Monohybrid Crosses

Gregor Mendel Austrian monk who started the study of genetics in his monastery’s garden in the 1860s Studied heredity in garden peas

Why did he study peas? 1.They had a variety of characteristics that occur in two different forms or.

Why did he study peas? 1.They had a variety of characteristics that occur in two different forms or alleles.

Why did he study peas? 1.They had a variety of characteristics that occur in two different forms or alleles.

Why did he study peas?

2.He could easily control which plants pollinated each other.

Why did he study peas? 2.He could easily control which plants pollinated each other. – Pea plants can, which is when a plant’s pollen, which contains the sperm, is used to fertilize the same plant’s egg. If he wanted pure breeding plants, he could allow the plants to self- pollinate over many generations.

Why did he study peas? 2.He could easily control which plants pollinated each other. – Pea plants can self-pollinate, which is when a plant’s pollen, which contains the sperm, is used to fertilize the same plant’s egg. If he wanted pure breeding plants, he could allow the plants to self- pollinate over many generations.

Why did he study peas? 2.He could easily control which plants pollinated each other. – Pea plants can self-pollinate, which is when a plant’s pollen, which contains the sperm, is used to fertilize the same plant’s egg. If he wanted pure breeding plants, he could allow the plants to self- pollinate over many generations. – Pea plants can also, which is when the pollen of one plant is used to fertilize another plant. He could do this by removing stamens or male parts of the flowers. He could brush pollen from one flower to the female parts of another flower.

Why did he study peas? 2.He could easily control which plants pollinated each other. – Pea plants can self-pollinate, which is when a plant’s pollen, which contains the sperm, is used to fertilize the same plant’s egg. If he wanted pure breeding plants, he could allow the plants to self- pollinate over many generations. – Pea plants can also cross-pollinate, which is when the pollen of one plant is used to fertilize another plant. He could do this by removing stamens or male parts of the flowers. He could brush pollen from one flower to the female parts of another flower.

Why did he study peas?

3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly.

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation-

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation- 1 st generation; parental (p) generation

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation- 1 st generation; parental (p) generation – F1 generation-

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation- 1 st generation; parental (p) generation – F1 generation- The first generation of offspring

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation- 1 st generation; parental (p) generation – F1 generation- The first generation of offspring F stands for filial or son.

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation- 1 st generation; parental (p) generation – F1 generation- The first generation of offspring F stands for filial or son. – F2 generation-

Why did he study peas? 3.Peas produce a lot of offspring quickly, so he could obtain lots of data quickly. – P generation- 1 st generation; parental (p) generation – F1 generation- The first generation of offspring F stands for filial or son. – F2 generation- The second generation of offspring; offspring of the F1 generation

3 Steps of Mendel’s Experiments 1. Produce a true-breeding P generation Long stemmed plant Short stemmed plant Self Pollination Long stemmed plant P generation Short stemmed plant P generation

3 Steps of Mendel’s Experiments 2. Producing an F1 generation Cross PollinationCross Pollination Long stemmed F1 Generation

3 Steps of Mendel’s Experiments 3. Producing an F2 Generation Cross PollinationCross Pollination ¾ Long Stemmed ¼ Short Stemmed F2 Generation

Mendel’s Law of Segregation Genes for different traits can segregate (or separate) independently during the formation of gametes This is because the two different alleles that an organism has are on different chromosomes in a homologous pair.

Mendel’s Law of Segregation Parent Cell Meiosis I Meiosis II Gametes

Practice What are the possible genetic contents of the gametes made by a person with the genotype BB? What are the possible genetic contents of the gametes made by a person with the genotype Tt?

Practice What are the possible genetic contents of the gametes made by a person with the genotype BB? B or B What are the possible genetic contents of the gametes made by a person with the genotype Tt?

Practice What are the possible genetic contents of the gametes made by a person with the genotype BB? B or B What are the possible genetic contents of the gametes made by a person with the genotype Tt? T or t

Making Sense of Mendel’s Findings Probability-

Making Sense of Mendel’s Findings Probability- the likelihood that a particular event will occur

Making Sense of Mendel’s Findings Probability- the likelihood that a particular event will occur – Scientists use probability to predict the phenotypes and genotypes of the offspring.

Making Sense of Mendel’s Findings Probability- the likelihood that a particular event will occur – Scientists use probability to predict the phenotypes and genotypes of the offspring. Punnett Square-

Making Sense of Mendel’s Findings Probability- the likelihood that a particular event will occur – Scientists use probability to predict the phenotypes and genotypes of the offspring. Punnett Square- a diagram that shows gene combinations that might result from a genetic cross

Making Sense of Mendel’s Findings Probability- the likelihood that a particular event will occur – Scientists use probability to predict the phenotypes and genotypes of the offspring. Punnett Square- a diagram that shows gene combinations that might result from a genetic cross – Punnett squares show predicted results, not actual results.

Punnett Square Parent 1 Parent 2 Gamete 1 Gamete 2 Gamete 1 Gamete 2 Offspring 1 Offspring 2 Offspring 3Offspring 4

CROSSES INVOLVING ONE TRAIT (MONOHYBRID CROSSES) Let’s take a look at Mendel’s crosses that he completed to determine his laws of heredity. We will use L to represent the allele for long stems and l to represent the allele for short stem.

Homozygous x Homozygous When he crossed two pure-breeding plants for the same version of the trait, all of the offspring shared the same phenotype as the parents.

Homozygous x Homozygous Parent 1 Parent 2 Gamete 1 Gamete 2 Gamete 1 Gamete 2 Offspring 1 Offspring 2 Offspring 3Offspring 4 LL LL L L

Homozygous x Homozygous

Test Crosses

We can’t tell by looking at an individual with a dominant phenotype if the individual’s genotype is homozygous dominant (BB) or heterozygous (Bb). What can we do to determine the genotype of an individual with a dominant phenotype? Test cross:

Test Crosses We can’t tell by looking at an individual with a dominant phenotype if the individual’s genotype is homozygous dominant (BB) or heterozygous (Bb). What can we do to determine the genotype of an individual with a dominant phenotype? Test cross: crossing an organism with a dominant phenotype, but unknown genotype, with a homozygous recessive organism, then observing the phenotypes of the offspring to determine the unknown genotype