5-4-18 Identifying Misconceptions about Dominant Traits

Take out your Homework - Mini Lab: Which is the dominant trait? Axial flower position, smooth pea pods, long stems, and yellow seeds are dominant; Terminal flower position, bumpy pea pods, short stems, and green seeds are recessive. The recessive trait (such as terminal flowering plants) are absent in the first generation and reappear in the second generation. Only the dominant trait (such as axial flower position) showed up in the first generation.

Do Now: Turn & Talk with your shoulder partner Do Now: Turn & Talk with your shoulder partner. State whether you agree or disagree with the following statements. Explain why. Like mixing paints, parents' traits always blend in their offspring. Disagree. Some traits may seem to disappear in offspring. However, the factors for traits remain and can reappear in later generations. If you look more like your mother than you look like your father, then you received more traits from your mother. Disagree. Humans are sexually reproducing organisms and thus receive 50% of their factors from each parent. Dominant factors will eventually replace all corresponding recessive factors for that trait in a population. The most commonly expressed trait in a population is dominant.

Examples of Human Diseases that follow Mendelian Inheritance Patterns Polydactyly Gene Responsible: GLI3 Type of Inheritance: Dominant; individuals with even just one copy of the mutated gene can have extra fingers or toes. Polydactyly only occurs in 1 in every 500-1000 births in the U.S.. This means it is very rare to have the gene mutation that causes polydactyly, even though it is dominant

Examples of Human Diseases that follow Mendelian Inheritance Patterns Huntington’s Disease (HD) Gene Responsible: Huntingtin (HTT) Type of Inheritance: Dominant; individuals with even just one copy of the mutated gene will have HD. HD is a fatal disorder that causes the progressive breakdown of nerve cells in the brain. It deteriorates a person’s physical and mental abilities and has no cure.

Examples of Human Diseases that follow Mendelian Inheritance Patterns Phenylketonuria Gene Responsible: Phenylalanine hydroxylase (PAH) Type of Inheritance: Recessive Phenylalanine is an essential building block of proteins we eat. Individuals with two copies of the mutated PAHgene are unable to make the protein PAH, so he/she cannot break down the amino acid phenylalanine. As a result, these individuals have high levels of phenylalanine in their urine and blood, which can eventually cause mental retardation and behavioral abnormalities.

Examples of Human Diseases that follow Mendelian Inheritance Patterns Cystic Fibrosis (CF) Gene Responsible: Cystic fibrosis conductance regulator (CFTR) Type of Inheritance: Recessive In people with CF, a recessive gene causes a thick, sticky buildup of mucus in the lungs, pancreas, and other organs. In the lungs, the mucus clogs the airways and traps bacteria leading to infections, extensive lung damage, and eventually, lung failure.

Which Traits will your Imaginary Offspring get? You will have an envelope containing cards with combinations of alleles for various traits: Ear lobes (E/e) Eye color (B/b) Widow’s peak (W/w) Red hair (R/r) Curly hair (C/c) Eye lashes (Y/y) Freckles (F/f) Dimples (D/d) Cleft Chin (H/h) 1. Determine your imaginary person’s expressed traits based on the cards in your envelope.

Which Traits will your Imaginary Offspring get? Pair up with another student. You will be creating an imaginary offspring with your imaginary parents. Take all of your cards out of your envelope and place them face down, being careful to keep you and your partner’s piles separate. One trait at a time, each partner should select one of the cards for that trait from their pile and reveal the card. (E.g., if you are focusing on ear lobes, each partner should select a pink card from their pile). List the factors that each parent passed on to the offspring. Determine which trait should be expressed by the offspring. Answer the Analysis Questions If time permits, draw a picture of your imaginary people.

E e

B b

W w

R r

C c

Y y

F f

D d

H h