino acids. Following mutation, it has only 20; 1-10 are the same as the normal peptide; 11-20 differ from the normal peptide. Which of the following mutations occurred?


A.Nucleotide deletion in the codon for amino acid 11 (codon 11)
B.Nucleotide deletion in codon 20
C.Nucleotide deletion in the intervening sequence
D.Nucleotide substitution in codon 11
E.Nucleotide substitution in codon 20

[ArchivalUser]

hi nija ....for question 1

Uridine is one of the four basic components of ribonucleic acid (RNA); the other three are adenosine, guanosine, and cytidine

---hence when we insert uridine at the end of a codon 135 (UAU) and at the start of codon 136 (UUA) let us the new pattern of the mRNA ....UAU + U+ UUA=UAUUUUA HENCE CODON 135 IS STILL THE SAME BUT
CODON 136 BECOMES UUU(FROM UUA)
Codon 137 becomes AUG (from UGU)
Codon 138 becomes UGU (from GUU)
Codon 139 becomes UAA (from AAU)

as u c from above the big changes are on Codon 137 ....change to initiation codon
and on Codon 139 which becomes a stop codon....

---and I dont think the change on Codon 137 can start a new protein synthesis becuase to end protein synthesis we need stop codons for sure .....

---hence I think the change in Codon 139 is the one which brings change in the number of aminoacids ...

---to finalize The new Codon 139 doesn't code for any aminoacid as it is a stop codon hence our protein will have 138 amonoacids ...counting upstream

[ArchivalUser]

1- E
2- q not clear
3- D

[ArchivalUser]

for Q 2----

Thalessemia Major ...let us for example beta thalessemia major (ie, homozygous beta

thalassemia), the production of beta-globin chains is severely impaired, because both

beta-globin genes are mutated. The severe imbalance of globin chain synthesis

(alpha >> beta) results in ineffective erythropoiesis and severe microcytic hypochromic

anemia (or viceversa in the case of alpha thalessemia Major )......

As u stated in ur question the nucleotide substitution mutation results in thalessemia

major ...which means there is severely decreased beta globin (protein )synthesis (if we say

this is beta thalessemia)....

---during protein translation ,mRNA is needed (which comes from DNA by transcription)

---as we see in ur question there is ? impaired beta globin which directly implies there is an

impared mRNA transcription due to the mutation...and these three nucleotides of the

wild-type sequence are needed for ...Binding positive-acting transcription factors ...


lack of binding site for positive acting transcription factors....causes lesstranscription...which

in turn causes less globin chains either alpha or beta (if not 0)

[ArchivalUser]

For question 3 the question is about frameshift mutation....

---as u know in frameshift mutation there is either deletion or substituition of a number of

nucleotides that is not divisible by three....

--As u explained in the question stem the number of aminoacids is decreased from 100 to

20...which means the frameshift mutation causes the Codon 21 to be a stop codon....

---and also u explained aminoacids from 11 -to 20 are different from the previous one but 1-10 are the same

---hence the frameshift mutation should happen after 10 but before 21 of the normal codon

---and because u said aminoacid 11 is changed the frameshift mutation should be at codon 11

---but the question is is it deletion or substitution ? and from the question stem I cant draw

any difference between the two....either deletion at codon 11 or substitution at codon 11

causing downstream effect....

[ArchivalUser]

Thanks a lot yeabiruh. fabulous explanation .After seeing ur answers i like to study molecular biology.Happy studying...........

[ArchivalUser]

The answer will be deletion........if the answer would be substitution then only amino acid no 11 would be different.....since all amino acid from 11 onwards are different, there must be deletion not substitution

[ArchivalUser]

I think argue is right ans shud be A Nucleotide deletion in the codon for amino acid 11