2.7 gene expression Flashcards
What is DNA
Deoxyribonucleic acid (DNA) is a double-stranded
helix made of chemical building blocks called
nucleotides
What is DNA made of
Nucleotides are made of:
- Sugar (deoxyribose)
- Phosphate
- Nitrogenous bases (adenine (A), thymine (T),
guanine (G), and cytosine (C))
What is the complementary based pairing rule
The complementary
base-pairing rules states
that:
- Adenine (A) always bonds
with thymine (T) - Cytosine (C) always bonds
with guanine (G)
What is tRNA
the nucleic acid which has an anticodon
that binds to mRNA bringing in the correct
amino acid during translation
What is transcription
process in the nucleus where the genetic
information on DNA is transcribed on to
mRNA using the complemenary base
pairing so A on DNA pairs with U on
mRNA, T on DNA pairs with A on mRNA
and C pairs with G
What is translation
the process where the genetic infromation
in the sequence of codons on mRNA
specifies the sequence of amino acids in a
polypeptide chain
What is mRNA
the nucleic acid which is complementary to
the template strand of DNA which carries
the genetic information from the nucleus to
the ribosomes. it’s sequence of 3 base
codons specifies the sequence of amino
acids in a polypeptide chain
What is the rRNA/ribosome
the place where translation occurs
What is a codon
three bases on the mRNA that specifies
(codes for) an amino acid
What is an anticodon
three bases on the tRNA that binds to the
codon on mRNA during translation
What is an amino acid
monomer of a polypeptide chain or a
protein
What is a polypeptide chain
a molecule made up of a specific sequence
of amino acids
What is a peptide bond
the bond that forms between the amino
acids in a polypeptide chain
What is a stop codon
the codon found at the end of the mRNA
which signals the end of translation. The
polypeptide chain is complete and no
more amino acids are added.
What is a start codon
the codon which tells the ribosomes to
start making the polypeptide chain - codes
for the methionine amino acid (AUG = satrt
codon
What is a ribosome
the place where mRNA is read
What is degeneracy
where more than one codon codes for an
amino acid - the third base of a codon can
change and still code for the same amino
acid. degeneracy leads to redundancy in
the code
What is a coding strand
the strand that is complementary to the
mRNA (used as a template to synthesise
mRNA during transcription) - often
synonymous with template strand, but
specify what the strand does in your
answer
What is protein synthesis
the making of a protein with a specific
sequence of amino acids determined by
the genetic code (base sequence) of a
gene
What is primary structure
the specific sequence of amino acids
(bonded by peptide bonds) in the
polypeptide chain
What is secondary structure
the primary structure (sequence of amino
acids) is folded into alpha helices, beta
sheets. this structure is maintained by
hydrogen bonds.
What is tertiary structure
the secondary structure folds into a 3D
shape which is maintained by hydrogen
bonds, di-sulfide and ionic bonds
What is a complementary base pair
the nucleotide bases in one strand of DNA
or RNA that are paired with those of
another strand; adenine pairs with thymine
or uracil, and guanine pairs with cytosine
What is an enzyme
a biological catalyst protein that speeds
up biochemical reactions
What is a gene
sequence of bases on DNA that codes for
a protein (polypeptide chain) and thus
determines a trait
What is a mutation
change in the base sequence of the DNA in a gene
What is a mutagen
any agent (an environmental factor) that
can induce a genetic mutation or can
increase the rate of mutation
What is a somatic mutation
mutation occurring in the body cells, non
inheritable - but may affect individual
during their lifetime
What is gametic mutation
mutation occurring in the germ cells or
gametes, heritable - if it is the gamete
chosen in sexual reproduction
What is a genotype
the combination of alleles for a given gene
What is a phenotype
the observable expression of a given gene
What is a protein
molecule that consists of one or more
polypeptide chains
What is gene expression
when the genetic information in the
sequence of bases in agene is used to
make a protein
What is a genetic code
the order of the bases on the DNA strands
(and the order on mRNA) determines the
order of amino acids in proteins
What is nucleic acid
DNA and RNA - composed of long chains of nucleotides
What is a template strand
the strand that is complementary to the
mRNA (used as a template to synthesise
mRNA during transcription) - often
synonymous with coding strand, but specify
what the strand does in your answer
What is substitution mutation
type of mutation where one base is
exchanged for another base in the DNA of a
gene
What is an insertion mutation
type of mutation where a base is inserted
into the base sequence of DNA of a gene,
causes a reading frameshift
What is deletion
type of mutation mutation where a base is
deleted from the base sequence of DNA of
a gene, causes a reading framshift
What is frameshift
a change in the sequence of triplets
following an insertion or deletion mutation.
What is a triplet
three nucleotides on a strand of DNA
What is redundancy
some amino acids are coded for by more
than one codon. degeneracy leads to
redundancy
What is a metabolic pathway
a sequence of enzyme controlled
biochemical reactions
What is metabolism
all the chemical reactions that occur in a cell
What is a substrate
the chemical / molecule that binds to the
enzyme then reacts to from a product
What is an environmental factor
factors that can change the phenotype (or
genotype if the environmental factor is a
mutagen). there are abiotic or biotic
environmental factors.
What is a nucleotide monomer
units that make up DNA and RNA
What is deoxyribose sugar/ribose sugar
part of a nucleotide monomer in DNA
(deoxyribose) and RNA (ribose)
What is a phosphate
part of a nucleotide (backbone of DNA/RNA molecule)
What is a nitrogenous base
part of a nucleotide - A, T, C, G, 4 bases in
DNA; A, U, C, G, 4 bases in RNA
What is the structural role of a protein
protein that forms part of body or cell
structure - fibrous proteins eg collagen,
keratin, muscle
What is quaternary structure
The fourth level of protein structure; the shape
resulting from the association of two or more
polypeptide subunits.
What is a polymer
large molecule made up of many monomers
What is a monomer
A simple molecule that can combine with other
monomer molecules to make a polymer
What is a hydrogen bond
bond between amino acids in secondary and
tertiary structure of a protein
What is an active site
Location on the enzyme where the substrate will
bind
What are the three stages of transcription
Translation has three stages:
- Initiation
- Elongation
- Termination
What is initiation
Translation begins when the ribosome
binds to the AUG codon on the mRNA
strand
- AUG (START codon) signals the start
of translation, and therefore the
beginning of the polypeptide forming - AUG codes for the amino acid
methionine (Met), which is brought by
the tRNA molecule - The ribosome moves from the 5’ to 3’
end of the mRNA strand
What is elongation
The tRNA anticodon binds to the
complementary mRNA codon using A-U, C-G
- If the codon and anticodon match, the
tRNA deposits its attached amino acid - Amino acids are added to the polypeptide
chain one by one by tRNAs as the ribosome
reads the mRNA codons - They are joined together by peptide
bonds - The tRNA leaves the ribosome and can be
reused to pick up another amino acid
What is termination
The ribosome reaches a STOP codon on the mRNA
- The stop codon does not code for a specific amino acid, it codes for
the ribosome to release the formed polypeptide - The newly released polypeptide can fold into its specific protein
structure - The ribosome and tRNA can be reused with multiple copies of the
mRNA strand to make many polypeptides at once
