What is Genetics? Genetics: Study of heredity Heredity: passing of traits from parent to child Patterns of relatedness can help predict offspring characteristics –Autosomal recessive –Autosomal dominance –Sex-Linked –Incomplete dominance –Codominance

When parents get together…they exchange their genes The genes combine to create a baby

“Father of Genetics” Famous for pea plant studies Mendel studied seven pea plant traits –Color, shape, texture, height, etc… Results shaped our understanding of genetics

Mendel’s 7 traits studied

F1 Generation P Generation Mendel crossed a purple and a white flower The flowers exchanged their genes to make babies Mendel was shocked! Even though 1 parent was white in color, every flower that was produced was purple!

Was white gone forever?

F2 Generation F1 Generation Mendel then took two of the newly created purple flowers and let them reproduce WOW! White returned! Even though both parents were purple!

Mendel found a 3:1 ratio for flower color. But what about the other traits he examined? Each trait had a 3:1 ratio. No way that can be a coincidence!

1 form of a gene may prevent the expression of the other –Dominant gene hides recessive gene Organisms inherit 2 copies of each gene –One from each parent

Dominant + Dominant Allele Homozygous Dominant

Recessive + Recessive Allele Homozygous Recessive

Recessive + Dominant Allele Heterozygous

Dominant + Recessive Allele Heterozygous

Genes are located on chromosomes Traits are determined by genes from mom and dad –Allele: Alternative forms of a gene Letters used to abbreviate alleles –Dominant Allele = Capital letter –Recessive Allele = Lowercase letter

Phenotype: Actual appearance of a gene  Ex: Purple flowers Genotype: Genetic makeup of an organism  Ex: 2 dominant alleles (PP) Genotype determines phenotype

Cross a homozygous dominant yellow (YY) plant with a homozygous recessive green (yy) plant Key Y = yellow y = green Probability of growing a yellow plant? _____________ Probability of growing a homozygous recessive plant? ____________ 100% 0% Probability of growing a homozygous dominant plant? ____________ 0%

Cross a heterozygous dominant yellow (Yy) plant with a heterozygous dominant yellow (Yy) plant Key Y = Yellow y = green Probability of growing a heterozygous plant? ________ Probability of growing a green plant? ________ Probability of growing pure yellow? _________ 50% 25% 25%

Maria is a heterozygous healthy (Hh) female and Jeff suffers from recessive cystic fibrosis (??). Key H = healthy h = cystic fibrosis Probability of having a healthy child? _________ Probability of having a homozygous dominant child? ________ 50%0%

Kobe Kuiz 1) How are dominant alleles expressed? Recessive? 2) Which of the following are genotypes? Phenotypes? TT Green yY Pp Purple gg Smooth 3) Which of the following are heterozygous genotypes? TT Green yY Pp Purple gg Smooth 4) Genes may often be found in two forms (dominant and recessive). What are these alternate forms of a gene called? 5) Genes are segments of DNA found on _______________. 6) If item A is found in a 2:1 ratio compared to item B, what percentage is item A? 7) If item A is found in a 4:1 ratio compared to item B, what percentage is item A? 8) George & Martha are planning a family. Each has a family history of autosomal recessive disorder and they agree to have their blood tested. George is found to be heterozygous healthy and Martha is found to be homozygous dominant healthy. What are the chances they have a healthy child? Homozygous dominant child? Heterozygous child? Homozygous recessive child?