1
Question
The association of histone H1 with a nucleosome indicates
The association of histone H1 with a nucleosome indicates
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Solution
The correct option is D The DNA is condensed into a chromatin fibre.
Occurrence of replication
The occurrence of replication on a DNA strand is indicated by the presence of a replication fork that is formed due to unwinding of the DNA strand. Unwinding of DNA strands exposes the DNA double helix.
DNA condensed into a chromatin fibre
DNA is a very long thread like molecule which has to be efficiently packaged to fit it within the nucleus of a cell. This is achieved with the help of nucleosome structures. Negatively charged DNA wrapped around the positively charged core of histone octamer forms a nucleosome. Linker DNA is a double-stranded DNA of 38-53 bp long in between two nucleosome cores. The H1 histone is the linker histone and binds to a part of the linker DNA. Linker DNA in association with histone H1, holds the cores together. Nucleosomes on DNA form a ‘beads on string’ appearance, where the nucleosome forms the beads and the linker DNA is seen as the string. Repeating units of nucleosomes form the chromatin which is further coiled to form the chromatin fibres.
Occurrence of transcription
Occurrence of transcription is indicated by the formation of a transcription bubble which is formed due to local unwinding of the DNA strand to allow the RNA polymerase to come and attach to the template strand.
Final answer
(B) The DNA is condensed into a chromatin fibre.
Occurrence of replication
The occurrence of replication on a DNA strand is indicated by the presence of a replication fork that is formed due to unwinding of the DNA strand. Unwinding of DNA strands exposes the DNA double helix.
DNA condensed into a chromatin fibre
DNA is a very long thread like molecule which has to be efficiently packaged to fit it within the nucleus of a cell. This is achieved with the help of nucleosome structures. Negatively charged DNA wrapped around the positively charged core of histone octamer forms a nucleosome. Linker DNA is a double-stranded DNA of 38-53 bp long in between two nucleosome cores. The H1 histone is the linker histone and binds to a part of the linker DNA. Linker DNA in association with histone H1, holds the cores together. Nucleosomes on DNA form a ‘beads on string’ appearance, where the nucleosome forms the beads and the linker DNA is seen as the string. Repeating units of nucleosomes form the chromatin which is further coiled to form the chromatin fibres.
Occurrence of transcription
Occurrence of transcription is indicated by the formation of a transcription bubble which is formed due to local unwinding of the DNA strand to allow the RNA polymerase to come and attach to the template strand.
Final answer
(B) The DNA is condensed into a chromatin fibre.
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