Reproduction, DNA and genetic inheritance：練習題

In genetics, an individual's physical characteristics are the result of their genes and their interaction with the environment. What term is used to describe the observable characteristics of an organism?

According to the theory of natural selection, how can a mutation lead to the evolution of a new species if two populations of the same species become geographically isolated?

(HT only) In the process of genetic engineering, enzymes are used to isolate a required gene from a chromosome. What is the specific role of a vector in this process?

Selective breeding is used by farmers to produce livestock with desirable characteristics. Explain one potential disadvantage of using selective breeding over many generations.

The theory of evolution by natural selection states that species change over time. Describe how a mutation that results in a new phenotype can lead to a relatively rapid change in a species if the environment changes.

Explain how the process of natural selection leads to an increase in the population of antibiotic-resistant bacteria when a course of antibiotics is started but not completed.

Cystic fibrosis is an inherited disorder caused by a recessive allele (f). A couple are both heterozygous for the disorder.

(a) Using a Punnett square diagram, determine the probability that their first child will have cystic fibrosis. Show your working and state the possible genotypes. (3)

(b) Describe the difference between the genotype and the phenotype of an individual. (2)

(c) Embryo screening can be used to identify genetic disorders before birth. Discuss one social and one economic issue associated with the use of embryo screening. (2)

The theory of evolution by natural selection states that all species of living things have evolved from simple life forms. Scientists use various types of evidence to support this theory.

(a) Explain how antibiotic resistance in bacteria provides evidence for the theory of evolution by natural selection. Include the role of mutations in your answer. (4)

(b) Fossils are the remains of organisms from millions of years ago. Describe two ways in which fossils can be formed. (2)

(c) Evolution can lead to the formation of new species. Explain the conditions necessary for two populations of the same species to be classified as two separate species. (2)