Chapter 10 1 Genetics Baker Academy Biology Hickox

Chapter 10. 1 Genetics Baker Academy Biology Hickox: Baker High School 1

Chapter 10 Genetics KEY CONCEPTS • Apply Mendel’s laws to determine phenotypic and genotypic probabilities of offspring • Defining important genetic terms, including monohybrid cross, phenotype, homozygous, heterozygous, recessive trait, incomplete dominance, codominance, and allele; • Interpreting inheritance patterns shown in graphs and charts; • Calculate genotypic and phenotypic percentages and ratios using a Punnett square. • The fact that the human body is formed from cells that contain two copies of each chromosome — and therefore two copies of each gene -- explains many features of human heredity, such as how variations that are hidden in one generation can be expressed in the next. Hickox: Baker High School Chapter 210

• Resultant of his experiments with pea plants, Mendel generated four hypotheses: • For each inherited trait, an individual has two copies of the gene – one from each parent. • There alternative versions of genes • When two different alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance. • When gametes are formed, the alleles for each gene in an individual separate independently of one another. • Patterns of heredity can be complex because most traits are not controlled by simple dominant-recessive alleles • Vocabulary: Heredity, Genetics, Gene, Recessive, Dominant, DNA, Chromosome, Gregor Mendel, Genotype, Alleles, Heterzygogous, Homozygous, phenotype, hybrid, cross pollinaion, Self pollination, Law of Segregation, Law of Independent Assortment, Codominance, Incomplete dominance, Pedigree, Punnett square, Monohybrid cross, Dihybrid cross. Hickox: Baker High School 3

Mendel’s Laws of Heredity Why Mendel Succeeded Gregor Mendel was the first person to predict traits. The study of traits is called GENETICS (1)_______ HEREDITY is the passing on of • (2) _____ characteristic from parents to offspring. • These characteristics are called TRAITS (3)____. Hickox: Baker High School 4

Mendel’s Laws of Heredity • Mendel used garden (4) peas for his experiments. • Garden peas produce male and female GAMETES sex cells called (5)_____ FERTILIZATION • (6)_______occurs when male sex cells units with the female sex cell and produces a new fertilized cell called ZYGOTE a (7)_______ Hickox: Baker High School 5

Mendel’s Laws of Heredity • In garden peas, as with most flowers, the male sex cells are grains of. POLLEN (8)____. • When pollen is transferred from the male reproductive organ. POLLINATION to the female reproductive organ, is called (9)______ • Hickox: Baker High School 6

Mendel’s Laws of Heredity • Garden peas are SELF - POLLINATORS (10)_________the pollen from a flower pollinates the female sex cell within that same flower. • Mendel wanted to unite gametes of different plants. Mendel opened the petals of flower and removed the male reproductive organs and dusted the female organ with the polled from a different plant. This is called. CROSS-POLLINATION Hickox: Baker High School 7

How did Mendel proceed? • Mendel studied one trait at a time • Studied tallness first TRUE BREEDING • Used plants that were (12)______ means they always produce that trait • Took pollen from a true-breeding tall pea plant and crossed-pollinated a true. MONOHYBRID breeding short plant. The study of one trait only is called a (13)______ Hickox: Baker High School 8

What were the results? • 6’ tall true-breeding X 2’ short truebreeding ALL TALL • Results? NOT (14)________ The short F 1 did (15)_______appear in the first generation or (16)_____. • Mendel allowed the offspring to self 75% pollinate. Fand out of 1000 plats in the second 2 generation or (17)___, ¾ or (18)_____ were tall and ¼ or 25% were short. MONOHYBRID The ratio was 3: 1 or 3 tall to 1 short • Mendel used similar (19)______crosses with seven different Hickox: Baker High School 9

Mendel’s Laws of Heredity • In each case the F 1 generation produced 100% for one of the traits and one trait did not appear. • In each case the F 2 produced a ¾ to ¼ or 3: 1 (20)______ratio • We now know that two factors control each of its traits. Genes exist in alternative forms: tall and short or round and wrinkled. The ALLELES alternative forms are called (21)_____ Hickox: Baker High School 10

