DNA and RNA Flashcards
what is the genome
Entire genetic material in an organism
What does both DNA and RNA stand for and what do they both do
DNA - Deoxyribonucleic acid
RNA - Ribonucleic acid
- found in all living cells
- Both needed to build proteins
- information - carrying molecules
What is the function of DNA and RNA
DNA - stores genetic information
- contains instructions for growth and development
RNA - Transfers the genetic code from DNA out of the nucleus and carries it to the ribosomes
What are DNA and RNA made up of and what is it formed from
Made up of repeating units called nucleotides
nucleotides are formed from :
- A pentose sugar (5 carbon atoms)
- Nitrogen containing organic base
- A phosphate group
What are the components of a DNA nucleotide
- Deoxyribose sugar with a hydrogen at carbon 2
- A phosphate group at carbon 5
- 1 of 4 nitrogenous groups - adenine (a), cytosine (c), guanine (g), thymine (t)
what are the components of an RNA nucleotides
- A ribose sugar with a hydroxyl group at carbon 2
- Phosphate group
- 1 of 4 nitrogenous groups - adenine (a), cytosine (c), guanine (G), and uracil (u) instead of thymine
How are the nitrogenous bases found
2 structural forms purines and pyrimidines
- purines = 2 rings (adenine, guanine)
- Pyrimidines = 1 ring (thymine/uracil, cytosine)
How do you form a polynucleotide
- Joined via a condensation reactions
- Occur between the phosphate group of one nucleotide and pentose sugar of the next
- forms a phosphodiester bond due to there being 2 ester bonds
- Chain of altering phosphate and pentose sugars are sugar-phosphate backbones
why are there 2 ester bonds in a polynucleotide and what do you call them
There are 2 ester bonds (phosphodiester) because there is
- one binding the 5th carbon from the pentose sugar to the phosphate group
- The second is binding the phosphate group to the pentose sugar of the next nucleotide
what is the structure of DNA
2 polynucleotide (chains made from phosphodiester bonds) side by side which are anti-parallel
what is the structure of each polypeptide strand of DNA
Said to have a 3 carbon and a 5 carbon end as the strands are anti-parallel one is known ad the 5 to 3 strand where the 5 is at
the top and t
other the 3 to 5 strand
How are the 2 strands of DNA held together
Held together by hydrogen bonds between nitrogenous bases
A-T = 2 hydrogen bonds
C-G = 3 hydrogen bonds
why do the bases A and T and then G and C always bind together
Because one is a purine and one is a pyrimidine meaning they are the right length for stable DNA
what bases are purines and what bases are pyrimidines
purines = A and G pyrimidines = C and T/U
who was DNA first discovered by and when
and what did he name it
- First observed by Swiss scientist Friedrich Miescher in 1800s
- He named it nuclein and defined it as a molecule in 1869
What did scientists doubt about DNA in the 1800s and why
They doubted it could carry the genetic code because :
- it has a relatively simple chemical composition as only composed of 3 parts
- It was hypothesised genetic material was carried by proteins as it has a more complexed chemistry
What happened in the 1940s in the structure of DNA
1940s - Role of DNA in genetic inheritance began to be researched and understood
what happened in 1953 in the discovering in the structure of DNA
It was confirmed DNA carried genetic codes
- it was understood despite only having 4 nucleotides the use of the triple code (A,T,T) enabled variation
- DNA protected in the nucleus enables security of genetic code rather that proteins in the cytoplasm’s susceptible to hydrolysis
what did Watson and crick do in 1953
Watson and crick confirmed the double-helix structure using Rosalind franklins X-ray DNA
they also came up with a model by which DNA might be replicated the theory was called semi-conservative DNA replication
How do the bases in DNA stabilise the structure
They form hydrogen bonds between the nitrogenous bases A+T and C+G stabilise the structure as many hydrogen bonds provide strength
what molecules make up the backbone of a polynucleotide
A chain of altering phosphate and pentose sugars are sugar-phosphate backbones
