| A | B |
|---|
| Law of Segregation | factors (genes) that occur in pairs are separated from each other during meiosis and recombined at fertilization |
| chromosomes | genes are found on these structures |
| gene | a sequence of nucleotides in DNA that codes for a particular protein |
| alleles | different forms of the same gene (ex: T or t) |
| homozygous | containing two alleles that are the same (ex: tt or TT) |
| heterozygous | containing two alleles that are different (ex: Tt) |
| genotype | the genetic makeup of an organism (ex: Tt) |
| phenotype | the physical trait that an organism develops as a result of its genotype (ex: tall) |
| Law of Independent Assortment | During meiosis, genes for different traits are separated and distributed to gametes independently of one another |
| intermediate expression | occurs when two alleles contribute to the phenotype;traits blend |
| codominance | both traits are expressed at the same time |
| multiple alleles | more than two alleles for the same trait (ex:blood type in humans) |
| genotype of a male | XY |
| genotype of a female | XX |
| sex chromosomes | chromosomes that determine the sex of an organism |
| sex-linked traits | traits that are controlled by genes on the sex chromosomes (usually the X) |
| examples of sex-linked traits in humans | hemophilia, color-blindness |
| linkage group | all of the genes that are on the same chromosome |
| crossing-over | pieces of homologous chromosomes are exchanged during meiosis |
| polygenic trait | when two or more independent genes affect one trait |
| nucleotides | building blocks of nucleic acids (RNA and DNA) |
| oncogenes | genes that cause some kinds of cancer |
| mutation | change in structure or amount of DNA |
| chromosomal mutation | change in the structure of all or part of a chromosome |
| gene mutation | change that affects a gene on a chromosome |
| mutagens | environmental factors that cause mutations |
| nondisjunction | the addition or loss of a whole chromosome due to failure of homologous chromosomes to separate during meiosis |
| point mutation | substitution of one nucleotide for another, resulting in change in one codon, one amino acid |
| frameshift mutation | deletion or addition of a nucleotide, resulting in change in every codon after that point |
| karyotype | a chart showing all of an organism's chromosomes, arranged in homologous pairs |
| genetic engineering | manipulation of DNA to produce changes in an organism |
| restriction enzymes | enzymes used to cut DNA into fragments in order to isolate a gene |
| recombinant DNA | DNA formed by inserting a gene from one organism into the DNA of a different organism |
| transgenic organism | an organism that contains genes from a foreign organism |
| gene therapy | replacement of defective genes by transferring normal genes into cells that lack them |
| genome | all of the genes possessed by an organism |
| dominant | a trait that masks another; represented by a capital letter |
| recessive | a trait that is only expressed in the homozygous form |
| Mendel | the father of genetics ( studied pea plants) |
| Punnett square | used to predict probable outcomes of crosses |
| trait | factors or characteristics of an organism |
| heredity | the passing of traits from parents to their offspring |
| genetics | the study of heredity |
| selective breeding | deliberately breeding certain individual organisms to get certain traits, ex:breeding cows to be resistant to anthrax |
| gene mapping | finding the position of specific genes on a chromosome |
| sex chromosome | the 23rd pair of chromosome in humans |
| carrier | the individual which carries the recessive gene for a trait |
| PKU | an inherited disease which causes brain damage and mental retardation, all babies are tested for this at birth |
| sickle-cell anemia | inherited disease which causes red blood cells to take on a sickle shape |
| F2 | second filial generation; the "grandchildren" |
| F1 | first filial generation; the "children" |
| P | parental generation |
| test cross | used to determine the genotype of an unknown individual; cross the individual with a homozygous recessive individual |
| pedigree | used to interpret patterns of inheritance within a family |
