Ch:14 DNA and RNA Flashcards
Chromosomes contain large numbers of genes which represent the ___(3 words)___
Fundamental heredity unit
__(2 words)__ is a polymer made from monomeric units called nucleotides.
Nucleic acids
Which of the following has 3 hydrogen bonds?
A. G-C
B. A-T
A. G-C
The ____ bonds and ____ interactions between the stacked bases inside the helix stabilizes the helical structure.
H-bonds and hydrophobic interactions
As we __increase/decrease__ the percent of GC we increase stability and melting point, since more hydrogen bonds are in GC than AT!!
Increase
A = T regions will be the first to melt and break!!
Is DNA found in bacteria or viruses?
YES both
If a DNA sample has 20% cytosine, what is the % of adenine?
30%
Discuss the water solubility of:
- the phosphate group
- the ribosyl group
- the nitrogen base
The ribosyl group and phosphate group are polar and will be hydrophilic… they are located on the outside of our helix and are water soluble
Purines and pyrimidines are relatively insoluble in water (hydrophobic); located in the helix interior
What biology or histology technique is used to identify chromosomal material or DNA?
We use the Feulgen stain. DNA stains reddish in color. Mild acid hydrolysis cleaves the molecule and a reaction reveals this red color.
Write the complementary sequence for:
5’ GATCAA 3’
3’ CTAGTT 5’
***strands are anti-parallel
DNA is wrapped around proteins called _____ which look like a bead with a string wrapped with it. This entire complex, DNA and histone = _________.
histones; nucleosome
Explain the differences between heterochromatin and euchromatin:
Heterochromatin:
- Dark stained
- DNA is NOT actively transcribed
- located mainly near the nuclear envelope
Euchromatin:
- Eukaryotic, DNA is available for transcription
- “true chromatin”
- more dispersed and less compacted
The famous ____________ experiment concluded that DNA and NOT protein is the actual genetic info!
Hershey-Chase experiment
Discuss the Fred-Griffith Transformation Experiment:
When he killed a pathogenic bacteria with heat and mixed the cell remains with living non-pathogenic bacteria, some of these harmless bacteria became pathogenic!
He found out that the DNA of bacteria is what caused this transformation
The _______ experiment in 1944 confirmed the work done by Fred Griffith to establish that DNA is indeed the genetic material.
Avery-McCarty experiment
Discuss the differences between:
- rRNA
- tRNA
- mRNA
rRNA: provides physical makeup of the ribosome
- Most abundant
tRNA: transports amino acids to ribosomes
- smallest
mRNA: carries DNA info to ribosomes
- shortest lived
Match rRNA, tRNA and mRNA to the following:
- Most abundant
- smallest
- shortest lived
rRNA = most abundant
tRNA = smallest
mRNA = shortest lived
Why does alkaline conditions partially denature (i.e. unwinds DNA in certain areas) the helix?
Would the regions that unwind be richer in A-T or G-C?
By increasing the pH, we ionize some of the nucleic acid bases, and all of the phosphate groups, thus increasing the # of negatively charged groups, which promote unwinding of the helix to reduce charge repulsion!!!
- Richer in A-T bc it only has 2 H-bonds as opposed to G-C which has 3
Which is more sensitive to base… DNA of RNA? Why?
RNA has a 2’ OH group that DNA lacks. This 2’ OH can launch an intramolecular attack
DNA —> RNA in a process called _______ and occurs in the _______.
Transcription; nucleus
How do histones bind so tightly to DNA?
Histones have positively charged amino acids and DNA is negatively charged which allows for tight binding
