| A | B |
|---|
| Law of Dominance | When an organism is hybrid for a pair of contrasting traits, only the dominant trait can be seen in the hybrid. |
| 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 |
| incomplete dominance | 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 |
| crossing-over | pieces of homologous chromosomes are exchanged during meiosis |
| DNA replication | forms two new molecules of DNA, each with one old strand and one new strand |
| messenger RNA | a strand of RNA that copies a genetic message from DNA |
| codon | a group of three bases on mRNA that specifies an amino acid |
| transfer RNA | a molecule of RNA that carries an amino acid to the ribosome in order to assemble a protein |
| anticodon | a sequence of 3 bases in tRNA that is complementary to the codon of mRNA |
| transcription | the formation of codons by the mRNA |
| translation | process by which information in mRNA is used by tRNA to assemble a protein |
| mutation | sudden change in structure or amount of DNA |
| types of chromosomal mutations | addition, deletion, translocation, inversion, nondisjunction, polyploidy |
| types of gene mutations | point mutation, frameshift mutation |
| 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 |
| human chromosomal disorders | Down syndrome, Klinefelter's syndrome, Turner's syndrome |
| 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 |
| gene therapy | replacement of defective genes by transferring normal genes into cells that lack them |
| genome | all of the genes possessed by an organism |
| pedigree | chart that shows the lineage of a particular trait |