Mendel’s Laws of Heredity • An organism can have two (22) ALLELES ____for tallness, two alleles for shortness, or one allele for tallness and one allele for shortness. • The organism receives or inherits one allele from the female parent and one allele from the male parent. Hickox: Baker High School 11

What is dominance? • Mendel called the observed tall trait that was only observed in the F 1 generation as DOMINANT (23)_____ • The trait that disappeared in the F 1 and later RECESSIVE returned in the F 2 is called (24)_____ • The allele for tall plants is (25)______ DOMINANT to the allele for short plants. TALL • The plants with two alleles for tallness were (26)____ • The plants with two alleles for shortness were (27)___ SHORT • The plants with one allele for tallness and one allele for short was (28)_____ TALL Hickox: Baker High School 12

What is dominance? • We us an uppercase “letter” for the dominant allele and a lowercase letter is used for a recessive allele. • The dominant allele is always written first. • Every organism has two alleles for each gene and when gametes are produced the alleles separate. Each gamete receives OF SEGREGATION one of. LAW these alleles, called (29)________ Hickox: Baker High School 13

Phenotype and Genotype • The way an organism looks and PHENOTYPE behaves is called (30)______ • The phenotype of a tall plant is tall. • This plant can have an allele Tt combination of (31)____ or (32)_____ TT • The allele combination of an organism is called. GENOTYPE the (33)_____ Hickox: Baker High School 14

HOMOZYGOUS SHORT PARENT Mendel’s Laws of Heredity LAW OF SEGREGATION tt HOMOZYGOUS TALL TT F 1 Tt HETEROZYGOUS TALL 3 - Tall 1 – Short F 2 Hickox: Baker High School 15

Mendel’s Laws of Heredity Hickox: Baker High School 16

Mendel’s Laws of Heredity Punnett Square • method to predict proportions of possible genotypes in offspring. HOMOZYGOUS SHORT T T t Tt Tt HOMOZYGOUS TALL HETEROZYGOUS TALL T t T TT Tt tt Hickox: Baker High School 1 HOMOZYGOUS TALL 2 HETEROZYGOUS TALL 1 HOMOZYGOUS SHORT 17

Mendel’s Laws of Heredity Punnett Square • method to predict proportions of possible genotypes in offspring. HOMOZYGOUS SHORT T T t Tt Tt T t T TT Tt tt Hickox: Baker High School PHENOTYPE: ALL TALL GENOTYPE: HETEROZYGOUS TALL PHENOTYPE: 3 - TALL 1 - SHORT GENOTYPE: 1: 2: 1 3 HOMOZYGOUS TALL 2 HETEROZYGOUS TALL 1 HOMOZYGOUS SHORT 18

Choosing the Traits- Mendel’s 7 Easily Recognizable Traits: Seed shape, seed color, pod shape, pod color, flower and position, and stem length (34) PHENOTYPE (physical characteristic) One can tell what a dog’s phenotype is by looking at him (35) HYBRIDS (offspring with different traits) Hickox: Baker High School 11. 119

SEGREGATION The Principle of (36)______ HOMOZYGOUS (AA or aa) HETEROZYGOUS (Aa) Monohybrid cross (single trait) PUNNET SQUARES Hickox: Baker High School 20 11. 2

Hickox: Baker High School ? ? ? ? 21

Genes, Alleles, and Chromosomes

Mendel’s Monohybrid Cross – P to F 1 A Punnett square, something we’ll cover in a moment.

Staying the Course – Mendel Continued Crosses to the F 2 (the grandchildren) What was learned? The green trait was not lost or altered, even though it disappeared in the F 1. One trait is dominant to the other in its expression. The reappearance of the recessive trait in ¼ of the F 2, suggests genes come in pairs that separate in the formation of sex cells.

