Mendel Genetics Review Powerpoint l Gregor Mendel the

Mendel & Genetics Review Powerpoint l Gregor Mendel, the father of genetics.

Genetics is the study of Heredity. Define Heredity. l The passing on of traits from one generation to the next. l Where is the genetic information for traits stored? l In each individual’s DNA on chromosomes containing many genes.

What did Mendel study to understand inheritance? l Common garden pea plants l Why did he choose pea plants? Give at least 3 reasons. l 1 --Fast growing with many offspring l 2 --Several traits—each had only two outcomes l 3 --Easy to cross pollinate—male and female reproductive organs in each plant

What did Mendel call true breeding? l plants that come from a long line of plants that show the same trait l When he crossed two truebreeding plants with opposite traits, he called this what? l The “P” cross for Parental generation l What did he get? l The F 1 generation that were 100% the dominant trait

What was Mendel’s next step? l He crossed two F 1 plants. l What results did he get? l The F 2 generation l What interesting ratio did he find? l They were 3: 1 (dominant to recessive)

What is the Law of Segregation? l 1 --Individuals must have two copies of genetic information for every trait– one from each parent l 2—each copy is passed randomly l 3—One of these copies (alleles) can mask the expression of the other, ie. Dominant alleles can mask recessive alleles when both are present

What is the Law of Independent Assortment? Alleles of different genes separate independently of one another during gamete formation l What does that mean? l The allele a parent gives for one trait does not affect what he/she gives for another trait so you can have many different combinations of traits given to the egg or sperm l

What are alleles? l Different forms of the same gene for a trait l When an individual has two of the same allele, the genotype is called. . l Homozygous l When there are two different alleles, it is. . l Heterozygous

What is the difference between genotype and phenotype? l Genotype is l the type of genes or alleles l Phenotype is l What is looks like--The physical appearance of the organism

Monohybrid vs. Dihybrid l Mono hybrid: a cross when there is just one trait involved, ex. l Height: Tt X tt l Di hybrid: Two traits are involved, ex. l The horse’s coat and gait are crossed l FFGg X Ffgg

Autosomal vs. Sex-linked l Autosomes are chromosomes not on the. . X or y chromosomes l l l Sex-linked characteristics are always on… The X-chromosome Give an example of a sex-linked condition Hemophilia Why does it occur more in males? Males have only 1 X-chromosome so have a better chance of having the condition.

Contrast a Punnett Square and a Pedigree l. A Punnett Square is… l a grid that predicts the types of possible offspring from a cross l. A Pedigree is. . l A diagram that shows a family tree and how traits pass from generation to generation

Pedigree or Punnett Square?

Is this a monohybrid or dihybrid cross?

Modes of Dominance: 1 --Complete dominance… l One allele is completely dominant over the recessive and the recessive is masked in a heterozygous individual l 2 --Incomplete dominance. . l The dominant does not completely mask the recessive and the heterozygous phenotype is a blend of the two- an intermediate variation. l There are three possible phenotypes. l

More modes of inheritance 3 -- Co dominance. . l More than one genotype is dominant and when two of these are together, they form another phenotype l l l l 4– Multiple alleles. . These traits have 3 or more alleles Example of both codominance and multiple alleles. . blood types. How many blood types are possible? Four-- They are. . A, B, AB, and O

Modes of Inheritance cont. l 5 -- Polygenic Inheritance: traits that are. . l controlled by many genes. l This makes many variations of color and trait possible l What are characteristics controlled by multiple alleles? l Human hair and eye color

Genetic Diseases: l l Sickle Cell Anemia causes. . Abnormal hemoglobin molecules and poor circulation of blood l l Cystic Fibrosis causes. . Build up of mucus in lungs and organs l l Hemophilia- sex linked condition that causes Bleeding and inability to clot l l Huntington’s Disease causes. . Deterioration of brain tissue and decreased muscle control