How many total chromosomes make up who you are? Remember… With the exception of gametes (aka egg and sperm), ALL CELLS in your body are diploid and contain two copies of each chromosome One copy from mom (in her egg) One copy from dad (in his sperm) How many total chromosomes make up who you are?

Genes: sections of DNA that provide instructions for making protein. Since a gene is a piece of a chromosome and we have two of every chromosome, we have two copies of instructions to make every protein in our body Alleles: different versions of the same gene We inherited a full set of chromosomes (containing genes) from each of our parents, but we may not have inherited the same version of every gene (Ex. Mom gave you a gene for blue eyes and dad gave you a gene for brown eyes) Homologous Chromosomes: the matching chromosomes from our mom and dad They contain the same genes in the same locations, but may contain different alleles

Gregor Mendel Gregor Mendel – Austrian monk who used pea plants to learn about genetics. He is known as the “Father of Genetics” 3 Laws of Inheritance: Law of Dominance Law of Segregation Law of Independent Assortment Mendel Image: © AndreaLaurel 2012 https://flic.kr/p/cnYjc9

Mendel’s Experiments Mendel studied and bred plants. He made 3 choices about his experiments: Had control over breeding Mendel used pea plants that typically self-pollinate. Used only purebred plants Purebred – type of organism whose ancestors are genetically uniform Observed “either-or” traits Chose pea shape, pea color, pod shape, pod color, plant height, flower color

What is a Cross? Cross – mating of 2 organisms P = parental generation F1 = first generation F2 = second generation

Law of Dominance A dominant (strong allele) will express itself over a recessive (weak) allele. Dominant = allele will always have that trait expressed (seen). Ex. letter B to represent the allele for brown hair. If you inherited the B allele from one or both of your parents, you will have brown hair. (BB or Bb = brown) Recessive = allele will only have that trait expressed when the dominant allele is NOT present. If brown hair is dominant over blonde hair, letter b represents the allele for blonde hair. The only way to get blonde hair is to inherit the b allele from both parents. (bb = blonde hair)

Genotype vs. Phenotype Genotype – the actual alleles inherited Ex: genes that code for flower color such as AA, Aa, or aa Phenotype – the physical characteristics or traits of an organism. Ex: purple flowers

The Significance of Alleles Alleles have assigned letters: Uppercase for dominant (Ex. A) Lowercase for recessive (Ex. a) Each individual has 2 alleles (one from each parent) Homozygous – 2 of the SAME alleles. Ex. AA or aa Heterozygous – 2 DIFFERENT alleles. Ex. Aa

Law of Segregation When chromosomes separate in meiosis, each gamete (egg or sperm) will receive only one chromosome from each pair Ex. If a man has alleles for brown hair and blonde hair (is heterozygous, Bb for hair color) his sperm cells can contain the allele for brown hair (B) OR the allele for blonde hair (b). Each sperm only gets ONE of the alleles

Law of Independent Assortment The assortment of chromosomes for one trait doesn‘t affect the assortment of chromosomes for another trait. Therefore any combination of maternal and paternal chromosomes could be passed on because homologous chromosomes line up RANDOMLY during metaphase.

Possible genotypes of offspring Punnett Square – a diagram that shows the probability of inheriting traits from parents with certain genes Possible genotypes of offspring

Monohybrid Practice