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RNA: ribonucleic acid
• Large nucleic acid built from many
nucleotides bonded together
• Remember a nucleotide consists of a
phosphate group, 5 carbon sugar and
nitrogen containing base
RNA nucleotide
• The 5-Carbon sugar is ribose
• The 4 nitrogen containing bases:
– Adenine
– Uracil
– Cytosine
– Guanine
3 types of RNA
• mRNA: messenger RNA: carries the
genetic code from the nucleus to the
ribosome
• rRNA: ribosomal RNA: builds ribosomes
• tRNA: transfer RNA: carries amino acids
to the synthesizing polypeptide
Wednesday 4/3/13
• AIM: How is mRNA translated?
• DO NOW: Explain the importance of
messenger RNA. Where does the
message come from?
• HOMEWORK: Text read page 306 answer
the reading check question
Modification of RNA
• The rough draft is called the primary
transcript
• Before it leaves the nucleus it gets
modified
• Addition of 5’cap and Poly-A tail
• The most important is RNA splicing
RNA modification
• 5’ cap and Poly A tail protect the RNA
from being broken down by cellular
enzymes
• They also help the ribosome recognize the
RNA
RNA splicing
• Introns: junk DNA that does not code for
proteins
• Exons: good DNA codes for protein
• Splicesome: enzymes that catalyze the
removal of introns and the connection of
exons
• Allows the human genome to produce a
variety of polypeptides
• One gene codes for one polypeptide
• How do your cells know which amino acids
it wants or needs?
• ANSWER: the genetic code determines
the polypeptide (sequence of amino acids)
Now the mRNA is ready to leave
the nucleus and enter the
cytoplasm
Quick Review
• What are the 3 major events that occur
during transcription?
• Why is it important to modify the primary
RNA before leaving the nucleus?
The Genetic code
• Codon: sequence of 3 nucleotides that
specify an amino acid
• There are 20 amino acids that build ALL
polypeptides
• It is the unique sequence of amino acids
that build polypeptide chains
• It is the unique folding of polypeptides that
build proteins
Codon: sequence of 3
nucleotides that specify an amino
acid
Period 7 Thursday 4/4/13
Friday 4/5/13
• AIM: How is the mRNA molecule
translated?
• DO NOW: In your own words explain how
the primary transcript is modified before it
leaves the nucleus.
• Why is it modified?
Codons to know
•
•
•
•
AUG
UAA
UAG
UGA
• So we know DNA can replicate and
transcribe. But what happens next?
Translation: RNA to amino acid
sequence
• Involves mRNA, tRNA, rRNA and
ribosomes
• Before mRNA leaves the nucleus, proteins
called splicesomes cut out and paste
together coding regions of the primary
mRNA transcript
• Plays a major role in polypeptide diversity
• Now it is ready for translation
RNA:ribonucleic acid
• Polymer made up of small subunits called
nucleotides
• Each nucleotide has a 5 C sugar,
nitrogenous base and phosphate group
• The 5 carbon sugar in RNA is ribose
• The four possible nitrogenous bases are
• Adenine, uracil, cytosine and guanine
• Instead of thymine,
adenine attracts a
uracil nitrogenous
base
mRNA: messenger RNA
tRNA: Transfer RNA carries amino acids to
the mRNA-ribosome complex
mRNA: messenger RNA
mRNA: codon
tRNA anticodon
• 3 base pair sequence complementary to the mRNA
codon
• Anticodon-codon complex allows amino acids to
bond in proper sequence
Ribosomal RNA builds ribosomes
• AIM: How are codons translated into
polypeptides?
• DO NOW: Handout. Label 1-10
• Homework: Handout
Translation- mRNA and tRNA
interact at a ribosome
Translation continued
Translation Stage of Protein
Synthesis
• Rectangles = amino
acids
• Crooked Cross =
transfer RNA with an
amino acid on top and
anticodon at bottom
• X = messenger RNA
molecule with
codons
• Double oval =
ribosome
What I want you to know about
translation
• Process that builds a polypeptide chain
from a mRNA molecule
• The original message comes from the
DNA template
• tRNA anticodon bonds to mRNA codon
bringing an amino acid into its proper
place
• Translation occurs in the ribosome
Translation
• There is a specific start AUG codon
• There are 3 possible stop codons that
terminate UAA,UAG or UGA
Reading frame
• Each codon specifies an amino acid
• The reading frame is the sequence of
codons in a gene
• If the reading frame is changed, the amino
acid sequence may be changed
• Possibly resulting in a dis-functional
protein
Lets build a protein
DNA :
mRNA:
tRNA:
aa:
TACCCTCAACTCTCAACT
AUGGGAGUUGAGAGUUGA
UACCCUCAACUCUCAACU
met - gly- val- glu- ser
Amino acid sequence
• MET-GLY-VAL-GLU-SER
• We got a polypeptide but is this a
functional protein?
