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Genetics
I. Genetics
A. Gregor Mendel
1. 1st study on heredity
a. passing of
characteristics from
parents to offspring.
2. Occupation: monk
3. Worked with pea plants
a. self-pollinators meaning inherit all
characteristics from the original plant or
identical: true-breeding.
b. Produce sexually sperm & egg: gametes
1) sperm: pollen; egg: ovule
4. Cross pollination – pollen from one plant
fertilizes egg from another
a. hybrid: offspring have different
characteristics from parents
5. Trait: specific characteristic
a. studied 7 traits – p. 262, Green 179)
b. original plant: P (parental)
c. 1st generation: F1 (first filial)
6. conclusions:
a. biological
inheritance is
passed from one generation to the next
genes
1) chemical factors
that determine
traits:
2) genes controlled by 2
different
characteristics per
trait: allele
ex. Height – short/tall
b. Principle of Dominance: some alleles are
dominant & some recessive.
1) upper case= dominant
ex: A
2) lower case= recessive
ex: a
7. Did the recessive alleles disappear? p. 261, 274
a. F1 crossed short & tall
plants= all tall
b. F2 self-pollination
1) ¼ of F2 generation
showed recessive
trait
8. Law of segregation: 2 alleles will separate during
gamete formation. p. 264
9. Law of independent assortment: genes for
different traits will sort independently.
ex: blue eyes/blonde hair
II. Probability & Punnett Squares
A. Principle of probability can be used to predict
outcomes of genetic crosses.
What is the probability that a tossed coin will come up heads?
B. Punnett squares show gene combination that
might result from a genetic cross.
1. Reginald Punnett
2. follows Mendel’s
principle
segregation
3. Homozygous
trait.
a. 2 identical alleles for a
ex: AA, aa
b. true breeding
4. Heterozygous
a. 2 different alleles
ex: Aa
b. hybrid
for a trait
5. Phenotype:
a. physical characteristic
ex: brown hair
6. Genotype:
a. genetic makeup
ex. DNA
7. Monohybrid cross: 1 trait ex: AA x Aa (p. 266, 276)
A
A
A
AA
AA
a
Aa
Aa
8. Dihybrid cross: 2 traits (p. 267, 187)
ex: TtYy x TTYY
(Tt) (Yy) = TY, Ty, Yt, ty
(TT) (YY) = TY, TY, TY, TY
TY
Ty
tY
ty
TY
TTYY
TTYy
TtYY
TtYy
TY
TTYY
TTYy
TtYY
TtYy
TY
TTYY
TTYy
TtYY
TtYy
TY
TTYY
TTYy
TtYY
TtYy
III. Beyond Dominant & Recessive Alleles
A. Incomplete Dominance: one allele is not
completely dominant over the other.
1. F1 generation of four o’clock plants:
a. red-flowered (RR) and white-flowered (WW)
b. offspring (RW): pink-colored flowers
x
=
B. Codominance: both allels contribute to the
phenotype of the organism.
1. Roan cows – have both red and white hair;
some can look pink
2. Sickle-cell anemia: homozygous, hemoglobin
forms crystal-like structures that change the
shape of the RBC.
a. cause slow blood flow, blockage, tissue damage
& pain
b. anemia: low # of RBC
C. Multiple Alleles: a gene could have more than 2
alleles.
1. coat color in rabbits
Full color: CC, Ccch, Cch, Cc
Himalayan: chch, chc
Chinchilla: cchcch, cchch, cchc
Albino: cc
2. Blood types p. 331
a. determined by presence or absence of
certain protein on surface of RBC
b. Phenotype A: Ia is
dominant to i
c. Phenotype B: Ib is
dominant to i
d. Phenotype AB: Ia & Ib are codominant.
e. Phenotype O: i allele is
surface protein
recessive & no
f. Rh factor
1. Rh positive:
Rh+/Rh+, Rh+/Rh/Rh-
2. Rh negative:
3. Parents donate 1
Rh factor
Rh-
D. Polygenic Traits: traits controlled by 2 or more
genes.
1. skin color in humans – 4 diff. genes control trait
IV. Meiosis
A. Diploid vs. haploid
B. Homologous chromosomes
C. 2 cellular divisions
D. Genetic recombination
E. Meiosis I
1. Prophase I:
a. crossing over
b. tetrad
F. Meiosis II
1. very similar to mitosis
G. Mistakes
1. Nondisjunction: failure of homologous
chromosomes to separate
2. Trisomy: gamete with an extra chromosome is
fertilized by a normal gamete.
a. Klinefelter Syndrome
3. Zygote with an extra 21st chromosome: Down
Syndrome
4. Monosomy: gamete with a missing chromosome
is fertilized with a normal gamete.
a. usually do not survive
b. Turner’s syndrome
5. A gamete with an extra set of chromosomes is
fertilized by a normal haploid gamete: triploid
ex. Apples (3n)
6. Organisms with more than the usual # of
chromosome sets are called polyploidy.
ex. Day lily
a. flowers & fruits are larger & plant
healthier
V. Human Heredity
A. Karyotype: picture of chromosomes arranged in
pairs from largest to
smallest.
1. Used to see chromosomal abnormalities or genetic
disorders.
2. 44 or 22 pairs of chromosomes are autosomes.
3. 2 of the 46 chromosomes are sex
chromosomes
a. 46XX; 46XY
4. Additional abnormalities:
a. Cri-du-chat
b. Williams Syndrome
1) fluorescent in situ
or
FISH
hybridization,
c. Reciprocal Translocation: Philadelphia Chromosome
d. Robertsonian Translocation
Find cause, symptoms, treatment for:
1. Klinefelter Syndrome
9. Tay-Sachs
2. Turner’s syndrome
10. Cri-du-chat
3. Williams Syndrome
11. Phenylketonuria
4. Philadelphia Chromosome
5. Robertsonian Translocation
6. Cystic Fibrosis
7. Huntington’s Disease
8. Sickle-cell Anemia
B. Pedigree Chart: shows relationships within a
family.
Key:
male
female
carrier
affected
1. Sex-linked traits: traits controlled by genes
located on sex chromosomes.
a. Thomas Morgan
1) Fruit flies
What can we
conclude?
eye color located on X
eye color located
on X
b. Color blindness, muscular dystrophy, &
anemia
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VI. Biotechnology
A. Manipulating DNA
1. Restriction Enzymes
a. Endonuclease
b. cut DNA at specific nucleotide sequences
c. blunt ends
d. sticky ends
2. Gel electrophoresis
a. once DNA is cut has to be sorted
b. done according to size
c. moves toward + end b/c DNA
is -
d. Small fragments move farther
e. Restriction map: shows length of DNA b/w
restriction sites
gel
B. DNA Fingerprinting
1. Looks at repeating DNA sequences
2. similar, but will not
all be the same
3. used in families, crime
scenes
C. Genetic Engineering
gene
1. clone: genetically
identical copy of a
a. take out nucleus
of cell
and replace with nucleus
of another cell –nuclear
transfer
2. controversial?
a. success rate is low
b. health problems
c. grow faster
d. expensive
3. Recombinant DNA: DNA that contains genes
from more than 1 organism.
a. Uses bacteria cell
b. plasmids: tiny rings of DNA found in
bacteria
4. Selective breeding: humans alter the genotype
and phenotype of organism
Ex: labradoodle
corn
5. Human Genome Project
a. 2 main goals:
in
- map & sequence all DNA base pairs
human chromosome
- identify all the genes within the
sequence
b. 13 year project: 1990-2003
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