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18 Cards in this Set

  • Front
  • Back
CHROMOSOME
length of DNA
1. 22 pair of autosomes (1a and 1b, 2a and 2b, etc...)
2. 1 pair of sex chromosomes
GENE
DNA segment carrying information about a certain trait (eg. eye color)
ALLELE
different forms of the same gene (eg. blue, brown)
HOMOZYGOUS
both chromosomes in a pair have same allele (1a - blue and 1b - blue)
HETEROZYGOUS
chromosomes in pair carry different alleles (1a - blue and 1b - brown)
GENOTYPE
list of the specific alleles on the chromosomes (1a - blue and 1b - brown)
PHENOTYPE
outward expression of the genotype (person has brown eyes)
DOMINANCE
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
RECESSIVENESS
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
CARRIER
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)
TYPES OF INHERITANCE:
* 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
SIMPLE DOMINANCE/RECESSIVENESS
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….
SIMPLE DOMINANCE/RECESSIVENESS II
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….
EXAMPLE
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
INCOMPLETE DOMINANCE (CODOMINANCE, SHARED DOMINANCE):
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
MULTIPLE ALLELE INHERITANCE
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
POLYGENIC INHERITANCE
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
SEX-LINKED INHERITANCE
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