Exam 3 Flashcards
What is the structure of DNA?
Pentose Sugar, Phosphate group, Nitrogenous Base (A, T,C, or G)
What are the four possible nitrogenous bases in DNA?
Adenine, Thymine, Cytosine, Guanine
What connects nucleotides in a strand?
Sugar-Phosphate backbone (Phosphodiester bond)
How are nucleotides read?
P to S… 5’ to 3’
How are the nitrogenous bases bonded to each other in DNA helices?
Hydrogen Bonds
How many hydrogen bonds does it take to bond Adenine with Thymine?
2
How many hydrogen bonds does it take to bond Cytosine with Guanine?
3
What is Chargaff’s Rule?
A-T, C-G
Used other people’s data and are accredited for realizing DNA is a double stranded helix
Watson and Crick
What did Watson and Crick discover about DNA?
DNA is a double helix of two nucleotide strands and is held together by complementary base pairs. The complementary strands run in opposite directions
What are the phases of the Eukaryotic Cell Cycle?
G1 cell growth and differentiation, S synthesis of DNA and replication of chromosomes, G2 cell growth
What is interphase?
The G1, S, G2, and G0 phases of the eukaryotic cell cycle
What is G0?
Phase in the eukaryotic cell cycle when matured cells are still active but have stopped growing.
What are the three steps of DNA replication?
- Separation of parental DNA helix which exposes nucleotide bases.
- Incorporation of complimentary nucleotides using DNA Polymerase.
- The mother DNA helix produces two daughter helices which each have 1 old strand and 1 new strand
What is the semiconservative Replication Model?
states that when the mother chromosome divides into two daughter chromosomes, each daughter chromosome has one new and one old strand. Both strands of original DNA serve as templates
What is a replication bubble?
The part of the DNA where the nucleotide bases are exposed and where DNA replication is taking place and continues along the strand in opposite directions
What is the difference between the two strands of DNA being replicated?
One is replicated as a continuous segment which allows DNA Polymerase to only put down new nucleotides in the P to S direction.
The other is a segmented (Okazaki fragments).
How is DNA replicated in Okazak Fragments?
Polymerase has to wait until enough of the template is exposed to put down segmented nucleotides P to S strands. Holes in the short fragments of DNA are fixed by joining S and P sides of the segment with the enzyme Ligase.
Enzyme that unzips DNA
Helicase
enzyme that adds free nucleotides to growing strands
DNA polymerase
enzyme that connects short strands of DNA together
DNA ligase
What is the central dogma of biology?
information flows from DNA to RNA to Protein
What is the process of DNA becoming RNA with the help of DNA dependent RNA polymerase
Transcription
What is the process of RNA becoming a protein
Translation
Where/what is mRNA used?
mRNA is used at the ribosomes to make proteins and contains codes to make proper sequence for amino acids to make proteins
What leads to different proteins?
Differences in genes (DNA sequence)
segment of DNA located at a particular place on a chromosome
Gene
What does DNA code for?
DNA codes for specific amino acid sequence in a protein or for the RNA that helps make proteins
type of RNA that contains the specific code for a specific amino acid
mRNA
type of RNA located in the ribosome that makes up the small and large subunits
rRNA
type of RNA that has an anticodon that comes from DNA and also has an attached amino acid
tRNA
What are the three steps in transcription?
initiation, elongation, and termination
Describe transcription in detail
Before transcription, the chromosome must be opened and unwound to make DNA accesible. Then the DNA is unzipped and the DNA-dependent RNA-polymerase comes in. Initiation: recognizes nucleotides and matches them up. Elongation: brings in each of the new nucleotides to the template strands. Termination: the mRNA falls off the single strand of DNA once a wrong sequence comes up and produces a single strand transcript of RNA, and the DNA zips back up.
How many possible codons are there (excluding stop codons)
61
What is the start codon for proteins?
AUG (methionine)
Where are codons found?
mRNA
What are the requirements for translation and where does it occur?
Translation requires rRNA, tRNA, mRNA, and amino acids. It occurs in the cytoplasm.
How many genes are in a human genome?
just under 20,000
What occurs in alternative splicing?
When the RNA is first transcribed, it makes introns and eons. Introns are spliced out when mRNA goes to maturity.