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Heredity 2


undefined, object
copy deck
represents the genetic material on a chromosome that contains the instructions for creating a particular trait. Since the formula for carrying out these instructions is described by a genetic code, a gene is often said to CODE for a trait
Multiplication Rule
When you multiply the probabilities of each event happening separately
one of several varieties of a gene
location on a chromosome where a gene is located, every gene has a unique locus on a particular chromosome
homologous pair
pair of chromosomes, one from each parent
Gene Pair
two genes on a pair of homologous chromosomes at any one particular locus
Homozygous Dominant
refers to the inheritance of two dominant alleles where the dominant trait is expressed
Homozygous Recessive
when two recessive alleles are inherited (pp) and the recessive trait is expressed
condition where two inherited allels are differnt (Pp) and only the dominant allele is expressed
actual expression of a gene
represents the actual alleles
law of segregation
refers to the random segregation of alleles and their chromosomes to separate gametes
Law of Independent Assortment
fact that homologous chromosomes, and the genes they carry, segregate independently of the segreation of other chromosome pairs
credited with discovery of laws of segregation and independent assortment = pea plants
mating two varieties of an organism
product of crossing
monohybrid cross
when a cross involves a gene for only one trait
P generation
represents the parents
F1 generation
offspring of crossing of the parents
F2 generation
offspring produced from crosses among the F1 (F= filial= sons and daughters)
Test Cross
mating of an individual whose genotyple you are trying to determine with an individual whose genotype is known
Dihybrid Cross
when genes for two different traits are observed at the same time
Incomplete Dominance
when the combined expression of two differnt alleles in the heteozygous condition produced a blending of the individual expressions of the two alleles
When both inherited alleles are completely expressed as n blood types of molecules that appear on surface of human red blood cells
foreign substances
what happens after antibodies attack the antigens and there is climping of the blood (after wrong blood types)
A blood type
B blood type
AB blood type
O blood type
universal donor
O blood type
occurs when one gene affects the phenotypic expression of a second gene (pigmentation)
snapdragons, wavy hair
examples of incomplete dominance
occurs when a single gene has more than one phenotypic expression
contintous inheritance, polygenic inheritance
the interaction of many genes to shape a single phenotype (opposite of pleiotropy)
Linked Genes
genes that reside on the SAME chromosome and thus cannot segregate independetly because they are physically connected, and they are usually inherited together
Linked Genes in fruit flies
body color and wing stucture are linked
Linkage Map
portrayal of the sequence of genes on a chromosome
cytological map
map portraying the true relative positions of the genes and requires additional experimental analyses
Sex Chromosomes
X and Y chromosomes
chromosomes that are not sex chromosomes
X-linked genes that reside on the X chromosome.
genes are possible but so few genes reside on the Y chromosome so it is rarely encountered
when one of the two X chromosmes in a female remains coiled as a dark compact body called a Barr body
Barr Body
result of x-inactivation and most of the only the alleles of the genes on the one active C chromosome are expressed by that cell , so there is a mixture of different traits like in a Calico cat
the chromosomes do not properly separate so BOTH members of a homologous chromosome pair migrate to the same pole so half the gametes will have an extra chromosome and they are usually sterile. leads to down syndrome and turner syndrome
Down Syndrome
occurs when an egg or sperm with an extra 21 chromosome fuses with a normal gamete and the result is a zygote with three copies of chromosome 21 (TRISOMY 21). these individtuals bear various abnormalities like mental retardation, heart defects, respiratory problems, and external deformities
Turner Syndrome
when there is nondisjunction of the sex chromosomes and sperm will either have XY or no chromosome (O). Eggs will also either be XX or O. The turner syndrome zygote (XO) is a female who has one X and no second crhomosome. Individuals are physically abnormal and sterile
when one or more chromosomes have portions deleted
when one or more chromosomes have portions duplicated
when one or more chromosomes have moved to another chromosome
when chromosomes are rearranged in reverse orientation on the same chromosome
autosomal recessive, inability to propoerly break down the amino acid- phenylaline. Accumulation of this amino acid in untreated children causes mental retardation. Sympotns can be avoided with diets low in phen.
Sickle-Cell Anemia
autosomal recessive- abnormal hemoglobin. Red blood cells of individuals with this defect are unable to effectively transport oxygen throughout the body
Tay-Sachs Disease
autosomal recessive- inability to break down certain lipids and the accumaltion of lipids in brain cells causes progressive nervous system dysfunction and is usually fatal by age four
Huntington's Disease
autosomal dominant- expression begins in middle age with mild mental illness and loss of motor control processing to total physical and mental incapability
sex-linked recessive- inability to code for a clotting factor required to form normal blood clots
red-green color blindness
sex-linked recessive- inablity to distingish red from green
Duchenne's muscular
sex-linked dominant- absence of an essential muscle protein, results in dystrophy deteriorating muscles and loss of corrdination
Klinefelter Syndrome
nondisjunction of sex chromosomes- XXY and male, union of XX gamete and normal Y gamete. Sterile and often metally retarded
Cri du chat syndrome
deletion in chromosome 5- physical and mental retardation and catlike cry (it is french of "cry of the cat")

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