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WELCOME BACK! Time to jump start your brain!
• What’s the purpose of mitosis?
• What’s the purpose of meiosis?
• How many chromosomes do somatic cells have?
• How many chromosomes do gametes have?
Heredity and Genetics
Mendel and Our Understanding of the Gene Pool
Gregor Mendel
• Gregor Mendel was an Augustinian friar who enjoyed gardening and science
• Though people had an idea about how traits were passed from parent offspring, it was Gregor Mendel who proved it using science
• Between 1856 and 1863, he raised pea plants, which he used to study genetic inheritance
• He is now known as the “Father of Genetics”
What did Mendel prove?
• The Law of Segregation - The two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes. Half the gametes carry one allele, and the other half carry the other allele.
• The Law of Independent Assortment - Genes for different traits assort independently of one another in the formation of gametes.
The Experiment
• There are three things that Mendel paid attention to in his experimental design:– He controlled over breeding– He used purebred plants– He observed only either/or traits, or traits that
manifest in only two forms• He followed 7 traits: pea shape, pea color,
flower color, flower position, pod shape, pod color, plant height
Vocab Check
• A gene is a piece of DNA that provides a set of instructions to a cell to make a certain protein.
• An allele is any of the alternative forms of the gene that may occur.
• A genome is all of an organism’s genetic information.
Punnett Squares
Types of Crosses
• Monohybrid Cross – involves the crossing of only one trait– Test Cross – A cross between an unknown
genotype and a recessive phenotype
Types of Crosses
• Dihybrid Cross – involves the crossing of two different traits
Mendel’s Second Law
• The Law of Independent Assortment – states that allele pairs separate independently of each other during gamete formation (meiosis)
Heredity Probabilities
• Probability is the likelihood that an event will occur
Genetic Variation
• One of the benefits of sexual reproduction (over asexual reproduction) is that it provides for abundant variation.
• There can be 8 million different combinations of chromosomes produced through meiosis.
• Crossing over occurs when homologous chromosomes exchange segments during meiosis.
Genetic Variation
• Each chromosomes contains hundreds of genes
• How do genes show independent assortment if they are on the same chromosome?
• Genes located close together on the same chromosome are said to display genetic linkage.