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GeneticsGenetics
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 characteristicsfrom 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
b. original plant: P (parental)
c. 1st generation: F1 (first filial)
6. conclusions:a. biological inheritance
is passed from one
generation to the next
1) chemical factors that determine traits: genes
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 segregation principle
3. Homozygous
a. 2 identical alleles for a trait.
ex: AA, aa
b. true breeding
4. Heterozygous
a. 2 different alleles for a trait
ex: Aa
b. hybrid
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
A
AA AA
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 Yt ty
TY
TY
TY
TY
TTYY
TTYY
TTYY
TTYY
TTYy
TTYy
TTYy
TTYy
TtYY
TtYY
TtYY
TtYY
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 molecule 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 recessive & no surface protein
f. Rh factor
1. Rh positive: Rh+/Rh+, Rh+/Rh-
2. Rh negative: Rh-/Rh-
3. Parents donate 1 Rh factor
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 Syndrome1) fluorescent in situ
hybridization, or FISH
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
eye color located on X
eye color located on
X
What can we
conclude?
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
1. clone: genetically identical copy of a gene
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:
- map & sequence all DNA base pairs in
human chromosome
- identify all the genes within the sequence
b. 13 year project: 1990-2003
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