DNA Replication Flashcards
Exam 2
What is DNA Duplication?
making exact copies
What is DNA Replication?
copies with some differences from original
What are the 3 models of DNA Replication?
- conservative model
- semi-conservative model
- dispersive model
Conservative Model
- conserve as much of the original as possible
- result: 2 old strands together, 2 new strands together
Semi-Conservative Model
- old strands will isolate and separate with new strands
- 1 old and 1 new strand together; 1 old and 1 new strand together
- more in Eukaryotes
Dispersive Model
result: 1 old segment, 1 new segment, 1 old segment, 1 new segment
How many total enzymes does DNA Duplication involve?
over 30
What are the 6 enzymes of DNA Duplication needed to know?
- Helicase
- Primase
- DNA Polymerase III
- DNA Polymerase I
- Ligase
- Gyrase
Which enzymes involved in DNA Duplication are categorized as Primosomes?
- helicase
- primase
What is the function of Helicase?
unwinds the double helix to be able to create templates
What is the function of Topoisomerase?
relieves the tension once the helix is unwinded by the helicase
What is the function of Primase?
primer that inserts into the DNA molecule to initiate the duplication process
What is the function of DNA Polymerase III?
- identify problems (cuts and knicks) on the strand of chromosome
- makes okazaki fragments
What are Okazaki Fragments?
short/fragmented copies of DNA
What is the function of DNA Polymerase I
- fixes the cuts and knicks found on the chromosome by DNA Polymerase III
- removes the Primase enzyme
What is the function of Ligase?
- joins together the okazaki fragments
- joins exons together to secrete and synthesize amino acids
What is the function of Gyrase?
supercoils the double helix back together
Where does DNA Replication start?
at the replication fork
What are the 3 characteristics of Genetic Code?
- universal
- redundant
- no ambiguity (it is what it is)
Explain the “universal” characteristic of genetic code
Provide and Example
- a codon in humans will be the same as a codon in a snake
- ex: UUU will always code for amino acid Phenylalanine
- ex: the complement to UUU will always be AAA
Explain the “redudant” characteristic of genetic code
- if you replace the third base, it will still be the same amino acid
- ex: replace third U with C, will still have Phenylalanine
What is the start codon?
AUG (Methionine)
What are the stop codons?
- UAA
- UAG
- UGA
How many amino acids are there without the stop codons?
- 61
- not including methionine: 60
What is an Exon?
a coding segment
What is an Intron?
a non-coding segment of mRNA that intervenes between coding segments
What does an Intron that is cut off become?
What cuts it off?
- it becomes a lariat
- it is cut off by a spliceosome
What does it mean that Eukaryotes are Monocistronic?
1 gene codes for 1 amino acid
What is the 5’ is also called?
- leading strand
- promoter
What is the 3’ also called?
- lagging strand
- Poly A Tail
What type of cell is Polycistronic?
What does it mean?
- prokaryotes
- 1 gene codes for multiple amino acids
What is an operon?
What are the 2 types?
- set of regulatory genes in prokaryotes that act as a single unit
- inducible operon
- repressible operon
Inducible Operon
define and provide an example
- turned on in the presence of the substrate
- ex: lac operon (lactose turns on in the presence of lactase for dairy)
Repressible Operon
turned off by accumulation of the end product
What is mutation?
- stable change/manipulation on a gene
- can have positive or negative effects
What are the 3 ways that mutation can occur?
define them
- predisposition (genetically inherited)
- behavioral (what expose your body to)
- spontaneous (just change, don’t know why)
What are the 2 types of Mutation?
- Point Mutation
- Frameshift Mutation
What is Point Mutation?
mutation takes place on a base (point), or on more than on base
What are the 3 types of Point Mutation?
- Missense Mutation
- Nonsense Mutation
- Silent Mutation
What is Missense Mutation?
Provide Example
- the mutation results in the synthesis of a different amino acid
- ex: UUU creates Phenylaline, but if one U is replaces with A, it produces Leucine
What is Nonsense Mutation?
Provide Example
- a normal codon becomes a stop codon (or vice versa)
- ex: UUU = Phenylalanine. If becomes UAA = stop codon
What is a Silent Mutation?
- mutation that may not result in the secretion of a different amino acid
- ex: UUU -> UUC = Phenylalanine (redundancy)
What is Frameshift Mutation?
the frame shifts after deletion or insertion of one base or pair of bases, creating nonfunctional molecules and issues
What are the 2 types of Frameshift Mutation?
Provide Definitions
- Deletion Mutation (delete one or pair of bases)
- Addition/ Insertion Mutation (addition of one base or pair of bases)
What is a Reading Frame?
the correct nucleotide sequence on a chromosomal strand (gene)
What are the 3 Modes of Gene Transfer?
- Conjugation
- Transformation
- Transduction
What is gene conjugation?
- transfer of genes through a sex pili (donor and recipient)
- there is direct contact
- plasmid is transferred
What is gene transformation?
- assimilation (through genetic alteration) of degenerated genome from the habitat/environment
- no direct contact
What is gene transduction?
- transfer of gene through bacteriophage
- no direct contact
What are Transposons?
- transposable segments of DNA, able to move from one location on the genome to another
- AKA “jumping genes”
What are the 2 types of Transposons?
provide definitions
- Direct Repeat: bases are repeated further down same chromosome and complemented on next strand (2 strands)
- Inverted Repeat: bases are complemented (inverted) on same strand (1 strand)
