DNA extraction

Figure 5 shows the times when Homo sapiens (modern humans) and some of their ancestors are thought to have lived.

Which term is used to describe changes in species over time?

Estimate the length of time Homo habilis is thought to have lived on Earth.

_........ million years

Describe two methods scientists used to date the fossils of Ardi or Lucy, as shown in Figure 5.

The ancestors of modern humans used selective breeding to improve the plants they used for food.

Complete the sentences using words from the box.

Selective breeding involves choosing parents with

desirable_........ .

The best offspring are bred together and this process is repeated over

many_........ .

Suggest one feature of a banana that could be improved by selective breeding.

The DNA of fruit can be modified to produce new varieties.

Figure 6 shows part of a method used to extract DNA from fruit.

State the purpose of both step 1 and step 2.

step 1_........

State why the cold ethanol was added in step 3.

Genetic disorders can be caused by mutations in the DNA of genes.

Cystic fibrosis is a recessive genetic disorder.

Figure 10 shows a family pedigree for the inheritance of cystic fibrosis.

Which row is correct for the mother, father and son?

Cystic fibrosis causes the build‑up of thick, sticky mucus.

Describe how the build-up of thick, sticky mucus affects the airways of a person.

Huntington’s disease is a condition caused by a dominant allele.

Explain the phenotypes of the offspring of a genetic cross between a person who is heterozygous for the Huntington’s allele and a person who is not affected.

Use the Punnett square as part of your answer.

*(c) Explain how DNA is extracted from strawberries.

Include in your answer:

• the reasons for each stage of the extraction process

• the structure of a DNA molecule.

Figure 2 shows a method used to extract DNA from strawberries.

Complete the sentences using words from the box.

Crushed strawberries are mixed with washing up liquid and

_........ solution.

Washing up liquid helps to release DNA by breaking open cell

Describe the method shown in stage 2.

What is the colour of the DNA precipitate?

A scientist used this method to find the mass of DNA in four strawberries.

Figure 3 shows the results.

The range is the difference between the largest value and smallest value in a set of numbers.

Which is the range of these results?

Calculate the mean mass of DNA.

mean mass of DNA =_........ ng

A student made a microscope slide of cells taken from the inside of their mouth.

The student wore gloves while using a swab to collect cells from their mouth.

Give one other safety precaution the student should take.

A light microscope was used to obtain an image similar to the one shown in Figure 3.

(Source: © STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY)

Figure 3

Describe how the student used the light microscope to view these cells at a magnification of 400.

The cytoplasm of a cell contains a nucleus.

Explain the role of one other structure in the cytoplasm of a human cell.

DNA can be extracted from human cells in a similar way to the method used to extract DNA from fruits.

Describe the stages of the method used to extract DNA from cells.

The Human Genome Project sequenced the order of the bases in the human genome.

Give two other outcomes from the Human Genome Project.

DNA molecules contain base pairs.

Describe how the base pairs are bonded together in a DNA molecule.

Figure 9 shows part of a DNA molecule.

Write the code for the complementary DNA strand in Figure 9.

Three bases code for each amino acid.

Which is the maximum number of amino acids coded for by this strand of DNA?

What is the shape of a DNA molecule?

A student wanted to extract the DNA from fresh peas.

The student crushed the peas and added washing up liquid and water.

The enzyme protease was then added to this mixture.

Explain why the enzyme protease was added to the mixture.

The mixture was then heated and filtered.

Finally, the student poured the filtrate into a test tube and ice‑cold ethanol was poured down the side of the test tube into the filtrate.

State why ice‑cold ethanol was poured into the filtrate.

The student wanted to compare the mass of DNA found in fresh peas with the mass of DNA found in fresh beans.

Give two variables the student would need to control to make this a valid comparison.

DNA molecules contain base pairs.

Describe how the base pairs are bonded together in a DNA molecule.

Figure 1 shows part of a DNA molecule.

Write the code for the complementary DNA strand in Figure 1.

Three bases code for each amino acid.

Which is the maximum number of amino acids coded for by this strand of DNA?

What is the shape of a DNA molecule?

A student wanted to extract the DNA from fresh peas.

The student crushed the peas and added washing up liquid and water.

The enzyme protease was then added to this mixture.

Explain why the enzyme protease was added to the mixture.

The mixture was then heated and filtered.

Finally, the student poured the filtrate into a test tube and ice cold ethanol was poured down the side of the test tube into the filtrate.

State why ice cold ethanol was poured into the filtrate.

Figure 8 shows a banana plantation.

After the bananas have been harvested, the old plants are cut down.

The suckers then develop into mature plants producing the next crop of bananas.

The tip of each sucker contains a group of cells called a meristem.

Describe the function of a meristem in the growth of a plant.

A student took a sample of cells from a meristem to view under a light microscope.

Describe how the student would prepare a microscope slide using these cells.

Figure 9 is a drawing of a eukaryotic cell.

Structure Z is found in plant leaf cells.

Name structure Z.

Give one function of the mitochondrion.

*(c) DNA is found in the nucleus of cells.

Describe the structure of DNA and how it can be extracted from plant cells.

James Watson and Francis Crick built a model that showed that DNA has a double helix structure.

Which statement about DNA is correct?

Figure 6 shows the percentage of each base in human DNA.

Describe how this data provides evidence for base pairing in DNA.

A scientist obtained a mass of 0.0062 nanograms of DNA from a diploid human cell.

Calculate the mass of DNA the scientist should obtain from a haploid human cell.

Give your answer in picograms.

(1 nanogram = 1000 picograms)

_........ picograms

A student used the method shown in Figure 7 to compare the mass of DNA extracted from strawberry fruit cells and from kiwi fruit cells.

State why ethanol is used.

State two variables the student needs to control when using this method to compare the mass of DNA from these two fruits.

The student repeated the experiment.

Give one reason why.

Mitosis and meiosis are processes that produce new cells.

Compare the outcomes of mitosis and meiosis.

A scientist obtained a mass of 0.0062 nanograms of DNA from a diploid human cell.

Calculate the mass of DNA the scientist should obtain from a haploid human cell.

Give your answer in picograms.

(1 nanogram = 1000 picograms)

_........ picograms

A student used the method shown in Figure 1 to compare the mass of DNA extracted from strawberry fruit cells and from kiwi fruit cells.

State why ethanol is used.

State two variables the student needs to control when using this method to compare the mass of DNA from these two fruits.

The student repeated the experiment.

Give one reason why.

Mitosis and meiosis are processes that produce new cells.

Compare the outcomes of mitosis and meiosis.

Figure 2 shows part of a DNA molecule.

What is the shape of a DNA molecule?

Which molecules are present in the DNA backbone?

State the type of bond that joins the bases together in the DNA molecule.

DNA can be extracted from fruit.

Describe how cells are broken down to release DNA.

In 2003, scientists finished sequencing the 3 billion base pairs in the human genome.

State two benefits that the Human Genome Project could have for medicine.