Mendelian Genetics

Gregor Mendel “The Father of Genetics” Austrian Monk and Mathematician in the 1800’s Even though he had no understanding of DNA as genetic material, he was able to correctly predict how traits were passed between generations.

Mendel’s Experiments Crossed pea plants Cross - a mating of two organisms *Each flower in the pic represents an entire pea plant

Experiment Explanation P Generation Purple flower plant x white flower plant F1 Generation All plants had purple flowers The trait for white seemed to disappear F1 Generation allowed to self fertilize F2 Generation Produced plants with purple flowers and plants with white flowers Result – the trait for white had not disappeared…it had been hidden/masked

Understanding the Vocabulary

Allele Alternative form that a single gene may have for a particular trait Each parent gives 1 allele Example: the gene for eye color has several alleles (or forms) like an allele for blue eyes, and allele for brown eyes, etc.

Genotype The actual alleles you inherit from your parents (1 from mom and 1 from dad). Usually expressed as letters. Ex. XX or XY

Phenotype The observable characteristic or outward expression of an allele pair Physical appearance Ex. XY is the Genotype; its phenotype is male.

Dominant Trait The allele that is expressed (it has dominance over another) Expressed as a capital letter Ex. B=brown, b=blue. Bb genotype, its phenotype is brown.

Recessive Trait An allele that is hidden or not expressed unless there are 2 recessive genes Written as a lower case letter Ex. bb=blue eyes

Homozygous 2 of the same alleles for a given trait (purebred) Ex. BB (homozygous dominant) or bb (homozygous recessive)

Heterozygous 2 different alleles for a given trait Ex. Bb

How Mendel’s Pea Plants Helped us Understand Genetics Ted-ed How Mendel’s Pea Plants Helped us Understand Genetics

Vocab Review A bug with the genotype L L is __________________ for leg genes. Homozygous heterozygous A bug with the genotype e e is __________________ for eye genes. Pure hybrid A bug with the genotype A a is __________________ for antenna genes. Pure hybrid

Monohybrid Cross A cross that examines the inheritance of 1 specific trait. Punnett Squares A grid system for predicting the possible genotypes and phenotypes of offspring.

Examples! Use a white board to conquer Punnett Squares!

FYI Pea plants with purple flowers are dominant to pea plants with white flowers Use “P” to represent the flowers in your Punnett Square

Homozygous x Homozygous Cross a homozygous dominant purple flower plant with a homozygous recessive white flower plant

Heterozygous x Heterozygous Cross a heterozygous purple flower plant with a heterozygous purple flower plant.

Heterozygous x Homozygous Cross a homozygous recessive plant (white flowers) with a heterozygous plant (purple flowers).

Find a partner and 2 pennies! Baby Lab Find a partner and 2 pennies!

Vocab Review What has to be true about the parents that show a DOMINANT allele for a trait, but have a baby that shows the RECESSIVE trait? A. both parents are HOMOZYGOUS for the trait B. both parents are HETEROZYGOUS for the trait C. both parents are PURE for the trait D. IMPOSSIBLE; Dominant looking parents can’t have a recessive looking offspring B – Both parents are heterozygous!