DNA Flashcards
DNA (deoxyribonucleic acid)
the genetic code for life
Nucleotide
The sugar deoxyribose
A phosphate group
One of four bases
Adenine (A)
Cytosine ( C )
Guanine (G)
Thymine (T)
Base Pairs
refers to two nucleotides held together by hydrogen bonds between their bases
Base pairing rules
Adenine (A) can pair only with thymine (T)
Cytosine ( C) can pair only with guanine (G)
Nucleosomes
“beads” made from short lengths of double-stranded DNA wound around histone proteins
Chromatin Fiber
This beads-on-a-string structure is compressed and coiled into a more compact form
DNA replication occurs in three steps
Proteins bind at origin of replication, unwind the DNA, and break the hydrogen bonds connecting the bases of the two strands
The enzyme DNA polymerase uses each strand as a template to construct a new strand starting at a primer, a short chain of nucleotides
When complete, there are two identical copies of the original DNA molecule
Semiconservative replication
Each new DNA double helix contains one old strand and one new strand. The template strand is conserved
Three types of point mutations can alter a gene’s DNA sequence
Substitution: One nucleotide is substituted for another in a DNA sequence
Insertion: One nucleotide is added to a DNA sequence
Deletion: One nucleotide is deleted from a DNA sequence
CRISPR
Is used for genome editing adding and deleting genes from organisms
Is a combination of a protein and two single-stranded molecules of RNA (ribonucleic acid), a macromolecule that stores genetic data
Is like a “molecular scalpel”
Is inexpensive
Allows researchers to alter the DNA of nearly any organism
CRISPR
Clustered regularly interspaced short palindromic repeats
A natural defense mechanism in bacteria
The CRISPR-Cas9 system
Composed of two RNA molecules that guide
Cas9 proteins to choose, precise sites in a
genome
Cas9 efficiently cuts both strands of the DNA.
