Guided Reading

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GUIDED READING - Ch. 15 - CHROMOSOMAL BASIS OF INERITANCE
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NAME: ________________________

Please print out these pages and HANDWRITE the answers directly on the printouts. Typed work or answers on separate sheets of paper will not be accepted.

Importantly, guided readings are NOT GROUP PROJECTS!!! You, and you alone, are to answer the questions as you read. You are not to share them with another students or work together on filling it out. Please report any dishonest behavior to your instructor to be dealt with accordingly. Get in the habit of writing legibly, neatly, and in a NORMAL, MEDIUM-SIZED FONT. AP essay readers and I will skip grading anything that cannot be easily and quickly read so start perfect your handwriting. Please SCAN documents properly and upload them to Archie. Avoid taking photographs of or uploading dark, washed out, side ways, or upside down homework. Please use the scanner in the school’s media lab if one is not at your disposal and keep completed guides organized in your binder to use as study and review tools. READ FOR UNDERSTANDING and not merely to complete an assignment. Though all the answers are in your textbook, you should try to put answers in your own words, maintaining accuracy and the proper use of terminology, rather than blindly copying the textbook whenever possible.

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Mendelian inheritance has its physical basis in the behavior of chromosomes [2]. 1. What is the ‘chromosomal theory of inheritance’?

2. a. IN YOUR OWN WORDS, explain what is demonstrated in 15.2 on page 287 in reference to the law of segregation. [3]

b. Use two different colored pencils to illustrate the segregation of alleles. Model your sketches on this. [2]

3. a. IN YOUR OWN WORDS, explain what is demonstrated in 15.2 on page 287 in reference to the law of independent assortment. [3]

b. To demonstrate that you understand this concept, consider a cell with two pairs of chromosomes. Sketch the two different ways these chromosomes might be arranged during metaphase I. [2]

4. List three reasons why Morgan’s choice of the fruit fly was a good one for genetic experiments?

5. What does ‘wild type phenotype’ and ‘mutant phenotype’ mean?

6. The notation for wild type and mutant traits follows some accepted conventions. Notation the following genotypes for a female fruit fly. a. a fly homozygous for red eyes

b. a fly heterozygous for red eyes

c.

a fly homozygous for white eyes

BE CAREFUL with the way the letters represent the traits. The + superscript means the mutant trait is absent. So vg+ means normal wings, not vestigial wings (vg)and w+ means normal red eye color, not white (w)! This is counterintuitive and appears backwards. Be careful with it while you read or you will get VERY confused. 7. Morgan’s work indicated that genes located on a sex chromosome exhibit unique inheritance patterns. How did Morgan determine that a fruit flies eye color was linked to its sex?

8. Propose a possible reason that the first naturally occurring mutant fruit fly Morgan saw involved a gene on a sex chromosome and not an autosomal chromosome? [1]

9. As you read, when Thomas Hunt Morgan mated white-eyed male fly with a red-eyed female, he came to the startling conclusion that the trait for eye color was located on the chromosome that determined sex. Show this cross. Begin with the parental generation, and go through the F2. Parental generation

F1 generation

F2 generation

Sex-linked genes exhibit unique patterns of inheritance [2]. 10. a. What is the SRY gene?

b. Where is it found? [2]

c.

Why is it important?

11. Explain the chromosomal basis of sex determination in the following organism. Complete the matching illustration as well. [2, 3] a. Mammals:

b. Grasshoppers:

c.

Birds and some fish:

d. Bees and ants:

12. a. What is a ‘sex-linked gene’?

b. In humans, a gene on what chromosome does it traditionally refer to?

13. When does a...
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