Monohybrid Crosses and the Principle of Segregation A cross between individuals differing in single character is a monohybrid cross. Principle of Segregation. . Genes come in pairs that separate in the formation of sex cells (and these sex cells unite randomly at fertilization).

Dihybrid Crosses: P 1: Smooth / Yellow (homozygous for both) P 2 Wrinkled / Green (homozygous for both) F 1 Generation (heterozygous for both) Are Different Characters Like Color and Shape Mendel performed dihybrid crosses to find out. Mendel’s conclusion: Different characters are inherited independently, called: (37) Independent Assortment

F 2 generation of a Dihybrid cross that demonstrates: (38) Independent Assortment always produces a: (39) 9 : 3 1 Phenotypic ratio

Dihybrid Cross: 28 Hickox: Baker High School

The human ABO blood group illustrates another genetic phenomenon – Codominance (40)________ Codominance occurs when the phenotype associated with each allele is expressed in the heterozygote. The AB phenotype (genotype IA IB) is an example of codominance

Incomplete & Codominance CODOMINANCE In cattle, the allele for red hair is codominant with the allele for white hair. The offspring has a MIXTURE of red and (38)_____ white hair and looks pinkish / brown from a distance. In some chickens black feather are (39) _______ with CODOMINANT white, the heterozygous offspring appear speckled. CODOMINANCE BOTH_____ ALLELES * (40)____ CONTRIBUTE TO THE PHENOTYPE OF THE ORGANISM Hickox: Baker High School 30 Chapter 10

Homozygous recessive Problems Problem: A white mouse whose parents are both white produces only brown offspring when mated with a brown mouse. The white mouse is a homozygous recessive. Explain why? A homozygous recessive (aa) for a particular trait is mated with a parent with a dominant phenotype (AA or Aa) • The result will have the phenotype of the dominant parent in the first generation. • Problem: In chickens, rose comb (R) is dominant to single comb (r). A homozygous rose-combed rooster is mated with a singlecombed hen. All of the chicks in the F 1 generation were kept together as a group for several years. They were allowed to mate only within their own group. What is the expected phenotype of the F 2 chicks. 31 Hickox: Baker High School

Incomplete Dominance INCOMPLETE DOMINANCE Some alleles are neither Dominant (41)_______ Recessive nor (42)______ called Incomplete (43)_______ Dominance A cross between four o'clock plants: F 1 generation (red) RR X (white) ww produces Rw that are neither red or white but (pink). Neither allele is dominant. Hickox: Baker High School 32 Chapter 10

Incomplete dominance in carnations Hickox: Baker High School 33 Chapter 10

Genotype: All heterozygous Phenotype: All pink r r R Rr Rr Incomplete Dominance F 1 GENERATION Hickox: Baker High School 34

Incomplete Dominance F 2 GENERATION Rr X Rr r R R r RR Rr Genotype: 1 : 2 : 1 Phenotype: 1 Red : 2 Pink : 1 White Hickox: Baker High School Rr rr

Punnett Square Problems 1. The ability to roll the tongue is dominant over the inability to do so in humans. a. If two heterozygous tongue-rollers have children, what genotypes and phenotypes could their children have? T T t t TT Tt Tt tt b. If a non-tongue-roller has children with homozygous tongueroller, what will their children’s genotype and phenotype be? t t Hickox: Baker High School T T Tt Tt 36

Punnett Square Problems 2. In an alien species, eye colors can be black, white or gray. The whiteeyed mother and a black-eyed father have all gray-eyed children. a. What genotypic pattern is most likely demonstrated here? ________________ INCOMPLETE DOMINANCE b. A gray-eyed couple has two babies: one white-eyed and one black-eyed. Does this confirm or deny your answer to part A. If necessary, revise your hypothesis. c. A gray-eyed alien and her black-eyed husband want a white-eyed baby. Is this possible? Why or why not? Hickox: Baker High School 37

Sex Chromosomes determine the sex of (44)___________ the offspring (XX = (45)_____, female XY = (46)_______) Hickox: Baker High School 38 10

Pedigree ______ analysis: A graphic representation of genetic inheritance. Hickox: Baker High School 39

