L3 DNA as genetic material Flashcards
What type of bond joins adjacent amino acids in a protein’s primary sequence?
Peptide bond
What are the three Mendelian laws of inheritance?
- Segregation
- Independent assortment
- Dominance
Who proposed the Sutton-Boveri theory of chromosomal inheritance?
Walter Sutton and Theodor Boveri
What does the term ‘transforming principle’ refer to in genetics?
Hereditary material that changes the genotype of bacteria
What is the purpose of the polysaccharide coat in S strain bacteria?
It protects some strains from the host immune system
What experiment did Frederick Griffith conduct to study bacterial transformation?
He injected dead S bacteria with live R bacteria into mice
What did Griffith conclude from his experiments?
Some hereditary material passed from S bacteria to R bacteria
What did Oswald Avery and his colleagues determine was responsible for transformation?
DNA
What component did Alfred Hershey and Martha Chase label to determine the genetic material of bacteriophages?
DNA and protein
What is a bacteriophage?
A category of viruses that infect bacteria
Which bacterium is the host for bacteriophage T2?
Escherichia coli
True or False: The protein coat of a bacteriophage is injected into the bacterial host.
False
Fill in the blank: The Sutton-Boveri theory provides a physical basis for Mendel’s _______.
Independent assortment
What happens when S strain bacteria are heated and injected into mice?
No infection is established
What are the steps in Avery’s transformation experiments?
- Systematically destroy each component
- Combine with live S bacteria
- Test for transformation
What is the significance of the polysaccharide capsule in virulent bacteria?
It helps to evade the host immune response
What did the experiments involving radioactive isotopes reveal about DNA?
DNA is the genetic material injected into bacteria
What was the main question Griffith sought to answer through his experiments?
Can he transform the rough bacteria into smooth ones?
Which type of bond is primarily responsible for holding together the primary structure of proteins?
Peptide bond
What is the role of chromosomes in heredity according to the Sutton-Boveri theory?
They carry Mendel’s factors (genes)
What was the outcome when live R bacteria were injected with dead S bacteria?
Infection was established
What was a common misconception about DNA in the early 20th century?
Many thought DNA was too simple to be the genetic material
What does the term ‘virulent’ refer to in the context of bacteria?
Bacteria that can cause disease
Boveri and Sutton observed worms and grasshoppers. Why?
They observed chromosomes in these species because their chromosomes are large and few in number, amd therefore easy to see
Which Streptococcus strain causes infection and illness?
S- strain
Smooth bacteria has polysaccharide coats that forms a capsule that protects itself from the host immune system
Is an infection established when dead S bacteria is injected into mice together with live R bacteria?
Yes, the mouse is now infected
The bacteria now has a polysaccharide capsule
Outline Hershey’s and Chase’s experiment
- Label bacteriophage DNA or protein with radioactive isotope
- Infect unlabelled bacteria with radioactive phage
- Seperate phage ghosts from infected bacteria
- Test bacteria and phage ghosts for radioactivity
How did Hershey and Chase get rid of the phage ghosts?
They used a blender to make the phage ghosts fall off the bacteria
Bacteria themselves remain intact
Is supernatent at the bottom of a centrifuged test tube or a pellet?
The pellet is at the bottom
What did Hershey and Chase discover in their experiment?
Discovered that radioactivity was present in bacteria , therefore, it is the DNA that is being injected and directing the formation of new phage
