Genetics Bill Nye Genes Quizzie n 1 A

Genetics

Bill Nye: Genes Quizzie

n 1. A specific part or segment of DNA is called a _______. n 2. DNA stands for _______ n 3. DNA is made of how many chemicals? n 4. What letters are used to represent the chemical that make up DNA? n 5. Thousands of genes come together to make structures called _______.

n 6. In your cells, which is greater, your number of genes or your number of chromosomes? n 7. Your genes tell your ______ what to do or how to function. n 8. The stronger form of a gene, represented by a capital letter, is called _______. n 9. The form of the gene that is masked is called _______. n 10. Give an example of a hybrid animal.

History of Genetics

Gregor Mendel n Particulate hypothesis n experiments on pea plants to study patterns of inheritance of traits n Father of modern genetics

Mendel’s experiments n First, identified purebred pea plants n Then, cross-fertilized purebreds with 2 different traits EXAMPLE Purple flowers white flowers X What color flowers did the offspring have?

Mendel’s results Mendel’s cross P = purple x white n F 1 = All purple n F 2 = ¾ purples ¼ white n

Mendel’s Conclusion n There are different forms of the same gene. The different forms are called alleles. n Alleles can be either dominant or recessive.

Mendel’s Conclusion n An organism has 2 alleles for each trait, one from each parent. If both alleles are the same = homozygous (or purebred) n If the two alleles are different = heterozygous (or hybrid). n n Principle of Segregation

Genotype vs Phenotype n The combination of alleles for a trait is called the genotype n Ex: PP; Pp; pp n The observable trait is called the phenotype n Ex: Purple; white

Practice 1 n In seeds, if round is dominant to wrinkled n What letter would represent the round allele? n What letter would represent the wrinkled allele? n What is the genotype of a homozygous round seed? n What is the genotype of a heterozygous seed? n What is the genotype of a wrinkled seed?

Practice 2 n In pea plants, if tall (T) is dominant to short (t) n What is the phenotype of a plant with genotype TT? n What is the phenotype of a plant with genotype tt? n What is the phenotype of a plant with genotype Tt?

Monohybrid cross n One trait is different n If P generation is purebred for different characteristics (purebred white and purebred purple) F 1 Generation =100% heterozygous n F 2 generation = 3: 1 ratio dominant trait : recessive trait n

Practice n In fruit flies, red eyes are dominant to white eyes. A heterozygous red-eyed fly is bred with a white-eyed fly What are the genotypes of the P 1? n Complete a Punnett square and determine the phenotypic probabilities of the cross. n

Practice n In guinea pigs, fur color is controlled by one gene, with the white allele being recessive to the brown allele. Suppose a homozygous brown guinea pig is bred with a white one. A. What are the genotypes of the parents? n B. What are the phenotypic probabilities of the F 1? n C. What are the genotypic probabilities of the F 1? n D. What are the phenotypic probabilities of the F 2? n

Practice n In the same guinea pigs, a heterozygous brown male is bred with a white female. A. What are the genotypes of the parents? n B. What are the phenotypic and genotypic probabilities of the F 1? n (WORKSHEET)

Do Now – Genetics Review 1. In Drosophila, grey body (G) is dominant to black body (g). A hybrid grey fly is crossed with a black. a. b. c. d. Give the genotypes of the parents Create a Punnett Square to show the possible outcomes of the offspring. Give the possible genotypes AND the probability of each. Give the possible phenotypes AND the probability of each.

2. There is a race of chickens known as Andalusians, some of which have black feathers, others white. When a black chicken (B) is crossed with a white chicken (W), the F-1 hybrid is a slate blue. a. b. c. d. What is the genotype of the F-1 generation? Create a Punnett Square to show a cross between 2 members of F-1 Give the possible genotypes AND the probability of each. Give the possible phenotypes AND the probability of each.

3. Suppose a father of blood type A and a mother of blood type B have a child of type O. What blood types are possible in their next children. Show the Punnett Square and give the phenotypic probabilities.

Do Now n In a species of plant, purple flowers are dominant to white. A plant has purple flowers. What are the possible genotypes of this plant? n What do you think you could do to determine the plant’s genotype? n

Testcross n There are 2 possible genotypes for a dominant phenotype n Testcross breeds the organism with unknown genotype with recessive organism

Independent Assortment & Dihybrid Inheritance

Principle of Independent Assortment n Inheritance pattern of one trait will not effect the inheritance pattern of another n During gamete formation, a particular allele for one trait can be paired with either allele for another trait

Dihybrid Cross n Crossing organisms with 2 different traits n Example: If yellow (Y) is dominant to green (y), and round (R) is dominant to wrinkled (r) n n n What is the genotype of a homozygous round homozygous yellow plant? What is the genotype of a green wrinkled plant? What are the odds of crossing a round yellow plant with a green wrinkled plant?

