Genetics part 2 Flashcards
What do structural genes code for?
Specific proteins
Structural genes are essential for various biological functions.
What is the first step in protein synthesis?
Transcription of a gene into mRNA
This process involves creating a sequence of nucleotide bases.
What is the role of mRNA in protein synthesis?
It is translated into an amino acid sequence of a protein
The sequence of amino acids determines the protein’s characteristics.
What initiates DNA replication?
Helicase unwinds a segment of DNA
This process opens up the hydrogen bonds between complementary strands.
What is the function of DNA polymerase during replication?
Adds new nucleotides to the free 3’ end of a nucleotide strand
It is crucial for synthesizing new DNA strands.
What is a short RNA primer’s role in DNA replication?
Provides a free 3’ starting point
It is essential for the initiation of DNA synthesis.
What are the two types of strands involved in DNA replication?
Leading and lagging strands
These strands are synthesized differently during replication.
What is the composition of the 70S ribosome?
Two sites for tRNA amino acids: the ‘P’ site and the ‘A’ site
The 80S ribosome has three sites.
Operons
- Only found in bacteria and archaea
- Consist of a coordinated set of genes regulated as a single unit
- can be inducible or repressible
This regulation saves energy for the cell.
What is a catabolic operon?
- Induced by the substrate of the enzyme(s) for which the structural genes code
- Only produce the enzyme when the substrate (nutrient) is present
It produces enzymes only when the substrate is present.
What defines a repressible operon?
Anabolic enzymes turned off by the product synthesized by the enzyme
This mechanism helps regulate metabolic pathways.
What is conjugation in bacteria?
Direct transfer of DNA between living donor and recipient cells
It involves a bridge formed between cells.
what does the donor cell in conjugation contain?
- pilus
- fertility plasmid
Commonly transferred genes in conjugation
- drug resistance
- resistance to metals
- toxin production
- enzymes
- adherence molecules
Transformation
- Free donor DNA (fragments)
- Live, competent recipient cell
- indirect transfer
Requires no direct contact between donor and recipient cells.
Commonly transferred genes in transformation?
polysaccharide capsule
What is transduction?
Indirect transfer of bacterial DNA through a bacteriophage
It involves indirect transfer and a lysed donor cell.
Transduction facts
- donor is lysed bacterial cell
- Defective bacteriophage is carrier of donor DNA
- Live recipient cell of same species as donor
- Indirect transfer
Commonly transferred genes in transduction?
- Toxins
- Enzymes for sugar fermentation
- Drug resistance
What are transposons?
‘Jumping genes’ that can shift within the genome
They can also transfer between chromosomes and plasmids.
Transposons fun fact
- Can be transferred from a chromosome to a plasmid, or vice verse; or from once cell to another in bacteria and some eukaryotes
- Some replicate themselves before jumping to the next location and some simply move
Transposons are involved in:
- changes in traits such as colony morphology, pigmentation and antigenic characteristics
- replacement of damaged DNA
- intermicrobial transfer of drug resistance (in bacteria)
mutation
any change to the nucleotide sequence in the genome
Mutations can involve …
the loss, addition, or rearrangement of base pairs
When are mutations most noticeable?
when a genotypic change leads to a change in phenotype
Wild type
a microorganism that exhibits a natural non-mutated characteristic
Mutant strain shows variance in:
- morphology
- nutritional characteristics
- genetic control mechanisms
- resistance to chemicals
- temperature preference
Spontaneous mutation
a random change in the DNA arising from errors in replication
Induced mutation
results from exposures to known mutagens
What are mutagens?
physical or chemical agents that disrupt DNA such as:
- Radiation (UV light, xrays)
- Chemicals (Nitrous acid)
What is a point mutation?
Addition, deletion, or substitution of single bases
This type of mutation can lead to significant changes in protein function.
What is a missense mutation?
Change in the code that leads to a different amino acid
It can create faulty proteins or alter their function.
Missense mutation can …
- create a faulty, nonfunctional protein
- produce a protein that functions differently
- cause no significant alteration
What is a nonsense mutation?
Changes a normal codon into a stop codon
This usually results in a truncated, nonfunctional protein.
What is a silent mutation?
Alters a base but does not change the amino acid (has no effect)
What is a back-mutation
When a gene reverse back to its original base composition
What is a frameshift mutation?
