Download Seminar powerpoint DNA

GENES ARE DNA & DNA
STRUCTURE AND REPLICATION
THE TUMORNATORS
GENES ARE DNA
In the 1940’s much of what was understood about DNA was mislead and
incorrect. DNA is not all the same in organisms. Different organisms have different base
pairing. That’s what differentiate one organism from the next. A gene is a small
segment of the DNA, these segments are called bases. There are for bases: Adenine,
Thymine, Guanine and Cytosine. DNA bases pair with one another. Base paring must
always link A with T and C with G. DNA has 3 components: 2’-dioxyribose with
triphosphate hanging off of the 5’ prime carbon and a base coming out of the 1’
prime. Chargaff studied DNA and discovered many traits. Chargaff’s rule states that
DNA must have a 1:1 ratio of the purines: Guanine to Adenine, and the Pyrimidines:
Cytosine to Thymine. In other words, A=T and G=C.
DNA STRUCTURE AND REPLICATION
DNA and RNA polymers have direction 5’3’ and polymerization must always go 5’3’. Basepairing must always be A-T (2 H-bonds) or A-U (2 H-bonds) and G-C (3 H-bonds). Bases can only be added to
the 3’ end of the DNA strand, not the 5’ end. Base paired strands must always be anti-parallel. DNA is
replicated by an enzyme that is called DNA polymerase. On the 5’ strand, DNA synthesis must re-start because it
is discontinuous. It’s considered the lagging strand. On the 3’ strand, DNA synthesis is continuous and therefore is
considered the leading strand.
Every human being has DNA. Any part of the human body contains cells, and those cells contain all the
DNA that are in the human body. DNA sequences are the same in all cells of the same person and are different
in different individuals. DNA can carry information. The order of the bases along a strand is a code. The code is
for making proteins. The backbone of a DNA molecule is held together through covalent bonds and the strands
are held together by two hydrogen bonds. A DNA molecule can “peel” apart the strands for replication and
transcription without breaking the backbone.
QUESTIONS
• How does radiation cause mutation in DNA? What happens when mistakes are made in DNA
replication and mutagens occur? What effect does it have in the body that causes the DNA
Polymerase to alter while doing its job to replicate correctly?
• Do certain frequencies of bases indicate anything for organisms? If we were to connect two
different strands of DNA from 2 different organisms (1 from each) and connect the bases, will
the DNA be able to transcribe?
• Is it possible to break apart a DNA, find the composition of the bases and take that
knowledge to replicate a DNA strand? What happens if a mutation occurs, when a base goes
in the wrong place in a DNA structure? How does the composition of A, T, C, G determine
traits?