Genetic Inheritance in Humans 40 Hickox: Baker High School

Large families provide excellent case studies of human genetics Hickox: Baker High School 41

• DNA fingerprinting cystic fibrosis Insulin color blindness Growth Hormone phenylketonuria Hemophilia Tay-Sachs disease sickle cell anemia Down’s syndrome Technology has made significant contributions to society, especially in the areas of agriculture and medicine. The process of manipulating genes for practical purposes is called genetic engineering. Most of the cells in a human contain two copies of each of 22 different chromosomes. In addition, there is a pair of chromosomes that determines sex: a female contains two X chromosomes and a male contains one X and one Y chromosome. Transmission of genetic information to offspring occurs through egg and sperm cells that contain only one representative from each chromosome pair. An egg and a sperm unite to form a new individual. The fact that the human body is formed from cells that contain two copies of each chromosome--and therefore two copies of each gene--explains many features of human heredity, such as how variations that are hidden in one generation can be expressed in the next. Hickox: Baker High School 42

Inheritance of Blood Type Problem: What are the results of a heterozygous blood type A mom ( IA i) and a heterozygous B father (IB i)? AB Hickox: Baker High School B A O 43

Problems: • Blood type in humans is controlled by three alleles, designated as IA , IB (both dominant alleles), an i (recessive allele). Genotypes for each of the four possible blood types are shown in the table. Blood Type Genotype(s) A man with blood type A, whose Mother has type O, has a child With a woman that has type AB Blood. Which blood types are possible in their children? Hickox: Baker High School A IA or IA i B I B or I B i AB I A IB O i i A, B, AND AB ONLY 44

Problems: • Egyptian Mau cats are genetically crossed for certain lengths of fur. A breeder knows that short hair is dominant over long hair. If 75% of the kittens are born with short hair, what are the parents’ MOST LIKELY genotypes? MALE - HETEROZYGOUS SHORTHAIR FEMALE – HETEROZYGOUS SHORTHAIR CAT Hickox: Baker High School 45

Problems: • In rabbits, black hair is dominant to brown. If a heterozygous black-haired rabbit and a brownhaired rabbit were crossed, what percentage of their offspring would be brown-haired? Hickox: Baker High School 50% 46

Problems: • Which genetic cross will produce all heterozygous offspring? A. RR x rr B. rr x rr C. RR x RR A. D. Rr x R r Hickox: Baker High School 47

Problems: • Brown eyes are dominant to blue eyes, and dark hair is dominant to blond hair. A woman is heterozygous for brown eyes and dark hair. A man is also heterozygous for both traits. What is the chance that their child will have blue eyes and blond hair? • Homozygous Brown eyes = BB; Heterozygous Brown eyes = Bb • Homozygous Blue eyes = bb; Homozygous blond hair = dd Woman: Bb Dd X Man: Bb Dd BD Bd b. D bd BD BBDd Bb. DD Bb. Dd Bd BBDd BBdd Bb. Dd Bbdd b. D Bb. Dd bb. DD bb. Dd bd Bb. Dd BBdd bb. Dd bbdd Hickox: Baker High School 48

Problems: • Brown eyes are dominant to blue eyes, and dark hair is dominant to blond hair. A woman is heterozygous for brown eyes and dark hair. A man is also heterozygous for both traits. What is the chance that their child will have blue eyes and blond hair? • Homozygous Brown eyes = BB; Heterozygous Brown eyes = Bb • Homozygous Blue eyes = bb; Homozygous blond hair = dd Woman: Bb Dd X Man: Bb Dd Blue eyes and blond hair has a genotype Bd b. D bd BD of [bb dd] Bb. DD Bb. Dd BBDD BD BBDd Bd BBDd BBdd Bb. Dd Bbdd b. D Bb. Dd bb. DD bb. Dd bd Bb. Dd BBdd bb. Dd bbdd Hickox: Baker High School 1 / 16 49

