Lecture #8 Flashcards
The recipe book of a bacteria is…?
DNA
What is genetics?
The science of heredity
What is molecular biology?
The science of dealing with DNA and photosynthesis
What is a genome?
The total DNA contained within a cell
What is included in a genome?
Chromsome and any plasmids present
Genes are contained on….?
Chromosomes
What are genes?
Sections of DNA that code for a functional product
DNA is a macromolecule composed of…?
nucleotides
What are nucleotides of DNA composed of?
- Nitrogenous Base
- Deoxyribose Sugar
- Phosphate Group
What are the 4 types of nitrogenous bases in DNA?
- Adenine
- Guanine
- Thymine
- Cytosine
DNA strands are held together by?
Hydrogen bonds between bases
Adenine always pairs with_____ via ____ hydrogen bonds
Thymine via 2 hydrogen bonds
Guanine always pairs with _____ via ____ hydrogen bonds
Cytosine via 3 hydrogen bonds
Why do high temperature organisms have more hydrogen bonds between base pairs?
Because it takes more hydrogen bonds so they don’t get broken by high heat
The sequence of one strand determines?
The sequence of the other
The strands of DNA are _____ to each other?
Complementary
Adjacent (side by side) nucleotides are linked together by
Phosphodiester bonds
How do eukaryotes replicate? Prokaryotes?
Eukaryotes- Vertical replication
Prokaryotes- Horiztonal replication
Carbon #_____ of one nucleotide is joined to carbon #_____ of the next nucleotide
5, 3
The carbons of one nucleotide that join to the carbon of another are called?
5’ prime
3’ prime
DNA occurs in what direction?
5’ to 3’
What is the central dogma of biology?
- DNA replicates before division so that each offspring receives on complete copy of the genome
- DNA is used within the cell to make protein
- DNA can flow between two different bacterial cells (recombination)
One parental double stranded DNA is used to make what?
Two identical double stranded DNA molecules
With the DNA strands being complementary, what does this allow for?
One DNA strand to serve as the template for the synthesis of the other strand
What is a replication fork?
A small segment of dsDNA unwound and strands separated
What does each strand of the replication fork serve as?
A template for the synthesis of a complimentary strand
What are the 3 steps of DNA replication?
- The enzyme DNA gyrate (only found in prokaryotes) and helices unwind and separate 2 DNA strands
- A short RNA primer is synthesized by the enzyme primase
- DNA synthesis occurs by the enzyme DNA polymerase
What enzyme found during DNA replication serves as a good antibiotic target? Why?
DNA gyrase, because it is found in only bacteria and not eukaryotic cells
The RNA primer found during DNA replication serves does what in order to form a new strand of DNA?
Serves as an attachment point for new nucleotides
What does the enzyme DNA polymerase do?
Links the nucleotides together with phosphodiester bonds
Nucleotides are placed in the correct order based on what?
The sequence of the parent strand
What direction can DNA polymerase only add nucleotides in? What does this say about the template being read?
5’ to 3’ direction, the template can only be read in the 3’ to 5’ direction
What is a leading strand? What is a lagging strand?
The synthesis of the first strand
The synthesis of the second strand
Is the leading strand continuous or discontinuous? Lagging strand?
Leading- continuous
Lagging- discontinuous
Which strand synthesis is faster and not as laborious?
Leading strand, lagging strand is slower and more labours
DNA polymerase can only make DNA in what direction?
5’ to 3’
Which way much the lagging strand be made in?
3’ to 5’
What are okazaki fragments? What direction are they made in?
Small fragments of DNA synthesized on the lagging strand. Made in the 5’ to 3’ direction
What enzyme links okazaki fragments together?
DNA ligase
What sugar is in RNA and what base is replaced?
Ribose sugar, thymine is replaced with uracil
DNA directs the synthesis of…?
Proteins
What are genes?
The section of DNA that have instructions for a functional protein product
Why is the promoter for starting transcription outside of the area of DNA info (genes)
Therefore nothing is lost
What is transcription?
Synthesis of a complementary strand of RNA from a DNA template
What are the 3 types of RNA?
- Messanger RNA
- Ribosomal RNA
- Transfer RNA
What does mRNA do?
Carries the coded info for making specific proteins
What does rRNA do?
Forms part of ribosomes which is where protein synthesis happens
What does tRNA do?
Carry specific amino acids to the ribosome in order to make proteins
Which type of RNA is a translated protein?
mRNA
Does transfer RNA get translated into protein?
Never
A strand of RNA is synthesized from _____
a particular gene
The mRNA synthesized is complementary to what?
the gene (5’ to 3’)
What 3 things does transcription require?
- The enzyme RNA polymerase
- A supply of RNA nucleotides
- A DNA template
What are the steps of transcription?
