DNA Structure & Replication PPT Flashcards
chemical compound that passes hereditary information from generation to generation
deoxyribonucleic acid (DNA)
What are the building blocks of DNA?
DNA is composed of a long chain of nucleotides.
Each nucleotide in DNA has ___ components and are attached with ___ bonds.
3,
covalent
How many different nucleotides make up DNA?
4
2 ring nitrogen base structure
purines
1 ring nitrogen base structure
pyrimidines
Which nucleotides have a purine base?
adenine,
guanine
Which nucleotides have a pyrimidine base?
thymine,
cytosine
Who discovered how the nucleotides are assembled and when?
Erwin Chargaff (1949)
How are the nucleotides assembled?
purines attach to pyrimidines (A=T and G=C)
Whose x-ray diffraction images suggested DNA structure?
Rosalind Franklin
Describe DNA structure.
- long and thin
- uniform diameter
- two varying repeats suggests a double coil/helix
determined the double helix structure of DNA and built a model to display it; won a Nobel prize
Watson and Crick (1953)
a twisted ladder structure; sugar-phosphate are the sides that make up a “backbone”; nitrogen bases attach across as the rungs (A=T and G=C); two strands run antiparallel and are complimentary to each other (3 prime to 5 prime)
double helix structure
Nitrogen bases in DNA attach with ___ bonds.
hydrogen
flow of information from DNA to RNA to protein
central dogma of molecular biology
process of creating a new DNA molecule
replication
process of creating RNA from DNA
transcription
process of creating proteins from RNA
translation
DNA replication must occur ___ cell division.
before
Cell must duplicate its genome before it ___.
divides
Each strand acts as a ___ to create a new strand.
template
Describe the origins of replication.
- Helicase enzyme unwinds DNA in both directions
- forms a replication bubble and binding proteins stabilize each strand
- at each end of the replication bubble is a replication fork
enzyme which adds only to an existing strand laid by a RNA primase enzyme; gets energy by breaking off two phosphates
DNA polymerase
What’s the problem with using DNA polymerase to add in free nucleotides?
only adds nucleotides to the 3 prime (3’) end
One strand is made continuously (5’-3’) while the other strand is made in sections called ___ and gaps are sealed in by ___.
Okazaki fragments,
DNA ligase
the end result is 2 identical DNA molecules formed from the original; during cell division one complete copy is given to the new cell while one is retained in the original cell; each new molecule consists of one old strand and one new strand
semi-conservative replication
Are mistakes possible in DNA replication?
yes
What enzymes can extract mistakes and repair DNA?
DNA polymerase,
DNA ligase
If an error in DNA replication persists, a ___ results.
mutation
DNA is contained in the nucleus as ___, but condenses into ___.
chromatin,
chromosomes
discreet packages of DNA
chromosomes
a sequence of DNA nucleotides that codes for a specific protein or RNA molecule
gene
all the genetic material in a cell
genome