Mendelian Genetics Notes PDF

# Concept 1 Notes: Mendelian Genetics ## Questions/Vocabulary ## Background - With the exception of gametes (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) - **Gene:** sec...

# Concept 1 Notes: Mendelian Genetics ## Questions/Vocabulary ## Background - With the exception of gametes (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) - **Gene:** section of DNA that provides the instructions for making a protein - Since a gene is a piece of chromosome and we have two of every chromosome, we have two copies of instructions to make every protein in our bodies. - **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 - 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's Experiments - In his experiments crossing pea plants he made sure that: - He had control over breeding. - Mendel used pea plants that typically self-pollinate. - He used only purebred plants. - **Purebred:** type of organism whose ancestors are genetically uniform. - He observed only "either-or" traits. - Chose pea shape, pea color, pod shape, pod color, plant height, flower color, and position. ## Terms - **What is a cross?** - **Cross:** mating of 2 organisms - **P:** parental generation - **F1:** first generation - **F2:** second generation - **Purple Flowers:** purple flowers - **White Flowers:** white flowers - **P Generation Cross Fertilization:** a cross between two parental organisms - **F1 Generation Hybrids:** offspring from parental cross - **F2 Generation:** offspring from the F1 generation ## The Significance of Alleles - Alleles have assigned letters: - **Uppercase:** for dominant (Ex. A) - **Lowercase:** for recessive (Ex. a) - Remember, each individual has 2 alleles (one from each parent) for every gene - **Homozygous:** 2 of the SAME alleles - Ex. AA or aa - **Heterozygous:** 2 DIFFERENT alleles - Ex. Aa ## Law of Dominance - A dominant (strong) allele will express itself over a recessive (weak) allele - **Dominant:** If present, allele will always have that trait expressed (seen) - Ex. If brown hair is dominant over blonde hair, b represents the allele for blonde hair and B represents brown hair. If you inherited the B allele from one or both of your parents, you will have brown hair. (whether you are BB or Bb = brown) - **Recessive:** allele will only have that trait expressed (seen) when the dominant allele is NOT present - The only way to get blonde hair is to inherit the b allele from both parents (bb = blonde hair) - **Genotype:** the actual alleles inherited - Ex: Genes that code for flower color such as FF, Ff, or ff - **Phenotype:** the physical traits/characteristics seen in an organism - Ex: Purple flowers ## Law of Segregation - When chromosomes separate in meiosis, each gamete (egg or sperm) will receive only one chromosome from each pair - **Example:** - If a man has alleles for brown hair and blonde hair, he is heterozygous (Bb) for hair color. - His sperm cells can contain the alleles 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. - This allows for any combination of maternal and paternal chromosomes to be passed on because homologous chromosomes line up RANDOMLY during metaphase. ## Heredity Unit *It's Not Rocket Science® 2020*