Exam 2- Intro To Nucleic Acids Flashcards
Name 5 nitrogenous bases
Purines- Adenine and Guanine
Pyrimidine- Cytosine, Thymine, and Uracil (in RNA)
What are purines and pyrimidines?
Purines- Pyrimidine ring attached to an imidazole ring
Pyrimidines- Pyrimidine ring
What are the two types of carbohydrates (sugars) that are found in Nucleic acids?
2’ deoxy ribose (in DNA)
Ribose (in RNA)
Nucleoside vs nucleotide
Nucleosides: a nitrogenous base attached to a carbohydrate unit
Nucleotides: nucleosides attached to a phosphate
In a nucleotide, indicate the glycosidic, ester, and anhydride bonds
Glycosidic bond: nitrogen-carbon covalent bond between nitrogenous base and sugar
- in purine, 9’ nitrogen to 1’ carbon
- in Pyrimidine, 1’ nitrogen to 1’ carbon on sugar
Ester bond: carbon on sugar attached to O on phosphate
Anhydride bond: phosphate to oxygen
Describe double helical structure of DNA
- DNA strands have distinct polarity in the direction of 5’ to 3’
- double helical structure that is held together by noncovalent hydrogen bonds
- A double bonded to T
- G triple bonded to C
- the strands are complimentary and anti-parallel to each other
- DNA backbone is held together by phosphodiester bonds
Each nucleotide in a DNA strand is linked together by a _________ bond.
Phosphodiester bond
Two anti-parallel DNA strands are held together by __________ bonds
Hydrogen bonds
Describe the major components of a typical prokaryotic and eukaryotic gene.
Eukaryotic:
- Exon: codes correspondingly to the useful part of the mRNA
- Intron: spliced out during post-transcription from the corresponding pre-mRNA
- Promoters: part of the gene that binds to transcription related proteins (transcription factors) that promote transcription
- Enhancers: regions of the DNA (generally located upstream to the promoters or anywhere in the gene) that binds to the TF’s and enhances transcription
Prokaryotic:
- Circular genome that is practically devoid of proteins (naked DNA)
- in addition to chromosomal DNA bacteria also have small circular DNA molecules called plasmids which can be transferred from one bacterium to another
- plasmids can confer antibiotic resistance proteins/enzymes
How many genes in humans?
23,000 genes
Describe nucleosome structure
Nucleosome- A single packaging unit of chromatin
In a nucleosome, negatively charged DNA molecule (~147 bp sequence) wraps around basic proteins (rich in arginine and lysine) called histones
What are histones?
A. Histones- basic proteins rich in arginine and lysine
B. There are several types of histone proteins called H-1, H2-A, H2-B, H-3, and H-4
C. Then core structure is composed of two each of H2A, H2B, H3, and H4
D. The linker DNA region that connects two adjacent nucleosome core is composed of H1
Name common mechanisms by which histones are post-translationally modified.
- Methylation of lysines and arginines
- N-acetylation of lysine
- Phosphorylation of serines
- Small ubiquitous like modification (SUMOylation) of lysine patterns of nucleosomes
Name different parts of the chromosome.
Chromosome: naked DNA are packaged into nucleosomes. Several nucleosomes are packaged further to form macromolecular structures called nucleofilaments, which further interact with proteins called scaffold proteins to form higher order macromolecular structures
Differences between DNA and RNA?
RNA is single stranded, Uracil in place of thymine, ribose sugar
Central theme of molecular biology.
- Transcription: DNA is transcribed into single stranded RNA catalyzed by RNA polymerase.
There are 3 types of RNA:
1. Messenger RNA- mRNA codes for proteins
2. Ribosomal RNA- rRNA constitutes part of the ribosome structure
3. Translational RNA- tRNA serves as the adapter molecule during translation - Translation: refers to the process of protein synthesis. The mRNA is translated to synthesize unique proteins.
Describe the various types of RNA involved in protein synthesis and their functions.
- Messenger RNA- mRNA codes for proteins
- Ribosomal RNA- rRNA constitutes part of the ribosome structure
- Translation RNA- tRNA serves as the adapter molecule during translation
What are chromatins?
Eukaryotic DNA is packaged with histones to create a higher order structure called chromatin
Describe euchromatin and heterochromatin
Euchromatin: structurally loose and transcriptionally active
- For example, interphase nucleus
Heterochromatin: structurally compact and transcriptionally inactive
- For example, mitotic nucleus
True or false: on a DNA strand the very end of the molecule (ie 3’ end) most of the time it would contain phosphate
True
True or False: metaphase chromosome is mostly heterochromatic in nature
True
Approximately how many protein coding genes are present in E. Coli?
5,000 genes
Penicillin is a Lactam that can be broken down to inactive metabolite by class of enzymes called Beta-lactamases. The genes for beta-lactamases are most often contained in ___________ DNA.
Plasmid
Antibiotic resistance can be transferred from one bacterium to another through ____________ DNA.
Plasmid
