unit 6: gene expression and regulation Flashcards
transformation
the process by which a cell in culture acquires the ability to divide indefinitely.
chargaff’s rules
-DNA base composition varies between species
-percentages of Adenine-thymine and cytosine-guanine will be roughly equal
three components of a nucleotide
-sugar molecule
-phosphate group
-nitrogenous base (adenine, thymine, cytosine, guanine)
Who built the first model of DNA and shared the 1962 Nobel Prize for discovery of its structure?
Rosalind Franklin obtained images of DNA using X-ray crystallography, an idea first broached by Maurice Wilkins. These images allowed James Watson and Francis Crick to create the double-helix model. Watson and Crick built the model and wrote a one pager report. Maurice Wilkins joined them in receiving the Nobel Prize.
Purines
adenine and guanine
pyrimidines
thymine and cytosine and uracil
leading strand
the new complementary DNA strand synthesized continuously along the template strand towards the replication fork in the mandatory 5’—3’ direction
lagging strand
Lagging strand is synthesized discontinuously, as a series of segments. The segments of the lagging strand are called Okazaki fragments. synthesized in a 5’—3’ direction away from the replication fork
helicase…
untwists and separates strands, holds DNA strands apart
primase…
synthesizes RNA primer
DNA polymerases
adds DNA nucleotides to new strand,
DNA polymerase I
removes RNA primer and replaces it with DNA nucleotide bases
Catalyzes the elongation of new DNA (ex. At a replication fork) by adding nucleotides to the 3’ end of an existing chain.
DNA ligase
joins DNA (Okazaki) fragments together
topoisomerase
relieves strain caused by unwinding of strands. breaks swivels and rejoins the parental DNA ahead of the replication fork.
what is gene expression
The process by which DNA directs the synthesis of proteins (or just RNAS) includes two stages: transcription and translation
5’ cap and poly-A tail functions
They facilitate the export of the mature mRNA from the nucleus.
They help protect the mRNA from degradation by hydrolytic enzymes
They help ribosomes attach to the 5’ end of the mRNA once the mRNA reaches cytoplasm.
introns
Introns: non-coding sequences present in the DNA; removed by RNA splicing before translation
exons
nucleic acid coding sequences, present in mRNA
mRNA
carries a genetic message from the DNA to the protein-synthesizing machinery of the cell. Attaches ribosomes in the cytoplasm and specifies the primary structure of a protein
tRNA
serves as a link between mRNA molecule and growing chain of amino acids. Helps decode an mRNA sequence into a protein
rRNA
part of the ribosome of the cell. responsible for reading the order of amino acids together. Non-Coding RNA component of ribosomes, carries out protein synthesis in ribosomes
anticodon
A nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule
mutation
change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus
point mutation
a change in a single nucleotide pair of a gene
frameshift mutations
A mutation occurring when nucleotides are inserted in or deleted from a gene and the number inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons.
nonsense vs. missense mutation
Nonsense: A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
Missense: a nucleotide pair substitution that results in a codon that codes for a different amino acid. Substitution that changes one amino acid to another.
promoter
a site where RNA polymerase can bind to DNA and begin transcription
operator
Switches on/off the metabolic pathway. In bacterial and phage DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon.
The operator is the “on switch” for gene regulation. it is positioned within the promoter or between the promoter
operon
The entre stretch of DNA required for enzyme production for the pathway. The operator, promoter and genes they control
How does a repressor protein work?
It binds to the operator and blocs attachment of RNA polymerase to the promoter, preventing the transcription of the genes.
Specific to the operator of a particular operon
regulatory gene
A gene that codes for a protein, such as a repressor, tht controls the transcription of another gene or group of genes.
Expressed continuously, although at a low rate.
Distinguish between inducible and repressible operons and describe one example of each type.
A trp operon is said to be repressible operon because its transcription is usually on bu can be inhibited (repressed) when a specific small molecule (in this case, tryptophan) binds allosterically to regulatory protein.
An inducible operon is usually off but can be stimulated (induced) to be on when a specific small molecule interacts with a different regulatory protein (ex. Lactose operon)
cell differentiation vs morphogenesis
Cell differentiation is when specialized structures and functions are achieved. Morphogenesis is the arrangement of cells to make organs/shapes
gel electrophoresis
a technique used to separate nucleic acids or proteins that differ in size or electrical charge.
a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by an electrical field through a gel that contains small pores.
DNA microarrays assays
DNA microarray assays: consist of tiny amounts of a large number of single-stranded DNA fragments representing different genes fixed to a glass slide in a tightly spaced array of dots. Ideally, these fragments represent all the genes of an organism.
The resulting pattern of colored dots after the addition of fluorescent labels and mRNAs reverse transcribed into complementary DNAs, reveals the dots to which each probe was bound and thus the genes that are expressed in the cell samples being tested.
bioinformatics
the use of computers, software, and mathematical models to process and integrate biological information from large data sets.
proteomics
systematic study of sets of proteins and their properties, including their abundance, chemical modifications and interactions
