UNIT 2 - DNA replication Flashcards
who discovered DNA
James Watson and Francis Crick
what is Chargaff’s rule
states that DNA from any cell should have a 1:1 ratio of purine bases and pyrimidine
how do the strands run in DNA?
antiparallel 5’-3’
what are the “rungs” of the ladder paired with in DNA?
nitrogen bases
how many base pair rungs make one full twist of the helix in DNA?
10 base pair rungs
what is a gene?
a specific section of chromosomes that codes for a protein
what is the process where DNA makes identical copies of itself called?
semi-conservative
what must happen within DNA before a cell can divide?
DNA must replicate before
what is interphase?
when cells prepare for division through growth and duplication of cell contents
what is mitosis?
nuclear division: duplicated chromosomes are separated and move to opposite poles of the cell
what is cytokinesis?
cell division: cell contents divide and two new daughter cells are produced
what is step 1 of DNA replication?
unzipping:
- DNA double helix unwinds
- Helicase enzyme breaks hydrogen bonds holding the nitrogenous bases
- strands separate at the replication fork
what is step 2 of DNA replication?
complementary base pairing:
- free nucleotides (from nucleoplasm) move to pair up with exposed bases of each template strand
- hydrogen bonds form between A&T and C&G
what is step 3 of DNA replication?
join adjacent nucleotides:
- sugar phosphate backbone forms when DNA polymerase forms covalent bonds between newly attached nucleotides
- result in 2 identical DNA strands
what is step 4 of DNA replication?
proof reading:
- DNA polymerase checks for mistakes in copying
what direction does replication of DNA occur?
replication only occurs in one direction: from 5’ to 3’
what enzymes are needed to form both strands in DNA replication
RNA primase, Ligase, DNA polymerase
where does protein synthesis occur?
on the ribosomes in the cytoplasm
what molecule cannot leave the nucleus
DNA
what is the role of proteins in DNA?
forms structure, drives the processes necessary for life’s functions
what are DNA and RNA’s similarities
- both has 4 nitrogenous bases
- both have nucleotide monomers
- both have sugar and phosphate backbone
- Both have A,C,G bases
what are the differences between DNA and RNA?
DNA:
-double stranded
- can replicate itself
- cannot leave the nucleus
-contains thymine
RNA:
- single stranded
- contains uracil
- 3 different kinds
- read by ribosomes
what are the 2 stages of protein synthesis?
transcription and translation
what is protein synthesis?
the process of creating protein molecules
what is transcription?
the process of DNA sequence copied into mRNA
where does transcription occur?
the nucleus
where does translation occur?
the ribosomes
what is translation?
the process of mRNA travelling to the ribosomes to link amino acids together with peptide bonds
what is step 1 of transcription?
helicase enzyme unzips the DNA strand
- starts at initiation region and continues until termination region
what is step 2 of transcription?
complementary RNA nucleotides combine to form mRNA strand
- joined and re-zipped by RNA polymerase
what is step 3 of transcription?
mRNA strand detaches and leaves nucleus through nuclear pores
what are codons?
3 letter segments in mRNA
what are ribosomes made of?
rRNA and protein
where is ribosomal RNA produced?
nucleolus
what is tRNA’s position in the cell?
floats freely in the cytoplasm
what is tRNA’s function?
carries amino acid to ribosomes for assembly
which molecule contains anticodon?
tRNA contains anticodon complementary to mRNA
what is step 1 of translation?
Initiation:
-ribosomal subunits join around mRNA
- start codon begins the process
what is step 2 of translation?
Elongation:
- tRNA anticodon and amino acid match up with the mRNA codon
- tRNA leaves to collect new amino acids
- ribosome moves along to read the next mRNA codon
- Peptide bonds form between amino acids
what is step 3 of translation?
Termination:
- when ribosome reaches stop codon in the mRNA translation stops
- ribosome subunits split again and mRNA detaches
what is polyribosomes?
(many ribosomes): often several ribosomes work together on one large protein
what happens to protein after its produced?
it gets sorted, repackaged, and transported through the endomembrane system