- RNA polymerase binds to DNA at a specific site promoter
- RNA polymerase assembles nucleotides into a new RNA chain
- RNA polymerase moves along the template as the new RNA chain grows
- RNA polymerase reaches the end of the gene terminator
- RNA polymerase and newly formed single stranded ENA are released
What direction is RNA made in?
5’ to 3’ (same as DNA)
When RNA polymerase assembles nucleotides, what does it use as a guide?
DNA
What is the purpose of transcription?
mRNA serves as a short term copy of the gene that can be used to direct protein synthesis (rRNA and tRNA assist with the process
What is translation?
Where info from mRNA is translated in order to make proteins
The info in mRNA for translation is in the form of what?
Codons
What are codons?
A group of 3 nucleotides
What does a codon mean/do?
A certain amino acid
What does the sequence of codons in mRNA determine?
Sequences of amino acids in the protein
What are the stop codons and what do they signal?
UAG, UAA, UGA, they signal the end of translation
What are the steps of translation?
- mRNA attaches to ribosome
- tRNA carrying the correct amino acid enters the ribosome and binds to the mRNA
- The next tRNA with the amino acid enters the ribosome and binds to the mRNA
- Two amino acids are joined by a peptide bond
- Ribosome moves down mRNA 5’ to 3’ direction and steps 3 and 4 repeat until stop codon
- mRNA and protein are released from ribosome
What is a mutation?
A change in the nucleotide sequence of DNA
What can a mutation cause?
A change in a protein encoded by a gene
What are two types of mutations?
- Point mutation (substitution)
2. Frameshift mutation
What happens in a point mutation?
A single nucleotide is replaced by another nucleotide
If a point mutation occurs, what changes during DNA replication? Translation and Transcription?
When it replicates, it results in a substituted pair
When is transcribed and translated, a missense mutation can result
What is a missense mutation?
an incorrect base resulting in an incorrect amino acid in the protein
What is frameshift mutation?
- Insertion (addition of a nucleotide is added)
2. Deletion ( a nucleotide is removed)
What does a frameshift mutation do to mRNA? What can it cause in the future steps?
- The mutations cause a change in the reading frame of mRNA
- The sequence of most of the protein is changed
- Stop codons may be introduced prematurely leading to truncated proteins
What is a truncated protein?
A shorter protein caused by a stop codon occurring too early due to a frameshift mutation
What are the two ways in which frameshift mutations can occur?
- Spontaneous
2. Due to mutagens
What is a spontaneous frameshift mutation?
Occurs due to occasional mistakes during DNA replication
What is a mutagen frameshift mutation?
Occurs because of agents with work to bring about mutations in DNA
ex. UV, Radiation, etc
What are 3 things mutations can cause?
- Incomplete truncated proteins which are usually non functional
- A protein with a different sequence which will then either have a different function or normal function
- A silent mutation which has no effect on the functional protein
What are plasmids?
Self replicating double stranded DNA molecules containing genes which are non essential
What are 3 types of plasmids?
- F plasmids- F-factor or Fertility plasmid
- R plasmids- Resistance Factors
- Vir Plasmids- Virulence Plasmids
What type of genes do each type of plasmid carry?
- F plasmid- gene to make F pili
- R plasmid- gene for antibiotic resistance
- Vir plasmid- gene for toxin production
Which type of plasmid is involved in bacterial mating (conjunction)
F plasmid
Which plasmid allows for the transfer of genetic material between bacteria?
F plasmid
What is an example of a R plasmid?
Enzymes that degrade antibiotics
What is horizontal gene transfer?
When DNA is transferred to other bacterial cells rather than to its own offspring
What are the 3 ways in which genetic material can be transferred?
- Transformation
- Conjunction
- Transduction
What is transformation?
The genetic alteration of a cell resulting in foreign DNA
In transformation, the DNA can come from where?
Dead cells or from released plasmids
What is recombination?
How pieces of DNA can be integrated into a chromosome during transformation
The male cell in conjunction has what type of pili and what is it referred to as? Female?
Male- F pili, F+: donor
Female- does not have a pili, F-: recipient
What does F pills allow for in conjunction?
Allows for the attachment of the F+ cell to the F- cell allowing a copy of the F plasmid to be to the F- cell
Once the F- plasmid is passed to the female plasmid, what occurs
It becomes a male cell (F+)
What is transduction?
When small fragments of DNA are transferred in between bacteria by a virus
What is a bacteriophage?
A virus that infects bacteria
What occurs in transduction?
- The page attached to the bacterial cell wall and injects DNA into the cell
- The phage DNA is replicated within the bacterial cell
- The phage DNA directs protein synthesis in order to make new phage
- New phages are assembled (pieces of bacterial DNA are accidentally packages into page protein coats)
- The accident phage can infect other bacterial cells
- DNA can now be incorporated into the bacterial chromosome
What is in a bacteriophage?
Everything that is needed to create bacteria
