Genetics Is the Field of Biology Devoted to Understanding

Name: ______

Biology Chapter 9 Vocabulary

1. ______is the field of biology devoted to understanding how characteristics are transmitted from parents to offspring.

2. Mendel’s knowledge of statistics later proved valuable in his research on ______—the transmission of characteristics from parents to offspring.

3. Mendel observed seven characteristics of pea plants. Each characteristic occurred in two contrasting ______: plant height (long or short stems), flower position along stem (axial or terminal), pod color (green or yellow), pod appearance (inflated or constricted), seed texture (smooth or wrinkled), seed color (yellow or green), and flower color (purple or white).

4. – 6. Mendel was able to document the traits of each generation’s parents by carefully controlling how the pea plants were pollinated. ______occurs when pollen grains produced in the male reproductive parts of a flower, called the ______, are transferred to the female reproductive part of a flower, called the ______.

7. – 8. ______-pollination occurs when pollen is transferred from the anthers of a flower to the stigma of either the same flower or a flower on the same plant. ______-pollination involves flowers of two separate plants. Pea plants normally reproduce through self-pollination.

9. Plants that are ______for a trait always produce offspring with that trait.

10. The term ______denotes plants that are pure for a specific trait. Mendel produced strains by allowing the plants to self-pollinate for several generations.

11. He called each strain a parental generation, or ______.

12. – 13. Mendel called the offspring of the P1 generation the first filial generation, or ______. He then allowed the flowers from the F1 generation to self-pollinate and collected the seeds. Mendel called the plants in this generation the second filial generation, or ______.

14. Mendel’s observations and his careful records led him to hypothesize that something within the pea plants controlled the characteristics he observed. He called these controls ______. Mendel hypothesized that each trait was inherited by means of a separate factor. Because the characteristics he studied had two alternative forms, he reasoned that there must be a pair of factors controlling each trait.

15. – 16. Mendel hypothesized that the trait appearing in the F1 generation was controlled by a ______factor because it masked, or dominated, the other factor for a specific characteristic. The trait that did not appear in the F1 generation but reappeared in the F2 generation was thought to be controlled by a ______factor.

17. The law of ______states that a pair of factors is segregated, or separated, during the formation of gametes.

18. The law of ______states that factors for different characteristics are distributed to gametes independently.

19. ______is the study of the structure and function of chromosomes and genes.

20. Each of several alternative forms of a gene is called an ______. Mendel’s factors are now called alleles.

21. The genetic makeup of an organism is its ______. The genotype consists of the alleles that the organism inherits from its parents.

22. The appearance of an organism as a result of its genotype is called its ______.

23. When both alleles of a pair are alike, the organism is said to be ______for that characteristic. An organism may be homozygous dominant or homozygous recessive.

24. When the two alleles in the pair are different, the organism is ______for that characteristic.

25. ______is the likelihood that a specific event will occur. A probability may be expressed as a decimal, a percentage, or a fraction. Probability is determined by the following equation:

Probability =number of times an event is expected to happen / number of opportunities for an event to happen

26. A cross between individuals that involves one pair of contrasting traits is called a ______cross.

27. Biologists use a diagram called a ______to aid them in predicting the probability that certain traits will be inherited by offspring.

28. The ratio of the genotypes that appear in offspring is called the ______ratio.

29. The ratio of the offsprings’ phenotypes is called the ______ratio.

30. You could perform a ______, in which an individual of unknown genotype is crossed with a homozygous recessive individual. This type of cross can determine the genotype of any individual whose phenotype is dominant.

31. Recall that in Mendel’s pea-plant crosses, one allele was completely dominant over another, a relationship called ______dominance where heterozygous plants and dominant homozygous plants are indistinguishable in phenotype.

32. Sometimes, however, the F1 offspring will have a phenotype in between that of the parents, a relationship called ______dominance. Incomplete dominance occurs when two or more alleles influence the phenotype, resulting in a phenotype intermediate between the dominant trait and the recessive trait.

33. ______occurs when both alleles for a gene are expressed in a heterozygous offspring. In codominance, neither allele is dominant or recessive, nor do the alleles blend in the phenotype.

34. A ______cross is a cross between individuals that involves two pairs of contrasting traits.