Mendel and heredity

Gregor Mendel Mendel was an Austrian monk during the 1800s, that studied the genetics of pea plants. Mendel is considered the father of genetics.

Gregor Mendel He chose to work with pea plants because they reproduce sexually, which means they need male and female sex cells. Mendel made three key decisions when it came to this experiment: He had control over breeding. Chose only purebred plants. Studied traits that were either or, not a blending.

Sexual reproduction Mendel had to transfer pollen from one plant to another, this is called making a cross.

Mendel’s first law Mendel came up with 2 laws the first is the law of segregation. The law of segregation comes in 2 parts: Organisms inherit 2 copies of each gene, 1 from each parent. Organisms donate only 1 copy of each gene in their gametes.

Turn and talk Why is Mendel considered the “father of genetics?”

Genes Genes are pieces of DNA that provide a set of instructions to cells to make a particular protein.

Genes Each gene has a particular spot on a specific chromosome. An allele is any possible variation of a particular gene.

Genes vs. Alleles An example of a gene is “eye color” An example of an allele is “Brown eyes”

Dominant alleles Dominant allele are the alleles that are expressed when an organism is a hybrid. They are always expressed with a capital letter. Example: Tt the capital T represents a tall allele. Also, the organism will be tall, because the capital T is dominant.

Recessive alleles Recessive alleles are the alleles that are hidden when an organism is a hybrid. They are always expressed with a lower case letter. Example: Tt the small t represents a short allele. Also, the organism will be tall, because the small t is hidden.

Environmental factor Factors other than genes effect the way an organism looks. poor nutrition, lack of sun, water or shelter can effect an organisms phenotype.

Turn and talk What is the difference between a gene and an allele?

Gene combinations There are different names for gene combinations. Homozygous Means same genes Either BB (homozygous (dominant) Brown eyes) the letters are the same bb (homozygous (recessive) blue eyes) the letters are the same

Gene combinations Heterozygous Means different genes Bb (heterozygous Brown eyes) the letters are different

Talk Time How do the color of your eyes compare to your parents or other family members? Why can’t a person be heterozygous recessive?

Genome A genome, is a map of all of the genetic information an organism has.

Genotype A genotype generally refers to the genetic combination of 1 trait for an organism. An example would be: BB (which are the genes that will yield a specific color)

Phenotype A phenotype generally refers to the physical appearance of 1 trait for an organism. An example might be: Sam has brown eyes.

Think to yourself and be ready to share out. Which one can you tell right away by looking at a person? Genotype or Phenotype? Explain.

Punnett squares A Punnett square is a system for predicting all possible genotypes resulting from a cross. The parents alleles go along the top and left hand edges of each box.

The Generations P: The parent generation of which the original cross is made F1: The first generation of offspring resulting from the cross F2: The second generation of offspring (usually a result of the F1 crosses)

monohybrid crosses monohybrid cross Mono=one A monohybrid cross shows a cross that examines the inheritance of a single trait.

monohybrid cross TTxtt

monohybrid cross TTxTt

monohybrid cross Tt x Tt

Turn and write Do a punnett square for a short woman and a heterozygous tall man.

Dihybrid crosses Dihybrid cross Di=two A Dihybrid cross shows a cross that examines the inheritance of 2 different traits.

Independent assortment Mendel’s second law: The law of independent assortment: Allele pairs separate independently of each other during gamete formation. Different traits are inherited separately from each other (twister).

Probability Probability is the likelihood that a particular event will happen. Predicts average; not exact. Frequency / outcomes