13.3 and 13.4 Flashcards
changes to
the bases of DNA or RNA
mutations
Change the DNA →
changes the mRNA
Change the mRNA →
changes the protein
Change protein →
changes trait
mutations are usually
Usually are spontaneous and random
Causes of mutations
Errors in DNA replication or transcription
Caused by environmental factors called mutagens
ex of mutations
Ex UV radiation, x-rays, some chemicals (pollutants,
pesticides, tobacco products & smoke)
Mutations can occur in:
somatic (body) and gametes (sex) cells
(not passed to offspring but does
affect the organism)
somatic (body) cells
(does not affect the organism
but will be passed onto offspring)
gametes AKA sex cells
affect a single gene, nucleotide bases
changed
gene mutations
produce changes in part of a
chromosome, the whole chromosome, or sets of chromosomes
Chromosomal mutations-
affect only 1 gene, usually
happen during replication, can be passed on to every cell that
is produced from it
gene mutations
2 types of gene mutations
point and frameshift
Change or substituting 1 letter for
another in DNA
May or may not change the protein
point mutations
point mutations are
substitutions
frameshift mutations are
(insertions or
deletions)
Adding or deleting 1 letter in DNA
These shift or change the “reading
frame” (the way the ribosome reads
the codons)
Causes big changes to protein
(proteins might not work)
frameshift mutations
CAA and CAT code for same a.a., DOESN’T change the amino acid so does
not change protein, so neutral mutation
Changes only 1 amino acid and sometimes no effect if they still code
for same amino acid called
silent mutations
Changes the codon to a STOP codon
Protein is shorter than usual and might not work
nonsense mutations
Disorders Caused by Point
Nonsense Mutations
Cystic fibrosis
Muscular dystrophy
Mutation that causes a lack of dystrophin, a
protein that keeps muscles intact
Leads to severe muscle weakness
Trouble walking, breathing, swallowing.
Often have a curved spine or difficulty in releasing
muscle tension
Live on average 40 or 50 years
Muscular dystrophy
Chronic lung infections due to buildup of thick
mucus in lungs and pancreas
Cannot be around others with CF
Live on average 40 years
Cystic fibrosis
(substitutions- point mutation) or (insertions and deletions
then called frameshift mutations)
Changes 1 amino acid because by changing 1 base in DNA which changes
the whole protein, if a frameshift mutation it is even worse because it
changes multiple amino acids
misense mutations
Changes every amino acid after the mutation by changing the
“reading frame” of codons, so changes protein
Frameshift Mutations
1 base is added to DNA
addition
1 base is deleted from DNA
deletion
Disorders Caused by
Frameshift Missense Mutations
Sickle Cell Anemia- 1 base
Progeria- substitution
Single base change causes a change in
hemoglobin shape
Sickle cells struggle to move through blood
vessels, leading to anemia (lack of oxygen),
fatigue, frequent pain
sickle cell amenia
Very rare disorder where the protein (progerin)
that slows aging gets easily destroyed. Cells age
very quickly, leading to stiff joints, hair loss, and
strokes.
13 year average life span
Leads to fatal heart complications
progeria
Disorder Caused by
Insertion
Huntington’s Disease
Insertion of a gene multiple times
Protein called Huntingtin carries molecules
outside of the cell
Disease causes destruction in the portion of
the brain that controls movement, emotion
and cognitive ability
Currently no cure
Generally affects those 30-50 years old
(inherited)
Huntington’s disease
Chromosomal Mutations-
deletion, duplication, Inversion-, translocation
1 section or gene of
chromosome deleted
deletion
1 section or gene of
chromosome is doubled
duplication
1 section or
gene(s) breaks off and
reattaches backwards
inversion
1 section
or gene(s) breaks off and
attaches to a NEW
chromosome
translocation
chromosomal deletion ex
Example: Cri-du-chat (5p minus) – a piece of
chromosome 5
Inherited disease of the peripheral nerves(myelin
sheaths) that control movement
Causes slow loss of function and movement in
arms/legs
Charcot-Marie Tooth Disease
Very rare disorder caused by a duplication of a
region on the 22nd chromosome
Heart and kidney defects
Fused fingers & toes
Some intellectual disabilities
cat eye syndrome
Disorders caused by Duplication
Charcot-Marie Tooth Disease
Cat Eye Syndrome
reverses the direction of parts of a chromosome.
chromosomal inversion
occurs when part of one chromosome breaks off and attaches to
another.
chromosomal translocation
chromosomal translocation
Example: acute myeloid leukemia (chromosomes 8
and 21)
When chromosomes do not properly
separate during meiosis (in anaphase)
when gametes are formed
nondisjunction
Nondisjunction Can happen during 2 different times:
anaphase I, anaphase II
Anaphase 1
Homologous chromosomes do not
separate
Anaphase 2
Sister chromatids do not separate
Effects of Nondisjunction
If one chromosome is involved, one extra is called trisomy
one less is monosomy
Have 3 copies of chromosome 21
Caused by non-disjunction of gametes, affecting
embryonic development
Delayed
learning and
physical
growth
Distinct facial
features
Down Syndrome (Trisomy 21)
If nondisjunction involves a set of chromosomes:
The condition in which an organism has extra sets of
chromosomes is called polyploidy.
polyploidy ex
Triploid (3n)
Tetraploid (4n)
Polyploid (many sets)
often make use of “good”
mutations.
