Genetics Practice Questions:

Transcription

1 Genetics Practice Questions: 1. Define the following Vocabulary Words: Fertilization fusion of a haploid nucleus of an egg cell and a haploid nucleus of a sperm cell haploid-- a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg) diploid -- a nucleus containing a double set of unpaired chromosomes (e.g. sperm and egg) chromosomes -- chromosome is a thread of DNA, made up of a string of genes Test cross an individual that might be heterozygous or homozygous dominant is crossed with an individual that is homozygous recessive Meiosis -- Define meiosis as reduction division in which the chromosome number is halved from diploid to haploid (details of stages are not required) Gametes haploid cells/ sex cells/ example: sperm and egg inheritance the transmission of genetic information from generation to generation phenotype -- phenotype as the physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed) genotype -- as genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG) allele -- as any of two or more alternative forms of a gene gene -- as a length of DNA that is the unit of heredity and codes for a specific protein. A gene may be copied and passed on to the next generation homozygous homozygous as having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding heterozygous - as having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding recessive allele as an allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g) dominant allele -- as an allele that is expressed if it is present (e.g. T or G) co-dominant -- two alleles may be expressed in the phenotype at the same time. That is, NO allele is truly dominant or recessive. Sex-linked gene -- a gene located on the sex chromosomes (usually the X chromosome) Non-sex-linked gene a gene that is NOT located on the sex chromosome independent assortment -- genes on separate chromosomes will independently assort into different gametes 1. How are a chromosome, DNA, and a gene interrelated. Draw a picture to support your answer. Chromosomes are made of DNA, DNA are made of Genes.

2 2. Below Given the Haploid number of chromosomes write down the diploid number of chromosomes: Haploid Number Diploid Number What type of cells have a haploid number? Gametes/ Sex Cells/ Sperm and egg. 4. What type of cells have a diploid number? Non-sex cells/ example: skin cells, heart cells, muscle cells. 5. What type of cells a formed through the process of meiosis? Gametes/ Sex Cells/ Sperm and egg.. 6. How many chromosomes does human sperm cell contain? Cross two heterozygous tall plants. T=tall t=short i. Write the cross described above. Tt X Tt ii. Draw a Punnett Square to represent the cross. T t T TT Tt t Tt tt iii. What percent of the offspring will be tall? 75% iv. If T= Tall plant and t= short plant what would be the phenotype for a heterozygous plant? Tall v. Organisms that have 2 identical genes such as TT or tt are said to be Homozygous. 8. W=Widow s peak, w=no widow s peak i. What is the genotype for a person that is heterozygous? What is the phenotype? a. Genotype Ww b. Phenotype Widow s peak 9. In corn, dark kernels are dominant to light. Show the cross between a heterozygous plant and a pure homozygous dominant plant. Please include the following: the symbols, the cross,, the Punnet square, and the genotypic and phenotypic ratios. a. The symbols _D=dark d=light b. The cross _ Dd x DD c. The Punnet square: D d D DD Dd D DD Dd d. What percent are dark? 100% 10. In rabbits, brown fur is dominant to white fur and long ears are dominant to short. Cross two brown long-eared rabbit that are heterozygous for both traits. Include the following: the symbols, the cross, the Punnet square, and the phenotypes of the offspring. a. The symbols _B=brown b= white; L=long l= short b. The cross BbLl x BbLl c. The Punnet square: BL Bl bl bl BL BBLL BBLl BbLL BbLl Bl BBLl BBll BBLl Bbll bl BbLL BbLl BbLL bbll bl BbLl Bbll bbll bbll d. The phenotypes: 9 brown long: 3 brown short: 3 white Long: 1 short white. 11. Hemophilia is a sex-linked trait. Write the cross for a hemophiliac man and a woman that is a carrier.

