Topic 6 - Inheritence, variation and evolution - reproduction

Question 1

What is DNA?

Answer 1

• deoxyribonucleic acid - chemical that all genetic material in a cell is made of
• contains coded information - instructions to put an organism together and make it work
• DNA determines inherited characteristics
• is a polymer - made up of two strands coiled together in double helix

Question 2

What is a gene?

Answer 2

• a gene is a section of DNA found on a chromosome
• each gene has a particular sequence of bases that codes for a particular sequence of amino acids (protein)
• only 20 amino acids are used

Question 3

What is a genome?

Answer 3

genome of an organism is the entire genetic material of an organism

Question 4

Why is the genome important?

Answer 4

• allows scientists to identify genes in the genome that are linked to different types of disease
• knowing which genes are linked to inherited diseases helps us understand them - helps us develop treatment for them

Question 5

What is a mutation?

Answer 5

• a random change in an organism’s DNA base sequence
• can sometimes be inherited

Question 6

When do mutations occur?

Answer 6

• mutations occur continuously and spontaneously in our cells e.g. when a chromosome isnt replicated properly
• carcinogens and radiation increase the risk of mutations

Question 7

How are mutations bad?

Answer 7

• mutations change sequence of DNA bases in a gene - produces a genetic variant
• as the sequence of DNA bases codes for the sequence of amino acids that make up a protein, mutations to a gene sometimes lead to changes in the protein that it codes for
• could change protein so it has different active site - therefore enzyme no longer fits the substrate

Question 8

Why do some mutations not matter?

Answer 8

• most mutations do not have significant effects - they mainly occur in non-coding DNA
• this can sometimes sometimes alter how genes are expressed

Question 9

What are the three types of mutation

Answer 9

• insertions
• deletions
• substitutions

Question 9

What are deletions?

Answer 9

• deletions are when a random base is deleted from DNA base sequence
• like insertions - they change the way that the base sequence is read and have knock on effects

Question 10

What are substitutions?

Answer 10

substitution mutations are when a random base in the DNA base sequence is changed to a different base

Question 11

What are insertions?

Answer 11

• insertions are when a new base is inserted into DNA base sequence where it shouldn’t be
• insertion change the way the groups of three bases are read - can change the amino acids they code for
• insertions can change more than one amino acids - they have a knock on effect on the bases further on in the sequence