Genetics

Gregor Mendel

Chapter 11

Mendel

• Austrian Monk

• Was a local high school science teacher

• Job was to grow food for the entire monastery

• Became interested in how traits are passed from parents to offspring.

Variations

Human Genetics

Principles of Inheritance

• E:\Early_Principles_of_Inheritance.asf

Mendel

• Crossed and controlled breeding of pea plants

• Used burlap sacks to control pollination of flowering pea plants

• Very controlled experiment

• Many generations in a short period of time

Mendel’s Work

• Crossed a tall pea plant with a tall pea plant, produced all tall plants.

• Crossed a short pea plant with a short pea plant, produced all short plants.

• Crossed a tall pea plant with a short plant, produced all tall plants.

• Took seeds from the previous cross, produced 3 tall plants and one short plant

Monohybrid Crosses

• E:\Introduction____Classical_Genetics_and_Monohybrid_Crosses.asf

Mendel’s Research

• E:\Gregor_Mendel_s_Research_and_Principles.asf

Mendel’s Discoveries

• E:\Mendel_s_Research_and_Discoveries.asf

Mendel’s Hypothesis

• Traits are controlled by factors (genes) which always occur in pairs

• Factors (genes) separate during the formation of sex cells (gametes).

• In a pair of factors (genes) one may mask or hide the effect of the other trait.

Possible Gametes

Punnett Square

Punnett Square

Punnett Square

Punnett Square

Punnett Square

Punnett Square

Punnett Square

Pea Plants

Mendel’s Crosses

Genetic Terms

• Homozygous- two alleles that are the same, TT or tt

• Heterozygous- two alleles that are opposite, Tt (hybrid)

• genotype- using letters to represent traits, TT, Tt, tt.

• Phenotype-a physical description of a trait,

• Homozygous tall, heterozygous tall.

Genetics

• In pigs white coat color is dominant to black coat color. Curly tails are dominant to straight tails.

• Cross a heterozygous white coat, heterozygous curly tail male with a heterozygous white coat, heterozygous curly tail female. Predict the possible results.

Probability

• E:\Probability.asf

Mendel’s research on Pea Plants

• E:\Gregor_Mendel_s_Reseach_on_Pea_Plants_and_His_Development_of_Theories_of_Inheritance.asf

Dihybrid Crosses

• E:\Introduction___Dihybrid_Crosses.asf

Dihybrid Cross

Dihybrid Cross

Breeding Song Birds

• E:\Breeding_White_Songbird_Canaries_Through_a_Dihybrid_Cross.asf

Incomplete Dominance

• E:\Incomplete_Dominance_in_Snapdragons.asf

Genetics

• In four ‘o’ clocks, red is incompletely dominant to white flower color. The heterozygous condition results in pink flowers.

• Cross a red flower with a pink flower and predict the results.

• Cross a pink flower with a pink flower and predict the results.

Multiple Alleles and Co-dominance

• E:\Multiple_Alleles_and_Co_Dominance_in_Human_Blood_Types.asf

Incomplete dominance vs. Co- dominance

• Incomplete- you get a mixture. Red and white, you get pink.

• Co-dominance- both traits appear. Red and white to make roan.

• A and B blood types combine to make AB.

Human Alleles

• E:\Possible_Combinations_of_Human_Alleles.asf

Fruit Flies

• E:\Research_on_the_Genetic_Make_up_of_the_Fruit_Fly_Drosophila.asf

Human Sex Chromosomes

Sex Linked Inhertiance

• E:\Introduction___Sex_Linked_Inheritance.asf

Sex Linked Inhertiance

• E:\Inherited_Human_Traits_and_Patterned_Sex_Linked_Inheritance.asf

Color Blindness

• E:\Color_Blindness.asf

Color Blindness

Hemophylia

• E:\Hemophylia.asf

Pedigree Charts

• E:\Organizing_Information_About_Sex_Linked_Inheritance_in_Pedigree_Charts.asf

Sex Linked Traits

• Traits carried on X or Y chromosome.

• Most are carried on X chromosome.

• Therefore a male is 70 times more likely to have a sex-linked trait than a female.

