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1) What is a locus?

1. A locus is the location of an allele on a chromosome

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2) Approximately how many genes do humans possess?

2. 21,500

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3) What is each version of a gene called?

3. allele

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4) What is the condition referred to if two copies of a gene are identical alleles?

4. homozygous

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5) What is the condition referred to if two copies of a gene are different alleles?

5. heterozygous

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6) What is an allele called when that allele's effect on a trait masks that of an allele paired with it?

6. dominant

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7) When an allele's effect on a trait is masked by that of an allele paired with it, what is the second allele referred to as?

7. recessive

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8) What is the genotype AA referred to as?

8. homozygous dominant

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9) What is the genotype aa referred to as?

9. homozygous recessive

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10) What is the genotype Aa referred to as?

10. heterozygous

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11) What are the alleles an individual inherits called?

11. genotype

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12) What are observable functional or physical traits called?

12. Phenotype

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13) What is the most accurate description of an organism with genotype AaBb ?

13. Dihybrid

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14) Gene A occurs on chromosome 5, gene B is on chromosome 21. Therefore, these two parts of the chromosomes can NOT be

14. Linked

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15) If two parent organisms have different alleles for a gene that an experimenter wants to test, what test will he or she perform?

15. Test cross

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16) What gametes will a parent with the genotype CC will produce?

16. C

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17) When homologues separate into different gametes after meiosis I, the genes of each pair separate as well. What is this principle called?

17. Segregation

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18) The principle of segregation applies most specifically to events occurring in preparation of what?

18. gametes

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19) What does the theory of segregation deal with?

19. explains the behavior of a pair of alleles during meiosis.

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20) If R is dominant to r, the offspring of the cross of RR with rr will have what phenotype?

20. the same phenotype as the RR parent

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21) If tall (D) is dominant to dwarf (d), and two homozygous varieties DD and dd are crossed, then what phenotypes of offspring will be produced?

21. all tall

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22) If all offspring of a cross have the genotype Aa, what would the parents of the crosses most likely be?

22. AA x aa

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23) What is a graphic tool used to determine the probable outcome of genetic crosses called?

23. Punnett square

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24) When the first generation parents are homozygous for different alleles, a 3:1 phenotype ratio will most likely appear in which generation of offspring?

24. F2

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25) In a monohybrid cross, what kind of genes "disappear" in the F1 generation?

25. recessive

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26) What is the F2 phenotypic ratio of a monohybrid cross?

26. 3:1

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27) In the cross Cc x Cc, gametes have a ____ chance of receiving either allele.

27. 50 x 50

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28) In a Punnett square, what do the letters within the little boxes represent?

28. offspring genotypes

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29) If short hair (L) is dominant to long hair (l), then to determine the genotype of a short-haired animal it should be crossed with what genotype animal?

29. ll

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30) When an individual with an unknown genotype is crossed with an individual that is homozygous recessive for the trait being studied, what is the procedure called?

30. testcross