Download ANTH 2301 - Week 4 DNA

10/11/16
Biological function
Analyzes an
organism
minus one
trait
GENES
Analyzes a
single trait
DNA
PROTEINS
DNA
DNA
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o
x x
o
x x
x
x
1. Source of
variation ??
x
o
o
3. Differential Survival
2. Selective Pressure
(MENDELIAN
o
xo o
o o
o o
GENETICS)
The Next
Generation
These two share 99.9% of
the same DNA
?
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These two share 98.7% of
the same DNA
Deoxyribonucleic Acid
¡
The DNA molecule provides the codes for
biological structures and the means to
translate this code.
¡
DNA provides information for building,
operating, and repairing biological
organisms.
DNA goes here
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Molecular Genetics
¡
The structure of DNA
÷
Ladder “rungs” represent
chemical units called
nucleotide bases.
÷
There are four possible types
of bases:
÷
A (adenine)
÷
T (thymine)
÷
G (guanine)
÷
C (cytocine)
A CT G
T G A C
3 billion
base pairs
Replication
• Double stranded DNA unzips (parent strand)
T GGT ACAGC T AG T CA T CG T A CCG T
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Replication
Formation of daughter strands
T GGT ACAGC T AG T CA T CG T A CCG T
Replication
T GGT ACAGC T AG T CA T CG T A CCG T
DNA Copy fidelity
• DNA replication, on average, has one mistake
per 109 bases (or 1 in 1,000,000,000)
• Which is fabulous…but it means you get 3 errors
on average every time your cells divide…
• You have
37 trillion cells
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Protein synthesis (doesn’t this look fun?!)
Protein Synthesis
replication
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Transcription - mRNA
• RNA bases match to DNA bases on one daughter
strand
C
AG
A
A CC
U
C
G
GUC
T GGT ACAGC T AG T CA T CG T A CCG T
Transcription
AT G GA C GTA
Take a strand of DNA
UA C C U G CA U
Matching RNA
Parental strand of DNA unzips, exposing two daughter strands of DNA
Free-floating RNA matches up to one exposed section of DNA
•
mRNA
(fraction)
Translation
CODON
UA C
AA1
A U G CA U G UA
G UA
RNA moves out into the
cytoplasm of the cell, binds
with amino acids, and connects
them into proteins
AA2
AA3
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Proteins
Insulin - comprised of 50 amino acids That means that
there are 150
base pairs
Genes
¡
Gene refers to a section of DNA that has an identifiable
function, such as the gene that determines a particular blood
group.
A G ............T C C
“Codes” for some protein. This is a
gene
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• Exons - Sections of
DNA that code for
amino acids which
make up proteins (1
%)
• Introns - Sections
of DNA which DON T
code for anything
(92%)
•
•
•
Junk DNA
Old Code
Regulatory genes don t code for proteins
but do regulate
development (7%)
¡ Meiosis: The creation of sex cells by replication
of chromosomes followed by 2 cell divisions. Each sex
cell then contains 50 percent of an individual s
chromosomes (one from each pair).
N
N
N
2N
N
N
N
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A
Gene is a section of DNA that has an identifiable function
• the formation of new and distinct species
• its easy to say that two species have diverged
and they will continue to grow apart
• it is much harder to say what caused that
divergence
Speciation
Mutations
¡ Mutations
are
changes in the
genetic code due to
DNA copy errors and
the ultimate source
of all genetic
variation.
¡ Most
mutations are
small and
unremarkable
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Blue eyes are a mutation too
Mutations
¡
Mutations are caused by a
number of environmental
factors such as background
radiation, heat, and ingested
substances such as caffeine.
You can t avoid this...radiation
comes from the ground and
space!
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Mutations
¡ Mutations
can take
place in any cell of
the body. To have
evolutionary
importance, the
mutation must occur
in a sex cell.
Mutations
— Evolutionary Significance of Mutations
¡
Specific mutations are random. There is no way of predicting when they will
take place.
Mutations
— Evolutionary Significance of Mutations
¡
Mutations can have different impacts on an organism, depending on the specific type
of mutation and the environment.
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Mutations
NOT inheritable
Full chromosome
mutations
Point Mutations
inheritable
Polyploidy
x
Aneuploidy
Monosomy
Trisomy
Point Mutations
¡
Mutations can involve changes in a single DNA base or in larger
sections of DNA
Sickle cell mutation
¡
Sickle cell mutation is an
example of a single base copy
error (aka point mutation)
¡
Mutation in the hemoglobin gene
¡ In the 6th amino acid, there is
a copy error which turns GTC
into GAC
¡
Causes blood cells to become
misshapen and not carry oxygen
efficiently
¡
NOT a recessive condition
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Sickle Cell Anemia
™ A person must be
HOMOZYGOUS for the sickle
cell allele to manifest sickle
cell anemia
™ Symptoms include:
™ fatigue
S
Sc
S
SS
S Sc
Sc
S Sc
Sc Sc
™ swelling of joints
™ chromic pain
™ difficulty breathing
™ shortened life expectancy
but...and it is a big but!
™ People who are heterozygous
for sickle cell mutation are not
affected by anemia
™ AND...they are highly resistant
to malaria
™ 33 % of all indigenous
inhabitants of sub-Saharan
Africa carry the mutation
™ 1/500 African Americans are
born with Sickle Cell Anemia
Full chromosome defects
¡
Mutations can involve changes
in an entire chromosome.
¡
Polyploidy – multiple evennumbered copies of
chromosomes (beyond the
normal 2)
¡
Aneuploidy – odd-numbered
copies of chromosomes
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¡ Meiosis: The creation of sex cells by replication
of chromosomes followed by 2 cell divisions. Each sex
cell then contains 50 percent of an individual s
chromosomes (one from each pair).
N
N
N
2N
N
N
N
Monosomy
Occurs in 1:2,000 females
¡
Monosomy is a condition in
which one chromosome rather
than a pair is present in body
cells.
¡
Very uncommon in humans generally the human dies
during gestation
¡
Exception - Turner Syndrome
¡ Woman receives one X
(instead of the usual 2 X’s)
¡
Results in physical
abnormalities, absence of
menstrual cycle, sterility
Trisomy
¡
Trisomy is a condition in
which three
chromosomes rather
than a pair occur in body
cells.
¡
Generally caused by
meiotic non-disjunction
¡
Very common
¡ Trisomy 16 occurs in
1% of human
conceptions
¡ Most common reason
for miscarriages
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Klinefelter s syndrome
™ Male receives XXY trisomy
™ 1 / 500 males
™ Phenotype:
™ Taller than average
™ Less muscle development
™ Increased development of
breast tissue
™ Lower serum testosterone
levels
Down Syndrome
™ Incidence of 1 in 800 births
™ Increases with age of mother
™ Numerous features - not all of which
are present in all individuals
™ mild-moderate mental
retardation, almond shaped
eyes, enlarged tongue, poor
muscle tone, general sterility
™ All have errors on the gene that
causes Alzheimer s
™ Average life expectancy - 60
Rates of mutations
¡
Specific mutations are relatively rare events.
¡
Estimated range in the rates of mutations in humans: 1 to 10
mutations per million genes per generation.
¡
Mutations are more apparent if they involve a dominant allele.
¡
Harmful mutations may result in spontaneous abortion before a
pregnancy is detected.
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o
x x
o
x x
x
x
1. Source of
variation (new DNA
copy errors)
x
o
2. Selective Pressure
o
3. Differential Survival
(Mendelian Genetics)
The Great
Biological
Synthesis
o
xo o
o o
o o
4. The Next
Generation
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