Chapter 5: Heredity
Section One: Mendel and His Peas
Heredity- the passing of genetic traits from parent to offspring
Dominant Trait- the trait observed in the first generation when parents that have different traits
Recessive Trait- a trait that reappers in the second generation after disappearing in the first generation when parents with different traits are bred
Chapter Five; Section One: Summary
Gregor Mendel characteristics for pea plants.
Section One was about Gregor Mendel. He wanted to know about inheritance He used pea plants because he could control which traits were passed. He studied one characteristic at a time. He used self pollinating, cross pollination, and true breeding plants. Self pollinating plants have female and male reproductive parts. During cross pollination, pollen from one plant fertilizes the ovule of another plant. True breeding plants self pollinate and all of its offspring has the same trait as the parent. Different forms of a characteristic are traits. He crossed two plants with different traits. His first experiments he crossed a plant with white flowers with one that had purple flowers. The first generation plants and purple plants. Purple flowers are dominant over the white flowers. the white flowers are recessive, so white flowers are a recessive trait. His second experiments he let the first generation plants self pollinate. The offspring, the second generation, had the recessive trait, white flowers. he did this for seven characteristics, some of the second generation had the recessive trait. he gathered the information and came to a three to one ratio. After Mendel died , he opened the door to genetic studies.
Section Two: Traits and Inheritence
Gene- one set of instructions for an inherited trait
Allele- one of the alternative forms of a gene that governs a characteristics, such as hair color
Phenotype- an organism's appearance or other detectable characteristics
Genotype- the entire genetic makeup of an organism; also the combination of genes for one or more specific traits
Probability- the likelihood that a possible future event will occur in any given instance of the event
Chapter Five; Section Two: Summary
The white turtle has albinism.
Section two was about genes. Genes are instructions for an inherited trait. Each parent gives one set of genes. The different forms of a gene are known as alleles. Genes affect traits of an organism. How an organism looks is its phenotype. Phenotypes of a pea would be white or purple flowers. Two alleles make an organism's genotype. Two dominant or recessive traits or called homozygous. One dominant and one recessive are called heterozygous. Punnet squares are used to show possible combinations of offspring. Punnet squares are not the definite outcome of offspring, it is just what the offspring will possibly look like. Incomplete dominance is when one trait is not completely dominant over another. Each trait has its own degree of influence. Sometimes one gene controls more than one trait. Sometimes many genes control one trait. An organism's environment also influences its genes.
Section Three: Meiosis
Homologous Chromosomes- chromosomes that have the same sequence of genes and the same structure
Meiosis- a process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, which results int he production of sex cell
Sex Chromosomes- one of the pair of chromosomes that determine the sex of an individual
Pedigree- a diagram that shows the occurrence of a genetic trait in several generations of a family
Chapter Five; Section Three: Summary
This rabbit was made using selective breeding.
Section two was about meiosis. Asexual reproduction occurs in single-celled organisms. It involves one parent cell splitting into two exact copies after copying its structures. Sexual reproduction is when two parent cells join to form offspring that are different than them. Sex cells have half the normal chromosomes of a normal body cell. Normal body cells have 46 pairs of chromosomes. Sex cells have 23 pairs of chromosomes. Meiosis produces sex cells. Walter Sutton discovered egg and sperm cells chromosomes were located in the nucleus. He also discovered genes are located on chromosomes. Chromosomes are copied once and the nucleus divides twice during meiosis. Females have two X chromosomes. Males have one X chromosome and one Y chromosomes. Males determine what gender the offspring will be. Sex linked disorders are usually found in males because females have two X chromosomes so they have a backup. Males only have one of each so it is more likely to find a disorder. Pedigrees are used to show if a certain trait will show up in later generations. Humans can also selectively breed animals and plants.
Now that you know about heredity, here is a song about genes and heredity.