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Comprehending Genes and DNA - Coggle Diagram
Comprehending Genes and DNA
DNA vs. RNA
DNA = double helix, 2 antiparallel strands
RNA = 1 strand
RNA = bases adenine, uracil, cytosine, guanine (A=U, G=C).
DNA = bases adenine, thymine, cytosine, guanine (A=T, G=C).
RNA = ribose sugar, has one more oxygen atom than deoxyribose.
DNA = deoxyribose sugar, doesn't have extra oxygen atom like ribose.
Types of RNA - messenger RNA, transfer RNA, and ribosomal RNA (makes up the ribosomes)
Nucleotides
Adenine and guanine are purine (one ring) nucleotides that are smaller.
Cytosine and thymine are pyrimidine (two ring) nucleotides that are larger.
Adenine to thymine has two hydrogen bonds, while cytosine and guanine has three hydrogen bonds.
The phosphates and sugars of DNA nucleotides make up the sugar-phosphate backbone.
Codons - each sequence of three nucleotide bases are called codons. Each codon codes for an amino acid. There are start and stop codons that tell the ribosome to start and stop translation respectively.
Protein Synthesis
Transcription: occurs in the cell nucleus, DNA is split by the enzyme RNA polymerase. The enzyme also attaches complementary RNA nucleotides to the corresponding DNA bases. These nucleotides are attached together, making mRNA.
Translation: occurs once the mRNA exits the nucleus, mRNA goes to the ribosome, or the organelle that creates proteins. It is read by one codon (three bases) at a time, each codon coding for an amino acid. The ribosome calls for the tRNA to bring the corresponding amino acid. The tRNA has a corresponding anticodon to the codon in order to temporaily bind to the mRNA and drop off the amino acid. The amino acids bond together (peptide bond), eventually forming a polypeptide.
Mutations
Frameshift- reading frame of DNA sequence changes due to a deletion or insertion, causing amino acid sequence to differ from original from that point on.
Nonsense- when a substitution causes the amino acid to be changed to a stop codon
Deletion- base(s) are deleted
Insertion- extra base(s) inserted
Substitution- one base is substituted with another base
Missense- when a substitution changes the amino acid itself
Silent- when a substitution doesn't change the amino acid
Gene Regulation
Transcription factors are proteins. They can either release chromatin that is tightly packed in order to attract RNA polymerase, thus encouraging more transcription of a certain gene. They can also restrict access to certain genes as well as bind to enhancer sequences in order help block transcription.
Homeotic genes control bod part identities of every organism. They tell the organisms’ cells and tissues how to differentiate as they grow. Even with a slight mutation, a body part may not grow as iit was supposed to, thus harming the organism. They are universal among species to ensure healthy growth and also because the homeotic genes are descendants from genes from common ancestors of multiple organisms.
PCR
Denaturation: Heat DNA up to 95 °C, causing hydrogen bonds between bases to break. Second denaturation occurs after for 30-60 sec.
Annealing: DNA primers now match up with the start of the amplification region, and the end of it on the other strand. Temp = 50-65 °C, causing hydrogen bonds to form between corresponding bases of the primers and DNA. Time = 5-230 sec.
Extension: Taq polymerase starts from each of the primers and takes the nucleotides added to the PCR mixture and connects them to the corresponding bases of the two strands of DNA multiple times.
Gel Electrophoresis
Before the gel is placed in the tray, rectangular holes are made for the DNA samples to be in. The gel is placed in the tray. A size standard is also inserted in the gel to measure the amount of base pairs per strand.
Buffer is poured into the tray with the gel inside.
Materials: Agarose gel, saltwater buffer, DNA samples
An electric charge is applied to the buffer, causing the DNA, negatively charged, to move towards the bottom of the tray with the positive charge.