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Introduction To Genetics
Transcript of Introduction To Genetics
What are Punnett Squares?
The Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding experiment.
Punnet Squares can be used to predict and compare the genetic variation that will result from a cross.
What are Genetics ?
What do Genes do ?
Genes tell each of your cells what to do and when to do it. Genes also tell your body how to make proteins.
Introduction To Genetics
What are Genes?
Gene: the molecular unit of heredity of a living organisms.
Genes are coded instructions for making everything the body needs, especially proteins.
Every living thing- plant or animal, microbe or human being - has a set of characteristics inherited from its parent or parents.
The scientific study of heredity and the variation of inherited characteristics
Genetics & Probability
The principles of probability can be used to predict the outcomes of genetic crosses.
Probability is the likelihood that a particular event will occur
States that genes for different traits can segregate independent traits during the formation of gametes.
Helps account for many genetic variations observed in plants, animals, and other organisms
Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.
For example, not all genes show simple patterns of dominant and recessive alleles.
The characteristics of any organism, whether bacterium, fruit fly, or human being, are determined solely by the genes it inherits.
Genes provide a plan for development, but how that plan unfolds also depends on the environment.
Phases of Meiosis
Meiosis is a process of reproduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
Meiosis usually involves two distinct divisions, called meiosis 1 and meiosis 2.
Meiosis 1 & Meiosis 2
Meiosis 1 : Prior to meiosis 1, each chromosome is replicated. The cells then begin to divide in a way that looks similar to mitosis.
Meiosis 2 : The two cells produced by meiosis 1 now enter a second meiotic division. Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis 2.
In male animals, the haploid gametes produced by meiosis are called sperm.
In many female animals, the cell divisions at the end of meiosis 1 and meiosis 2 are uneven, so that a single cell, which becomes an egg, receives most of the cytoplasm.
Comparing Mitosis and Meiosis
Mitosis results in the production of the two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells.
The Work of Gregor Mendel
Around 1854 Mendel began to research the transmission of hereditary traits in plant hybrids.
Some genetic conditions are caused by mutations in a single gene.
These conditions are usually inherited in one of several straightforward patterns depending on the gene involved.
He chose to use peas for his experiments due to their many distinct varieties, and because offspring could be quickly and easily produced.
The Work of Gregor Mendel Continued
He cross-fertilized pea plants that had clearly opposite characteristics—tall with short, smooth with wrinkled, those containing green seeds with those containing yellow seeds, etc.—and, after analyzing his results, he reached two of his most important conclusions: the Law of Segregation and Law of Independent Assortment.
Mendel wondered where the recessive alleles. Had they disappeared?
To answer this question, he allowed all seven kinds of F1hybrid plants to produce an F2 (second filial) generation by self pollination.
When Mendel compared the F2 plants, he discovered that the traits controlled by the recessive alleles had reappeared.
Roughly 1/4 of the F2 plants showed the trait controlled by the recessive allele.
Each new cell in the growing embryo receives a full set of genes. But not every cell needs to make every protein and cells, they make some proteins only at certain times.Some genes are instructions for proteins that regulate the activity of other genes.
The F1 Cross
One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.Together, they determine the genotype of their host organism.
Alleles that determine some aspect of the phenotype, the physical appearance of an organism, are said to be “coding alleles."
There are numerous combinations of alleles, ranging from simple pairs to complex relationships between multiple ones that determine someone's appearance. When both of the alleles in a pair are the same, they are said to be “homozygous,”
The gene combinations that might result from a genetic cross can be determined by drawing a diagram.
Genetic recombination is the transmission-genetic process by which the combinations of alleles observed at different locations in two parental individuals become shuffled in offspring individuals.