FINAL Flashcards
What is central dogma and what is the exception to the rule
CENTRAL DOGMA: DNA–transcription->RNA–Translation–> protein
EXCEPTION: “reverse transcription” some viruses that have RNA (HIV reverses the genome)
What is DNA made out of
-phosphate group
-sugar group
-1 out of 4 nitrogen bases
what are complementary bases for DNA
A-T
G-C
What are genes
-molecular unit of heredity
-stretch of DNA sequence coding for a protein (or RNA)
What is gene expression
the process of converting information encoded in DNA into usable products
How is DNA held together
they are held together by hydrogen bonds by complementary base pairs (A-T,G-C)
What is a genome
-complete set of DNA that make up an organism
A genome is defined as?
A)The study of all the genetic information in an organism and how those genes interact with each other and the environment
B) The physically observable expression of genes
C) The particular variants an organism or cell possesses for one particular gene
D) all the genetic information in an organism or cell
D. all the genetic information in an organism or cell
are all sequences in the genome, genes
only a portion of the genome is made of genes coding for RNA/protein
Do all RNA’s code for proteins
-only mRNA codes for proteins
-tRNA, rRNA, miRNA, and snRNA DO NOT code for proteins
what is origin of replication
-two replication forks moves bidirectionally in two opposite directions
CIRCULAR DNA
-prokaryotes
-one origin
LINEAR DNA
-eukaryotes
-multiple origins
What are the steps of replication
INITIATION
-DNA is unwinded creating the replication fork
ELONGATION
-helicase helps unwind the DNA
-DNA polymerase add nucleotides (it builds)
TERMINATION
-RNA primers are degraded
-The gaps created on the lagging strand are filled by DNA polymerase
-The fragments are connected by DNA ligase
-in prokaryotes the circular DNA are separated by topoisomerase
Why is there a lagging and a leading strand at each fork? Which is leading, which is lagging?
- The lagging strand exists because DNA is antiparallel and replication always occurs in the 5’ to 3’ direction.
- The leading strands are A & D
- The lagging strands are B & C
What are telomeres?
- Telomeres are required for cell division
- Found at the ends of chromosomes
- They cap and protect the end chromosome like the end of a shoelace
What is the end replication problem?
- The DNA at the very end of the chromosome cannot be fully copied in each round of replication, resulting in a slow, gradual shortening of the chromosome.
- Replicated DNA keeps getting shorter and shorter each time
- Replicated DNA is never the same “length”.
RNA molecules are processed after transcription in what
- Eukaryotes
- because in Prokaryotes, bacteria, it transcription and translation happens at the same time
Difference between promoter and enhancer?
- Promoters are fairly large nucleotide sequences that initiate the process of transcription.
- Enhancers are short nucleotide sequences that enhance the transcription rate in the genome.
Is replication conservative or semi-conservative?
- semi-conservative
- means one strand of DNA molecule is old and one is new
What does DNA polymerase do?
- “The Builder”
- Enzyme responsible for synthesis of new DNA
- works in 5’ to 3’ direction (adding new nucleotides to the 3’ end)
- Must be initiated from a short RNA sequence (Primer)
What does Primase/Primer to?
- Primer helps Polymerase. Help direct Polymerase to let them know where to build.
- ## Primase is required because DNA polymerases cannot initiate polymer synthesis on single-stranded DNA templates; they can only elongate from the 3′-hydroxyl of a primer.
What are Okazaki Fragments?
- Part of the lagging strand
- Short segment of DNA synthesized on the lagging strand (Discontinuous)
What does Helicase do?
- “Unzipping enzyme”
- Opens the DNA helix by breaking hydrogen bonds between the nitrogenous bases
How does the DNA, during Helicase, prevent itself from coiling?
- Single stranded DNA binding protein (SSB)
- binds SS DNA and prevents reannealing / coiling
What is the Leading Strand?
the single strand of the replication fork that is synthesized continuously
