Lecture 1 - Introduction and Genetics Flashcards
What is the simplest eukaryote studied?
Yeast (S. cerevisiae) because it has all the same cellular organization as a human
What model plant is studied?
Arabidopsis (mustard seed)
What is the simplest multicellular eukaryotic model organism?
C. elegans, a tiny worm because it is so small with approximately 900 cells, is see-through which helps to observe the division and formation of cells, and they multiply quickly
What common sophisticated multi-cellular organism is studied?
Drosophila melanogaster - study how brain and memory work and valuable for studying developmental environment
What are the two accessible models for studying vertebrate development?
Zebrafish, because they are see-through and an alternative to using mice to study genetics, and frogs because they have giant eggs that represent a great source of protein for biochemical studies - Both fairly distant relatives of humans
What is the predominant mammalian model organism?
Mouse because they are basically identical to humans at the cellular level
What does DNA consist of?
Two complementary chains of nucleotides
What is a nucleotide made up of?
Sugar, phosphate, and nitrogenous base
How are the sugars in the DNA backbone attached?
Via phosphodiester bonds
How are nitrogenous bases connected?
H-bonds
What are the constraints for base pairing?
1) Two purines or two pyrimidines cannot form base pairs because purines are too large and pyrimidines are too small
2) A is only complementary to T and U and C is only complementary to G
How is eukaryotic DNA packaged?
Into chromatin (DNA, histones, and proteins) which is then condensed into chromosomes
How can you immediately see if chromosomes have abnormalities?
Taking a human cell in mitosis at its most condensed stage to create a human karyotype and add fluorescent dye
What does each DNA molecule that forms a linear chromosome have to contain?
A centromere, two telomeres, and replication origins
Why are centromeres important?
Important for cell division since mitotic cells recognize it and allow chromosomes to separate
What are telmoeres?
The ends of chromosomes
What is heterochromatin?
The parts of the chromosome where the DNA is extra compacted and tends to have a low number of genes and regions near the centromere
What is euchromatin?
Part of the chromosome that is gene-rich and less compact but more accessible to transcription factors
What is the central dogma of genetics?
1) DNA to DNA - replication
2) DNA to RNA - transcription
3) RNA to protein - translation
What is the useful function of transcription?
Makes lots of RNA copies that can be translated to make the same protein
Exons vs. Introns?
Exons are the only ones left after splicing because they form mRNA and introns are left out
What does RNA polymerase need to bind and initiate transcription?
Promoter
What is forward genetics?
Classical approach of studying genes by observing a phenotypic difference and working your way back to the gene that caused it by random mutagenesis - chemical mutagen or insertional mutagenesis
What is reverse genetics?
Making deliberate mutations in a gene to study the phenotype by site-directed mutagenesis - homologous recombination and gene editing - or by RNAi which knockdown genes
What is the general process of transfection/transformation and what can it be?
It is the introduction of genes into cells or animals and it can be transient (DNA will eventually be lost from the cell) or stable (DNA is integrated into the host genome)
What happens if a transgene is passed on to germline cells
Transgenic animals can be obtained
How can transgenes be used to study gene function?
Overexpression, gene reporters, epitope or GFP tag, structure/function studies
How can genes be cloned using bacteria?
1) Circular double-stranded plasmid DNA is cleaved with restriction nuclease
2) DNA fragment to be cloned is covalently linked by DNA ligase
3) Double-stranded recombinant plasmid DNA is introduced into a bacterial cell
4) Cell culture produces hundreds of millions of new bacteria
5) Many copies of the purified plasmid are isolated from lysed bacteria
How is an entire genome represented in a DNA library?
1) Double-stranded DNA is cleaved with restriction nuclease
2) Millions of genomic DNA fragments are inserted into plasmids
3) Recombinant DNA molecules in plasmids are now introduced into bacteria
* Good genomic library should have a plasmid for every sequence of DNA
What is PCR?
The polymerase chain reaction is a powerful and versatile method for amplifying DNA and provides a straightforward approach to DNA cloning, particularly in organisms whose complete genome sequence is known
What are the steps for PCR?
1) Denature dsDNA by heating at 95 degrees C for 30 seconds
2) Anneal primers by cooling to 58 degrees C for 1 minute
3) Incubate mixture with DNA polymerase and four deoxyribonucleoside triphosphates
4) Extend DNA using DNA polymerase (Taq) which starts at the primers when cooled to 62 degrees C for 2 minutes
5) Repeat
What is the key to PCR?
Taq polymerase because it is immune to boiling
