8 - Genetics Flashcards
Describe the bacteria chromosome:
- single circular chromosome
- singular DNA molecule
- attached to plasma membrane
- has coding and noncoding regions
DNA replication
genetic information can be transferred between generations of cells (aka DNA synthesis)
Leading strand
is the new strand synthesized by DNA polymerase (going towards replication fork)
Lagging strand
DNA polymerase starting at replication fork and is synthesized discontinuously and made in Okazaki fragments
Topoisomerase
relieves supercoiling
Gyrase
relieves supercoiling
Helicase
separates two strands from each other
DNA polymerase
zips down toward the replication fork - only makes DNA strand 5’-3’ also can proofread
DNA ligase
connects fragments to make a complete strand on the lagging strand
DNA Replication Steps
- supercoiling relieved by topoisomerase (gyrase)
- double helix unwound by helicase
- new nucleotides are added to two separated strands - DNA polymerase adds to 3’ end of new strand so the new strand is made 5’ - 3’ and parent strand copied 3’ - 5’
- Parental strand is unwound further to continue replication at the replication fork
What is DNA transcription?
process of copying DNA into into RNA - DNA is transcribed into RNA by RNA polymerase
What are the 3 steps of transcription?
- Initiation: RNA polymerase binds to specific regions (promoters) of DNA to start transcription
- Elongation: RNA polymerase moves down the DNA template (3’-5’) synthesizing the RNA (5’-3’)
- Termination: RNA polymerase reaches a DNA sequence that serves as a terminator sequence
What is DNA translation?
RNA is used to make proteins - RNA is translated to proteins, in ribosomes
Codon
every 3 bases
Reading frame
sequence of code
How many total codes and how many total amino acids?
total codes = 64
total amino acids = 20
What are the four properties of the genetic code?
- redundant (a.a. are coded by more than one codon)
- unambiguous (single codon never codes for more than one a.a.)
- Universal (codons specify the same a.a. in all organisms)
- Conservative: codons that specify the same amino acid have the same first 2 bases)
Transfer RNA (tRNA)
recognizes the codon and transports the corresponding amino acid and binds with anticodon
What are the 3 sites of the ribosome?
- E: tRNA with no amino acid, about to leave = “exit”
- P: holds growing peptide chain = “peptide”
- A: tRNA enter with an amino acid attached = “acceptor”
Central dogma
DNA -> RNA -> protein
What are some differences in transcription and translation between prokaryotes and eukaryotes?
- location of transcription (p- cytoplasm; e- nucleus)
- prokaryotes can transcribe and translate at the same time since prokaryotic cells RNA doesn’t have to leave membrane-bound organelles
- eukaryotes have introns and exons - splicing
What is gene regulation?
not all genes are needed all the time - cells conserve energy by only producing proteins they need
What is a constitutive gene?
always expressed (i.e. glycolysis)
What are operons?
specific for bacteria - set of genes that have a similar function that are controlled together - will make all or will make none
What are the 3 parts of an operon?
- promoter: where RNA polymerase initiates transcription
- operator: acts as stop or go signal for transcription
- operon genes: set of genes with similar function or goal that are controlled together
Repressible operon
always on unless turned off (tryptophan synthesis genes)
Inducible operon
always off unless turned on (inducible operon-Lac operon)
What are mutations?
permanent change in an organism’s DNA
How are mutations caused?
- spontaneously - mistakes during replication
- mutagens - chemicals/radiation
Missense mutation
point mutation changes amino acid sequence
Silent mutation
point mutation does not change amino acid sequence (3rd base)
Nonsense mutation
base substitution results in a nonsense codon
Frameshift mutation
nucleotides are deleted or added, changing the codons
What are the general purpose of different mutant tests?
identifying mutants and the mutation rate (probability a gene with mutate)
Positive selection test
detects mutants by rejecting non-mutants
Negative selection test
selects cells that cannot perform a function
Ames test
tests a chemical/potential mutagen to determine if it cause mutations
Recombination
exchange of genes b/w 2 DNA molecules; gives new gene combos
Transformation
genes are transferred as “naked” DNA - bacteria release DNA into the environment other bacteria pick it up and insert into chromosome - only competent cells are able to pick it up
Conjugation
transfer of a plasmid through a sex pilus - requires cell-cell contract
Transduction
DNA is transferred inside a bacteria (bacteriophage)
Bacteriophage
virus that carries DNA and infects bacteria
What is the main difference b/w replication in prokaryotes and eukaryotes?
in prokaryotes the 2 replication forks meet when replication is complete
Vertical gene transfer
from organism to its offspring
Horizontal gene transfer
between organisms of the same generation
