Unit 2 Biology Revision Lesson 1

Unit 2 Biology Revision Lesson 1

Part 1

Genes, Genomes, Alleles

Open Ended

What was the purpose of the Human Genome Project? Provide an example of how the results from the project have been used. (2 marks)

Your answer should include:

• The HGP was conducted to map the sequence of human genes, to identify the human 'blueprint' (1 mark)

• It has been used to: identify mutations in genes, develop treatments for genetic diseases/disorders, improved genetic testing, new knowledge of human evolution, personalised medicines (1 mark for one of those or similar)

Open Ended

What are the four nucleotide bases of DNA? (2 marks)

Which bases bond together? (2 marks)

Answer

• Adenine, Guanine, Cytosine, Thymine (half mark each)

• Adenine bonds with Tymine (1 mark) and Guanine with Cytosine (1 mark)

Open Ended

How can scientists determine how related two organisms are using DNA? (1 mark)

Answer

The more genes that the organisms have in common, the more related they are (from an evolutionary standpoint) (1 mark)

Part 2

Chromosomes

Open Ended

What features can be used to determine that these chromosomes are a homologous pair? (2 marks)

Answer

• Size

• Location of centromere

• Similar banding pattern

• Genes at the same loci

• (1 mark per correct feature)

Open Ended

If a human body cell contains 46 chromosomes, how many would you expect to find in a human sperm or egg cell? (1 mark)

Answer

23 chromosomes

Open Ended

What substances can be found within a chromosome that make up chromatin? (2 marks)

Answer

• DNA

• Histones (a protein that the DNA wraps around)

• 1 mark per correct response

Open Ended

Use the picture to answer the following questions:

What is the name of the picture showing the entirety of an organism's chromosomes? (1 mark)

The picture shows a trisomy. What is a trisomy? (1 mark)

Which genetic condition does this particular trisomy cause? (1 mark)

Answer

• A karyotype or karyogram (1 mark)

• Having three chromosomes at a location rather than a pair (1 mark)

• Down's syndrome (1 mark)

Open Ended

In a eukaryotic cell, where are the chromosomes found? (1 mark)

Answer

Within the cell nucleus

Open Ended

Does this karyotype belong to a male or female? Explain your answer. (2 marks)

Answer

• Female (1 mark)

• Because it contains two X chromosomes (1 mark)

Open Ended

How many homologous pairs of chromosomes would you expect to find on a human male's karyotype? Explain how this differs from a female. (3 marks)

Answer

• 22 homologous pairs (1 mark)

• Differs from a female as females have 23 homologous pairs (1 mark)

• The X and Y allosomes in males do not match, thus are not homologous, whereas females have homologous XX allosomes. (1 mark)