• NO! Remember it is the unique shape of a
protein that gives it a specific function
Assessment
• Handout 1-5 and A-E
Wednesday 4/27/2011
• AIM: How is the reading frame effected if
the base pair sequence changed?
• DO NOW: How would mRNA and amino
acid sequence change if the following
DNA template changed?
Original DNA: TACCCTCAACTCTCAACT
Changed DNA: TACCCTCATTCTCAAC
DO NOW ANSWER
• If the gene sequence is changed and
causes a change in the amino acid
sequence (polypeptide), the physical
characteristic changes
Homework
• Textbook Read Page 266. Using Science
graphics questions 1-3
Are all genes in each cell
expressed in every cell?
NO!
All of the 30,000 genes are in each
body cell but only specific genes are
expressed in specific cells
Differentiation
• The regulation of gene expression
• Different genes are expressed in different
cells
• Different cells build different proteins
Thursday 4/28/11
• AIM: How is human phenotype effected by
genetic mutations?
DO NOW: 1- How many base pairs make up
a single codon?
2- How many amino acids build all human
proteins?
Homework: Read 267-269. Reading Check
pages 267 and 269
DO NOW ANSWER
• 3 nitrogen bases=codon
• 64 codons in total
• 20 amino acids build all
proteins
• More than one codon for
a single amino acid
• This is why some
mutations have NO effect
on the polypeptide chain
How do you make a
polypeptide?
Gene-mRNA-ribosomecodon/anticodon bonding which makes
a long chain of amino acids
How are polypeptides related
to physical characteristics?
Polypeptides build proteins which
lead to chemical reactions that
cause physical traits
Functional protein
• Polypeptide: Long chain of
amino acids
– Combine with other
polypeptides
– Folds into a unique shape
– This makes a functional
protein
– The shape of a protein is
unique to its function
– If you change the shape, you
change the function
Denaturing a protein
• Changes the shape of the protein
• If the shape of the protein changes the
function changes or it does not function at
all.
• How would a protein get denatured?
– Gene mutation
– Mistake in mRNA modification
– Mistake in translation
– Mistake in polypeptide folding
• If my DNA makes a mistake, how will the
protein behave?
– The protein will have a different shape, and
without its shape, it cannot function properly
– Proteins are shape specific
– Denature: changes the shape of a protein
GENE Mutations
• Change in nucleotide sequence of bases
in a DNA molecule (gene)
• May or may not change the amino acid
sequence
• Nonsense mutation: gene sequence
changes but amino acid does not
• EX: normal DNA CTT mutated DNA: CTC
Assessment
How many amino acids build
all of the human proteins?
20
How many nitrogen bases
build RNA? 4
How many nitrogen bases make
up a codon? 3
How many codons are there?
64
Gene Mutations
• Nucleotide
substitutions: single
base pair is replaced
with a different
incorrect pair
• Insertion: addition of
1 or more base pairs
• Deletion: removal of
one or more base
pairs
Mutations
• How is the polypeptide changed if the
reading frame of an mRNA molecule is
changes from GGC to AGC?
• amino acid in the polypeptide chain is
changed from SER to GLY
• Mutation in reading frame of a gene could
result in protein dysfunction
Sources of mutations
• Mutagen: any chemical that causes a
change is nucleotide sequence of a gene
– Chemicals
– Medication
– Vaccine
– Radiation
– carcinogens
How are mutations inherited?
• If a mutation is in a gamete (sperm or
egg), it will be inherited by the zygote
Wednesday 3/10/10
• AIM: How can a genetic mutation effect
the phenotype of a human being?
• DO NOW:
How is the human genome
organized?
