Genetics & Heredity 1

Who was Gregor Mendel? 2

Who was Gregor Mendel? Gregor Mendel was an Austrian monk who studied mathematics and science. In 1856, he grew pea plants and found that patterns of traits developed over time. The traits were passed from one generation to the next. He is called the “Father of Genetics” 3

Heredity is the passing of traits from parent to offspring. Define HEREDITY Heredity is the passing of traits from parent to offspring. 4

Genetics is the study of how traits are inherited from parents. What is GENETICS? Genetics is the study of how traits are inherited from parents. 5

What is a GENE? A gene is a section of DNA on a chromosome that contains instructions for traits. Genes come in pairs. 6

Describe the following terms: Allele Trait 7

ALLELE An allele is the different forms of a trait that a gene may have Alleles may be a dominant trait or a recessive trait Alleles are one form of a gene. 8

TRAIT A trait is a characteristic an organism shows or exhibits. Examples of some traits are: hair color, eye color, dimples and blood type. 9

Two Types of TRAITS Dominant Recessive 10

Describe DOMINANT TRAIT A dominant trait is one that covers over or dominates another form of that trait. This trait always shows up, even when only one of the two alleles is in the dominant form. Dominant traits are shown by a capital letter. “A” 11

Describe RECESSIVE TRAIT A recessive trait is covered over, or dominated, by another form of that trait and seems to disappear. It is hidden when the other copy of the gene contains the dominant allele. A recessive allele shows up only when there is no dominant allele present. Recessive traits are shown with a lower case letter. “a” 12

What is HOMOZYGOUS? 13

What is HOMOZYGOUS? Homozygous is when both alleles [forms of the gene] are the same. AA or aa When offspring inherit two dominant genes/alleles, (one dominant gene from each parent) they are said to be homozygous dominant AA When offspring inherit two recessive genes/alleles, (one recessive gene from each parent) they are said to be homozygous recessive aa 14

What is HETEROZYGOUS? 15

What is HETEROZYGOUS? Heterozygous is when alleles occur in different forms. Bb When offspring inherit one dominant gene and one recessive gene, they are said to be heterozygous Bb Since the dominant gene will be expressed, they are said to be heterozygous dominant Bb 16

Describe Incomplete DOMINANCE 17

Describe Incomplete DOMINANCE Incomplete dominance is when two parent organisms carry dominant alleles for a trait RR (red) x WW (white) = PP (pink) A dominant red flower crossed with a dominant white flower = pink flower The organism shows a trait that is a blend of the traits represented by the two crossed sets of alleles. 18

Define GENOTYPE Genotype is an organism's genetic makeup. Genotype is the letters (genes) that describe the organism. AA, Aa, aa 19

Define PHENOTYPE Phenotype is the outward physical appearance and behavior of an organism. It is the descriptive words that tell characteristics of the organism. Phenotypes examples: tall, white, wrinkled or widow’s peak 20

What is a PUNNETT SQUARE? A Punnett square is a tool to predict the probability of certain traits in offspring. 21

What is POLYGENIC INHERITANCE? 22

What is POLYGENIC INHERITANCE? Polygenic inheritance occurs when a group of gene pairs acts together to produce a trait. “ poly” means many The effects of many alleles produces a wide variety of phenotypes. Polygenic inheritance examples are height, eye color, skin color. 23