Probability and Genetics Genes and Alleles Gene segment

Probability and Genetics

Genes and Alleles • Gene - segment of DNA that codes for a traits • Alleles - different versions of a gene Gene Eye color Flower color Alleles Brown, Blue Purple, White

Genotypes and Phenotypes • Genotype genetic makeup (which alleles do they have? ) • Phenotype physical trait (due to the genotype)

Heterozygous and Homozygous • Heterozygous 2 different alleles for a gene • Homozygous 2 of the same alleles for a gene

Law of Dominance • Dominant allele - one or two copies of this allele results in the dominant trait • Recessive allele - you need two copies of this allele to show the recessive trait (or you need to NOT have the dominant allele)

Probability and Genetics Review

What role does probability play in genetics? • Probability is the likelihood that something will happen • Which allele you pass on is random - like flipping a coin!

What about sample size? • More trials gets closer to expected results… • Flip a coin twice…would you be surprised if you got 2 heads? • Flip a coin 100 times…would you be surprised if you got 80 heads, 20 tails?

Are predictions reality? • It’s just odds…

What does meiosis have to do with inheritance? • Meiosis splits up alleles • Each gamete has a different combination of alleles

How is variation guaranteed in offspring? • Crossing over

How is variation guaranteed in offspring? • Independent assortment

How is variation guaranteed in offspring? • Random Fertilization • Men make 200, 000 sperm a day – Which one reaches the egg? ? • Women start off at birth with 200, 000 eggs – Which one will be released that month? ?

How do we use Punnett Squares? • We use Punnett Squares to PREDICT the outcomes of matings (or crosses) • It’s not necessarily going to turn out that way • These are just odds or probabilities