Autosomes: 1-22
23 pair sex chromosomes
XX=female
XY=male
Sex genetic disorders
Found on Y chromosome
• Deletion of SRY
• Deletion of DAZ
Found on X chromosome
• Red-green
colorblindness
• Hemophilia
Deletion of the SRY gene can
lead to XY females
• SRY: sex determining
region
Deletion of DAZ gene leads to
infertility in males
Sex-linked disorder
• found on the X chromosome
• female can have one copy of the allele
and be a carrier
• a male with one copy always display the
trait
Red Green Colorblindness
Hemophilia: on the X chromosome
• Inability for blood to clot
• People do not produce one of the proteins
necessary for proper blood clotting
Autosomal Genetic Disorders
• Found within Chromosomes 1-22
• If you mutate a gene, it may change the
shape of the protein that it codes for
Human Recessive Autosomal
Genetic disorders
• Homozygote Recessive is the only way to
display
• Heterozygotes are carriers
• Ex:
Achondroplasia (Dwarfism)
Sickle cell anemia
Cystic fibrosis
Albinism
PKU
Tay Sachs
Achondroplasia
• Dwarfism
• “without cartilage
formation”
• the defect is not in
forming cartilage but
in converting it to
bone
Sickle cell anemia
Sickle cell anemia
Sickle cell anemia
Sickle Cell Anemia
• Effects mostly South African Descendants
• Hemoglobin: protein in the red blood cell
that carries oxygen
• People with Sickle Cell Anemia make a
sickled shape hemoglobin protein
• Symptoms:
– Inability to carry oxygen
– Shortness of Breath
– Pain in Joints
– Coagulation of RBC’s
Cystic Fibrosis
• European descent
• 1:2500
• Lack of a cell
membrane protein
• Causes cells to
produce a thick
sticky mucous
Renal (kidney) cystic fibrosis
Albinism
• Albinism:
homozygous
recessive allele for
the enzyme
tyrosine which
builds melanin
• Melanin: protein
that gives skin
pigment
Phenylketonuria (PKU)
• Base substitution( G-A)
– Changes amino acid from ARG-GLU
Changes the shape of hydrooxylase enzyme
Enzyme cannot break down the amino acid PHE
(Phenylalanine)
• increases the levels of a substance called
phenylalanine in the blood
– Causes mental retardation and other serious
health problems
• If detected early, it can be treated by dieting
Phenylketonoria PKU
• Accumulation of the amino acid
phenylaline in the blood
• Mental Retardation
• Abnormal skin color
Tay Sachs disease
• Lipid accumulation in
brain cells
• Mental deficiency
• Blindness
• Death in childhood
• Blue stain shows
swollen neurons
Period 2 Friday 3/12/10
• AIM: How do chromosomal disorders differ
from genetic disorders?
• DO NOW: Explain why a heterozygote does
not display albinism but could have a child
with albinism.
• HOMEWORK:
• Textbook read pages 650-651. Observe fig
22.13. Is that child a male or female? How
do you know?
Human Dominant Disorders:
Huntington disease
• Genetic duplication: repeat of CAG
codon
• Causes string of glutamines (glu) in the
polypeptide chain of the huntington
protein
• Causes change in shape of huntington
protein
• Slow deterioration of brain and nervous
system
Huntington’s disease
Huntington Disease
• People usually have symptoms for up to 10 years before they find
out they have Huntington's disease.
• Most people are diagnosed between the ages of 30 and 50,
although this can happen much earlier or later.
• Symptoms are often overlooked, as they are mild and commonly
experienced by well people
• mild tremor
• clumsiness
• lack of concentration
• difficulty remembering things
• mood changes, including depression
• sometimes, aggressive antisocial behavior
per 6 Friday 3/12/10
• AIM: How are gene mutations different
from chromosomal mutations?
• DO NOW:Explain why a heterozygote
does not display albinism but could have a
child with albinism.
In your own words, explain the
relationship between genes and
chromosomes.
Gene vs chromosome
• Genes are on chromosomes
• Gene mutations: occur at the single gene
• Chromosomal mutations: loss or gain of
entire chromosome
Hypertrichosis: genetic disorder
excessive hair
growth over and
above the normal
for the age, sex
and race of an
individual
Exact cause is
unknown but has
been linked to a
spontaneous
mutation
Nondisjunction:
• Uneven distribution of chromosomes during
gamete formation
• Usually leads to spontaneous abortion or
severe disorders
Autosomal Disorders
•
•
•
•
Trisomy 21
Trisomy 8
Trisomy 13
These are the only trisomy’s that will lead
to full term fetal development
• Any other trisomy will cause spontaneous
abortion (miscarriage)
Nondisjunction and Down’s
syndrome
•
• one gamete has two 21st the
resulting fertilized egg has
three 21st chromosomes.
• 90% of the abnormal cells are
the eggs
• Trisomy 21
Mental retardation
Physical abnormalities
Down’s syndrome
Trisomy 8 and 13
Trisomy 8
• low-set or abnormally shaped ears and a
bulbous-tipped nose, eye abnormalities
• bone and tissue abnormalities,
• various structural heart problems,
• palate abnormalities
• mild to moderate mental delays
• deep hand and feet creases.
