Notes : 2.5 - 2.8 + 2.11 + 2.15 + 2.16 - DNA & Genetics Flashcards
What are the three components of nucleotides?
A pentose sugar (either ribose or deoxyribose), attached to a phosphate group and an nitrogen-containing base (either adenine, guanine, cytosine, thymine or uracil).
Describe the structure of DNA.
Double stranded. Made up of deoxyribose mononucleotides, linked through condensation reactions.
Possible bases are A,C, G and T. C pairs with G, A pairs with T.
How does DNA form a double stranded helix?
Bases on the nuclei acid strand form hydrogen bonds with each other, holding the two strands together.
• Stacking of many mononucleotides results in a helix (twisted) shape.
Describe the structure of RNA.
Single stranded. Made up of ribose mononucleotides, linked through condensation reactions. Possible bases are A,C, G and U. C pairs with G, A pairs with U.
How is the DNA sequence converted into proteins?
- Transcription; reads DNA sequence and produces mRNA.
- Translation; reads mRNA sequence and produces proteins.
What are Nucleic Acids
Nucleic acids are long chains (polymers) of lots of nucleotide monomers joined together by phosphodiester bonds. Thats why its called (DNA - deoxribose nucleic acid as dna is made up of lots of nucleotides joined together) - aka a nucleic acid.
What can nucleotide’s be split into.
1 - Mononucleotide (Consisting of one base,phosphate group and sugar).
2 - Dinucleotide ( Double so it will have 2 bases)
3 - Trinucelotide (Trinucleotide so will have 3 bases)
Poly - Many nucleotides.
Outline the process of transcription.
An enzyme called RNA polymerase attaches to the promoter region the gene. (This signals to the RNA polymerase that this is where of the process of the transcription should start).
- RNA polymerase(Il) separates the DNA strands, exposing a the template strand for transcription.
- RNA polymerase moves along the template strand of DNA, reading each base. Synthesizing an mRNA strand by joining the complementary nucleotides through phosphodieseter bonds.
What is the promoter region ?
The promoter region is a regulatory region which does not code for amino acids but facilitates the process of transcription by helping RNA polymerase bind to the gene.
Name some differences between DNA and RNA
- the pentose sugar in DNA is deoxyribose and in RNA is ribose. The difference is that deoxyribose has one less oxygen atom.
- RNA contains uracil instead of thymine
- DNA is double-stranded whereas RNA is single-stranded
Explain the detailed version of DNA synthesis.
- Initiation: Enzymes called DNA helicases unwind and separate the two strands of the DNA double helix, forming a replication fork.
- Primer Binding: Primase an enzyme, synthesises short RNA primers at the replication fork. These primers provide a starting point for DNA synthesis.
- Leading Strand Synthesis : DNA polymerase attaches to the leading strand. is synthesized continuously in the 5’ to 3’ direction toward the replication fork. DNA polymerase continuously adds nucleotides to the growing leading strand. following the base-pairing rules (A with T, C with G).
- Lagging Strand Synthesis : The lagging strand is synthesised discontinuously in short fragments called Okazaki fragments. Primase synthesizes RNA primers for each Okazaki fragment, and DNA polymerase then adds nucleotides to each fragment, creating short DNA segments.
- Okazaki Fragment Processing : The RNA primers in the Okazaki fragments are replaced with DNA by DNA polymerase. DNA ligase joins the adjacent Okazaki fragments, sealing any gaps in the DNA backbone.
- Termination : DNA synthesis continues until the replication fork reaches the end of the DNA molecule. The newly synthesized DNA strands separate, and the process is complete.
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Types of RNA:
- Blurt everything you know about mRNA
Messenger RNA (mRNA)
o Produces during transcription – RNA polymerase uses DNA as a template to provide mRNA strand
o Carries the genetic code from the nucleus to the cytoplasm – provides the instructions for making a protein on the ribosome in translation
o Read in triplets.
Summarise the process of DNA replication.
- Double helix unwinds and the hydrogen bonds break, catalysed by DNA helicase.
- Complementary base pairing occurs between the template strand and free nucleotides.
- The nucleotides are joined by phosphodiester bonds, catalysed by DNA polymerase.
Explain the process of transcription.
- RNA polymerase binds to the beginning of a gene in an area known as the promoter region.
- RNA polymerase separates the DNA strands, producing a single DNA template for transcription.
- As RNA polymerase moves along one of the DNA strands (the template strand), it adds complementary nucleotides and connects them through the formation of phosphodiester bonds.
4.The other strand is referred to as the coding strand and will have an identical sequence to the newly synthesised RNA, except for the presence of thymine instead of uracil.
- Eventually RNA polymerase will reach a stop codons. A molecule of messenger RNA (mRNA) has been formed which will leave the nucleus and enter the cytoplasm.
What are promoter regions ?
The promoter region is a regulatory region which does not code for amino acids but facilitates the process of transcription by helping RNA polymerase bind to the gene.