Question 3 0 pts Below is an amino acid alignment for Histone H4 in Arabidopsis

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Question 3 0 pts Below is an amino acid alignment for Histone H4 in Arabidopsis thaliana (plant) althouglh the sequence is conserved throughout all eukaryotes (103 amino acids). You have recently discovered a mutant strain (mut205) of A. thaliana that has a propensity to die off early in development. You have narrowed down what is causing the problem to mutations in histone H4. Using the alignment below, explain what effect these changes might have on histone H4 function (I'll give you a hint, the changes are in surface amino acid residues). Don't forget to speculate on why these specific changes are detrimental (lethal) early in development. Be specific with your answer. In the alignment, conserved positions (i.e. no changes to the amino acid sequence) are indicated with “*" while differences in sequence are indicated with "." or nothing. wildtype wildtype aut205 IFLESVIRDAVTYTEHARRRTVTANDWYALKRGRTLYGFGG 103 IELENVIRDAVTYTEHADDRTVTAMDVVYALDEGRTLYGEGG 103

Explanation / Answer

Histones are positively charged proteins that contain basic amino acids. They wrap around the DNA and help in its compaction.
They contain many basic amino acids such as Lys, Arg and His. These amino acids exist as positive ions at the physiological pH so they can bind to negatively charged DNA.
In the given case,
Many mutations are non-synonymous. i.e, they have changed positively charged amino acids such as H, R, and K to negatively charged amino acids such as Asp and Glu. These mutations make histones more negatively charged. Hence the mutant protein may not be able to strongly bind to the DNA. This results in developmental abnormalities and eventual lethality as DNA maintainance is disturbed.

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