6.4 Mechanisms of Inheritance Further Questions and Answers

6.4 Mechanisms of inheritance – Further questions and answers

Q1.

Bk Ch6 S6.4 FQ1

Describe the evidence gathered by Watson and Crick that pointed to the complementarity of the nucleotide bases adenine, guanine, cytosine and thymine.

A1.

Bk Ch6 S6.4 FA1

Watson and Crick observed that the same amount of the nucleotide bases adenine and thymine occurred in DNA and that the same pattern occurred for cytosine and guanine. They also established that the DNA molecule is constructed of two DNA strands twisted together to form a double helix. From this information they hypothesised that the bases adenine and thymine always occurred together, or were complementary to one another and that the same applied for cytosine and guanine.

Q2.

Bk Ch6 S6.4 FQ2

Use a flow chart to model the process through which the DNA of cells controls the manufacture of cellular proteins.

A2.

Bk Ch6 S6.4 FA2

DNA contains genes.
Each gene codes for a particular protein.
Genes contain the nucleotide bases that code for the amino acids of which proteins are constructed.
A nucleotide triplet of bases is called a codon.
Each codon is transcribed onto an mRNA strand in the nucleus.
The mRNA strand moves into the cytoplasm and becomes attached to a ribosome.
At the ribosome tRNA reads the codons on the mRNA and the corresponding anticodon delivers a particular amino acid.
As amino acids continue to be delivered they become linked to form a polypeptide.

Q3.

Bk Ch6 S6.4 FQ3

Draw a concept map demonstrating your understanding of the factors involved in the process of evolution. Include sources of variation, natural selection, isolating mechanisms and genetic drift.

A3.

Bk Ch6 S6.4 FA3

Example concept map:

Q4.

Bk Ch6 S6.4 FQ4

Outline the potential impact on the evolution of living organisms from mutagens released into the environment by human activity.

A4.

Bk Ch6 S6.4 FA4

Mutagens could potentially cause mutations, which could initially lead to an increase in variation in species. Some mutations could be favourable but many would reduce the ability to survive and reproduce, eventually reducing the variation within species.

Q5.

Bk Ch6 S6.4 5

Outline research that led to the development of the ‘one gene, one polypeptide’ hypothesis.

A5.

Bk Ch6 S6.4 FA5

The ‘one gene, one polypeptide’ hypothesis was suggested by Beadle and Tatum following experiments in which they observed that changes in only one protein altered the phenotype of an organism. They were able to establish a link between different genes and the proteins they coded for. In experiments on bread mould they showed that a series of genetic mutations were co-incidental with particular positions on the chromosomes of the mould. From this they concluded that each site or gene was responsible for coding a particular protein, in this case an enzyme. That is, one gene, one polypeptide.

6.4 Mechanism of inheritance FQApage 1 of 3