DNA Flashcards
What material contains all of the genes that are responsible for expression of all of the traits that appear in humans and other organisms?
DNA
What is the structure of DNA?
A very large molecule that consists of 2 strands of deoxyribonucleotides linked together- each deoxyribonucleotide consists of 3 parts - a deoxyribose sugar, a phosphate group and a nitrogenous base. The backbone of the polymer strand is composed of deoxyribose alternating with a phosphate. A base is attached to each deoxyribose. The shape of DNA is like a ladder. The sugar and phosphate groups form the uprights and the bases form the rungs. Hydrogen bonds link the complementary bases in the adjacent strand together. The two strands of deoxyribonucleotides are intertwined and coiled into a structure called a helix (in this case a double-stranded helix)
What holds the two strands of DNA together?
The hydrogen bonds between the complementary bases of each strand. Adenine forms two hydrogen bonds to every thymine in the opposite strand. Guanine forms 3 hydrogen bonds to every cytosine in the opposite strand. These bonds are relatively weak but they are plentiful.
What is DNA replication? When does it occur within mitosis?
An exact copy of the nuclear DNA is made. This occurs during interphase. It takes place prior to mitosis or meiosis to produce the pair of joined sister chromatids.
What is the 1st step in replication of the DNA strand?
The double helix must be unzipped…. the enzyme DNA helicase breaks the hydrogen bonds that link the complementary bases of the adjacent strands and the DNA strands stand on their own.
What is the second step of DNA replication?
On each strand starting from the top, free nucleotides (containing the complementary base) are lined up along the intact nucleotides and DNA polymerase catalyzes the linking of these free nucleotides and the intact nucleotides.
What is the third step of replication?
The free nucleotides are then progressively joined to one another (as the sugars join to the phosphates) until a new complementary strand is assembled alongside each previously existing strand.
The fourth step of replication ?
After the end of each strand is reached, there will be two identical DNA double helix strands. Each contain an original mother strand and a newly formed complementary daughter strand.
Why is replication said to be semi conservative?
Since each DNA double helix conserves one of the original strands, the replication process is said to be semiconservative.
What determines the amino acid sequence for all of the proteins in your body?
The code found in DNA
What is a gene?
The section of a DNA molecule that determines the sequence of amino acids in a single polypeptide chain of a protein. Genes are portions of DNA that code for a particular protein.
What is transcription ?
A copy of the DNA strand is transcripted onto a mRNA strand. In order for proteins to be synthesized (formed from the linkage of amino acids) the genetic code must be copied from the DNA in the nucleus and sent to the ribosomes.
What is the location for protein synthesis?
The ribosomes within the cytoplasm
What happens in transcription?
Transcription is very similar to replication in that the double DNA helix is first unzipped and unwound. But instead of DNA nucleotides being brought in to bind with DNA, RNA nucleotides are brought in by RNA polymerase. The new RNA nucleotides are linked together in a similar fashion to the formation of new DNA. The difference being that only a single strand of RNA is formed. In other words, only one side of the DNA double helix is encoded at one time. The new single stranded RNA is known as messenger RNA (mRNA). After its formation the mRNA separates from the DNA strand and moves out of the nucleus to take the “message” to the ribosomes.
Where does mRNA go after being transcribed?
It carries its code to the ribosomes for protein synthesis?