3 a. The Cross:_X h Y x X H X h b. Make the punnet square: X h Y X H X H X h X H Y X h X h X h X h Y Pedigree Practice c. What percent of the males do you expect to be hemophiliacs? _50% d. What percent of the females do you expect to be hemophiliacs? _50% e. What percent of the females do you expect to be carriers? 50% 12. Which members of the family above are afflicted with Huntington s Disease? I-1, II-2, II-3, II-7, III-3 ** 13. There are no carriers for Huntington s Disease- you either have it or you don t. With this in mind, is Huntington s disease caused by a dominant or recessive trait? ** DOMINANT 14. How many children did individuals I-1 and I-2 have? ** SIX= How many girls did II-1 and II-2 have? 2** How many have Huntington s Disease? The pedigree to the above shows the passing on of Hitchhiker s Thumb in a family. Is this trait dominant or recessive? ** Recessive 17. How do you know? ** you know because III-4 & III-5 both don t have hitchhikers thumb, but they both pass it on to their children (IV-2 and IV-4) Thus they both must carry the allele,but they don t show it because it is recessive 18. How are individuals III-4 and III-5 related? ** III-4 is III-5 are cousins 19. Name 2 individuals that have hitchhiker s thumb. ** IV-2 & IV Name 2 individuals that were carriers of hitchhiker s thumb. ** III-4 & III-5

4 21. Is it possible for individual IV-3 to be a carrier? Yes *Why? She could have inherited the recessive allele from her mother or father. 22. The pedigree to the above shows the passing on of colorblindness. What sex can ONLY be carriers of a. colorblindness? ** FEMALES 23. Why does individual IV-7 have colorblindness? ** She inherited the recessive allele from both her mother and father. 24. Why do all the daughters in generation II carry the colorblind gene? ** Because they all inherit an X chromosome from their dad and his X chromosome contains the allele for color blindness 25. List 2 IV generation colorblind males. ** IV-1, IV What is a test cross? Select the best answer below: A. Crossing a possible heterozygote with a homozygous recessive B. Any genetic cross to determine genotype C. Crossing a possible homozygote with a homozygous dominant D. Crossing a possible heterozygote with another heterozygote 27. A parent organism of unknown genotype is mated in a test cross. Half of the offspring have the same phenotype as the parent. What can be concluded from this result? A. The parent is homozygous dominant for the trait. B. The trait being inherited is polygenic. C. The parent is heterozygous for the trait. D. The parent is homozygous recessive for the trait. 28. A woman has a heterozygous genotype for blood group B. She is expecting a baby with a man who is homozygous Group A. What are the possible blood groups for their baby? SHOW YOUR WORK/ PUNNET

5 SQUARE (genetic diagram) Symbols: I B = Type B i = Type O I A = Type A Cross: I B i X I A I A I B i I A I A I B I A i I A I A I B I A i Type A or Type AB 29. If a man has blood group O and a woman has blood group AB, what is the probability that their child will be blood group O? SHOW YOUR WORK/ PUNNET SQUARE (Genetic Diagram) Symbols: I B = Type B i = Type O I A = Type A Cross: i i X I A I B i i I A I A i I A i I B I B i I B i 0% of their children can become type O blood In Border Collies, black coat (B) is dominant to red coat (b). A breeder has a black male that has won numerous awards. The breeder would like to use the dog for breeding if he is purebred or BB. To learn this information, she test crosses him with a red female (bb). Answer the following questions A, B, C, and D. A. If the black male is BB, what kind of gamete (sperm) can he produce? Only B B. If the red female is bb, what kind of gamete (eggs) can she produce? Only b C. If the black male is Bb, what kind(s) of gametes (sperm) can he produce? Either B or b D. If any of the puppies are red, what is the father's genotype? Only Bb The gene that controls whether or not a person can produce the pigment melanin which contributes to the color of skin, eyes and hair. Some people have the hereditary condition, albinism; they are not able to produce melanin and have little or no pigment in their skin and hair. Two different versions of the same gene are called alleles. One allele of this gene codes for melanin production and normally pigmented skin and hair; it is symbolized by A. Another allele of this gene codes for albinism; it is symbolized by a.

6 Both parents are heterozygous for albinism. Complete the Punnett square (right) that illustrates this marriage. What are the phenotypes of the children? 3 unaffected and 1 with albinism What is the probability that a child will have albinism? 1 in 4 A a A AA Aa a Aa aa 10. The ability to curl your tongue up on the sides (T, tongue rolling) is dominant to not being able to roll your tongue. A woman who can roll her tongue marries a man who cannot. Their first child has his father's phenotype. What are the genotypes of the mother, father, and child? Mother Tt Father tt Child tt T t t Tt tt t Tt tt

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