DNA is a large chemical molecule made of smaller chemical groups. It carries the genetic code of all living organisms.

Nucleotides are the chemical groups that are the building blocks of DNA. The four types are coded A, T, C and G.

A mutation is a change in the nucleotide base sequence in the DNA of the genome.

Ionising radiation (e.g. X-rays, gamma rays and high-energy ultraviolet) can cause mutations in DNA.

A genetic variant is produced when a mutation causes a change in the genetic sequence of a gene or a non-coding region of DNA.

Mutations and genetic variants

Biology

The genome

The chemical structure of DNA

The genome, the environment and phenotype

The genetic code

Protein synthesis

Genetic variants in genes can influence phenotype

Genetic variants in non-coding DNA can influence phenotype

Pupils will learn about dominant and recessive alleles, and how to use models of single gene inheritance to make predictions about the genotypes and phenotypes of offspring.

Pupils learned about flower structure, wind and insect pollination, fertilisation, seed and fruit formation and dispersal.

This unit covers the structure and function of eukaryotic and prokaryotic cells, DNA as the genetic material, and key genetic terms. It also explains protein synthesis, genetic variants, and how DNA structure affects proteins. The emphasis is on using models to explain scientific concepts.

DNA and the genome

The sequence of amino acids in a protein.

The sequence of nucleotides bases in a protein.

What is the best description of the genetic code?

This is part of a genetic code: **TAC CAG TCA CAG**. A mutation changes the code to **TAC CAT TCA CAG**. What kind of mutation has taken place?

Andeep: “A region of non-coding DNA.”

Aisha: “A region of DNA in which the nucleotide base sequence has changed.”

Lucas: “A protein in which the amino acid sequence has changed.”

a change in the nucleotide base sequence in the genome

a substance that can cause changes to DNA

a type of ionising radiation that can cause changes to DNA

Mutations change the genetic code in a gene. A change to the gene can change the structure of the {{}} that is made when the code is read.

Deletion mutations remove a base from a triplet code.

Deletion mutations add a base to a triplet code.

Deletion mutations change every triplet code before the mutation.

Deletion mutations change every triplet code after the mutation.

Deletion mutations swap one base for another in a triplet code.

Deletion mutations have a greater effect on the genetic code than substitution mutations. Why?

DNA has two nucleic acid chains, each made from nucleotides. The chains are held together because subunits of the nucleotides pair up. Which subunits of a nucleotide molecule pair up?

True or false? An mRNA molecule has two nucleic acid strands.

Transcription and translation take place in the nucleus.

Transcription and translation take place on ribosomes.

Only translation takes place in the nucleus.

Only translation takes place on a ribosome.

The protein myoglobin is found in muscles and is made from a chain of 153 amino acids. How many nucleotide bases code for this chain of amino acids?

There are 64 triplet codes for 64 amino acids.

There are 20 triplet codes for 64 amino acids.

There are 64 triplet codes for 20 amino acids.

These are 20 triplet codes for 20 amino acids.

The table shows the four triplet codes that code for the amino acid Val. A change to which of the three bases could cause this triplet to code for an amino acid other than Val?

Mutations and genetic variants

Lesson outcome