A1.2 - NUCLEIC ACIDS

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state the central dogma of biology

what is DNA

• deoxyribonucleic acid, primary genetic material responsible for storying and transmitting hereditary info

• essential for heredity, evolution, and the functioning of living organisms

  • EXCEPTION: VIRUSES

    • some use RNA rather than DNA as the genetic material

state the structure of DNA

double helix: molecule is double stranded, linked by complementary base paring between nitrogenous bases (A-T, C-G)

strand orientation: antiparallel strands (2 strands run in oppo direction 5’-3’, 3’-5’), 5’ has a phosphate group attached to the fifth carbon of the sugar, 3' end has a hydroxyl group attached to the third carbon of the sugar

nucleotides: phosphate group, pentose sugar (deoxyribose), nitrogenous base (adenine, thymine, cytosine, guanine)

state the function of DNA

genetic info storage: contains code needed for development, growth, function and reproduction within an organism

gene expression: DNA sequences (genes) transcribed into RNA, then translates into proteins within the cell

state the location of where DNA can be found

eukaryotic cell: nucleus, mitochondria, chloroplast

prokaryotic cell: located in a region called the nucleoid

nucleotide to nucleic acids

• nucleotides are monomers of nucleic acids

• link by covalent bonds

  • condensation reaction is created

• creates sugar phosphate backbone

• 5’ carbon links to 3’ carbon

• hydrogen bonds hold nucleotide bases of opposite strands together

nitrogenous bases

5 types: adenine, thymine, uracil, cytosine, guanine

purines: adenine, guanine (double ring structure - bigger)

pyrimidines: thymine, uracil, cytosine (single ring structure - smaller)

• A-T/A-U (2 hydrogen bonds)

• C-G (3 hydrogen bonds)

explain why purines always pair with pyrimidines

• purines pair with pyrimidines due to complementary structures which enables stable hydrogen bonding and maintaining the structural stability of the DNA double helix

• base pairing is important to stabalise the double helic structure of the DNA

what is RNA

ribonucleic acid, carries genetic information, regulates gene expression, participate in protien synthesis

state the structure of RNA

single stranded: RNA is single-stranded, connected by phosphodiester bonds

state the function of RNA

1) mRNA (messenger RNA): carries genetic information from DNA to ribosomes

2) tRNA (transfer RNA): brings amino acids to the ribosome during protein synthesis

3) rRNA (ribosomal RNA): part of the ribosome structure and plays a role in protein synthesis

4) RNA in viruses: serves as genetic material, encodes information required for viral replication and infection

state the location of where RNA can be found

eukaryotic cell: nucleus, cytoplasm, ribosome, mitochondria, chloroplasts (in plant cells)

state the function of a nucleosome

• regulate transcription and gene expression

• condense long strands of DNA into a more compact form, allowing it to fit within the nuclei

• keeps them organised: protect DNA from damage and prevent it from becoming tangled

state the structure of a nucleosome

• found in eukaryotes

• consists of DNA wrapped around histone protiens

  • eight histones in core (octamer)

• “linker” histone attaches to DNA to bind DNA to the core

• histone H1 binds to the linker DNA and helps stabilize the nucleosome structure

outline the results of the Hershey and Chase experiment

study that provided crucial evidence for DNA as the genetic material, proved that DNA is the genetic material, not protein (1952)

outline how radioisotopes provide technological breakthroughs in science

“labels” the molecule and can “track” the location and movement of the labelled molecule

• allowed scientists to trace atoms and molecules in bodies and cells

explain how Chargaff’s data falsified the tetranucleotide hypothesis

• the “tetranucleotide” hypothesis early idea about the structure of DNA

  • presented that nucleotides were arranged in repeating sequences of the four bases: ATCG, ATCG, etc

  • %A = %T = %C = %G, %AT = %GC

• chargaff proved this hypothesis wrong as he extracted and analyzed the nucleotides from a variety of species

• led him to discover that:

  • A ≈ T , C ≈ G in a given DNA sample

  • A pairs with T and C pairs with G in the DNA structure

  • total amount of A, T, C, and G varied among different organisms