8. DNA structure and replication Flashcards
What is DNA wound around ?
DNA is wound twice around a histone core
Why is it necessary that the DNA is wound around his tones?
Important as it allows the DNA to fit in the nucleus and can help regulate transcription
What is the whole structure of dDNA around one histone protein called?
Nucleosome
What is the first structure of DNA packaging called?
Beads on a string
What is the second structure of packaging called?
Solenoid
What is euchromatin?
Euchromatin is beads on a string - where gene expression takes place because DNA is more accessible as it not as tightly packaged
What is heterochromatin?
Heterochromatin is the solenoid - DNA that is not transcribed because it is tightly wound and packaged so not accessible for transcription factors.
What causes the change from euchromatin(active chromatin) to heterochromatin(inactive chromatin)?
DNA methylation
Histone deacetylation
What causes the change from heterochromatin (inactive chromatin) to euchromatin(active chromatin)?
DNA demethylation
Histone acetylation
What do chromosomes consist of?
Chromosomes consist of many solenoids wrapped tightly around - meaning that genes are not expressed in a chromosome as the DNA is so tightly packed that it is not accessible for transition and translation
What are genes?
- Genes are section of DNA that carry the code for proteins
* Genes have a fixed chromosomal location
What is the genome?
• Genome is the entire DNA sequence
How many chromosomes in the human genome?
- Human Genome is 24 chromosomes
* (22 plus 2 sex chromosomes X and Y)
What is the difference between nucleoside and nucleotide?
Base + sugar = nucleoside
Base + sugar + phosphate = nucleotide
What are the two peso f pentose sugars?
Ribose and 2-deoxyribose
What is the difference between Ribose and 2-deoxyribose ?
In ribose, there is an OH group on carbon 2 whereas in deoxyribose, there is a H on carbon 2