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.

• 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)

Genetics

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.

• Test cross – cross an unknown genotype with a known genotype (an individual showing the recessive trait, homozygous recessive)– # 8 in your monohybrid crossList 3 reasons why Gregor Mendel used pea plants1. Easy to grow/grow fast 2. Easy to pollinate b/c produce 2 distinct sex cells 3. Show sharply contrasting traits (round vs

wrinkled, green vs yellow, tall vs short)

Genetics