Heredity 2
Terms
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- Gene
- 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
- Allele
- one of several varieties of a gene
- Locus
- 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
- Heterozygous
- condition where two inherited allels are differnt (Pp) and only the dominant allele is expressed
- Phenotype
- actual expression of a gene
- Genotype
- 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
- Mendel
- credited with discovery of laws of segregation and independent assortment = pea plants
- Crossed
- mating two varieties of an organism
- hybrid
- 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
- Codominance
- When both inherited alleles are completely expressed as n blood types of molecules that appear on surface of human red blood cells
- antigens
- foreign substances
- aggulination
- what happens after antibodies attack the antigens and there is climping of the blood (after wrong blood types)
- IAIA
- A blood type
- IBIB
- B blood type
- IAIB
- AB blood type
- ii
- O blood type
- universal donor
- O blood type
- epistasis
- occurs when one gene affects the phenotypic expression of a second gene (pigmentation)
- snapdragons, wavy hair
- examples of incomplete dominance
- Pleiotropy
- 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
- autosomes
- chromosomes that are not sex chromosomes
- Sex-Linked
- X-linked genes that reside on the X chromosome.
- Y-linked
- genes are possible but so few genes reside on the Y chromosome so it is rarely encountered
- X-inactiviation
- 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
- nondisjunction
- 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
- deletion
- when one or more chromosomes have portions deleted
- duplication
- when one or more chromosomes have portions duplicated
- translocation
- when one or more chromosomes have moved to another chromosome
- inversion
- when chromosomes are rearranged in reverse orientation on the same chromosome
- Phenylketonuria
- 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
- Hemophilia
- 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")