• Since both the father and mother are heterozygous for two traits, hair color and eye color, what is the phonotypical ratio for the offspring? 9 : Brown Hair Brown Eyes 3 : Brown Hair Blue Eyes 3 : Blond Hair Brown Eyes 1 : Blond Hair Blue Eyes BD Bd b. D bd BD BBDd Bb. DD Bb. Dd Bd BBDd BBdd Bb. Dd Bbdd b. D Bb. Dd bb. DD bb. Dd bd Bb. Dd BBdd bb. Dd bbdd Hickox: Baker High School 50

Problems: • In pea plants, the allele for round seeds is dominant over wrinkled seeds. Plant 1 has round seeds, and plant 2 has wrinkled seeds. When these plants are crossed, 50% of their offspring have round seeds and 50% have wrinkled seeds. What are the parent genotype? Two possibilities! • Round: RR, Rr • Wrinkled: rr R R r Rr Rr Hickox: Baker High School R r r Rr rr 51

Problems: • In lions, white color is a recessive trait, and color brown is dominant. If a white lion mates with a homozygous brown lion, approximately what percentage of their offspring would be white? • Brown: BB, Bb White: bb B B b Bb Bb 0%. . no white lions! Hickox: Baker High School 52

Problems: Study the figure below. Which statement is the most reasonable explanation of these experimental results? a. One parental plant was homozygous for dark flower color, and the other was homozygous for light flower color b. One parental plant was heterozygous, and other was homozygous for dark flower color. c. Both parents plants were homozygous for dark flower color. d. Both parental plants were heterozygous. Hickox: Baker High School 53

Problems: • Gray fur (B) in mice is dominant over white fur (b). Two mice that are homozygous for white fur color are crossbred. If they have a total of 334 offspring, approximately how many can be expected to have gray fur? Hickox: Baker High School 54

Problems: • Which genotype is heterozygous for two traits? a. gg. Tt b. Gg. Tt c. Gg. TT d. GGTT Hickox: Baker High School 55

Problems: • In gerbils, brown fur is dominant to black fur. Which Punnett square shows a cross between one brown-furred gerbil and one black-furred gerbil that could produce offspring with black fur? • BB = brown, Bb = brown, bb = black B b b Bb bb Hickox: Baker High School 56

Problems: In a certain squirrel population, a black fur gene is dominant to a gray fur gene. Which genotypes show a cross between a homozygous black-furred squirrel and a homozygous gray-furred squirrel? BB = Black, Bb = Black bb = gray A. B. C. D. GG x gg Gg x Gg GG x GG Gg x gg A. Hickox: Baker High School 57

Application of Genetics and DNA • DNA fingerprinting: (video) • Genetic Disorders: Most genetic disorders are caused by ______ alleles. RECESSIVE • cystic fibrosis, Insulin, color blindness, phenylketonuria – lacks enzyme to proce protein (PKU test), Hemophilia, Tay -Sachs disease, sickle cell anemia, Down’s syndrome. (video) DISEASE • HUNTINGTON’S ____________: a lethal genetic disorder caused by a rare _______ allele. DOMINANT • ___________: Human traits that are carried SEX-LINKED TRAITS on the X Chromosome (most of them)…_______, HEMOPHILIA an X-Linked disorder Hickox: Baker High School 58

Hemophilia A Hickox: Baker High School 59

Great links to practice!! • http: //anthro. palomar. edu/mendel/quizzes/mendqu i 2. htm (yeuozt) • http: //library. thinkquest. org/C 004367/be 1. shtml (yftlnr) • http: //www. cellsproject. org/examples/sc/page 22. ht ml (ymdrvm) • http: //biology. clc. uc. edu/courses/bio 105/geneprob. htm (36 r 6 f) Hickox: Baker High School 60

• Week 6 & 7 Chapter 10 • Mendelian Genetics, Punnett Square • Pedigree, Genetic Diseases, Genetic Tech • Baker Academy Biology DNA & RNA: Structure and Functions 11. 1 – 11. 3 The Need for Energy Hickox: Baker High School 61