In this IBDP Biology Blog post, we wil learn about:
- The structure of a DNA
- DNA non- coding
- difference between DNA and RNA
DNA Structure
- The sugar-phosphate backbone is on the outside bases are on the inside
- The strand is held together by Hydrogen bonds between the bases
- Complementary Base Pairing: A only pairs with T. C only pairs with G
- Anti-parallel strand: Two strands run in opposite directions
- DNA twists into a double helix through the use of Hydrogen bonding
- Covalent bond: Link between 5' and 3' ends of carbon molecules
Nucleosomes
Prokaryotic DNA: Naked circular DNA and plasmids [not associated with Histone proteins]
Eukaryotic DNA: DNA is associated with Histone proteins
Nucleosome: Length of DNA of approcimately 150 base pairs wrapped around a core of 8 Histone proteins [two pairs of four]
Nucleosomes are formed by wrapped DNA around Histone proteins
Eukaryotic DNA is supercoiled to:
- Be able to pack genetic material into the nucleus
- Organize DNA to allow cell division to occur
- To control DNA expression
- Allow cells to specialize
- Transcription of chromatin can be promoted or inhibited
Nucleosomes helps supercoil the DNA
Non-coding DNA
During Splicing:
- Introns are edited out of mRNA
- mRNA is translated by Ribosomes into Polypeptides
- Only exons code for Polypeptides
Telomeres: Repetitve sequences at the ends of chromosomes that protect the ends of the chromosome
With every cell devision short stretches of DNA are lost from the Telomeres. Prevents at the ends of chromosomes from being lost each time DNA Replication occurs
Genes for tRNA and rRNA
Genes that code for RNA molecules that do not get transcribed instead fold and form tRNA molecules [important in Translation]. rRNA forms ribosomal RNA that forms the structure of the ribosome
Differences Between DNA and RNA
DNA and RNA both consist of nucleotides which contain a sugar, a base and a phosphate group. However there are a few differences.
- Firstly, DNA is composed of a
double strand forming a helix, RNA is only composed of one strand.
- The sugar in DNA is
deoxyribose whereas in RNA it is ribose.
- both DNA and RNA have the bases adenine, guanine and cytosine, however DNA also contains thymine which is replaced by
uracil in RNA.
That's it! well done!
References:
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fbyjus.com%2Fbiology%2Fdna-structure%2F&psig=AOvVaw3uCOnpAg5Jq6vM-EQBgLNI&ust=1626104124557000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCIignIis2_ECFQAAAAAdAAAAABAD
- https://www.google.com/url?sa=i&url=http%3A%2F%2Fib.bioninja.com.au%2Fhigher-level%2Ftopic-7-nucleic-acids%2F71-dna-structure-and-replic%2Fnucleosomes.html&psig=AOvVaw1Biiv79tmfHQe4d2sDR78r&ust=1626104215893000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCIiWtris2_ECFQAAAAAdAAAAABAD
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.technologynetworks.com%2Fgenomics%2Flists%2Fwhat-are-the-key-differences-between-dna-and-rna-296719&psig=AOvVaw1ZQSBeXbsmaTZ8bfMMsD0Z&ust=1626104474895000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCMCrn6-t2_ECFQAAAAAdAAAAABAJ
Drafted by Venetia (biology)