DNA Structure
What two scientists determined the structure of DNA in 1953
Watson and Crick
also kind of Rosalind Franklin
what is DNA replication?
DNA replication is the process of copying one DNA double helix into two identical double helices.
Double-stranded structure of DNA allows each original strand to serve as a template for a complementary strand.
how many copies of each gene does each person have?
2 copies
during transcription what serves as a template to produce mRNA?
gene (segment of DNA) serves as a template to produce an RNA molecule.
What is a codon? how many are there?
a 3 nucleotide sequence which codes for a specific amino acid.
64
the two strands of DNA are antiparalell what does this mean?
they run in oposite directions:
5'-----> 3'
3'<-----5'
In what direction is DNA replicated and whre does this take place.
5'---->3'
can remember this by rememering "down stream" or "from larger to smaller"
in the nucleus
define genome
All the genetic content in a cell
what are the basic definitions of transcription and translation?
transcription- DNA to mRNA
translation- mRNA to a protein
what is an anticodon
it is the opposite of the codon. the anticodon is on the tRNA
example: codon: CCG anticodon: GCC
DNA makes ____
RNA makes ____
DNA makes RNA
RNA makes proteins
On what strand do the okazaki fragments occur, and why?
The lagging strand beause it is positioned 3'--5' DNA polymerase does not postion base pairs continueously, it makes fragments that are then stitched together.
what is a gene? What is it made up of?
A gene is the basic physical and functional unit of heredity.
Genes are made up of DNA.
Where does transcription take place? translation?
Transcription- nucleus
translation-cytoplasm (ribosome)
what determines the order of amino acids the tRNA adds to the amino acid chain?
The order of codons on the mRNA.
what are purines and pyrimidines? Definition and what bases are which types.
purines are bases with a double ring: A and G
Pyrimidines are bases with a single ring: T and C
1 pyrimidine matches with 1 purine.
DNA replication is semiconservative, explain why?
Each daughter DNA double helix consists of one new strand of nucleotides and one old strand conserved from the parent DNA molecule.
The two daughter DNA molecules will be identical to the parent molecule.
how many genes do humans have (a range) and what percent of our genes is actually used?
20,000- 25,000 genes
1% is actively used
What two things does RNA polymerase do in Transcription?
begins transcription by binding to DNA
joins new RNA nucleotides in a sequence complementary to that on the DNA.
what is a stop codon? what are the 3 stop codons?
Terminates the synthesis of a protein.
UAA, UGA, UAG
What are the three components of DNA?
Phosphoric acid (phosphate).
A pentose sugar (deoxyribose).
A nitrogen-containing base (A,T,C,G)
describe what each of these enzymes does in DNA replication.
DNA helicase
DNA polymerase
DNA ligase
DNA helicase-unwinds and “unzips” the double-stranded DNA by breaking the hydrogen bonds between paired bases.
DNA polymerase - positings and joins new complementary DNA nucleotides fit into place along separated strands by complementary base pairing
DNA ligase- connects Okazaki fragment and seals breaks in the sugar-phosphate backbone.
What is gene expression
process of using a gene sequence to synthesize a protein.
What are the 3 types of RNA used in gene expression and their function
•Messenger RNA (mRNA): carries protein building instructions from the nucleus to the ribosome
•Transfer RNA (tRNA): delivers amino acids to the ribosome
•Ribosomal RNA (rRNA): Perform Protein Syntheses
what forms as new amino acids arrive at the ribosome?
a polypeptide chain