Chapter 8 Genetics

Detached Earlobes Rolling Tongue DimplesRight - handed FrecklesCurly Hair AllergiesLeft over Right See green and red Straight Hairline HH Thumb Traits Inventory Lab

__________ - is the passing of traits from parents to offspring. to offspring. Heredity The study of heredity started with an Austrian Monk named _______________________. He was considered the _______________________. Gregor Johann Mendel “Father of Genetics” Background Information - He was a peasant and grew up in a family of farmers. - Became a priest. -Went to the University of Vienna and studied math and science - He wanted to study genetics and so, repeated experiments that had been done by a former British scientist named T.A. Knightly. Mendel counted the offspring that he bred and analyzed data. He studied garden peas

Why Pea Plants??? 1. There are several characteristics that are ___________________________.clearly distinct and different 2. The _______________ reproductive parts are on the same plant. They can __________________ or pollinate each other. male and female self-pollinate 3. The plants are _______________, _________________________ and ____________________________ so results can be observed quickly. smallmature quickly produce many offspring

Mendel’s Results Mendel performed a ________________ – a cross between two plants for one trait. He focused on __________________. monohybrid cross flower color Step 1 – He allowed plants to self pollinate called _________________, to ensure that the plants only carried two genes for the same trait. true-breeding *He called them the P (parent) generation. Step 2 – He crossed 2 true-bred plants with opposing traits (Ex. one white and one purple) *He called them the F 1 (filial) generation. Step 3 – He crossed 2 plants from the first generation. *He called them the F 2 (filial) generation. Mendel Discovered: In the P generation, the plant only had the gene it was bred for. In the F 1 generation, the four offspring were carriers of the recessive gene but is was not expressed. The recessive gene started to show in the F 2 generation.

Mendel’s 4 Hypothesis 2. There are alternative versions of each gene. Like brown and blue eye color. These versions are called alleles. 1. For each trait, you get one gene from your mother and one gene from your father. 3. When two genes come together, one might be completely expressed (observable) and the other one might not be observable. These are called dominant and recessive traits. 4. When gametes are formed, they separate and only have one allele for each trait.

People thought that offspring were a blend of their parents – not so. Each organism inherits one copy of a trait from each parent. Therefore each organism carries _______ genes for each trait. The variety of genes that an organism can inherit for a particular trait is called an ____________. 2 allele _______________________ - the two alleles that a person carries for a trait separates during meiosis when the sperm or egg are formed. Law of Segregation _____________________________ - alleles for different genes separate independently of one another when sperm and egg are formed. In other words, just because the allele for blonde hair and brown eyes are on the same chromosome does not mean they will end up in the same gamete (do to crossing over) Law of Independent Assortment Mendel Had Two Laws!

There are two types of genes DominantRecessive 1. Represented by a capital letter. 2.If it is present, it will always be expressed. 1. Represented by a lower case letter. 2. It is a trait that will never be expressed if a dominant allele is present. The only way the trait will be expressed is if the organism has two recessive alleles for the same trait. Examples include: free earlobes (A), freckles, dimples, curly hair, rolling tongue, long eye lashes Examples include: attached earlobes (B), no freckles, no dimples, straight hair, not being able to roll the tongue, long eye lashes. A person has two alleles for each gene. They can either be -____________________ - two of the same alleles (two dominant or two recessive). -____________________ - the organism has one dominant and one recessive allele. Homozygous Heterozygous ________________ – the actual genes you have (using the letters) ________________ - the physical appearance of the genes (how the person looks) genotype phenotype

Expected and Observed Results We can only predict what possible traits a child will have. The only way to truly know what a child will look like or how his or her body will work, is by observing the child after birth. To predict the possible traits of a child, will use a _______________. punnett square

Step 1 – Determine the two genes that each parent is carrying for a particular trait. -Determine what the trait is: Example - eye color, hair color, long ears. -Determine the letter that represents that trait. -Determine what each parent is: -Homozygous Dominant - 2 capital letters -Heterozygous – 1 capital and 1 lower case letter -Homozygous Recessive – 2 lower case letters.

Dominant traits are represented by a ________________ Recessive traits are represented by a _________________ Capital letters are always written first! capital letter lower case letter

Draw a square. Place the mother’s two genes on the top and the father’s two genes on the left side. Cross a mother and a father who are both heterozygous for free ear lobes. Free ear lobes are represented by a “F”.