- one or more bases are inserted or deleted
- changes the reading frame of the mRNA
- nearly always results in a nonfunctional protein
It nearly always results in a nonfunctional protein.
Single nucleotide polymorphism
- Only a single nucleotide is altered
- passed on genetically
- identification is critical to personalized medicine (customized to a person’s genetic makeup)
Thrombophilia
a point mutation in the gene for a clotting factor cause an arginine to become a glutamine
What is the role of DNA photolyase?
Repairs UV damage in DNA using visible light and light sensitive enzyme
This repair mechanism works for a limited number of UV mutations.
UV damage repair
- successful only for a small number of UV mutations
- cells cannot repair severe widespread damage and will die
What is excision repair?
Involves enzymes breaking bonds to remove defective bases and filling the gap with DNA polymerase I and ligase
It fills gaps with DNA polymerase I and ligase.
What is the difference between spontaneous and induced mutations?
Spontaneous mutations arise from replication errors; induced mutations result from mutagens
Mutagens can include radiation and chemicals.
What are restriction endonucleases?
recognize foreign DNA and break phospodiester bonds between adjacent nucleotides on both strands of DNA
They are crucial for recombinant DNA technology.
What do restriction endonucleases protect?
Protects bacteria against incompatible DNA of bacteriophages or plasmids
What is the relationship between restriction endonucleases and recombinant DNA technology?
- Restriction endonucleases is necessary for recombinant DNA technology
- Allow biotechnologists to cleave DNA at desired sites
- Recognize and clip at palindromes
Palindromes
Sequences of DNA that are identical when read from the 5’ to 3’ direction on one strand and the 3’ to 5’ direction on the other strand like “RACE CAR”
Ligase
- seals sticky ends together
- used in final splicing of genes into plasmids and chromosomes
Reverse transcriptase (RT)
- converts RNA into DNA to make cDNA
- used in replication of the AIDS virus
Complementary DNA (cDNA)
- Made from messenger, transfer, ribosomal and other forms of RNA
- used to synthesize eukaryotic genes from mRNA transcripts, free from introns
What is PCR?
A technique to rapidly increase DNA amounts in a sample
It can amplify DNA from a few copies to billions within hours.
How sensitive is PCR?
sensitive enough to detect cancer from a single cell or diagnose an infection from a single gene copy
Primers in PCR
DNA strands 15 to 30 bases long, serve as landmarks for DNA amplification start
DNA polymerases from Thermophilic Bacteria in PCR
Taq polymerase remains active at elevated temperatures used in PCR
Thermal cycler in PCR
automatically performs cyclic temperature changed required for PCR
gel electrophoresis
- Produces DNA fragments of different lengths
- Samples placed in agar gel and subjected to electrical current
- Phosphate groups have a negative charge, causing DNA to move toward positive pole
- Larger fragments migrate more slowly and vice versa
- Position determined by staining the gel
DNA moves toward the positive pole due to its negative charge.
Sequence maps
exact order for bases in a plasmid, chromosome or entire genome
Shotgun sequencing
Genome broken into fragments, separated through gel electrophoresis, inserted into plasmids and cloned, purified, sequenced, overlaps identified by computer, contigs put in order, editing for irregularities
High throughput sequencing
DNA fragmented and fitted with adaptors, sequences added to PCR machine, immobilized and copied, sequenced, aligned using software
Genomics
systematic study of an organism’s genes and their functions
Proteomics
study of an organism’s complement of proteins and functions mediated by the proteins
Metagenomics
study of all the genomes in a particular ecological niche
metabolomics
- study of the complete complement of small chemicals present in a cell at any given time
- provides a snapshot of the physiological state of the cell and the end products of its metabolism
What is recombinant DNA technology?
- Deliberately removing and combining genetic material from different organisms
- bacteria genetically engineered to mass-produce hormones, enzymes vaccines
It allows for the mass production of hormones and vaccines.
Synthetic biology
creating new biological molecules and organisms from scratch
Craig Venter
created a self-replicating bacterial cell from DNA nucleotides in 2010
Synthetic biology has the potential to revolutionize medical science through:
creation of precise chemicals, customizes immune components, biological molecules targeting cancerous cells or pathogens
Gene therapy
replacing faulty gene responsible for disease with healthy gene
What is CRISPR?
A technology that allows scientists to cut DNA at specific locations
It is used for gene editing and therapeutic applications.
