Deck 1: Introduction to Genetics

Question 1

Describe Mendel's conclusions about how traits are passed from generation to generation.

Answer 1

Mendel planted the garden peas and observed the changes in their characteristics for different generations. His quantitative observations were later calculated into ratios. He calculated the ratios of different physical characteristics of the offspring. He concluded that offspring inherit the physical characteristics from their parents.
During Mendel time, the concept of chromosomes, genes and alleles are not known. Hence, Mendel coined the term hereditary factor for alleles. Hereditary factor is a unit of inheritance. Pair of alleles together encodes a character. Now-a-days, the genes are called hereditary units.
According to Mendel, each parent contributes one hereditary factor for a trait to the offspring. Hence, the offspring receives two hereditary factors from both the parents to express a trait. For example, one pea plant receives two hereditary factors for seed color. The color of the seed depends on the type of hereditary factor that a plant received from its parents.
According to the Mendel, the dominant alleles will be expressed, while the recessive alleles will be hidden. For example, if yellow is the dominant seed color and green is the recessive seed color. A plant with yellow seed allele and a green seed allele will express yellow seed color. Thus, it proves the dominant alleles offset the effects of the recessive alleles.
Hence, by conducting several experiments on garden pea plants Mendel proved that the traits are carried from generation to generations. He also compared the records of his experiments to perform calculations in favor of his statements.

Question 2

Review the Chapter Concepts list. Most of these are related to the discovery of DNA as the genetic material and the subsequent development of recombinant DNA technology. Write a brief essay that discusses the impact of recombinant DNA technology on genetics as we perceive the discipline today.
CHAPTER CONCEPTS
▪Genetics in the twenty-first century is built on a rich tradition of discovery and experimentation stretching from the ancient world through the nineteenth century to the present day.
▪Transmission genetics is the general process by which traits controlled by genes are transmitted through gametes from generation to generation.
▪Mutant strains can be used in genetic crosses to map the location and distance between genes on chromosomes.
▪The Watson-Crick model of DNA structure explains how genetic information is stored and expressed. This discovery is the foundation of molecular genetics.
▪Recombinant DNA technology revolutionized genetics, was the foundation for the Human Genome Project, and has generated new fields that combine genetics with information technology.
▪Biotechnology provides genetically modified organisms and their products that are used across a wide range of fields including agriculture, medicine, and industry.
▪Model organisms used in genetics research are now utilized in combination with recombinant DNA technology and genomics to study human diseases.
▪Genetic technology is developing faster than the policies, laws, and conventions that govern its use.

Answer 2

These studies can also lead to the development of therapeutics to prevent certain diseases. Recombinant DNA allows for the injection of DNA which codes for human proteins into bacterial genomes to use bacterial machinery to produce human products such as insulin or targeted ligands for human cell surface receptors.
Recombinant DNA also allows for the development of new diagnostic tools which can identify specific DNA/RNA/protein sequences in fast and efficient assays.

Question 3

What is the chromosome theory of inheritance, and how is it related to Mendel's findings?

Answer 3

Chromosome theory of inheritance is also called "Sutton-Boveri theory." This theory was proposed by Walter Sutton and Theodor Boveri in 1902 and 1903 independently. According to this theory, the chromosomes are the chief carriers of genetic material. It states that chromosomes are linear thread like structures, which have genes that are situated at specified locations. These specified locations are termed as loci.
The Chromosome theory of inheritance supports the Mendelian inheritance, because it identified the chromosomes as particles or paired factors. Gregor John Mendel also termed chromosomes as paired factors and proposed the Mendelian theory of independent assortment and segregation.
Mendel's law of independent assortment states that different traits are assorted randomly from each other. This is automatically the case in alleles found in different chromosomes. Since, during anaphase chromosomes are randomly assorted and distributed to gametes. However, in alleles whose genes are on the same chromosome the homologous chromosomes goes through crossing over and linkage which mixes the alleles.
The monohybrid cross is between two parents with heterozygous genotype such as Aa for a some trait. This is explained by Mendel's law of segregation, which states that alleles are separated. In meiosis, each allele is coded in genes found in each homologous chromosome. For example, A may be found in chromosome C and a in the homologous chromosome C'. Homologous chromosomes are separated during anaphase II which explains segregation of alleles.
In the initial days, the definitive evidence and documented work of "Eleanor Carothers" on grasshoppers in 1913 has proved that the genes assort independently according to the chromosome theory of inheritance. However, the debate has continued until Thomas Hunt Morgan's divorced genetic linkage in the Drosophila melanogaster. This finally supported and believed that the chromosome theory of inheritance is relates to the Mendel's findings.

Question 4

Define genotype and phenotype. Describe how they are related and how alleles fit into your definitions.

Question 5

Given the state of knowledge at the time of the Avery, MacLeod, and McCarty experiment, why was it difficult for some scientists to accept that DNA is the carrier of genetic information?

Question 6

Contrast chromosomes and genes.

Question 7

How is genetic information encoded in a DNA molecule?

Question 8

Describe the central dogma of molecular genetics and how it serves as the basis of modern genetics.

Question 9

How many different proteins, each with a unique amino acid sequence, can be constructed with a length of five amino acids?

Question 10

Outline the roles played by restriction enzymes and vectors in cloning DNA.

Question 11

What are some of the impacts of biotechnology on crop plants in the United States?

Question 12

Summarize the arguments for and against patenting genetically modified organisms.

Question 13

We all carry about 20,000 genes in our genome. So far, patents have been issued for more than 6000 of these genes. Do you think that companies or individuals should be able to patent human genes? Why or why not?

Question 14

How has the use of model organisms advanced our knowledge of the genes that control human diseases?

Question 15

If you knew that a devastating late-onset inherited disease runs in your family (in other words, a disease that does not appear until later in life) and you could be tested for it at the age of 20, would you want to know whether you are a carrier? Would your answer be likely to change when you reach age 40?

Question 16

Why do you think discoveries in genetics have been recognized with so many Nobel Prizes?

Question 17

The Age of Genetics was created by remarkable advances in the use of biotechnology to manipulate plant and animal genomes. Given that the world population has topped 6 billion and is expected to reach 9.2 billion by 2050, some scientists have proposed that only the worldwide introduction of genetically modified (GM) foods will increase crop yields enough to meet future nutritional demands. Pest resistance, herbicide, cold, drought, and salinity tolerance, along with increased nutrition, are seen as positive attributes of GM foods. However, others caution that unintended harm to other organisms, reduced effectiveness to pesticides, gene transfer to nontarget species, allergenicity, and as yet unknown effects on human health are potential concerns regarding GM foods. If you were in a position to control the introduction of a GM primary food product (rice, for example), what criteria would you establish before allowing such introduction?

Question 18

The BIO (Biotechnology Industry Organization) meeting held in Philadelphia in June 2005 brought together worldwide leaders from the biotechnology and pharmaceutical industries. Concurrently, BioDemocracy 2005, a group composed of people seeking to highlight hazards from widespread applications of biotechnology, also met in Philadelphia. The benefits of biotechnology are outlined in your text. Predict some of the risks that were no doubt discussed at the BioDemocracy meeting