Theme 1- Module 4 (Nucleic Acids) Flashcards
True or false: bacterial cells have a cell membrane but no cell wall
False
They have a cell membrane AND a cell wall
True or false: all genetic material in the bacterial cell is contained in the chromosomes
False
Also contained in plasmids
What are plasmids?
Small, circular DNA molecules that carry only one or two genes (such as those that contribute to anti-biotic resistance)
What causes the rapid spread of genes (i.e. antibiotic resistance) in bacterial populations?
Caused by plasmids replicating independently of the core genome and transferring from one cell to another
What are chromosomes?
Word that describes the organization of double-stranded DNA in its association with proteins and RNAs
What is the difference between prok chromosomes and euk chromosomes?
Prok chromosomes = small, circular
Euk = large, linear
True or false: mitochondria have their own chromosomes
True
E.Coli chromosomes are a 1000 times longer than the diameter of the cell, and yet it is able to fold up within the nucleoid. How?
The circular chromosomes are able to SUPERCOIL into many loops and associate with proteins to compact the DNA into the nucleoid region
True or false: only euk DNA have a double helix structure
False
Prok DNA are also in double helixes
What is supercoiling?
Coiling that occurs in addition to the coil of the helical DNA structure
Why is supercoiling advantageous?
Preserves the double helix
Compacts DNA
True or false: chloroplasts AND mitochondria contain their own genomes
True
Streptococcal bacteria reside where?
Human upper respiratory tract
True or false: virulent strains of Streptoccal bacteria are harmless and not associated with any disease symptoms
False
Benign strains = harmless
Virulent = dangerous
Who found out that there were two diff strains of Streptococcus pneumon? How did he find out?
Fred Neufeld
Inserted two diff strains of bacteria into mice. One strain did nothing (Benign) and the other caused death by pneumonia (virulent)
Describe Griffith’s hypothesis and how he came about it
Heated the virulent bacteria in order to kill them (all macromolec still there, the cell is just dead)
Inserted the dead strain into mouse; did not die
Hypothesis: all info that makes a cell virulent was still present, but the cell carrying that information had been killed
Describe Griffith’s experimental setup
Set up three control mice (injected one with virulent, one with benign, one with killed virulent bacteria)
In fourth mouse, he killed virulent strain and incubated remains with living cells of benign bacteria.
Describe Griffith’s results and his conclusions
The fourth mouse died, indicating that the benign cells were now virulent
Concluded that the benign cells had acquired the ability to be virulent from the dead cells via transformation
What is transformation?
A change in cell behaviour resulting from the incorporation of genetic material from outside of the cell
Describe Oswald’s experimental setup
Build on Griffith’s experiment; find out which macromolecule is responsible for carrying hereditary info
One control flask with protein, RNA, and DNA
Three other flasks with non-virulent bacteria
- Protein + DNA, protein + RNA, RNA + DNA
- Selectively eliminated each type of macromolecule from cell extracts (i.e. eliminated RNA with RNAase)
Then added killed virulent bacteria in each flask
Describe Oswald’s results and conclusion
Results: All of the flasks (three in total) that had DNA had the bacteria turn from non-virulent to virulent (underwent transformation. The one flask without the DNA still had non-virulent bacteria
Conclusion: transformation requires the presence of DNA; the macromolecule that det the characteristics of the cell was contained in DNA
What did Rosalind Franklin do?
Rosalind Franklin was the first to use a technique called x-ray diffraction to aim x-rays at DNA to create images based on the diffraction of the x-rays by the atoms of the DNA molecule
What is the significance of Photo 51?
From this image that the helical nature of DNA was identified
What are the three components of a nucleotide?
Phosphate group
5-carbon deoxyribose sugar (H on bottom)
Nitrogenous base
Diff between pyrimidines and purines?
Pyrimidines
= single ring
Purines
= two rings (pyrimidine ring fused to an imidazole ring)
= larger
Cytosine, Adenine, Thymine, Guanine. Sort these into pyrimidines and purines
Pyrimidines
= Cytosine
= Thymine
Purines
= Adenine
= Guanine
What is the bond between two nucleotides called?
Phosphodiester bond
Describe how the nucleotides are linked along the phosphoribose backbone
Phosphate group on 5’ carbon on deoxyribose forms a bond with the HYDROXYL GROUP on the 3’ carbon on the next
Which way does DNA run, 5’ -> 3’ or 3’ -> 5’?
5’ -> 3’
True or false: new nucleotides are added to the 5’ end of the strand
False
Added to 3’ end
What are Chargaff’s rules?
DNA from any cell of all organisms should have a 1:1 ratio of pyrimidines and purines
A pairs with T
C pairs with G
True or false: covalent bonds form between the nucleotide bases (i.e. A-T)
False
Hydrogen bonds
How many hydrogen bonds exist between thymine and adenine?
2
How many hydrogen bonds exist between guanine and cytosine?
3
True or false: the two strands of DNA run parallel
False
Run antiparallel
What does RNA polymerase II do?
Transcribes DNA into RNA
What are the different categories of RNA?
Messenger RNA
Ribosomal RNA
Transfer RNA
RNA Polymerase
What’s the difference between the deoxyribose sugar and the ribose sugar?
Ribose has a hydroxyl group (-OH) on the carbon 2
Deoxyribose has a hydrogen (-H) on the carbon 2
DNA has A, T, G, C
RNA has A, U, G, C
(Uracil replaces the Thymine)
What’s the difference between uracil and thymine?
Uracil has a hydrogen (-H) where Thymine has a methyl (-CH3) group
Is uracil a pyrimidine or a purine?
Pyrimidine
What types of bonds are formed in the RNA backbone?
Phosphodiester bonds
True or false: new ribonucleotides are added to the 5’ end of the polymer
False
Added to 3’ end
What are ribosomal RNAs (or rRNAs)?
Forms (along with proteins) the functional ribosome complexes that perform translation of mRNAs into proteins
True or false: most of the RNA in the cell are rRNAs
True
Which rRNAs comprise the large ribosomal subunit and which comprise the small subunit?
23S RNA + 5S RNA = large subunit
16S RNA = small subunit
How are DNA molecules organized in euk cells?
DNA molecules are linear and organized around proteins (histones) to form chromatin fibres. Chromatin fibres coil more and make chromatids.
What is a nucleosome?
Length of DNA coiled around a core of histones
What is the difference between euk DNA and prok DNA?
Euk chromosome is much greater than prok nucleoid
Euk genome is greater than the prok genome
What’s similar between the euk DNA and prok DNA?
Same nucleotides, same double helix, similar gene codings for proteins (i.e. RN A polymerase)