Dihybrid results n If P 1 is purebred for different traits (RRYY x rryy) n F 1 generation are all heterozygous for both traits (Rr. Yy) n F 2 generation: Dominant Recessive recessive Dominant Recessive Dominant recessive 9 : 3 : 3 : 1

Practice Question 1 In pea plants, tall is dominant to short and purple flowers is dominant to white. A heterozygous tall white plant is crossed with a short homozygous purple plant. a. What are the genotypes of the parents? b. What are the possible gametes? c. Do a Punnett square to determine the phenotypic probabilities

Practice Question 2 4. In horses black is dominant (B) and chestnut is recessive (b). The trotting gait is due to a dominant allele (T), and the pacing gait to its recessive allele (t). A homozygous black pacer is mated to a homozygous chestnut trotter. a. Give the genotypes of the parents b. What are the possible phenotypes and genotypes of the F 1 generation? c. State the phenotypic probabilities of the F 2. (WORKSHEET)

Practice Questions! n 1. In Drosophila, grey body (G) is dominant to black body (g). A grey fly is crossed to a black fly (GG x gg). The F-1 generation is inbred and produce 400 offspring in the F-2. a. How many of the F-2 would be expected to be homozygous dominant? b. How many of the F-2 would be expected to be heterozygous? c. How many of the F-2 would be black? e. How many of the F-2 would be grey?

n 2. Two grey flies are bred with each other and they produce 153 greys and 49 blacks. a. Which color is dominant? b. Give the genotypes of the parents

n 3. In humans, brown eyes are dominant to blue eyes. Two brown eyed people have a blue-eyed child. a. What are the genotypes of the parents?

n 4. In garden peas, tall (T) is dominant to short (t), and red flower (R) is dominant to white (r). A pure tall red plant is crossed with a white short one. a. Give the genotypes of P b. Give the genotypes of F 1 c. Give the phenotypic ratio F 2

n 5. The ability to taste bitter is hereditary. Being able to taste is due to a dominant gene, not tasting is recessive. If a taster marries a non-taster, some of their children are tasters and some are not. n What are the genotypes of the parents?

n What are the possible gametes for the following genotypes 1. Aa 2. AA 3. Aa. Bb 4. Aa. BB

n The ability to roll the tongue (R) is determined by a dominant gene while the recessive gene results in the inability to roll the tongue (r). A man and his wife can both roll their tongues and are surprised to find that their son cannot. Explain this by showing the genotypes of all three persons.

n In humans, straight toes (S) is dominant over curled toes (s). For a cross between a recessive male and a heterozygous female, n n n Give the genotypes of the parents Give the gametes of the parents Create a Punnett square to predict the phenotypic probablities of this cross.

n Wolves are sometimes observed to have black coats and blue eyes. Assume that normal coat color (N) is dominant to black (n) and brown eyes (B) are dominant to blue (b). Suppose the alpha male and alpha female of a pack (these are the dominant individuals who do most of the breeding) are black with blue eyes and normal colored with brown eyes, respectively. The female is also heterozygous for both traits. Do the Punnett Square to determine the probabilities of the phenotypes.

Variations of Inheritance

What do you think… n In a species of flower, red is dominant to white. Suppose a homozygous red flower crosses with a white flower, producing 100 offspring, all of which are pink. Suggest an explanation for what’s going on here.

Incomplete dominance n If the heterozygous genotype produces a blend of the dominant and recessive trait, this is called incomplete (or intermediate) dominance.

Incomplete dominance: Hair texture n In humans, curly hair is incomplete dominant to straight hair.

What do you think… n In a species of flower, red is dominant to white. Suppose a homozygous red flower crosses with a white flower, producing 100 offspring, all of which are red AND white. Suggest an explanation for what’s going on here.

Codominance n Some traits have more than two alleles n If a heterozygous genotype expresses both traits, this is called codominance

Codominance: Blood Type n Blood type has 3 alleles: A, B, and O n A and B are codominant, O is recessive

Polygenic Inheritance n When a trait is controlled by more than one gene, this is called a polygenic trait n Can you think of any human traits that might be polygenic? Skin color, height, eye color, fingerprints (WORKSHEET)

Do Now 1. Give the possible gametes for the following genotype Ccdd 2. Suppose a father of blood type A and a mother of blood type B have a child of type O. a. What are the genotypes of the parents? b. What blood types are possible in their next children? Show the Punnett Square and give the phenotypic probabilities. c. What type of inheritance is this?

3. Yellow (Y) guinea pigs crossed with white (y) ones always produce cream colored offspring. A homozygous yellow guinea pig is crossed with a white one. Give the phenotypic probabilities of the F 2 cross. (Show the Punnett Square) 4. In snapdragons, red is incompletely dominant to white. When a red flower and a white flower cross, they produce all pink flowers. What are the genotypes of the parents?

