Mollecular

Question 0

what is the charge of the DNA and how it forms the NUCLEUSOME?

Answer 0

Negatively charged DNA loops twice around the positively charged histone octamer to form nucleusome “beads on a string”.

Question 1

How DNA exists where and in what form?

Answer 1

DNA exists in the condensed, Chromatin form in order to fit into the NUCLEUS.

Question 2

how does the nucleosome look like?

Answer 2

it looks like beads on a string.

Question 3

what amino acids are in the Histones?

Answer 3

Histones are rich in the amino acids Lysine and Arginine (remember Histones have LA in them)

Question 4

what histones are in the nucleosomes ?

Answer 4

H2A, H2B, H3 and H4 ( double each = x2 ) “ remember nucleosomes have all the histones except 1 which is H1”

Question 5

what does H1 role in the DNA?

Answer 5

H1 binds to the nucleosome and to “linker DNA”, thereby stabilising the chromatin fibre. “ remember it binds so it means stability to the chromatin”.

Question 6

in what cell cycle and phase, chromosomes are formed?

Answer 6

In Mitosis, DNA condenses to form chromosomes.

Question 7

synthesis of DNA and Histones ?

Answer 7

DNA and histone synthesis occur during S phase.

Question 8

condensed and appear darker on EM

Answer 8

Heterochromatin

Question 9

transcriptionally inactive and sterically inaccessible?

Answer 9

Heterochromatin

Question 10

HeteroChromatin

Answer 10

Highly Condensed

Question 11

inactive X chromosomes and they are HeteroChromatin

Answer 11

Barr Bodies

Question 12

Less Condensed, appears lighter on EM

Answer 12

EuChromatin

Question 13

Transcriptionally active, sterically accessible

Answer 13

EuChromatin

Question 14

EuChromatin

Answer 14

Eu= true, “ truly transcribed”

Question 15

DNA Methylation

Answer 15

favours C “cytosine”.

Question 16

DNA Methylation

Answer 16

template strand Cytosine and Adenine are Methylated in DNA Replication, which allows Mismatch Repair enzymes to distinguish between Old and New strands in Prokaryotes.

Question 17

what does DNA Methylation at CpG islands do to the transcription?

Answer 17

DNA Methylation at CpG islands represses transcription. “remember CpG Methylation Makes DNA Mute”

Question 18

Methylation that causes Reversible repression of DNA transcription?

Answer 18

Histone Methylation

Question 19

Histone Methylation

Answer 19

Usually reversibly represses DNA transcription, but can Activate it in some cases depending on methylation Location.

Question 20

Histone Acetylation

Answer 20

makes DNA Active, by relaxing the DNA coiling, allowing for transcription. “ remember Acetylation = Active”