Plant and animal breeders
when a complete set of chromosomes fails to
separate during meiosis, the ________ that result may produce
triploid (3N) or tetraploid (4N) organisms.
gametes
are often larger and stronger than
diploid plants.
Polyploid plants
Important crop plants—including _______ and ______—have been produced this way.
bananas and limes
Polyploidy also occurs naturally in _____ plants, often
through spontaneous mutations.
citrus
Without mutations, organisms cannot evolve, because
mutations are
the source of genetic variability in a species.
Sickle cell disease is caused by a point mutation in one of the
polypeptides found in
hemoglobin
the blood’s principal
oxygen-carrying protein.
hemoglobin
Among the symptoms of sickle cell disease are
anemia, severe pain,
frequent infections, and stunted growth.
mutations have helped many insects resist
chemical pesticides
Some mutations have enabled _________ to adapt to new
chemicals in the environment.
microorganisms
Flow of information from DNA to
protein to trait
gene expression
used to synthesize
proteins thus influencing traits
DNA sequences
In humans, some genes are always
“turned on” for day to day function
(Ex:
enzymes for cell respiration)
Genes that are “turned on” will be
transcribed and translocated into a protein
Controlling gene expression by turning genes “on” and “off”
Controlled differently in prokaryotes and eukaryotes
gene regulation
Bacteria regulate gene expression by
blocking transcription if protein not
needed
prokaryotic regulation
group of genes regulated
(turned on and off) together
These genes usually have the
same or similar functions
Operons-
Operons contain regulatory DNA sequences that allow regulatory proteins to
turn the expression
up or down
regions allow RNA polymerase to bind to DNA, 1st right before gene
promoter
regions of DNA where repressor proteins can bind, right after the
promoter, 2nd before the gene
operators
blocks RNA polymerase and turn operons “off”= no transcription so
no mRNA made
repressors
turn operons “on” = binds to DNA for RNA polymerase to allow
transcription to occur so mRNA made
activators
Lac operon in E. coli turns on & off when bacteria needs to use
lactose
The lac operon is turned ___ when lactose is present.
on
Lactose binds to the repressor, allowing it to detach from the operon and for RNA
polymerase can transcribe ____.
mRNA
is used to make enzymes needed to digest lactose (so gene is expressed).
mRNA
Most genes controlled
individually
Different cells will express different sets of genes (even though they all contain the same DNA) → this makes cells specialize
Controlled by transcription
factors (see next slide)
Eukaryotic Gene Regulation
Eukaryotic Gene Regulation includes the
TATA box
Proteins that form a binding site
at TATA box to specific DNA
sequences (promoter) to enhance
or repress transcription by:
Help RNA polymerase bind
to DNA promoter turn “on”
OR
Block access to promoter
turn “off”
Most genes controlled by many
Most genes controlled by many
transcription factors
(Eukaryotes only)
Transcription Factors
Cells contain very small RNA sequences (called microRNA or
miRNA) that aren’t mRNA, tRNA or rRNA
These miRNA sequences become silencer complexes that bind
to any mRNA that is complementary to the miRNA
which blocks expression of that mRNA
RNA interference
A powerful way to study gene expression in the laboratory.
May provide new ways to treat and perhaps cure diseases.
Using RNAi (RNA Interference) Technology
Make miRNA to synthetically turn off the expression of genes from
viruses and cancer cells
caused by a single autosomal dominant mutant gene.
The gene produces a protein that causes brain abnormalities, which in turn
interfere with coordination, speech, and mental abilities.
Huntington’s disease
helps cells undergo differentiation & become
specialized in structure & function.
gene regulation
regulate organs that develop in specific parts of the body.
Homeotic genes-
similar 180-base DNA sequence found in homeotic genes.
Homeobox-
group of homeobox genes.
located side by side in a single cluster
tell the cells of the body how to differentiate as the body grows.
Nearly all animals, from flies to mammals, share the same basic tools
for building the different parts of the body.
Hox box
Common patterns of genetic control exist because
all these genes have
descended from the genes of common ancestors.
Environmental Influences on Gene Expression ex
Presence of lactose influences
expression of lac gene in E. coli
Himalayan rabbits develop dark
spots in areas where heat is lost if
reared in colder temps.
Tadpoles speed up metamorphosis
if they’re surrounded in a pond
with many predators and little
food