5. In wolves, normal coat color (N) is dominant to black (n) and brown eyes (B) are dominant to blue (b). Suppose the alpha male of a pack is black with blue eyes and the alpha female is normal colored with brown eyes, all homozygous. a. What are the genotypes of the parents? b. What are the possible genotypes of their offspring? c. List the possible phenotypes of the F 2 AND the probability of each (out of 16).

6. In horses black is dominant (B) and chestnut is recessive (b). The trotting gait is due to a dominant allele (T), and the pacing gait to its recessive allele (t). A homozygous black pacer is mated to a homozygous chestnut trotter. a. Give the genotypes of the parents b. What are the possible phenotypes and genotypes of the F 1 generation?

Do Now n Genes are held on structures called ____. n How many chromosomes does the average human have in each diploid cell? n What are the female sex chromosomes? n What are the male sex chromosomes? n A picture of someone’s chromosomes is called a ______.

Chromosome Theory

Chromosome Theory n The chromosome theory of inheritance states that n n genes are located on chromosomes Behavior of these chromosomes during meiosis accounts for inheritance patterns

Chromosome structure n Diploid cells have two sets of homologous chromosomes n Alleles for a trait are found at the gene locus n Is this gene homozygous or heterozygous?

Independent Assortment

Crossing over n Crossing over allows genes on the same chromosome to sort independently n Results in more variation

Sex Chromosomes

Sex chromosomes

Sex-linked traits n Traits determined by these genes on sex chromosomes are called sex-linked traits color-blindness hemophilia

n In humans, pseudohypertrophic muscular dystrophy is a condition in which the muscles gradually waste away, ending in death in the early teens. In some families it is dependent upon a sex-linked recessive gene. This type occurs only in boys and has never been reported in girls. Why is it not to be expected in girls?

A woman has parents with normal color vision and a red-green colorblind brother. She marries a colorblind man and they have a colorblind daughter. What is the probability that a son will also be colorblind?

n In poultry, sex-linked allele B, which produces barred feather pattern, is completely dominant to its allele, b, for nonbarred pattern. Autosomal allele R produces a rose comb; its recessive allele, r, produces a single comb in the homozygous state. A homozygous barred, homozygous rose-combed female is mated to a non-barred single comb male. What is the phenotypic ratio of their offspring?

n In pigs, a gene that produces a white belt around the animal’s body is dominant over its allele for a uniformly colored body. Another gene produces a fusion of the two hoofs on each foot, a condition known as syndactyly; this gene is dominant over its allele, which produces normal hoofs. Suppose a uniformly colored hog homozygous for syndactyly is mated with a normal footed hog homozygous for the belted character. What would be the phenotype of the F-1? If the F-1 individuals are allowed to breed freely among themselves, what phenotype rations would you predict in the F-2?

Chromosomal Disorders

Damaged Chromosomes n Some chromosomal disorders are caused by changes in chromosome structure Duplication Deletion Inversion Translocation

Put the definition in the correct place n Involves reversing a fragment of the original chromosome n Occurs when part of a chromosome is repeated n Occurs when a fragment of one chromosome attaches to a non-homologous chromosome n When a piece of a chromosome is lost

Damaged chromosomes n Duplication n When part of a chromosome is repeated n Deletion n When a piece of a chromosome is lost

Damaged chromosomes n Inversion n When a piece of chromosome is reversed n Translocation n When a piece of a chromosome attaches to a nonhomologous chromosome

n What is the relationship between P, F 1 and F 2?

n WITHOUT DOING A PUNNETT SQUARE, what is the result of crossing a homozygous green flower (GG) with a yellow one (gg)?

n WITHOUT DOING A PUNNETT SQUARE, what is the result of crossing two heterozygous green flowers?

n What are the possible gametes for the following genotypes n n n 1. AA 2. Aa. Bb 3. Aa. BB

n In humans, straight toes (S) is dominant over curled toes (s). In a cross between a recessive male and a heterozygous female, what are the PHENOTYPIC PROBABILITIES?

n The ability to roll the tongue (R) is determined by a dominant gene while the recessive gene results in the inability to roll the tongue (r). A man and his wife can both roll their tongues and are surprised to find that their son cannot. n Show the GENOTYPES of all three persons.

n Describe the genetic cross that you would expect to have a phenotypic ratio of 9: 3: 3: 1?

n In iris, purple (P) is incompletely dominant over white (p). Two lavender plants are crossed. n Give the PHENOTYPIC PROBABILTIES of the cross

n In cattle, red (R) is incompletely dominant over white (r) hides. Roan is the name of the color that results from incomplete dominance. n What are the possible results if a white male mates with a roan female

n If a parent with AB has a child with a parent with AO, what is the probability the child has blood type A?

n 1. The chromosomes that do NOT determine gender are called _______. n 2. The event that allows for genes on the same chromosome to sort independently is called ______________. n 3. Create a Punnett Square that shows the probability of having a color blind child if the father is color blind and the mother is a carrier (but not color-blind)