DNA Structure and Function

Watson and Crick suspect that DNA is a helix. This means that two sugar-phosphate chains run in opposite directions and paired bases in the inside. They were the first to create a model of DNA which is a double helix. They worked with Rosalind Franklin (She calculated that DNA is very long and identified a repeating pattern). Watson and Crick were awarded the Nobel Peace Prize 1962.

Chargraffs Rule states that any cell of all organisms should have a identical amounts meaning they should have a 1:1 ratio. The amount of Adenine should be equal to Thymine and Guanine should be a 1:1 ratio to Cytocine. Chargraff's Second Rule says that DNA of different species differs in its proportions of adenine and guanine. This makes sense because the difference in Adenine and Guanine is what makes the species different and unique.

How do base pairs bind? Base pairs bind by hydrogen bonds bonding between the internally positioned bases hold the two strands together. The two kinds of base pairings are Adenine to Thymine and Guanine to Cytosine.

A Chromosome is structure that consists of DNA and associated proteins. This means that chromosomes carry a part or all of a cell's genetic information.

What is a karyotype? A karyotype is an image of an individual’s diploid set of chromosomes. This means that karyotypes are visual displays and profiles of a person's chromosomes.

How does DNA replicate? DNA replicates by enzymes breaking the hydrogen bonds that held the DNA strand together. This causes the DNA to unwind and and separate. This all takes place using the enzyme Helicase. The separation of the DNA strands creates a y-shaped figure called a replication "fork". While this is all going on another enzyme is creating primers (short, single-stranded nucleotides). The primers already attached to the end of the DNA strand now serve as attachment points for DNA polymerase which is the enzyme that assembles the new strands of DNA. DNA polymerase attaches to the hybridized primers and begin DNA synthesis. When this is all completed the enzyme DNA ligase seals any gaps, so that the new strands are continuous. Finally, as the DNA begins to lengthen and stretch out it winds back into a double helix. Through this whole production two copies of a DNA molecule are created. One DNA strand of each copy is new and the other one is the parental strand.

What damages DNA? DNA can be damaged when ionizing radiation from x-rays, most UV light, and gamma rays may cause DNA damage. This damage can break the DNA, cause covalent bonds to form between bases of opposite strands, fatally alter nucleotide bases. Damaged DNA is very bad because it can turn into mutations which at times can be fatal. Most cancers begin with mutations.

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Created with images by mknowles - "Lego DNA"

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