Chapter 9 Patterns of Inheritance Flashcards
Allele
One of several alternative forms of a particular gene.
Autosome
A chromosome that occurs in homologous pairs in both males and females and that does not bear the genes determining sex.
Codominance
The relation between two alleles of a gene, such that both alleles are phenotypically expressed in heterozygous individuals.
Cross-Fertilization
The union of sperm and egg from two individuals of the same species.
Crossing Over
The exchange of corresponding segments of the chromatids of two homologous chromosomes during meiosis.
Dominant
An allele that can determine the phenotype of heterozygotes completely, such that they are indistinguishable from individuals homozygous for the allele; in the heterozygotes, the expression of the other (recessive) allele is completely masked.
Dystrophin
Muscle cells are firmly tired together by a gigantic protein called dystophin. The almost 3,700 amino acids of dystrophin from a supple yet strong rod that connects the cytoskeleton inside a muscle cell to proteins in its plasma membrane, which in turn attach to proteins that form a fibrous support surrounding each muscle.
Gene
A unit of heredity that encodes the information needed to specify the amino acid sequence of protiens and hence particular traits; a functional segement of DNA located at a particular place on a chromosone.
Genotype
The genetic composition of an organism; the actual alleles of each gene carried by the organism.
Heterozygous
Carrying two different alleles of a given gene; also called hybrid.
Homozygous
Carrying two copies of the same allele of a given gene; also called true-breeding.
Incomplete Dominance
A pattern of inheritance in which the heterozygous phenotype is intermediate between the twe homozygous phenotypes.
Inheritance
The genetic transmission of characteristics from parten to offspring.
Law of Independant Assortment
The independant inheritance of two or more distince traits; states that the alleles for one trait may be distributed to the gametes independantly of the alleles for other traits.
Law of Segregation
Gregor Mendel’s conclusion that each gamete recives only one of each parent’s pair of genes for each trait.
Linkage
The inheritance of certain genes as a group because they are parts of the same chromosome. Linked genes do not show independant assortment.
Locus(plural, loci)
The physical location of a gene on a chromosome.
Muscular Dystophy
A group of inherited disorder that result in degeneration of muscle tissue.
Nondisjunction
An error in meiosis in which chromosomes fail to segregate properly into the daughter cells.
Pedigree
A diagram showing genetic relationships among a set of individuals, normally with respect to a specific genetic trait.
Phenotype
The physical characteristics of an organism; can be defined as outward appearance (such as flower color), as behavior, or in molecular terms (such as glycoproteins on red blood cells.)
Pleitropy
A situation in which a single gene influences more than one phenotypic characteristic.
Polygenic Inheritance
A pattern of inheritance in which the interaction of two or more functionally similar genes determine phenotype.
Punnett square method
An intiutive way to predict the genotypes and phenotypes of offspring in specific crosses.
Recessive
An allele that is expressed only in homozygotes and is completely masked in heterozygotes.
Self-fertilization
The union of sperm and egg from the same individual.
Sex Chromosone
One of the pair of chromosomes that usually determines the sex of an organism; for example, the X and Y chromosomes in mammals.
Sex-linked
Referring to a pattern of inheritance characteristic of genes located on one type of sex chromosone (for example, X) and not found on the other type (for example, Y); also called X-linked. In sex-linked inheritance, traits are homozygous recessive, whereas males express whichever allele is on their single X chromosome.
