Genetics Terms

Genetics Heredity – passing of traits from one generation to the next. Genetics – “study of heredity” Traits – inherited characteristics

Genetics Allele – different copies or forms of a gene controlling a certain trait (eye, hair color) Dominant – the observed or expressed trait (prevents the expression of a recessive allele) Recessive – trait that can be hidden by a dominant gene. * not expressed unless homozygous

Genetics Gene – “basic unit of heredity” Gamete – egg or sperm cells with haploid # of chromosomes (sex cells) Homozygous – when alleles for a specific trait are the same (BB/bb) Heterozygous – when alleles for a specific trait are different (Bb)

Genetics Genotype – genetic makeup of an organism. The combo of alleles that an organism inherits for a certain trait. “Letters” (BB, Tt, Dd) Phenotype – the expression of the genotype or physical appearance that an organism shows. “Look like” (brown, tall, dimples)

Genetics Haploid – (n) ½ the # of chromosomes *having 1 set of chromosomes Diploid – (2n) 2x’s the haploid # of chromosomes *having 2 sets of chromosomes Chromosome – a strand of DNA that functions in the transmission of traits. Zygote – a cell resulting from the union of the gametes *fertilized egg

Genetics Hybrid – organisms that are heterozygous and result from two different pure lines. Parent generation – 1st generation of parents F1 generation – 1st generation of offspring F2 generation – 2nd generation of offspring

Genetics Law of Dominance – when pure organisms are crossed with contrasting traits, all offspring will show the dominant trait.

Genetics Law of Segregation – during egg/sperm formation, the pair of genes/alleles for a trait separate so that each gamete has only one of the genes for the trait (one from mom and one from dad) Individuals have two genes for each trait, one from the mother & one from the father. During sperm & egg formation, these two genes separate, so that each sperm or egg has only one gene. (Note: this applies only to diploid individuals & simple traits.) Example, a child gets one blue-eyed gene from the mother and one brown-eyed gene from the father. When this child reproduces, each egg or sperm will contain only one of the eye color genes.

Genetics Law of Independent Assortment – as gametes are formed the genes for various traits separate independently of each other. Exp….eye color does not influence hair color Exp: The eye color genes are Brown (B) and blue (b) and the ear lobe genes are free (F) and attached (f). The genes assort independently, so that each egg or sperm obtains 1 of each trait (BF, Bf, bF, bf).

Genetics Punnett square – indicates ratio of genotypes and phenotypes of possible offspring. Cross – an exchange of genetic information.

Genetics Test cross – cross an unknown genotype with a known genotype (an individual showing the recessive trait, homozygous recessive) # 8 in your monohybrid cross List 3 reasons why Gregor Mendel used pea plants Easy to grow/grow fast Easy to pollinate b/c produce 2 distinct sex cells Show sharply contrasting traits (round vs wrinkled, green vs yellow, tall vs short)