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18 Cards in this Set
- Front
- Back
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CHROMOSOME
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length of DNA
1. 22 pair of autosomes (1a and 1b, 2a and 2b, etc...) 2. 1 pair of sex chromosomes |
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GENE
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DNA segment carrying information about a certain trait (eg. eye color)
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ALLELE
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different forms of the same gene (eg. blue, brown)
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HOMOZYGOUS
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both chromosomes in a pair have same allele (1a - blue and 1b - blue)
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HETEROZYGOUS
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chromosomes in pair carry different alleles (1a - blue and 1b - brown)
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GENOTYPE
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list of the specific alleles on the chromosomes (1a - blue and 1b - brown)
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PHENOTYPE
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outward expression of the genotype (person has brown eyes)
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DOMINANCE
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allele expressed in homo or heterozygous state eg. allele for brown eyes
1. 1a - blue and 1b - brown, phenotype = brown 2. 1a - brown and 1b - brown, phenotype = brown |
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RECESSIVENESS
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allele is expressed in homozygous state or if no dominant allele is present
Example: allele for blue eyes 1. 1a - blue and 1b - brown, phenotype = brown 2. 1a - blue and 1b - blue, phenotype = blue |
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CARRIER
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a person who expresses the dominant trait, but has a recessive allele
example: 1a – Brown and 1b - blue, phenotype = brown eyes (carrier of blue allele) |
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TYPES OF INHERITANCE:
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* one set of chromosomes come from sperm (c# 1-23)
* one set of chromosomes come from ovum (c# 1-23) * blending of alleles on chromosomes determines genotype and phenotype of new individual |
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SIMPLE DOMINANCE/RECESSIVENESS
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1. dominant alleles expressed in homo or heterozygous state (represent dominant alleles
with capital letter) inheritance of: tongue rolling, free earlobes, freckles, widows peak, polydactyly, brown eyes, hypercholesterolemia, Huntington’s disease, non- schizophrenia, non-cystic fibrosis, non-flat feet, non-TaySachs, non-PKU, not abino…. |
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SIMPLE DOMINANCE/RECESSIVENESS II
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2. recessive alleles expressed only in homozygous state (represent recessive alleles with
lower case letter) inheritance of: schizophrenia, albinism, flat feet, cystic fibrosis, blue eyes, Tay Sachs, PKU, non-tongue rolling, attached earlobes, no freckles, round hair line, five digit count, non-Huntington’s disease, normal cholesterol levels…. |
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EXAMPLE
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inheritance of brown and blue eyes
Key: B = brown allele b = blue allele mom genotype = Bb, phenotype = brown eyes dad genotype = Bb, phenotype = brown eyes potential contents of eggs: b or B potential contents of sperm: b or B potential ratio of offspring:(use Punnett square to determine) Mom Dad B b B BB (brown eyes) Bb (brown eyes) b Bb (brown eyes) bb (blue eyes) possible genotypes of offspring: 1BB: 2 Bb: 1 bb possible phenotypes of offspring: 3 brown eyes: 1 blue eyes |
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INCOMPLETE DOMINANCE (CODOMINANCE, SHARED DOMINANCE):
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allele is always expressed as well as at least one other allele for the gene
inheritance of: Thalassemia (hypochromic, abnormal RBCs), SICKLE CELL ANEMIA KEY: RS = sickled RBC's RN = normal RBC's genotype RS RN =, phenotype = 1/2 normal, 1/2 sickled RBC's |
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MULTIPLE ALLELE INHERITANCE
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more than two forms of the gene, more than
two alleles inheritance of ABO blood types is both incomplete dominance & multiple allele inheritance KEY: IA = A antigens on RBCs genotype phenotype IB = B antigens on RBCs IA IB type AB io = no antigens on RBCs IA i type A IA IA type A io io type O IB IB type B IB io type B |
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POLYGENIC INHERITANCE
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more than one gene (with associated alleles) is responsible for the phenotype of a trait. Results in many forms of the trait.
inheritance of skin color, height |
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SEX-LINKED INHERITANCE
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genes found only on the X chromosome are responsible for the trait (remember, the X chromosome carries more information than the Y chromosome).
inheritance of hemophelia, male pattern baldness, Duchenne muscular dystrophy, fragile X syndrome, ocular albinism, cleft palate, red-green colorblindness (all sex-linked - recessive) KEY: Xb = bald genotype phenotype XB = normal XB Xb normal female Y = no allele for Xb Xb bald female Baldness XB Y normal male Xb Y bald male |
