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GENETICS AND THE PUNNETT SQUARE

GENETICS Genetics - the study of how characteristics are passed from generation to generation It is the branch of biology that focuses on heredity Genetics uses predictions and probabilities to determine genetic outcomes

HISTORY Gregor Mendel is considered the “father of genetics” He published work that later became the basis of modern genetics Hello, I am Gregor Mendel

HISTORY Born in Austria in 1822 Austrian Monk (man of a religious order and lives in a monastary) Excellent student at the University of Vienna

GARDEN PEAS – Pisum sativum Mendel worked with garden peas and predicted patterns of heredity Peas were easy to work with – Produced a large number of offspring in a short amount of time – Two different forms of peas with many contrasting traits

GARDEN PEAS – Pisum sativum Contrasting traits of peas – Yellow vs green seed – Round vs wrinkled seed

GARDEN PEAS – Pisum sativum Contrasting traits continued –Green vs yellow pod –Tall vs short plant –White vs purple flower

GARDEN PEAS – Pisum sativum Peas can self-pollinate – Flower can fertilize itself (both male and female parts) – Male = stamen – produces pollen – Pollen = sperm – Female = pistil – produces ovule – Ovule = egg

MENDEL’S EXPERIMENTS Crossed two pure breeding plants by cross pollination Cross pollination – transferring pollen of one plant to the ovule of another plant P generation – two pure bred parents F1 generation – first offspring from P generation parents Cross two F1 offspring and get an F2 generation

MENDEL’S EXPERIMENTS Monohybrid cross – cross that involves only one pair of contrasting traits Example: – Trait = flower color redblue P generation + red F1 generation red + F2 generation redblue

MENDEL’S EXPERIMENTS Dihybrid cross – a cross that involves two different contrasting traits Example: –Trait = speed – Trait = long hair Result = fast and slow dogs with long and short hair

GENES Genes – factors for traits resulting from fertilization – Example - genes for tall plants or genes for short plants – Example - genes for long hair or genes for short hair

TRAITS Inherited traits – individuals inherit traits from their parents, one trait from each parent, thus two copies of each gene –Two genes for eye color, nose size, ear length, hair color, etc Alleles – two versions of one gene, dominant or recessive

ALLELES Dominant allele designated by a capital letter Recessive allele designated by a lower case letter Genotype is expressed by two alleles (or genes) BB, Bb, bb Phenotype is the physical characteristic determined by the genotype red hair, long legs, big nose, freckles, dimples kjbpyw KJBPYW

ALLELES Dominant trait – a dominant trait will be expressed if at least one dominant allele is present BB or Bb Recessive trait – a recessive trait will be expressed only if two recessive alleles are present bb

ALLELES Example –The gene for freckles is designated using the letter “F” –Having freckles is dominant and designated as “F” –Not having freckles is recessive and designated as “f” If FF then the person has freckles If Ff then the person has freckles If ff then the person doesn’t have freckles

HOMO vs HETERO Alleles can be categorized in one of two ways –Homozygous – both alleles for a gene are the same, either both dominant or both recessive BB or bb –Heterozygous – both alleles for a gene are different, one dominant and one recessive BbBb

PUNNETT SQUARE Invented by Reginald Punnett It is a diagram that predicts the expected outcomes of genetic crosses B b B b BB Bb bb

PUNNETT SQUARE Parent alleles are positioned on the top and sides of the punnett square Then the alleles are added to make an F1 generation B b B b BB Bb bb Father Mother (P generation) (F1 generation)

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