DNA structure

Figure 3 shows a sperm cell.

Name the part labelled R.

Draw one straight line from each part of the sperm cell to its function.

Animal and plant cells are both eukaryotic.

State one structure found in a plant cell that is not found in an animal cell.

DNA is found in cells.

Figure 4 shows part of a DNA molecule.

Which type of large molecule is DNA?

Describe how the bases of a DNA molecule are held together.

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

Cystic fibrosis is a recessive genetic disorder.

Figure 13 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.

Mendel crossed pea plants that always produced purple flowers with pea plants that always produced white flowers.

The flowers of the offspring were all purple, as shown in Figure 5.

Which conclusion can be made about the characteristic for purple flowers?

Mendel used two of the offspring with purple flowers in another cross.

The pea plants he obtained from this cross produced purple flowers or white flowers in a ratio of 3: 1.

Calculate the expected number of pea plants with purple flowers, in a sample of 160 pea plants.

A pea plant producing purple flowers had the genotype Aa.

This pea plant was crossed with a pea plant producing white flowers.

Complete the Punnett square to show the possible genotypes of the offspring.

Show the percentage of pea plants that produce white flowers in your answer.

Asexual reproduction can be used to produce flowering plants.

Give two advantages of using asexual reproduction to produce flowering plants.

Flower colour is controlled by genes.

Which is a definition of a gene?

The two strands of a DNA molecule are linked by complementary bases.

Describe how the complementary bases are linked in a DNA molecule.

DNA molecules contain base pairs.

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

Figure 16 shows part of a DNA molecule.

Write the code for the complementary DNA strand in Figure 16.

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 14 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 15 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.

Figure 5 shows a great tit on a bird feeder.

Scientists have found that great tits living now have longer beaks than great tits living 50 years ago.

Genetic analysis shows changes in the sequence of the bird’s DNA.

Give the complementary strand sequence for this DNA template.

Which statement correctly describes a DNA molecule?

State the term used to describe a change in the sequence of DNA bases.

Scientists think that great tits living now have longer beaks because of the increased use of bird feeders during the last 50 years.

Explain how natural selection could have caused an increase in beak length because of the use of bird feeders.

Birds are classified in the domain Eukarya.

Why are the cells from birds described as eukaryotic?

Give one reason why the three domain classification system was proposed.

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

Which statement about DNA is correct?

Figure 13 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)

A student used the method shown in Figure 14 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.

(a) Yeast cells can be genetically modified to produce a painkiller.

This painkiller is usually obtained from opium poppies.

One method for genetically modifying a yeast cell uses a plasmid containing the desired gene.

Explain how a gene can be inserted into a plasmid.

Discuss the possible benefits and risks of producing painkillers from genetically modified yeast cells rather than extracting the painkillers from poppies.

Figure 17 shows the structure of a DNA nucleotide.

Structure A is a

*(ii) In 2003, the first complete human genome was sequenced.

The genomes of different people have small changes in the sequence of the DNA bases.

Describe how these changes in DNA sequence can affect the individuals and how sequencing a person’s genome could influence their medical treatments.