Sex limited traits

• Traits carried by both sexes and controlled by the presence of sex hormones.

• Secondary sexual characteristics.

• Females- estrogen and progesterone

• Female traits- higher % of body fat vs. lower % of muscle tissue. Breast growth and production of eggs.

Sex Limited Traits cont.

• Males

• Voice change, growth of beard, production of sperm, Higher % of muscle tissue vs. lower % of body fat.

Sex Influenced Traits

• Traits that are dominant in one sex and recessive in the other trait.

• Male pattern baldness.

Polygenic Inheritance

• More than one pair of alleles codes for a trait.

• Skin color

• Hair color

• Eye color

• The more dominant traits, the darker, more recessive, lighter the color.

Selective Breeding

• Luther Burbank worked with potato plants to produce a potato that was resistant to disease.

• You take the best two individuals with qualities that are favorable, and allow them to mate.

• Hopefully the traits are passed to offspring.

Hybridization

• Crossing of two different organisms and trying to pass the traits to the offspring.

• Cross between a cow and a buffalo and producing a beefalo.

• Done with some domestic animals hoping to produce a new breed.

• Many hybrids are sterile.

Hybrids

• Crossing of two closely related but different individuals

• The goal is to get the best qualities of each individual

• Example beefalo

• Goal was to get an individual that had good tasting meat but was able to survive extreme harsh weather conditions.

Hybrids

Genetic Disorders

• Human disorders can be caused by dominant, or recessive genes. Some may exhibit co-dominance.

• Many of these disorders are from particular areas of the world. They have become more prevalent due to the breaking down of geographic and social barriers.

Genetic Disorders

• Most genetic disorders are autosomal, which means they occur on an autosome or any chromosome other than sex chromosome.

• Sex linked- occur on X or Y chromosome

• Color blindness, hemophilia

Sickle Cell

Nondisjunction

• Failure of a pair of chromosomes to separate during meiosis

• Trisomy- three chromosomes instead of the normal pair.

• Monosomy- one chromosome instead of the normal pair.

• May occur in any pair of chromosomes

Trisomy 21

• Downs Syndrome- results from nondisjunction in the 21st pair of chromosomes, they have 3 chromosomes instead of the normal pair.

Karotypes

• Used by Geneticist to determine genetic disorders.

• Take a photograph of chromosomes and then line them up to see if correct number exists or if part of a chromosome is missing.

Karotypes

• E:\Karyotype___A_Key_to_the_Study_of_Sex_Linked_Inheritance.asf

Karotypes

Cloning

• E:\Cloning.asf

Human Genome

• E:\An_Introduction_to_the_Human_Genome.asf

Becoming an Identical Twin

• E:\Becoming_an_Identical_Twin.asf

Identical Twins

• E:\Identical_Genes__The_Science_of_Identical_Twins.asf

Twins and Environment

• E:\Separated_at_Birth__Environment_vs__Heredity_in_Identical_Twins.asf

Genetics and Behavior

• E:\Novelty_Genes__Genetics_and_Behavior.asf

Hunting Down Genes

• E:\Hunting_Down_the_Genes_Involved_in_Disease.asf

Tracking Traits

• E:\Tracking_Specific_Traits_Through_Genetic_Code.asf

Mutation

• Any change in the genetic code.

• Most mutations are harmless

• Most mutations correct themselves during the next cell division.

• Mutations may cause an abnormal growth of some types of cells, this may lead to various types of cancer.

Mutations cont.

• Mutations can be on the DNA level, allele level, or the chromosome level.

• Mutations may be harmful or lead to a genetic change.

• Some genetic change may be positive.

Genetic Engineering

• Manipulating DNA

• Gene Splicing, cut DNA at a specific point so that a new sequence of DNA can be introduced. Ex. Injecting the gene to produce insulin into bacteria so that it will produce insulin.

Gene Splicing

DNA to Solve Crimes

• E:\Using_DNA_Evidence_to_Solve_Crimes.asf

X Chromosome turned off

Aging

• E:\The_Molecular_Process_of_Aging__Telomeres_and_the_Death_of_Cells.asf