DNA Stuff Flashcards
Genes
A unit of inheritance
All of our physical characteristics are a result of the genes we inherit from our parents
Genes are located on chromosomes in the nucleus of our cells
Made of proteins and DNA
Who performed experiments to show DNA was the genetic material
Hershey and chase
How did they show DNA is the genetic material
Bacteriophages (phages), viruses that infect bacterial cells
Phages labeled with radioactive sulfur to detect proteins or radioactive phosphorous to detect DNA
Results of DNA experiment
Sulfur-labeled protein stayed with the phages outside the bacterial cells, phosphorous labeled DNA detected inside cell
Cells with phosphorous labeled DNA produced new bacteriophages with radioactivity in DNA but not in protein
DNA
Deoxyribonucleic acid
An organism’s genetic material that is capable of replicating
Type of macromolecule called a nucleic acid (include DNA and RNA)
Nucleic acids are long polymers made up of many monomers called nucleotides
Shape of DNA
Double helix
Discovered by Watson and crick
Two polynucleotide strands, held together by hydrogen bonds
Two strands twist to form the double helix
Nucleotides
Small molecules that bind together to form nucleic acids
Made of one sugar (deoxyribose), one phosphate group, and one nitrogenous base
Four nitrogenous bases
Adenine, guanine, thymine, cytosine
Purines
Adenine and guanine (larger)
Pyrimidines
Thymine and cytosine (smaller)
Chargaff
Discovered A = T and G = C
Hydrogen bonds between the base pairs hold the two strands of DNA together
Strands
DNA’s sugar phosphate backbones run in opposite directions
Each strand has a 3’ end and a 5’ end
Primed numbers refer to the carbon atoms of the nucleotide sugars
Sequence of nucleotides is…
Different for every organism
Sequence variation = genetic variation
RNA
Single stranded nucleic acid
Functions in protein synthesis
DNA vs RNA
RNA contains ribose instead of deoxyribose
RNA contains uracil instead of thymine
DNA replication
When DNA makes a copy of itself
Replicates when a cell divides to make two new cells, each cell must have own copy of DNA
Base paring in rules provide copying mechanism for DNA
Semi conservative model
Each new copy of DNA contains one original strand and one new strand
How does DNA replicate
Requires enzymes
Helicase
Unzips a strand of DNA, exposing free bases
DNA polymerase
Adds nucleotides one at a time to the free bases
DNA ligase
Links fragments of nucleotide strands that occur on one side of the DNA molecule
Which side can nucleotides be added to
Nucleotides can only be added to the 3’ end of the parental strand of DNA
Daughter strand synthesized continuously
Goes in, starts at 3’ so it begins w 5’
Daughter strand synthesized in pieces
Okazaki fragments, goes out, starts at 3’ but goes out to 5’ so end is 3’
Why does DNA replicate
Cell replication and organism reproduction
Cell replication
Growth of the body and repair of wounds
DNA replication allows a body to grow larger because it is made of more cells
Organism reproduction
Asexual reproduction: single called organisms divide into two cells, each cell gets identical DNA
Sexual reproduction: half the DNA from two parents combine in a new cell, offspring has a mix of parents’ genes
Smallest to largest
nitrogenous base, nucleotide, gene, nucleic acid, nucleus, cell
strand synthesized continuously
leading strand
strand synthesized in pieces
lagging strand
central dogma of life
DNA becomes RNA becomes a protein