Chapter 10

form dominant recessive  Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) two  Dihybrid - cross involving two traits e.g. flower color & plant height stronge recessive  Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R). Masks recessive alleles. phenotypes both equally  Codominance – Pattern where phenotypes of both homozygote parents are produced in heterozygous offspring so that both alleles are equally expressed. first parents  F 1 generation - the first-generation offspring in a breeding experiment. (1st filial generation, your parents)

second you  F 2 generation - the second-generation offspring in a breeding experiment. (2nd filial generation, you) heredity characteristic  Gene - a unit of heredity; a sequence of DNA nucleotides that determines a single characteristic. heredity  Genetics - science of heredity trait  Genotype - gene combination for a trait (e.g. RR, Rr, rr) passing  Heredity - passing of traits from parent to offspring dominant recessive  Heterozygous (heh tuh roh ZI gus) or Hybrid - gene combination of one dominant & one recessive allele (e.g. Rr)

2 2  Homozygous (ho muh ZI gus) or true breeding (pure) -gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr) Chart unusual  Karyotype – Chart of chromosome pairs used to identify unusual chromosome numbers in cells dominant traitRed White Pink  Incomplete Dominance – Pattern where one allele is not completely dominant over the other. Generally displays a new trait. ( Parents = Red Flower, RR and White Flower, rr; Offspring are all Rr with Pink flowers) random gametes  Law of Independent Assortment - Mendelian law stating that a random distribution of alleles occurs during the formation of gametes. two meiosis  Law of Segregation - Mendelian law stating that two alleles for each trait separate during meiosis

single  Monohybrid – a cross involving a single trait e.g. flower color parental grandparents  Parental P 1 Generation - the parental generation in a breeding experiment.(your grandparents) Graphic  Pedigree – Graphic representation of genetic inheritance used by geneticists to map genetic traits. observable genotype  Phenotype - observable characteristic that is expressed as a result of genotype (e.g. red, white) two genessame chromosomes  Polygentic Traits – traits controlled by two or more genes; genes may be on the same or different chromosomes

diagram genotypesphenotypes  Punnett Square - a diagram showing the gametes that can be produced, including the joining of gametes, to produce offspring. The resulting diagram shows the possible genotypes and phenotypes of the offspring and the ratios of each produced. geneless r  Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r). Is not seen if a dominant allele is present. genes sex  Sex Linked Traits – traits controlled by genes located on sex chromosomes ( X and Y chromosomes) inherited  Trait — characteristic that is inherited; can be either dominant or recessive

father of genetics  Known as the “father of genetics”  Austrian Monk inheritance pea plants  Studied the inheritance of traits in pea plants rule of dominance laws of inheritance  Developed the rule of dominance and laws of inheritance 20th century  Mendel's work was not recognized until the turn of the 20th century

small area  Can be grown in a small area  lots  Produce lots of offspring pure self- pollinate  Produce pure plants when allowed to self- pollinate several generations cross – pollinated  Can be artificially cross – pollinated

 Pollen sperm stamen  Pollen contains sperm which is produced by the stamen  Ovary inside eggs  Ovary (found inside the flower) contains eggs stamen pistol ovary fertilization Pollen carries sperm to the eggs for fertilization Self-fertilization Self-fertilization can occur in the same flower Cross-fertilization Cross-fertilization can occur between flowers

cross- pollinated  Mendel cross- pollinated flowers using a paintbrush stamens self-pollination He could snip the stamens to prevent self-pollination several generations  He traced traits through the several generations

pure self-pollinate  Mendel produced pure strains by allowing the plants to self-pollinate for several generations

(R) (r) 1. Seed shape --- Round (R) or Wrinkled (r) (Y) (y) 2. Seed Color ---- Yellow (Y) or Green (y) (S) (s) 3. Pod Shape --- Smooth (S) or wrinkled (s) (G) (g) 4. Pod Color --- Green (G) or Yellow (g) (G) (g) 5. Seed Coat Color ---Gray (G) or White (g) (A) (a) 6. Flower position ---Axial (A) or Terminal (a) (T) (t) 7. Plant Height --- Tall (T) or Short (t) (P) (p) 8. Flower color --- Purple (P) or white (p)  He studied only one trait at a time to control variables, and he analyzed his data mathematically.

mono single height  Mendel’s first experiments are called monohybrid crosses because mono means “one” and the two parent plants differed from each other by a single trait—height

tall shortP 1  Mendel cross-pollinated a tall pea plant with pollen from a short pea plant (P 1 generation; both true breed) talltaller F 1  All of their offspring were as tall or taller than the parent plants. (F 1 generation) self pollinate These plants were allowed to self pollinate  Three-fourths One- fourth F 2  Three-fourths of the plants were as tall as the tall plants in the parent and first generations and One- fourth of the offspring were as short as the short plants in the parent generation. (F 2 generation)

P1P1 Short pea plant Tall pea plant F1F1 All tall pea plants F2F2 3 tall: 1 short tall short three one In the second generation, tall and short plants occurred in a ratio of about three tall plants to one short plant.(3:1)

disappearF 1 reappearF 2  In every case, he found that one trait of a pair seemed to disappear in the F 1 generation, only to reappear unchanged in one-fourth of the F 2 plants. two  Mendel concluded that each organism has two factors that control each of its traits. genes chromosomes  We now know that these factors are genes and that they are located on chromosomes.

alleles different female male  An organism’s two alleles are located on different copies of a chromosome—one inherited from the female parent and one from the male parent. dominant recessive  Mendel called the observed trait dominant and the trait that disappeared recessive.

samedifferent  When recording the results of crosses, it is customary to use the same letter for different alleles of the same gene. uppercase dominant lowercase recessive  An uppercase letter is used for the dominant allele and a lowercase letter for the recessive allele. dominant first  The dominant allele is always written first. Tall plant TT T T Short plant tt t t