every organism has an inherited set of characteristics from their parent or parents. these are our...

CHAPTER 11: GENETICS

18 THINGS YOU SHOULD KNOW ABOUT GENETICS

Every organism has an inherited set of characteristics from their parent or parents. These are our genes.

Genetics is the study of heredity.

GENETICS

Passing of genes from parent to offspring Asexual reproduction: One parent

Low diversity Essentially mitosis

Sexual reproduction: Two parents High diversity Mixes up DNA through meiosis

GREGOR MENDEL

Father of genetics Austrian monk born

in 1822 A priest who studied

science an mathematics

Worked at a monastery and taught high school

GREGOR MENDEL

Carried out a series of experiments in the monastery’s garden Observed

fertilization process of garden peas

MENDEL’S FIRST EXPERIMENT Crossbred truebreeding plants

Truebred – an organism who produce identical offspring to themselves

Observed 7 traits in offspring Trait: A specific characteristic that varies

based on what genes are inherited.

Pea flowers are normally self-pollinating, which means that sperm cells in pollen fertilize the egg cells in the same flower. The seeds then grow plants with the same characteristics as the single parent.

Mendel wanted to produce seeds via cross-pollination (joining male and female reproductive cells from two different plants.)

SEXUAL REPRODUCTION IN PLANTS

Mendel accomplished cross-pollination by cutting away the pollen-bearing male parts & then dusting pollen from another plant onto the flower.

This process produced seeds that had two different plants as parents. This made it possible for Mendel to cross-breed plants with different characteristics, and study the results.

MENDELS’S FIRST EXPERIMENT

P: Parent generation Cross 2 truebreds

F1: Filial 1 generation Produced hybrids:

Resulting offspring from two truebred parents with different traits

Next, cross-fertilized hybrids from F1 generation

F2: Filial 2 generation

MENDEL’S CONCLUSIONS

1) Biological inheritance is determined by “factors” that are passed from one generation to the next.

2) Principle of dominance: states that some alleles are dominant and others are recessive.

WHAT WE CALL “FACTORS” TODAY

• Genes are the chemical factors that determine traits.

• The different forms of a gene are called alleles.

• Genes are located in specific positions on chromosomes.

Mendel had one more question remaining about his crosses… What happened to the alleles that disappeared? Ex: Cross a Tall and a Short plant and all of the F1 offspring were tall.

When Mendel allowed the F1 generation to self pollinate, he was shocked to see the missing alleles reappear.

MENDEL’S CONCLUSIONS

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

Mendel correctly assumed that the allele for shortness was masked by the dominant tall allele, but was still puzzled on why it showed up again in the F2.

He knew that the short allele must have separated or SEGREGATED from the tall allele at some point.

Mendel again correctly hypothesized that this segregation may have happened during sex cell or gamete formation.

During gamete formation, alleles segregate so that each gamete carries a single copy of each gene.

LAW OF SEGREGATION