Trisomy 13
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Cleft lip or palate
Close-set eyes -- eyes may actually fuse
together into one
Decreased muscle tone
Extra fingers or toes (polydactyly)
Hernias: umbilical hernia, inguinal hernia
Hole, split, or cleft in the iris (coloboma)
Low-set ears
Mental retardation, severe
Scalp defects (absent skin)
Seizures
Single palmar crease
Skeletal (limb) abnormalities
Small eyes
Small head (microcephaly)
Small lower jaw (micrognathia)
Undescended testicle (cryptorchidism)
Nondisjunction of sex
chromosomes
•
Turner’s syndrome:
• XO: no sex hormones
lead to no
menstruation and no
secondary sex
characteristics
• Infertility
• Short stature, folds on
neck, more X linked
recessive disorders,
color blindness,
hemophilia etc.
Trisomy X
• 1 in every 1000 woman have 3 X
chromosomes
• Very tall
• Below normal intelligence
Klinefelter syndrome
• 1 in every 1000
males have XXY
• Most never even
know they have it
• partial breast
development,
widening of the hips
and small testis
• These men are
usually infertile
XYY males
•
•
•
•
High levels of testosterone
Severe acne
More than 6 feet tall
Lower IQ
Per 7
• AIM: How can pregnant woman get tested
for genetic and chromosomal disorders?
• DO NOW: In your own words, explain
what would happen to a zygote if it
contained 3 autosome 3’s.
How are genetic disorders
different from chromosomal
disorders?
Fetal Testing
•
•
•
•
•
Ultrasound
Amniocentesis
Chorionic Villus Sampling
Fetoscopy
Newborn Screening
Ultrasound
• Sounds waves are used to produce an
image
Fetoscopy
• Viewing scope is
placed into the
uterus creating an
image
• Enables blood
samples to be taken
• Detects Spina bifida
• Only done if there is
a history of birth
defects
Amniocentesis
• 14th-16th week
• 10 mL of amniotic fluid
• Looks at chemicals and molecules
present
• chromosomal disorders, including
Down’s syndrome, trisomy
13,18,Turner’s syndrome,
Kleinfelter’s syndrome
• Sickle Cell, Tay Sachs
• spina bifida and anencephaly
Chorionic Villus Sampling
8th-10th week
• Insert through the cervix
into the uterus
• Take a tissue sample
from the placenta
• Contain fetal cells which
divide more rapidly than
amniotic cells
New born Screening
• Examines newborn blood to detect genetic
disorders
• PKU: phenylketonoria
• Tay Sacs
• Treated with diet regulation
End Friday notes
Viruses: Genes in packages
• Basically is a piece of nucleic acid
surrounded by a protein
• Survives by infecting other cells with its
nucleic acid and taking over the cell
• Using the cells organelles to produce new
viral cells
Animal viruses
• Such as influenza or the mumps
• Surrounded by protein coat
• Protein coat attaches to cell membrane
and injects its nucleic acid in to the cell
cytoplasm
• New viral proteins and mRNA are
synthesized and often the animal cell is
destroyed
HIV: Human Immunodeficiency
virus
• Virus that causes AIDS:
autoimmunodeficiency syndrome
• Similar to the flu and mumps in that it is
surrounded by a protein coat
• Its nucleic acid is RNA: it is called a
retrovirus
• An RNA virus that reproduces by means of
a DNA molecule
HIV a retrovirus
• Carry molecules of RNA and a specific
enzyme called reverse transcriptase
• Reverse transcriptase: cause the
synthesis of a DNA strand from an RNA
template
Steps in HIV infection
• Reverse transcriptase makes a single strand of
DNA from an RNA template
• The new strand of DNA then builds a second
complementary strand
• The resulting double strand then enters the
nucleus and inserts itself into the genome:
provirus
• NOW EVERY TIME THE CELL DIVIDES THE
VIRAL DNA IS REPLICATED AND
TRANSCRIBED
HIV
• Infects and eventually kills several kinds of
white blood cells
• Causing the body to become susceptible
to many diseases
• SECONDARY infections cause the
development of AIDS
• AIDS: collection of symptoms
Treatment for HIV and AIDS
• Drugs interfere with the reproduction of the
virus
• AZT: blocks the synthesis of the HIV DNA
by binding to reverse transcriptase during
transcription.
– Structurally similar to Thymine
• Proteases: inhibit the synthesis of HIV
proteins making the virus unable to be
transmitted