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UNDERSTANDING HEREDITY. GENETICS AND MUTATIONS. Genetics. Part One. Genetics is…. The scientific study of heredity. A gene is…. A sequence of DNA that codes for a protein and determines traits. What is an allele?.
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UNDERSTANDING HEREDITY GENETICS AND MUTATIONS
Genetics Part One
Genetics is… • The scientific study of heredity
A gene is… • A sequence of DNA that codes for a protein and determines traits
What is an allele? • One of two or more alternative forms of a gene that are found at the same place on a chromosome.
What does the term heterozygous mean? • The organism has two different alleles for a trait. • Example: Tt Bb
What does the term homozygous mean? • The organism has two of the same alleles for a trait. • Example: TT or tt BB or bb
Complete section determining heterozygous or homozygous genotypes
What is a genotype? • The actual genetic makeup of an organism.
What is a phenotype? • The physical characteristics of an organism.
Who was Gregor Mendel? • The “Father” of genetics
What was his contribution? • His experiments laid the foundation of the science of genetics. • He noticed that traits could disappear in one generation and reappear in later generations.
Gregol Mendel Born July 20, 1822 HeinzendorfbeiOdrau, Austrian Empire (now Hynčice, Czech Republic) Died January 6, 1884 (aged 61) Brno (Brünn), Austria-Hungary (now Czech Republic) Nationality Empire of Austria-Hungary Fields Genetics Institutions St Thomas's Abbey Alma mater University of Olomouc University of Vienna Known for Creating the science of genetics
Complete section on monohybrid crosses • Now start “Practice with Crosses”
Genetics Part Two
Define Independent Assortment • Independent segregation of genes during the formation of gametes. • Remember: Meiosis is the formation of gametes.
Define Law of Segregation • Separation of alleles during gamete formation. • Example: 1 of 2 alleles for eye color will go to each sperm or egg
Define Co-dominant • Both alleles of a gene contribute to the phenotype • Examples: Type AB blood; 1 blue eye and one green eye; speckled chickens
Define Incomplete Dominance • One allele cannot dominate another; the final phenotype is a blend of the 2 alleles • Example: cross a red carnation with a white carnation makes a pink carnation
Co-Dominance How many phenotypes are there? Three: AA,BB, AB Three How many genotypes are there?
Incomplete dominance How many phenotypes are there? Three: RR-red rr-white Rr-pink Three How many genotypes are there?
Genetics Part Three
Sex chromosomes What are the male sex chromosomes? XX XY What are the female sex chromosomes?
What does it mean for a trait to be sex-linked? • It is carried on one of the sex chromosomes, most likely the X
Examples of sex-linked traits would be… • The ability to see color (color blindness) • Having a full head of hair (baldness) • Blood clotting properly (hemophilia)
What is a di-hybrid cross? • A cross between two individuals with two different traits that you are studying • Complete examples and problems
What is a mutation? • Genes code for… • Mutations are… • Proteins • Mistakes in genetic code that affect the final protein
What is a point mutation? A mistake in one nitrogen base of an mRNA codon
Types of point mutations: • Substitution – 1 nucleotide is switched for another Example: CAT GCA CAT GCG • Insertion or deletion – 1 nucleotide is inserted/deleted in sequence Example: CAT GCA CAT GAC A Example: CAT GCA CAT CA
Effects of point mutations • Substitution • Insertions/deletions • Might have no effect on/or will only effect one amino acid • Change how the sequence is read – called a frameshift mutation
What is a chromosomal mutation? A change in the number or structure of chromosomes.
Types of chromosomal mutations • Deletion - entire gene(s) deleted • Duplication – an extra copy of gene(s) added • Inversion – segment of chromosome is flipped over and reversed in place • Translocation – segment of chromosome breaks off/relocates to another
Result of: Duplication Can be the result of: Inversion, deletion or translocation
When mutations go… Right Disruption of biological activities Disability Death Source of genetic variation May allow some members of a species a better chance to survive Wrong