Classical Genetics Do Now: 1. Take out homework: p.151 #1-3 so I can check it 2. Begin writing the introduction to the lab you just received.

Onion Cell Mitosis Web Lab Question: What phase of mitosis does a cell spend most of its life in? How can we figure it out? Web lab – Due MONDAY

Basic Genetics You, like most animals, are diploid. During reproduction, haploid gametes from two parents combine to make a new diploid organism. Thus, only half of an organism’s genetic information is passed on to its offspring

Meiosis Meiosis is cell division that makes haploid gametes. The chromosome number is reduced by ½. Only 1 of each homologous pair of chromosomes gets passed on to the offspring.

Genes, Alleles, and Traits A trait is a characteristic. For example, brown eye color is a trait most humans have. A gene is a part of a chromosome that carries information for one trait. For example, humans have one major eye color gene. An allele is a certain form of a gene. In humans, the most common eye color alleles are brown and blue.

Follow the alleles The 2 chromosomes shown are a homologous pair. The chromosomes carry different genes. What % of the haploid cells have the red allele? What % have the blue allele?

Probability Since there is an equal chance of each chromosome ending up in an offspring, it’s similar to flipping a coin.

Genetics: The Study of Biological Heredity Do Now: If you flip a coin twice, what is the probability it will come up heads twice? What is the probability it will come up heads once and tails once? What is the probability it will come up tails twice?

Make A Prediction Please Write: If the two pea plants shown were crossed (mated), what % of the offspring do you predict will be purple? Why?

Metacognition: Predictions What thinking steps did you use to make your prediction? –C–Consider prior knowledge: what do you already know about inheriting characteristics? –M–Modify prior knowledge to apply to new situation: What’s different about this situation? –S–State prediction. Let’s think scientifically…

State a Prediction and Hypothesis PREDICTION: If those two pea plants are mated, then ?? % of their offspring will be purple. HYPOTHESIS: ?? % of their offspring will be purple because…

Anyone Predict 100% Purple? The first plant was PURE BREEDING for purple flowers – meaning when it was SELF-FERTILIZED all of the offspring had purple flowers. The second plant was pure breeding for white flowers. Which flower color would you describe as DOMINANT in pea plants?

Gregor Mendel Monk from Austria Studied statistics at the University of Vienna Garden enthusiast High school teacher The importance of his discoveries was only understood and appreciated years after his death Mendel “Father of Genetics”

Mendel’s Experiments Make another prediction: –If two of the offspring from the first cross (the ones that were all purple), what % of the offspring would be purple? Why?

A Word About Plants (Angiosperms = flowering plants)

From Seed to Seedling

Back to the Genetics Approximatly 75% of the offspring will have purple flowers. Mendel’s study of probability and statistics led him to hypothesize that each plant had two “factors” controlling flower color, one from each parent. How did he know???

Probability If you flip a coin, what is the probability it will come up heads? What is that probability expressed as a decimal? If something has a probability of 1.0 will it happen? You just flipped a coin 4 times and it came up tails all 4 tries. What is the probability it will come up tails if you flip it again? If you flip a coin twice, what is the probability it will come up heads both times?

Classical Genetics is Based on Probability! You have 2 copies of each gene, but only one copy or the other is passed on to your offspring. Which copy of the gene that gets passed on is random. This is exactly what was happening in the pea plants – see if you can come up with an explaination tonight!

Homework Read 9-1 pp SR #1 p. 169