bio project11

Basic Genetics Razan Albishri Gr:11

Mitosis • What is Mitosis: it is the second main stage of the cell cycle • What happens in mitosis? The cell’s replicated DNA divides and 2 genetically identical diploid daughter cells are produced • What are the stages of mitosis? 1. Prophase 2. Metaphase 3. Anaphase 4. telophase • Prophase: • 1st stage of mitosis • Longest stage of mitosis • It is divided into 2: early prophase & late prophase aka prometaphase ✓ What happens in prophase? • the chromosomes condense and become visible • spindle fibers emerge from the centrosomes • the nuclear envelope breaks down • the centrosomes move toward opposite poles

• Metaphase: • 2nd stage of mitosis ✓ What happens in metaphase? • Chromosomes line up at the equator of the cell • Each sister chromatid is attached to a spindle fiber originating from opposite poles • Anaphase: • 3rd stage of mitosis • Shortest stage of mitosis ✓ What happens in anaphase? • Centromeres split into two • Sister chromatids(chromosomes) are pulled towards opposite poles • Certain spindle fibers begin to elongate the cell

• Telophase: • 4th and last stage of mitosis ✓ What happens in telophase? • The chromosomes arrive at opposite poles and begin to decondense • Nuclear envelope material surrounds each set of chromosomes • Spindle fibers continue to push poles apart Cytokinesis: • Towards the end of mitosis the cell begins another process called cytokinesis • Its different in plant and animal cells • What happens in cytokinesis? • The cytoplasm will divide • It results in 2 cells each with an identical nuclei

Meiosis: • What is meiosis? It is a Reduction division process occurring only in reproductive cells. • What happens in meiosis? one diploid(2n) cell produces 4 haploid(n) cells that are not genetically identical. • What are the stages of meiosis? Meiosis I : Meiosis II: 1. prophase I 5. Prophase II 2. Metaphase I 6. Metaphase II 3. Anaphase I 7. Anaphase II 4. Telophase I 8. Telophase II ➢ Prophase I: ✓ What happens in prophase I? • Pairing of homologous chromosomes occurs • Crossing over produces exchange of genetic information • The nuclear envelope breaks down • Spindle forms ➢ Metaphase I: ✓ What happens in metaphase I? • Chromosomes centromeres attach to spindle fibers • Homologous chromosomes line up at the equator

➢ Anaphase I: ✓ What happens in anaphase I? • Homologous chromosomes separate and move to opposite poles of the cell ➢ Telophase I: ✓ What happens in telophase I? • The spindle breaks down • Chromosomes uncoil and form 2 nuclei • The cell divides ➢ Prophase II: ✓ What happens in prophase II? • Chromosomes condense • Spindle forms in each new cell • Spindle fibers attach to chromosomes ➢ Metaphase II: ✓ What happens in metaphase II? • Centromeres of chromosomes line up randomly at the equator of each cell ➢ Anaphase II: ✓ What happens in anaphase II? • Centromeres split • Sister chromatids separate and move to opposite poles

➢ Telophase II: ✓ What happens in telophase II? • 4 nuclei form around chromosomes • Spindles break down • Cells divides Difference between mitosis and meiosis MITOSIS MEIOSIS Occurs in the body or somatic cells Occurs in germ cells No pairing of synapsis takes place between the Pairing or synapsis occurs between the homologous homologous chromosomes chromosomes Duplication of chromosomes takes place in early Duplication of chromosomes occurs in late prophase prophase The exchange of genetic material between the The exchange of genetic material takes place between homologous chromosomes doesn’t occur the chromatids of homologous chromosomes The chromosome number remains the same Chromosomes number is reduced into half 2 daughter cells are formed 4 daughter cells are formed

Mendelian genetics Who is Mendelian? He is an Austrian monk named Gregor Mendel • he introduced a new theory of inheritance based on his experimental work with pea plants • He believed that heredity is the result of discrete units of inheritance and every single gene was independent in its actions in an individual’s genome. What are the 3 principles of mendelian genetics? 1. Law of independent assortment 2. Law of dominance 3. Law of segregation ➢ Law of independent assortment: • The Law of independent assortment says that genes for different traits segregate independently of each other. It means that separate traits are separately inherited. This is because during meiosis the chromosomes line up randomly before the cell divides, allowing for gamete formation. • ➢ Law of dominance: • The law of dominance says that there are dominant and recessive traits. dominant traits are defined as whichever phenotype is expressed in an organism that is heterozygous for the trait.

➢ Law of segregation: • The law of segregation says that everyone has two versions (called alleles) for each trait one from each parent and that these alleles segregate randomly during meiosis. ➢ Punnett squares: • a chart that allows you to determine the expected percentages of different genotypes in the offspring of two parents • It is named after Reginald Crundall Punnett who devised the approach

THE END DONE BY RAZAN ALBISHRI GRADE:11