Mendelian Genetics Genetics is the scientific study of heredity. Heredity is what makes each species unique.

Gregor Mendel??? Known as the Father of Genetics: His experiments with Pea plants from 1856-1863 began our understanding of how traits, things like hair or eye color, height, weight, ect……., were passed down from generation to generation. He came up with the principles of heredity that still hold true today His work started and formed the base of all genetics, a field we learn more about every day.

Introduction Mendel started the idea of particulate inheritance, which we use today. ???? WHY Peas 1. trait are in 2 very different forms, like flowers are either purple or white and seeds yellow or green and shape round or wrinkled 2. Male and female reproductive parts are contained in the same flower, you can control mating

Cont….. 3. It is small and grows easily and quickly producing many offspring. All Good Reasons

How did He do it Mendel would cross-pollinate (hybridize) two contrasting, true-breeding pea varieties. He got true breeders by allowing self pollination. The true-breeding parents are the P generation and their hybrid offspring are the F1 generation. Mendel allowed the F1 hybrids to self-pollinate to produce an F2 generation. Here he came up with his 2 famous laws of segregation and independent assortment.

Mendel reasoned that the heritable factor for white flowers was present in the F1 plants, but it did not affect flower color. This is where dominant and recessive come in. He found a 3:1 ratio in many traits.

The Principle of Dominance The principle of dominance states that some alleles are dominant and others are recessive. Dominant alleles are always expressed. Represent by a capital letter. (B – Dominant for Brown eyes) Recessive alleles are only expressed if both alleles are recessive. Represented by a lower case letter (b – recessive for blue eyes)

The Law of Segregation 1. different version of genes (alleles) account for variations in inherited characters or traits Alleles vary in their nucleotide sequences in genes. Ex Blue and Brown eyes, both eye color genes just different versions 2. For each trait, organisms inherit 2 alleles, one from each parent. 3. If two alleles differ, then one, the dominant allele, is fully expressed while the other, Recessive, is masked or only partially shown 4. The two alleles for each trait segregate during gamete, sex cell, production. (Meiosis)

Punnett Square Predictions

Genetics Vocabulary organism with two identical alleles for a trait is homozygous. ( TT or tt) Big letters= Dominant small or lower case = recessive. Organisms with two different alleles for a character is heterozygous ( Tt or Pp) The physical expression of the genes is known as the phenotype Ex) What it looks like, tall, short ,white, black ect…. The actual genetic makeup is known as the genotype. Ex) Homo. D or R, Hetero. D or R.

Test Cross Tales the Tale

Law of Independent Assortment The Law states that the alleles of different genes separate independently of each other during gamete formation presence of one specific allele for one trait has no impact on the presence of a specific allele for the second trait. So one trait does not influence or control another. Not all dark haired people have dark eyes. Ect…... Show probability just like dice and coin toss

Sound Simple Right The relationship of genotype to phenotype is rarely simple like in our examples because there are exceptions to all rules. Intermediate inheritance and codominance are two examples of how genetics is not always as smiple as we would like. Mendel lucked out in picking peas plants because each trait is controlled by 1 gene, genetically simple. But this is rare….

Intermediate Inheritance some alleles show Intermediate Inheritance where heterozygotes show a distinct intermediate phenotype, not seen in homozygotes. When two dominant genes come together and neither are fully expressed. This results in a new MIXED phenotype. Snapdragons come in Homozygous Dominant Red and Homozygous dominant white. When these two plants are crossed the flowers are heterozygous pink. A mix between red and white This is also called incomplete dominance

Snapdragons

Co-dominance codominance 2 alleles affect the phenotype in separate, distinguishable ways 2 dominant alleles expressed at the same time. When both alleles are dominant for a different trait and both are expressed separately. (NOT MIXED) Flowers can often be co-dominant. When you see a flower with 2 different color petals it is an example of co-dominance. Both colors are expressed and not mixed Other examples include snakes and chickens Ex. Is blood type. DRAW. This is also s multiple allele gene have 3 alleles present. A,B,O

Co-dominant Skin colors

Co-dominant chicken feathers

Linked Genes The tendency of some genes to be inherited together is known as linked genes. Ex – red hair and freckles Ex – Red hair and fair skin

Sex Linked Genes If a gene is found only on the X chromosome and not the Y chromosome, it is said to be a sex-linked trait Baldness is a recessive sex linked trait. Found on the X chromosome. Females usually don’t go bald because they have two copies of the gene and usually 1 works properly. XX But males only have one X chromosome. (XY) There is no matching gene on the y chromosome. So if mom gives the X chromosome with the recessive allele then her son will go bald. Word to your mother

Sex Linked Disorders Hemophilia color blindness muscular dystrophy

polygenic polygenic inheritance, the additive effects of 2 or more genes on a single phenotypic trait. It can cause a great range in the phenotypic out come of an individual. Ex. Human skin color controlled by 3 genes AABBCC individual is dark and aabbcc is light crosses between two AaBbCc heterozygote individuals would yield offspring covering a vast range of shades. See pic..

Pleiotropic and Epistasis most genes are pleiotropic, affecting more than one phenotypic trait extensive symptoms of sickle-cell anemia are owed to a single gene. epistasis, a gene at one locus, or location, alters the phenotypic expression of a gene at a second locus Ex. Mice and other mammals 1 gene determines if there is pigment in the hair C, there is, c, is not, and another determine color B,black or b, brown. Cc is albino

Pleiotropic

Epistasis

Phenotype and Environment An individuals phenotype depends on the environment as well as on genes. Nature Vs. Nurture . . . . . .genes vs environment . . . .which one effects who you are more? Ex. nutrition influences height and weight, exercise alters build, sun-tanning darkens the skin, and experience improves performance on intelligence tests Ex. Hydrangea- Acid soil = blue flower and basic soil = pink. Genes are the same for both. Ex. Artic Fox turns brown in summer and white in winter so does snow shoe hair and grouse. Ex. Fur color in Siamese cats influenced by temp. and so is, Sex in many animals reptiles esp. is determined by temp. Ex. Identical twin raised in different environment can very in personality and physical appearance.