Untit 1.4

Question 1

What is the purpose of DNA replication?

Answer 1

To carefully preserve the genetic information encoded within the nucleotide base sequence.

Question 2

What are mutations?

Answer 2

Changes in the genome that occur during DNA replication or cell division.

Question 3

What are the two possible results of a mutation?

Answer 3

1. No protein is expressed. 2. An altered protein is expressed.

Question 4

What are single-gene mutations?

Answer 4

Mutations that affect only a few bases.

Question 5

What are chromosome structure mutations?

Answer 5

Mutations that affect the structure of one or more chromosomes.

Question 6

What is a substitution mutation?

Answer 6

The replacement of one nucleotide with another in a DNA sequence.

Question 7

What is an insertion mutation?

Answer 7

The addition of one or more nucleotides into a DNA sequence.

Question 8

What is a deletion mutation?

Answer 8

The removal of one or more nucleotides from a DNA sequence.

Question 9

What is a point mutation?

Answer 9

A mutation that results in a change affecting only one codon.

Question 10

What are the three types of point mutations?

Answer 10

Missense, nonsense, and splice-site mutations.

Question 11

What is a missense mutation?

Answer 11

A mutation that changes the codon so a different amino acid is produced.

Question 12

What is a potential result of a missense mutation?

Answer 12

It may change the shape of the protein, making it unable to carry out its function.

Question 13

Can all missense mutations significantly affect the protein?

Answer 13

No, some changes in amino acids may not have a significant effect.

Question 14

What is a nonsense mutation?

Answer 14

A mutation that changes a codon from an amino acid to a stop codon.

Question 15

What is the effect of a nonsense mutation?

Answer 15

It results in a shorter protein, which is generally non-functional or its function is affected.

Question 16

What is a splice-site mutation?

Answer 16

A mutation that affects the boundaries between exons and introns (splice sites).

Question 17

How does a splice-site mutation affect a protein?

Answer 17

It can prevent splicing at that site, potentially leading to a very different protein due to post-transcriptional processing, with some introns included or exons removed.

Question 18

Why are shortened proteins from nonsense mutations usually non-functional?

Answer 18

Because they are incomplete and lack essential regions for proper function.

Question 19

What is a frame-shift mutation?

Answer 19

A mutation caused by insertions or deletions that shifts the codon reading frame by one codon.

Question 20

What happens to the amino acids in a frame-shift mutation?

Answer 20

Completely different amino acids are coded for from the point of the mutation onwards.

Question 21

What is the effect of a frame-shift mutation on the protein?

Answer 21

The resulting protein is significantly altered and is usually non-functional.

Question 22

What are chromosome structure mutations?

Answer 22

Alterations that affect whole chromosomes and whole genes rather than just individual nucleotides.

Question 23

What causes chromosome structure mutations?

Answer 23

Errors in cell division that cause a section of a chromosome to break off, be duplicated, or move onto another chromosome.

Question 24

What is a deletion mutation in chromosomes?

Answer 24

A mutation where a section of a chromosome is removed.

Question 25

What is a translocation mutation in chromosomes?

Answer 25

A mutation where a section of a chromosome is added to another chromosome that is not its homologous partner.

Question 26

What is an inversion mutation in chromosomes?

Answer 26

A mutation where a section of a chromosome is reversed.

Question 27

What is a duplication mutation in chromosomes?

Answer 27

A mutation where a section of a chromosome is added from its homologous partner.

Question 28

Why are chromosome structure mutations often lethal?

Answer 28

Because they alter the structure of the chromosome, disrupting essential genetic information.

Question 29

What is a mutation?

Answer 29

A rare, random change in a gene or chromosome that can be inherited.

Question 30

How do mutations occur?

Answer 30

Mutations occur continuously and can be spontaneous or caused by factors such as ionising radiation or chemical mutagens.

Question 31

What are examples of ionising radiation?

Answer 31

Gamma rays, X-rays, and ultraviolet rays.

Question 32

What is an example of a chemical mutagen?

Answer 32

Tar from cigarette smoke.

Question 33

What effect can mutations have on proteins?

Answer 33

Mutations can create faulty proteins by switching genes on or off, affecting their synthesis or function.

Question 34

How can a mutation affect enzymes?

Answer 34

If a mutated enzyme’s active site is altered, the substrate may no longer fit, preventing the enzyme from functioning properly.

Question 35

How can a mutation affect structural proteins like collagen?

Answer 35

It might cause the protein to lose its strength.

Question 36

Do all mutations significantly affect proteins?

Answer 36

No, most DNA mutations do not alter a protein or only slightly alter it without changing its appearance or function.

Question 37

What are the possible results of mutations in coding vs. non-coding DNA?

Answer 37

• Coding DNA: May change protein activity. • Non-coding DNA: May change how genes are expressed.

Question 38

What are the possible consequences of mutations?

Answer 38

Mutations may result in phenotype changes, hidden effects, or serious conditions like genetic diseases (e.g., cystic fibrosis).