Mendelian Genetics Genetics The Scientific Study of Heredity

Mendelian Genetics

Genetics: The Scientific Study of Heredity n Mendel –Austrian Monk n n Born 1822 Spent years studying science and mathematics Worked at a Monastery and taught High School. Also in charge of the monastery garden- This work is where Mendel developed his theories on Genetics

Sexual Reproduction n n Mendel understood that pollen contained the male reproductive cells and that the female portion of the flower produces the egg. When the male and female sex cells are joined together this is called fertilization and a seed is formed. http: //anthro. palomar. edu/mendel_1. htm

Pea Plants: n Pea plants can self-pollinate-meaning the pollen of a plant can fertilize the same flower (Inbreeding). This produces a seed with the same characteristics as the parent plant (true-breeding/homozygous). n These plants would produce only green seeds only yellow seeds, only tall seeds, etc

Cross-Pollination n n Mendel wanted to produce seeds by joining male and female reproductive cells from different plants-so he dusted pollen from one plant on to another to cross-pollinate. This can also be done naturally by pollinators such as bees. http: //www. fs. fed. us/wildflowers/pollinators/images/xpollination_ani. gif http: //www. dkimages. com/discover/previews/955/738361. JPG

Data/Observation Pollen Pictures Day 2 Lilium oriental (+) control After 120 min ~100 µm Pollen tube Picture by Charles Beckius

Genes vs. Alleles

Genotype – the actual codes for a trait ex. BB, Bb, bb n Phenotype- the traits seen

Dominant vs. Recessive n Principle of dominance states that some alleles are dominant and others are recessive. n n Capitol Letters =dominant traits=if gene is present, trait will always be seen. Lower case letter =recessive traits=hidden traits. BB x bb = Bb

True-breeding/homozygous n BB or bb pure characteristics from having all the same alleles

Hybrids/heterozygous n The offspring of crosses between parents with different traits are called hybrids. BB x bb = Bb brown x blue Hybrid brown

Traits n Mendel studied 7 different pea plant traits. n n n n Seed shape- round vs. wrinkled Seed color – yellow vs. green Seed coat color- gray vs. white Pod shape- constricted vs smooth Pod color green vs. yellow Flower position – axial vs. terminal Plant height- short vs. tall

haploid + haploid Diploid http: //www. mansfieldct. org/schools/mms/staff/hand/genpunnet 1. htm

Monohybrid cross

Mendel’s n P, F 1, and F 2 Generations P-parent generation t t T T Tt Tt TT x tt Offspring of the P generation is the F 1 generation Cross the F 1 -1 st filial generation T T t Tt x Tt t TT Tt Tt tt To get the F 2 “filial generation

n MENDEL's first law is the principle of uniformity. It says that, if two plants that differ in just one trait are crossed, then the resulting hybrids will be uniform in the chosen trait. http: //dwb. unl. edu/Teacher/NSF/C 08 Links/www. rrz. uni-hamburg. de/biologie/b_online/e 08/08 a. htm

n MENDEL's second law is the principle of segregation. It states that the individuals of the F 2 generation are not uniform, but that the traits are segregated

n MENDEL's third law is also called the principle of independent assortment. It says that every trait is inherited independently of the others and it thus covers the case that new combinations of genes can arise, which were not existing before. We know today that this principle is just valid in the case of genes that are not coupled, i. e. that are not located at the same chromosome.

n MENDEL's 4 th law is also called the principle of attraction. It says that since every sperm and egg are polar and that since sperm are slightly positive and ova is slightly negative they are always attracted to each other. In addition some alleles are also polar which increase the combination of certain characteristics combining together. For example blonde hair and blue eyes are more likely to developed together since those alleles are polar opposites. However this only occurs if the alleles are not located at the same chromosome.

Incomplete Dominance n http: //dwb. unl. edu/Teacher/NSF/C 08 Links/www. rrz. uni-hamburg. de/biologie/b_online/ge 08/01. gif

In-complete dominance

Co-Dominance http: //media. nasaexplores. com/lessons/02 -064/images/image 2. jpg

Dihybrid Cross http: //bio. winona. edu/berg/ILLUST/mend 7. gif

A i o i http: //www. biologycorner. com/resources/bloodtype_chart. gif o i B i

http: //www. bioweb. uncc. edu/1110 Lab/notes 1/images/lab 7. h 28. jpg

Sex-Linked Traits http: //www. biologycorner. com/bio 2/specialgenetics. html http: //www. uni. edu/walsh/xlink 2. gif

Pedigree http: //www. koshland-science-museum. org/img/sub/teachers/webquest-gd-007. jpg