Bellwork: Thurs. Jan. 12, 2017 cross: Tt x Tt     The different genotypes (“letters” or “genes”) are: ______, _____, and _____ 2. The different phenotypes (what is their “Physical” appearance?) of the above cross?___________________________ 3. The percent of the plants are tall in this cross:______________ 4. The percent of the plants are short in this cross?_______________

More on Genetics http://serendip.brynmawr.edu/sci_edu/waldron/pdf/GeneticsProtocol.pdf

Children tend to resemble their parents in appearance like: similar eye color, hair texture, height and other characteristics because children inherit genes that control specific characteristics from their parents.

Where are genes found in our bodies? Researchers have shown that genes are parts of DNA molecules, and DNA molecules are packaged in chromosomes in the nucleus of each cell in our body.

How does a baby inherit genes from his or her mother and father? Caught Between Dark and Light http://www.youtube.com/watch?v=OrX5HflxQQs

genes inherited from one generation to the next, show how gene-carrying chromosomes behave during meiosis and fertilization. For example, think about how the mother's and father's chromosomes divide during meiosis and fertilization. Each cell in a baby's body has two copies of each gene, one copy from his or her mother and one copy from his or her father.

Inheritance of Albinism A gene controls if a person can produce the pigment melanin contributing to the color of skin, eyes and hair. Some people have the hereditary condition, albinism and cannot produce melanin and have little or no pigment in their skin and hair. (Remember 2 different versions of the same gene are called alleles. One allele of this gene codes for melanin production and normally pigmented skin and hair; it is symbolized by A. Another allele of this gene codes for albinism; it is symbolized by a.)

We'll analyze inheritance for the case where each parent has one A allele and one a allele (i.e. both parents are Aa). What different combinations of A and/or a alleles would you expect to observe in the children of these parents?   Biologists use a Punnett Square to answer this type of question

This is a Punnett square showing a mother who is Aa, half of her eggs will have a chromosome which carries the A allele, and the other half will have a chromosome with the a allele. Similarly, half of the father's sperm (Aa) will have an A allele, and half will have the a allele.

What fraction of this couple's children would you expect to be AA What fraction of this couple's children would you expect to be AA? ____ What fraction of this couple's children would you expect to be Aa? ____ What fraction of this couple's children would you expect to be aa? ____ Genotypic Ratio: Phenotypic Ratio:

Suppose a father has aa alleles and a mother has Aa alleles Suppose a father has aa alleles and a mother has Aa alleles. determine what fraction of this couple's children would be expected to have albinism… Genotypic Ratio: Phenotypic Ratio:

More for 4th period: The children who have AA alleles will have normal pigmentation, and the children who have aa alleles will have albinism. What pigmentation will be observed for the children who have Aa alleles? _________ (This type of combination of two different alleles is called heterozygous.) What fraction of a couple's both with Aa would you expect to have normal pigmentation? ____ What fraction of this couple's children would you expect to have albinism? ____

Probability and Coin Flips You flip a coin one time. What is the probability that it lands heads up? Tails up? # of outcomes = 2 (heads or tails) ½ or 50% for heads ½ or 50% for tails The probability of flipping heads is 50%. If you flip a coin and it lands tails up, does probability mean that you are guaranteed to flip heads on the next flip? NO!

A a LAB: Will you have an albino? The way genes behave can be simulated using a penny Tails = recessive allele controlling pigment production (a). Heads = dominant allele (A). Say a parent is heterozygous (Aa) Tossing a coin & checking for tails up vs. heads up represents 50-50 chance that an egg or sperm produced by the parent will include an a allele or an A allele. To simulate a mating between two heterozygous (Aa) parents, two students will each toss a coin and the result of the pair of coin tosses will indicate the pair of alleles contributed by an egg and a sperm to the baby that results from that mating.

Probability and Coin Flips I flipped a coin 10 times while recording the number of times it lands heads up and the number of times it lands tails up. Heads Tails IIII (4) IIIIIII (6) Based on 10 flips, it would seem that the probability of flipping a heads is 40% while the probability of flipping tails is 60%.

Probability and Coin Flips I then flipped the coin 30 more times while still recording the number of times it lands heads up and the number of times it lands tails up. Heads Tails IIIIIIIII IIIIIIIIIIIII (22) IIIIIII IIIIIIIIIII (18) Based on 40 flips, it would seem that the probability of flipping a heads is 55% while the probability of flipping tails is 45%. Closer but still not 0.5 and 0.5.

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