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origin of water on earth
many collisions occur with water-rich asteroids
goldilocks zone
habitable zone and refers to the orbital distance from a star that will result in liquid water
the two gases that formed the majority of earth’s early atmosphere
methane and ammonia
when life originated
between 3.5 and 3.9 years ago
temperature on early earth
75 to 95 degrees celsius
LUCA
hypothetical last universal common ancestor
capsid
protein shell of a virus that surrounds and protects the genetic material
virus
small infectious particles
virus traits
capsid
dna or rna as genetic material
few or no enzymes
20 to 500 nm
single-stranded RNA
HIV
double-stranded RNA
rotavirus
single-stranded DNA
parvovirus
double-stranded DNA
bacteriophage lambda
viral envelope
membrane made of lipids and proteins that surrounds the capsid
obligate intracellular parasites
living organism that lives in or on a host that’s restricted to a certain function or mode of life and dependent on host cell
endosome
membrane-bound vesicles, formed by the process of endocytosis
receptor-mediated fusion
the process by which a virus binds to a receptor on a host cell membrane to fuse with the host cell membrane and enter the cell
lytic cycle
a viral reproductive cycle involving rapid production of viral progeny which lyse and destroy the cell
viroids
an infectious entity affecting plants that viruses may have evolved from
transposons
sequences of nucleic acid (DNA or RNA) that are able to move position within the genome
convergent evolution
pattern of evolution where distantly related organisms evolved similar traits in response to environmental similarities which viruses are thought to demonstrate
horizontal gene transfer
the process viruses can do that is the exchange of genetic material between individuals that does not involve reproduction
dna replication
copying of dna to create a new dna molecule
transcription
the process in which the dna is used as a template to produce rna
translation
the process in which the transcribed rna is translated by the ribosomes to produce proteins
purine
two ring compound. adenine and guanine
pyrimidine
one ring compound. cytosine, thymine, and uracil
histone
proteins around which eukaryotic dna is wrapped, forming nucleosomes. this organization helps regulate gene expression and protect the structural integrity of dna
nucleosome
structural unit of eukaryotic chromatin, consisting of dna wrapped around a core of histone proteins
what hershey and chase proved
that it was dna, not protein, that made up genetic material
what chargaff proved
that equal amounts of cytosine and guanine and equal amounts of adenine and thymine meant that dna was double helix
directionality
the orientation of polarity of a dna strand, referring to the 5’ (phosphate) to 3’ (hydroxyl) directionality of nucleotide addition during dna synthesis
leading strand
the dna strand that is synthesized continuously in the 5’ to 3’ direction during dna replication
lagging strand
the dna strand that is synthesised discontinuously in short fragments called okazaki fragments during dna replication
replication fork
the y-shaped structure formed during dna replication where the dna double helix is unwound and new strands are synthesised
okazaki fragments
short dna fragments that are synthesised on the lagging strand during dna replication and later joined together
helicase
unwinds and unzips the dna molecule by breaking the hydrogen bonds that hold complementary bases together
single stranded binding proteins
proteins that bind to and stabilize single-stranded dna during dna replication or repair
gyrase
enzyme that moves ahead of helicase to relieve tension created by unzipping the double helix
dna primase
attaches small rna primers to template strand which allows dna polymerase iii to attach
dna polymerase iii
assembles the new strands of dna by placing free nucleotides in the correct sequence. only able to build new strands in the 5’ to 3’ direction
dna polymerase i
removes dna nucleotides of the primers and replaced them with the correct dna nucleotides. also does dna proofreading
dna ligase
catalyses the formation of the phosphodiester bonds between the okazaki fragments
promoter
non-coding region of dna to which rna polymerase binds to initiate transcription
transcription factors
a group of proteins that bind in the correct orientation to the promoter so rna polymerase can bind and begin transcribing dna to rna
regulators of gene expression
non-coding regions that regulate gene expression. include enhancers and silencers
introns
non-coding regions in eukaryotic genes that get removed at the end of transcription
telomeres
non-coding regions that are repetitive sequences that protect the ends of the chromosomes. with every cell division, short stretches of dna are lost from the telomeres
genes for trna and rrna
these genes code for rna molecules that do not get translated into proteins, but instead fold to form trna or rrna
exons
coding regions within a gene that contain the instructions for synthesising a protein and are retained in the mature rna molecule
pre-mrna
initial rna molecule transcribed from dna which contains both introns and exons
5G cap
modified guanine nucleotide added to the 5’ end of pre-mrna during post-transcriptional modification, providing stability and assisting in mrna processing and transport
poly-A tail
multiple adenine nucleotides added to the 3’ end of a mrna transcript to protect and stabilise the molecule
splicing
the process of removing introns from pre-mrna and joining the exons together to produce mature mrna that can be translated into a protein
alternative splicing
a mechanism by which different combinations of exons within a gene can be spliced together to generate multiple mrna isoforms and increase protein diversity
three stages of translation
initiation, elongation, and termination
proteasome
protein complexes that degrade and recycle damages or unwanted proteins
genetic engineering
the process of altering the dna of an organism in order to introduce new characteristics, remove unwanted traits or modify existing ones
gene knockout
a genetic engineering technique in which a specific gene is intentionally made inoperative to study its function
crispr
a specific region of dna that is found in bacteria that contains short, repeated sequences and unique spaced sequences that are incorporated from foreign dna encountered by the bacteria
cas9
an endonuclease enzyme that can be used to cut dna at specific target sites on a chromasome
single guided rnas
a synthetic rna molecule that is used in the crispr-cas9 gene editing system that scientists have adapted for use in genetic engineering
conserved sequences
sequences that remain identical or similar across a species or a group of species over evolutionary time
highly conserved sequences
regions of dna or rna that exhibit an exceptionally high level of similarity across different species
homology
similarity or shared characteristics between different organisms, genes, or proteins due to their common ancestry
gene expression
the process by which genetic information is used to produce rna and proteins
phenotypic plasticity
the ability of an organism to exhibit variations in its physical characteristics or traits in response to environmental influences
stages in gene expression
transcription and translation
rna polymerase
enzymes that use a dna template to synthesise rna
activator proteins
specific types of regulatory proteins that bind enhancers to activating the transcription of nearby genes
operon
a group of genes that share a promoter
repressor proteins
transcription factors that can block the binding of rna polymerase or other transcription factors to a promoter, downregulating gene expression
epigenesis
the process by which cells and organisms differentiate through the interaction between dna and environmental factors
dna methylation
addition of a methyl group to dna
histone modification
addition of chemical groups to histone proteins
heterochromatin
the highly condensed and transcriptionally inactive form of chromatin
euchromatin
the less condensed and transcriptionally active form of chromatin
acetylation
the addition of an acetyl group to a molecule
epigenetic inheritance
the inheritance of non-genetic information that can influence gene expression and phenotypic traits
