Words to know… Heredity - the passing of traits from parent to offspring. Genetics - the study of heredity. Trait- a specific characteristic Gene- chemical factor that determines a trait Allele- A segment of a gene Hybrid- the offspring crosses between parents with different traits

Gregor Mendel Father of Genetics He lived in a monastery; He was a teacher and took care of the garden Mendel’s knowledge helped us understand heredity. He studied the pea plant most of all.

Mendel's Process Mendel took a true-breeding (or pure) plants that always produce offspring with the same trait when they self-pollinate and cross pollinated it with a true breeding plant with a different trait. The P generation is the true-breeding generation or the parent generation.

Pollination Self pollination occurs when pollen is transferred from the anthers (male) of one flower to the stigma (female) of the same flower. Cross-pollination occurs between two plants.

The F1 generation is the offspring of the P generation. Mendel called the plants in the second generation the second F2

Mendel established three principles (or Laws) from his research The Principle of Dominance and Recessiveness - one trait is masked or covered up by another trait Principle of Segregation - the two factors (alleles) for a trait separate during gamete formation Principle of Independent Assortment - factors of a trait separate independently of one another during gamete formation; another way to look at this is, whether a flower is purple has nothing to do with the length of the plants stems - each trait is independently inherited

copyright cmassengale Mendelian Genetics 3/25/2017 Mendel’s Laws copyright cmassengale

Results of Monohybrid Crosses Mendelian Genetics 3/25/2017 Results of Monohybrid Crosses Inheritable factors or genes are responsible for all heritable characteristics Phenotype is based on Genotype Each trait is based on two genes, one from the mother and the other from the father True-breeding individuals are homozygous ( both alleles) are the same copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Law of Dominance In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. All the offspring will be heterozygous and express only the dominant trait. RR x rr yields all Rr (round seeds) copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Law of Dominance copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Law of Segregation During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. copyright cmassengale

Applying the Law of Segregation Mendelian Genetics 3/25/2017 Applying the Law of Segregation copyright cmassengale

Law of Independent Assortment Mendelian Genetics 3/25/2017 Law of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another. This law can be illustrated using dihybrid crosses. copyright cmassengale

Dominant- stronger & mask other genes; the trait that shows up more frequently represented by a capital letter Recessive- “weaker” the trait that shows up less frequently represented by a lower case letter

A chromosome is made up of DNA A chromosome is made up of DNA. A gene is a segment of DNA on a chromosome that controls a particular hereditary trait. Each of two or more alternative forms of a gene is called an allele. Mendel’s factors are now called an allele.

Particulate Inheritance Mendelian Genetics 3/25/2017 Particulate Inheritance Mendel stated that physical traits are inherited as “particles” Mendel did not know that the “particles” were actually Chromosomes & DNA copyright cmassengale

Probability is the likelihood that a specific even will occur. It is the mathematical chance that something will occur.

copyright cmassengale Mendelian Genetics 3/25/2017 Punnett Square Used to help solve genetics problems copyright cmassengale

Types of Genetic Crosses Mendelian Genetics 3/25/2017 Types of Genetic Crosses Monohybrid cross - cross involving a single trait e.g. flower color Dihybrid cross - cross involving two traits e.g. flower color & plant height copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 More Terminology Genotype - gene combination for a trait (e.g. RR, Rr, rr) Phenotype - the physical feature resulting from a genotype (e.g. red, white) copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Genotypes Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure  Heterozygous genotype - gene combination of one dominant & one recessive allele    (e.g. Rr); also called hybrid copyright cmassengale

?????? What is the phenotype of a heterozygous flower? What is the genotype of a heterozygous flower? What is the genotype of a homozygous dominant?

copyright cmassengale Mendelian Genetics 3/25/2017 Dihybrid Cross RY Ry rY ry RY Ry rY ry copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Test Cross A mating between an individual of unknown genotype and a homozygous recessive individual. copyright cmassengale

Its not all that easy! Multiple alleles- trait that is determined by more than two alleles (ex. Human blood types) Polygenic traits- trait influenced by several genes; genes may be on same chromosome or on different one (ex. Human eye color, weight, skin tone)

Incomplete dominance The phenotype is in between that of the parents. It is like a mixture (pink flower) Example: Snap Dragon

Codominance Both alleles are expressed. With Codominance you can see two dominant alleles.

copyright cmassengale Mendelian Genetics 3/25/2017 Codominance Two alleles are expressed (multiple alleles) in heterozygous individuals. Example: blood type 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Codominance Problem Example: homozygous male Type B (IBIB) x heterozygous female Type A (IAi) IB IA i IAIB IBi 1/2 = IAIB 1/2 = IBi copyright cmassengale

Another Codominance Problem Mendelian Genetics 3/25/2017 Another Codominance Problem Example: male Type O (ii) x female type AB (IAIB) i IA IB IAi IBi 1/2 = IAi 1/2 = IBi copyright cmassengale

copyright cmassengale Mendelian Genetics 3/25/2017 Codominance Question: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? boy - type O (ii) X girl - type AB (IAIB) copyright cmassengale

Thomas Hunt Morgan Discovered that females have XX chromosomes and males have XY by studying a fruit fly. Sex Chromosomes determine the sex of an organism. He discovered that the gene for eye color in fruit flies is a sex linked trait carried on the Y chromosome

copyright cmassengale Mendelian Genetics 3/25/2017 Sex-linked Traits Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y XX genotype for females XY genotype for males Many sex-linked traits carried on X chromosome The genes interact with other genes scattered throughout the genome copyright cmassengale

Blood Type Blood Type Antigen Antibody Can donate to Can receive from AB O

Karyotype of Kleinfelters and Turners

Pedigree

Sex linked