CHROMOSOMES AND INHERITANCE

Transcription

1 SECTION 12-1 REVIEW CHROMOSOMES AND INHERITANCE VOCABULARY REVIEW Distinguish between the terms in each of the following pairs of terms. 1. sex chromosome, autosome 2. germ-cell mutation, somatic-cell mutation 3. translocation, nondisjunction 4. deletion, inversion 5. substitution, frameshift mutation MULTIPLE CHOICE Write the correct letter in the blank. 1. Genes that belong to the same linkage group tend to be a. located on different chromosomes. b. inherited together. 2. Two genes that are one map unit apart are separated by crossing-over a. 1% of the time. b. 20% of the time. c. 50% of the time. d. 100% of the time. 3. Mutations that can be inherited arise in c. found only in males. d. found only in somatic cells. a. somatic cells. b. body cells. c. germ cells. d. skin cells. 4. Which of the following sequences could result from an inversion of the sequence GAGACATT? a. GAGCATT b. GTGACATT c. CTCTGATT d. GATACAGT 5. Which of the following is a point mutation that does not produce a frameshift? a. substitution b. insertion c. deletion d. inversion Modern Biology Study Guide 61

2 SHORT ANSWER Answer the questions in the space provided. 1. In humans and fruit flies, which parent determines the sex of the offspring? Explain why. 2. How did Morgan determine that red-eye color in Drosophila is an X-linked trait? 3. Explain why traits that are controlled by genes on the same chromosome do not always appear in the expected ratio in offspring. 4. Critical Thinking Would a frameshift mutation have a more serious effect if it occurred near the beginning of a gene or the end of a gene? Explain your answer. STRUCTURES AND FUNCTIONS Use the data in the table below to indicate the position of these genes on the chromosome map shown below. Assuming that the gene for white eyes has a chromosome map unit number of 1, write the map unit numbers above each gene s position on the chromosome map. The Drosophila genes for white eyes, vermilion eyes, and miniature wings are located on the same chromosome. The table shows how often these genes are separated by crossing-over. Genes Vermilion eyes and miniature wings 3% White eyes and vermilion eyes 30% White eyes and miniature wings 33% 0 40 Frequency of crossing-over 62 Section 12-1 Review

3 SECTION 12-2 REVIEW HUMAN GENETICS VOCABULARY REVIEW Name a trait or genetic disorder that is caused by each of the following patterns of inheritance. 1. polygenic inheritance 2. multiple alleles 3. autosomal dominant 4. sex-influenced trait 5. incomplete dominance MULTIPLE CHOICE Write the correct letter in the blank. 1. Which individual(s) in the pedigree shown below must be a carrier? a. 1 only b. 4 only c. 3 only d. both 1 and Since the ABO blood group alleles are codominant, an individual with the genotype I A I B will have blood type a. A. b. B. c. AB. d. O. 3. Which of the following human traits is not a polygenic trait? a. skin color b. eye color c. height d. ABO blood type 4. A trait whose expression is affected by the presence of sex hormones is said to be a. sex-influenced. b. sex-linked. c. X-linked. d. Y-linked. 5. In humans, PKU can be treated by 3 4 a. insulin injections. c. gene therapy. b. diet. d. surgery. Modern Biology Study Guide 63

4 SHORT ANSWER Answer the questions in the space provided. 1. Why is pattern baldness more common in men than in women? 2. Briefly describe how amniocentesis and chorionic villi sampling are used in genetic screening. 3. Explain the difference between a sex-linked trait and a sex-influenced trait. 4. Critical Thinking A couple has four children, and each child has a different ABO blood type. What are the blood types and genotypes of the children and the parents? STRUCTURES AND FUNCTIONS In the two pedigrees below, indicate all possible offspring in generation II by correctly filling in the male and female symbols for generation II. Use a completely filled symbol to represent an individual who displays the trait and a half-filled symbol to represent a carrier. Generation I X-linked recessive trait Autosomal recessive trait Generation II 64 Section 12-2 Review

5 Section 12-1 VOCABULARY REVIEW 1. A sex chromosome contains genes that determine an individual s sex. An autosome is a chromosome that is not directly involved in determining sex. 2. A germ-cell mutation occurs in one of an organism s gametes; a somatic-cell mutation occurs in one of the other cells in an organism s body. 3. Translocation occurs when a chromosome piece breaks off and attaches to a nonhomologous chromosome; nondisjunction occurs when homologues fail to separate during meiosis, so that one gamete receives both homologues. 4. A deletion is a loss of a piece of chromosome due to breakage. An inversion occurs when a broken piece of chromosome is reattached backwards. 5. In a substitution, one nucleotide in a codon is replaced with a different one; in a frameshift mutation, the loss or addition of a nucleotide causes the remaining codons to be incorrectly grouped. MULTIPLE CHOICE 1. b 2. a 3. c 4. d 5. a SHORT ANSWER 1. The male parent determines the offspring s sex. Offspring that receive an X chromosome from the male parent will be female; those that receive a Y chromosome will be male. Modern Biology Study Guide Answer Key 9

6 2. Morgan crossed a white-eyed male with a female homozygous for red eyes, and then crossed members of the F 1 generation resulting from the first cross. He found that all of the white-eyed flies in the F 2 generation were male. 3. Crossing-over during meiosis causes homologous chromosomes to exchange alleles, resulting in new combinations of alleles in the offspring. 4. A frameshift mutation would have a more serious effect if it occurred near the beginning of a gene, since it would change nearly all of the codons in the gene. The resulting protein likely would be nonfunctional. STRUCTURES AND FUNCTIONS white eyes (map unit number 1), vermilion eyes (31), miniature wings (34) Section 12-2 VOCABULARY REVIEW 1. skin color, eye color, height, or hair color 2. ABO blood groups 3. Huntington s disease 4. pattern baldness 5. wavy hair MULTIPLE CHOICE 1. d 2. c 3. d 4. a 5. b SHORT ANSWER 1. Pattern baldness is controlled by the allele B. Testosterone interacts with the heterozygous genotype (BB ) to produce baldness. Since males have higher levels of testosterone, BB males are more likely to lose their hair than BB females. 2. A small sample is removed from the amniotic fluid surrounding the fetus or from the chorionic villi between the uterus and the placenta. Fetal cells in the sample are used to construct a karyotype, which may reveal chromosomal abnormalities. 3. A sex-influenced trait is influenced by the presence of sex hormones and its genes are not located on sex chromosomes, while a sex-linked trait is linked to a sex chromosome. 4. Children: type A, I A i; type B, I B i; type AB, I A I B ; type O, ii. One parent is type A, I A i; the other parent is type B, I b i. STRUCTURES AND FUNCTIONS X-linked recessive trait: one filled square, one open square, one half-filled circle, and one open circle. Autosomal recessive trait: one half-filled square, one open square, one half-filled circle, and one open circle. 10 Modern Biology Study Guide Answer Key