CRCT Review

 The passing of traits from parents to offspring is know as heredity.  The study of heredity is called genetics.  Modern genetics can be traced back to the experiments of a priest named Gregor Mendel in the 19 th century.

 Dominant allele is one that always shows up even if a different allele is present.  An allele that is hidden when a dominant allele is present is called the recessive allele.  An organism with 2 identical alleles is called purebred or homozygous.  An organism that has 2 different alleles for a trait is called hybrid or heterozygous.  The allele combination (letters) is the genotype.  The physical appearance of the trait is called the phenotype.

 A Punnett square is a diagram that shows all of the possible combinations of alleles that might result from a cross.

 If black bears are dominant to brown bears, what are the possible offspring of two heterozygous bears?

 If black bears are dominant to brown bears, what are the possible offspring of a heterozygous black brown and a brown bear?

1. A scientist crossed a purebred long- winged male fruit fly. Long wings are dominant over short wings. What is the probability that the offspring will have long wings? a. 25% b. 50% c. 75% d. 100%

2. In humans, the allele for a cleft chin (C) is dominant. A woman with the genotype cc has children with a man with the genotype Cc. If the couple has six children, how many children would you logically expect to have a cleft chin? a. 0 b. 1 c. 3 d. 6

 In selective breeding, humans use genetic patterns that occur naturally in plants and animals to pass desired traits on to the next generation.  Inbreeding is crossing very similar individuals.  Crossing genetically different individuals is known as hybridization.  Genetic engineering is the process of removing bits of genetic material from one organism and inserting it into another.  Cloning uses genetic information from a single cell to produce another organism with the exact same genetic information.

1. A scientist crossed potato plants to combine the disease resistance of one plant with the food producing capacity of another. He used the process of a. Inbreeding b. Crop roation c. Hybridization d. cloning

2. Excessive inbreeding among cheetahs has resulted in a higher death rate among the cheetah population. Why is this true? a. Inbreeding decreases genetic variation. b. Inbreeding increases genetic variation. c. Inbreeding produces the worst traits. d. Inbreeding produces more organisms that other breeding methods.

 Evolution is the process in which organisms change over time.  Finches – Darwin observed small birds while on the Galapagos islands. He observed that the birds had beaks adapted to their food source.  Peppered Moths – Moths that blend into the tree bark are harder to see and catch than moths that are a different color. Camouflaged moths are more likely to survive and reproduce.

 Darwin observed 13 species of finches on the Galapagos Islands. What did Darwin conclude about the finches? a. They evolved from a common ancestor. b. They all came from different continents. c. They evolved from 13 different types of birds. d. They developed from other types of organisms.

Why did the population of peppered moths in England change from light to dark after the Industrial Revolution? a. Light moths were killed by soot. b. Dark moths were produced by industrial processes. c. The birds that ate the dark moths were killed by the soot. d. Light moths were more obvious against the soot-stained trees.