Question

1. When a stop codon is in place at the ribosomal A site, a ________________ factor binds to the site instead of a new aminoacyl-tRNA.
2. List two specific causes of DNA mutations.
3. One of the ways chromatin remodeling occurs to allow gene expression is ____________________ of ______________ residues of histones.
4. During translation, elongation factors EF-Tu and EF-G use hydrolysis of the energy molecule  ________ to successfully complete their tasks
5. The __________________________________ sequence is a consensus sequence (in prokaryotic mRNAs only) that signals the start of translation.
6. In transcription, RNA polymerase only binds to one of the DNA strands, known as the ______________ strand

Answer 1

1. When a stop codon is in place at the ribosomal A site, a release factor binds to the site instead of a new aminoacyl-tRNA. (A release factor is a protein that allows for the termination of translation by recognizing the termination codon or stop codon in an mRNA sequence. They are named so because they release new peptides from the ribosome.)
2. One of the ways chromatin remodeling occurs to allow gene expression is removal of H1 residues of histones.(Removal of H1 histones exposes 50-80 basepairs.There transmission can start and proceeds.

   Chromatin remodeling is the rearrangement of chromatin from a condensed state to a transcriptionally accessible state, allowing transcription factors or other DNA binding proteins to access DNA and control gene expression. Chromatin is the complex of DNA and proteins that are packed within the nucleus of mammalian cells. To form chromatin, DNA is tightly condensed by being wrapped around nuclear proteins called histones. This repeating DNA-histone complex, which consists of 146 base pairs of double-stranded DNA wrapped around eight histone proteins, is called a nucleosome. The repeating nucleosomal units are commonly referred to appear as “beads on a string” when seen under a microscope.

   In general, the more condensed the chromatin, the harder it is for transcription factors and other DNA binding proteins to access DNA and perform their duties. When chromatin is tightly packed, and not actively being transcribed it is called heterochromatin. When chromatin is more loosely packed, and therefore accessible for transcription it is called euchromatin. Chromatin remodeling is highly implicated in epigenetics. Epigenetic modifications to histone proteins such as 3) group from S-adenosylmethionine to a cytosine nucleotide or lysine or arginine residue.">methylation/3) group.">demethylation and 3CHO) group. Acetyl co-enzyme A is used as the acetyl group donor.">acetylation/deacetylation can alter the structure of chromatin resulting in transcriptional activation or repression. Pls refer Phundan Singh, Fundamentals of Genetics, pg. 381 if you can )

3. During translation, elongation factors EF-Tu and EF-G use hydrolysis of the energy molecule GTP to successfully complete their tasks
4. The Shine Delgarno sequence(AGGAGG) is a consensus sequence (in prokaryotic mRNAs only) that signals the start of translation. (The Shine-Dalgarno (SD) Sequence is a ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG. The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon.)
5. In transcription, RNA polymerase only binds to one of the DNA strands, known as the template/anti-sense/non-coding strand(The DNA strand that mRNA is built from is called the template strand because it serves as a template for transcription. It is also called the antisense strand. The template strand runs in a 3' to 5' direction.)
6. List two specific causes of DNA mutations.

• Natural cause : DNA fails to copy accurately. When a cell divides it make a copy of it's DNA and smetime the copy is not perfect.
• External influences/Mutagens :These are Physical or chemical materials that changes genetic material ,usually DNA of an organism and increases the frequency of mutation above the natural level.