DNA Flashcards
who discovered DNA in 1953?
James Watson and Francis Crick (officially)
Rosalind Franklin
what did Watson and Crick do?
interpreted the x-ray diffraction patterns produced by Rosalind Franklin to propose a model for the molecule of life
what does DNA stand for?
Deoxyribose Nucleic Acid
what was their model called?
helical model
what is DNA?
molecule of heredity
what’s the formula for DNA?
Belongs to pentose sugar C5H10O5
deoxyribose means O4
what’s the structure of DNA?
It is a long macromolecule of polymer consisting of two helical chains coiled around a common axis.
The monomers of these chains are nucleotides
describe the nucleotides
of a 5-carbon sugar a phosphate group and a nitrogen containing organic base
what are the organic bases called?
Adenine, Guanine, Thymine, Cytosine
describe the properties of each base
Adenine and Guanine are the larger bases, described as PURINES.
Thymine and Cytosine are the two smaller bases, described as PYRIMDINES.
whats a purine?
it has two rings
whats a pyrimidine?
made of 1 ring- when we pair them we get 3 rings meeting in the middle.
e.g. Thymine is a pyrimidine base- a single nitrogen containing ring is part of its structure
what’s the position of a chromosome called?
locus
what’s a gene?
short section of DNA that codes for a protein – has a specific locus on a chromosome
what’s a recessive gene?
non-functioning protein (doesn’t do its job) e.g. cystic fibrosis
what’s a dominant gene?
functioning protein (always does its job) e.g. Huntington’s disease
what’s a type of nucleic acid?
ATP
Adenosine Triphosphate
name some reactions ATP is essential for
Photosynthesis, respiration, movement, metabolism, active transport, thermoregulation, bioluminescence
how is ATP used in metabolism?
Light energy is converted by plants into chemical energy during ph/s -> The chemical energy from ph/s in the form of organic molecules, is converted into ATP during respiration -> ATP is used by cells to preform useful work
how does ATP release energy?
the 3 phosphate groups are joined together by 2 high energy bonds.
when hydrolysed the bond breaks which releases a large amount of energy
what is ADP?
Adenosine diphosphate.
what enzyme catalyses the hydrolysis of ATP?
ATPase
what is lost during the hydrolysis of ATP/making of ADP?
the phosphate group
in ways can ATP reform to make ADP+Pi?
- Photophosphorylation
- Oxidative photophosphorylation
- Substrate–level phosphorylation
when does photophosphorylation happen?
occurs in the chlorophyll during photosynthesis
when does oxidative photophosphorylation happen?
occurs in the mitochondria during the electron transport chain (part of respiration)
when does substrate-level phosphorylation happen?
when phosphate groups are transferred from donor molecules to ADP
why could ATP be a better source than glucose?
-The energy released from the splitting of ATP into ADP releases energy in small, manageable bursts
-Hydrolysis of ATP to ADP is a single reaction, glucose breakdown requires a long series of reactions
It is immediate energy souce bc its made by 1 reaction
advantages of ATP:
-instant source of energy in the cell
-releases energy in small amounts as needed
-it is mobile and transports chemical energy to where it is needed in the cell
-Universal energy carrier and can be used in many different chemical reactions
what are the 4 differences between DNA and RNA?
-RNA has the sugar ribose instead of deoxyribose
-RNA has the base uracil instead of thymine
- RNA is usually single stranded
- RNA is usually shorter than DNA
where is the phosphodiester bond created?
between the sugar of one DNA molecules and the phosphate of another
steps for DNA replication
1.An enzyme called helicase attaches to the DNA molecule and moves along its length (unzipping).
2. Hydrogen bonds holding the DNA strands together are broken and the two strands of the helix begin to sperate.
3.The enzyme DNA polymerase join together the activated nucleotides to form the new sugar-phosphate backbone
4.Free nucleotides from the nucleoplasm are attracted to their complementary bases on each separated strand of DNA
5.The nucleotides bond together by the enzyme DNA polymerase
6.Two identical DNA molecules are formed
what did Watson and Crick propose?
during replication, the strands of DNA separate and each strand acts as a template from the formation of a new strand of DNA. OG strand is conserved
describe the molecular structure of DNA and explain how a sequence of DNA is replicated in the bacteria (7)
made of nucleotides
Adenine, Cytosine , Thymine , Guanine
sugarlgosphate backbone
AT CG
held by hydrogen bonds
semi conservative replication
DNA polymerase
explain why specific base pairing is important in DNA replication (3)
to make exact copies the base sequence must be the same as the original DNA. both strands act as a template
explain how the structure of DNA is related to its function (6)
-sugar phosphate backbone gives strength
-coiling gives compact shape
-long molecule allows info to be stored
-double helix protects weak hydrogen bonds
-chains held together by weak hydrogen bonds
-chains can split for replication
describe two features of DNA which make it a stable molecule (3)
strong sugar phosphate backbone coiling reduces chance of molecular damage as it protects hydrogen bonds
explain how DNA replicates (5)
hydrogen bonds are broken
semi conservative replication
nucleotides line up
complimentary base pairing AT CG
DNA polymerase
explain why DNA replication is described as semi-conservative (2)
each strand acts as a template
explain why DNA replication is described as semi-conservative (2)
each strand acts as a template
