Happy Thursday! Please do the following: have out your Karyotyping lab pick up the handouts

Genetics and Heredity

Watch this video before completing your foldable or taking notes. http://ed.ted.com/lessons/how-mendel-s-pea-plants-helped-us-understand-genetics-hortensia-jimenez-diaz

Use slides 4 – 18 to aide you in completing your Genetics Foldable

Heredity The study of how traits are passed from parents to offspring.

Genes and Alleles A gene is a segment of DNA that codes for a specific trait. Ex. Gene for hair color An allele is an alternative form of a gene Ex. Allele for brown hair

Dominant Trait that is always observed; masks the recessive form of a trait. Represented by CAPITAL LETTERS W : Widow’s Peak H : Hitchhikers thumb E : Unattached earlobes

Recessive Only observed when TWO recessive alleles are present. Represented by a lower case letter. w : Straight hair line h : Absent hitchhikers thumb e : Attached earlobes

Homozygous Same alleles joined together Examples: Homozygous Dominant RR, HH, TT, LL Homozygous Recessive rr, hh, tt, ll

Heterozygous Different alleles joined together Examples: Ww, Hh, Ee

Genotype Combination of alleles in an organism

Phenotype The physical appearance The outward expression of a gene What an organism looks like

Interpreting a Genotype G: dominant allele for green pea g: recessive allele for yellow pea GG Gg gg

Theory of Heredity Inherited allele for purple P HOMOZYGOUS purple flower PP

Theory of Heredity Inherited allele for purple flower (P) Inherited allele for pink flower (p) HETEROZYGOUS purple flower (Pp)

Theory of Heredity Inherited for pink flower (p) HOMOZYGOUS pink flower (pp)

Phenotype for Fur Color G = Gray fur, g= White fur Subject A Subject B Subject C Genotype for Fur Color GG Gg gg Phenotype for Fur Color

Now, read through slides 22 – 29 Now, read through slides 22 – 29. In your notebook or on the back of your foldable, summarize Mendel’s conclusions and define: - Law of Segregation - Law of Independent Assortment

Gregor Mendel Studied patterns of heredity (passing on of characteristics from parent to offspring) Used the common garden pea in experiments

Why did Mendel use peas? Sexually reproducing: able to isolate both male and female gametes Easy to identify traits (characteristics that are inherited) Short life cycle: able to be grown quickly

Tall true breed x short true breed 75% tall hybrids, 25% short hybrids Mendel’s Experiment PARENT GENERATION (P1) Tall true breed x short true breed FILIAL GENERATION (F1) All tall hybrids FILIAL GENERATION (F2) 75% tall hybrids, 25% short hybrids

What did Mendel observe? When a true-breeding tall plant is crossed with a true-breeding short plant in the P generation, the F1 height trait is always predictable. 100% are tall plants. P generation F1 F2

What happens when the F1 tall plants are crossed together? Mendel observed that the F2 generation, the offspring of F1 plants, are always in a fixed ratio of 3:1 tall:short. Why? P generation F1 F2

Mendel’s Conclusions There must be two variations for every trait, where each variation is called an allele. Each offspring inherits only one allele from each parent. The alleles are either dominant or recessive. To show the recessive trait, two recessive alleles must be inherited.

Mendel’s Conclusions - Law of Segregation Mendel concluded only one allele is passed from parent to offspring for each trait. F1 plants must be heterozygous because the P generation only passed on one tall allele and one short allele. The F1 plant will then pass on to its offspring either a tall or a short allele, never both.

Mendel’s Conclusions - Law of Independent Assortment Because organisms are made up of more than one trait, Mendel concluded that the inheritance of one trait does not influence the inheritance of a second trait. Example: Height of the pea plant does not influence the color of the peas Height is independently assorted from color.