Genetics

Question 1

Describe the production of gametes in meiosis.

Answer 1

In meiosis, one diploid cell splits into four haploid cells - for example gametes. They are not genetically identical, having different combinations of maternal and paternal DNA.

Question 2

Compare sexual and asexual reproduction.

Answer 2

Asexual reproduction creates clones - not allowing for adaptation in the way sexual does. However sexual requires more effort - most obviously because it needs two individuals rather than just one.

Question 3

Explain fully the structure of DNA.

Answer 3

DNA is a double helix consisting of 2 sequences of nucleotides. These contain a deoxyribose sugar and a phosphate, with a base attached to the sugar. Bases from opposite sequences (i.e. the other side of the double helix) are joined by hydrogen bonds in complementary pairs (AT and CG).

Question 4

Name the 4 bases in DNA.

Answer 4

Adenine, Thymine, Cytosine, Guanine

Question 5

What are genes and genomes?

Answer 5

Genes are sections of DNA that code for synthesis of a specific protein, the genome is the entire genetic material of the organism.

Question 6

Explain how DNA can be extracted from fruit.

Answer 6

Add a teaspoon of salt and a small volume of washing up liquid. Heat at 60°C for 5 minutes. Filter, cool the filtrate with an ice bath. Gently pour chilled ethanol, then you will see DNA strands between the filtrate and ethanol.

Question 7

Describe the work of Gregor Mendel.

Answer 7

Mendel crossed red-flowered and white-flowered plants, and all offspring were red. Then some of their offspring were white. This is explained by the red being a dominant allelle.

Question 8

Describe codominance in ABO blood groups.

Answer 8

A and B are not dominant over each other, but are over O. Blood group O requires both alleles as O, while AB requires one each of A and B. Others are A or B depending on which is present.

Question 9

How do mutations create variation in a population.

Answer 9

Mutations result in the spread amongst a population over generations of a new allele. Some alleles may affect phenotype, extremely rarely quite significantly, creating phenotypic variation.

Question 10

Describe how the Human Genome Project could be applied in medicine.

Answer 10

• Search for genes linked to different types of disease.
• Understand inherited disorders and their treatment.
• Trace human migration patterns from the past.