Hereditary

Gregor Mendel - Austrian - Used Peas in for experiments Heredity - Passing of traits - From Parents to Offsprings Offspring - Product or child - From reproduction

- Have male and female reproductive structures Self- Pollinating Plant - Can fertilize itself - Can self-pollinate True-Breeding Plant - Offspring is identical to parent - Involves two different plants Cross-Pollination - One plant fertilizes another

3. 1. 2.

Characteristic - Feature - in different forms - Ex: Hair color, Eye color, Height Trait - Different forms of characteristics Breed - To mate or fertilize with another organism

Mendel’s First Experiments - Crossed pea plants - Focused on 7 characteristics - One trait seemed to always disappear - One trait seemed to always stay Dominant Trait - The trait that stayed - The trait that disappeared Recessive Trait

- Mendel studied one characteristic at a time - Mendel only used true-breeding plants - So he would know what to expect

Mendel’s Second Experiments - Investigating recessive traits - First generation offspring were bred - Some recessive traits reappeared - Recessive traits didn’t show up as much as the dominant traits - 3:1 ratio - Realized two sets of instructions were needed - Opened the doors to modern genetics

Traits and Inheritance Chapter 5: Section 2

Genes - Provide instructions - Control inherited traits Alleles - Different forms of genes - Can be the same or different details Phenotype - An organism’s appearance - Physical features - Determined by genes Genotype - An organism’s genes - Different combinations of alleles

- Used to organize different combinations Punnett Squares - Possible genotypes of offspring - Dominant traits  Capital Letters - Recessive traits  lower case letters - Two alleles per trait (two sets of instructions) - Helps calculate probability Probability - Mathematical chance something will happen - Expressed in a fraction or percentage Homozygous - Both alleles are the same, dominant or recessive Heterozygous - Have one dominant and one recessive allele

- Used to organize different combinations Punnett Squares - Possible genotypes of offspring

- Both traits appear Incomplete Dominance - Neither trait is dominant nor recessive Ex: Red flower + White flower = Pink flower - One gene ONLY One gene – Many traits - Can influence many traits - Several genes involved One trait – Many genes - ONLY one trait influenced Ex: Skin color, Hair - Environment can influence traits too - Sometimes genes are not the only factor

Meiosis

- Only one parent needed Asexual Reproduction - Offspring is identical to parent Mitosis - Method used for eukaryotic cells to divide - Asexual reproduction is a type of mitosis

- Involves two parents Sexual Reproduction - Needs sex cells - Offspring are different from parents - Pair of chromosomes Homologous Chromosomes - Carry the same genes - Sex cells only have one of the pair Meiosis - Making of sex cells - Sex cells have half as many chromosomes as non-sex cells

Walter Sutton - Studied meiosis in grasshoppers - Determined that genes are located on chromosomes Steps in Meiosis - Two phases: Phase A and Phase B - Chromosomes are copied only once - Chromosomes divide twice - New cells have half as many chromosomes

Meiosis Interphase Meiosis is preceded by interphase. The chromosomes have not yet condensed. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Interphase The chromosomes have replicated, and the chromatin begins to condense. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Prophase I The chromosomes are completely condensed. In meiosis (unlike mitosis), the homologous chromosomes pair with one another http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Metaphase I The nuclear membrane dissolves and the homologous chromosomes attach to the spindle fibers. They are preparing to go to opposite poles. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Anaphase I The chromosomes move to opposite ends of the cell. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Telophase I & Cytokinesis The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of maternal and paternal chromosomes. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Prophase II The cell has divided into two daughter cells. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Metaphase II As in Meiosis I, the chromosomes line up on the spindle fibers. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Anaphase II The two cells each begin to divide. As in Meiosis I, the chromosomes move to opposite ends of each cell. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Telophase II & Cytokinesis With the formation of four cells, meiosis is over. Each of these prospective germ cells carries half the number of chromosomes of somatic cells. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

- Carry genes that determine traits Sex Chromosomes - Carry genes that determine traits - Determine sex of organism (male or female) - Females have 2 X chromosomes (XX) - Males have 1 X and 1 Y (XY) - During meiosis, on of each of the chromosome pairs end up in a sex cell. - Y chromosome does not carry all of the genes of the an X. Females have 2 X chromosomes, so they carry 2 copies of each gene found on the X. Back up gene available if one gets damaged. Sex-Linked Disorders - Sex chromosomes carry genes for certain disorders Ex: Color blindness is on the X chromosome Mutation in a gene on the X chromosome.

Pedigree - Diagram used to trace traits - Studies family history of traits - Used by genetic counselors - Traits are selected or desired Selective Breeding - Organisms with those traits are bred

A circle represents a female A square represents a male Mom Marriage Dad On a pedigree: A circle represents a female A square represents a male A horizontal line connecting a male and female represents a marriage A vertical line and a bracket connect the parents to their children A circle/square that is shaded means the person HAS the trait. A circle/square that is not shaded means the person does not have the trait. Children are placed from oldest to youngest. A key is given to explain what the trait is. Has the trait Male- Son Male-Son Female-Daughter Male – Son Oldest to Youngest Unaffected male Unaffected Female Affected male Affected Female

I II III IV A pedigree chart shows an x linked disease if most of them males in the pedigree are affected.

Congenital colorblindness is much more common in males since males have one X and one Y chromosome and females have two X chromosomes. Females are typically carriers for the disease because only one of their chromosomes are infected. It is very rare that both X chromosomes in a sex-linked disease are mutated since both parents would have to have be infected and give the disease on both of the daughter's X chromosomes. A female with the colorblindness defect in one X chromosome is a carrier of colorblindness. Male children of a female carrier are likely to be colorblind. Male children of a male with colorblindness and a female carrier are extremely likely to be colorblind (Web Exhibits). Notice that when the mother is a carrier then she has a 50% chance of passing off her "bad" gene to her children. If she is colorblind then she will cause her sons to be colorblind but her daughters will be carriers. If both parents are colorblind then it is impossible for their children not to be colorblind as well.

Appears in both sexes with equal frequency, both sexes transmit the trait, does not skip generations, affected offspring must have an affected parent unless new mutation. When one parent is affected (heterozygous, and the other parent is unaffected, approx ½ the offspring will be affected. Unaffected parent do not transmit A pedigree chart shows an autosomal disease if there is a 50/50 ratio between men and women inheriting disease. An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.