AQA Bio A Level Unit 8

Question 1

What is a gene mutation?

Answer 1

A gene mutation is a change in the base sequence of DNA that may result in the alteration of a protein’s structure and function.

Question 2

What are the two main types of gene mutations?

Answer 2

The two main types are point mutations (e.g., substitution, deletion, insertion) and frameshift mutations, which alter the reading frame of the gene.

Question 3

How can mutations be beneficial?

Answer 3

Beneficial mutations can lead to genetic variation, which may result in traits that provide an evolutionary advantage, increasing an organism’s fitness.

Question 4

What is a mutagen?

Answer 4

A mutagen is an agent (e.g., chemicals, radiation) that increases the frequency of mutations in DNA.

Question 5

What is meant by a silent mutation?

Answer 5

A silent mutation is a change in the DNA sequence that does not alter the amino acid sequence of the protein due to the redundancy of the genetic code.

Question 6

What is a missense mutation?

Answer 6

A missense mutation results in the substitution of one amino acid for another in the protein sequence, potentially altering the protein’s function.

Question 7

What is a nonsense mutation?

Answer 7

A nonsense mutation introduces a premature stop codon, leading to a truncated, usually non-functional protein.

Question 8

How can mutations lead to cancer?

Answer 8

Mutations in proto-oncogenes or tumor suppressor genes can lead to uncontrolled cell division, which may result in cancer.

Question 9

What is epigenetics?

Answer 9

Epigenetics is the study of heritable changes in gene expression that do not involve changes to the DNA sequence, often through modifications such as DNA methylation and histone acetylation.

Question 10

What is DNA methylation, and how does it affect gene expression?

Answer 10

DNA methylation involves adding a methyl group to cytosine bases, usually silencing the gene by preventing the binding of transcription factors.

Question 11

What is histone acetylation?

Answer 11

Histone acetylation is the addition of acetyl groups to histones, reducing the positive charge on histones, which loosens the DNA structure and allows transcription factors to access the DNA, enhancing gene expression.

Question 12

What is siRNA, and how does it affect gene expression?

Answer 12

Small interfering RNA (siRNA) binds to mRNA, causing its degradation and preventing translation, effectively silencing gene expression.

Question 13

What is a stem cell?

Answer 13

A stem cell is an undifferentiated cell that can divide and differentiate into various specialised cell types.

Question 14

What are totipotent stem cells?

Answer 14

Totipotent stem cells can differentiate into any type of cell, including embryonic and placental cells, and are found in early embryos.

Question 15

What are pluripotent stem cells?

Answer 15

Pluripotent stem cells can differentiate into almost any cell type, except placental cells, and are found in the inner cell mass of the blastocyst (early stage of an embryo)

Question 16

What are multipotent stem cells?

Answer 16

Multipotent stem cells can differentiate into a limited range of cell types, usually within a specific tissue or organ system (e.g., hematopoietic stem cells can form various blood cells).

Question 17

What are induced pluripotent stem cells (iPSCs)?

Answer 17

iPSCs are adult somatic cells (body cells, NOT gametes) that have been genetically reprogrammed to behave like pluripotent stem cells, with the ability to differentiate into many different cell types.

Question 18

What is gene expression?

Answer 18

Gene expression is the process by which information from a gene is used to make functional gene products, such as proteins or RNA, usually through transcription and translation.

Question 19

What is transcription?

Answer 19

Transcription is the process by which a specific segment of DNA is copied into messenger RNA (mRNA) by the enzyme RNA polymerase.

Question 20

What is a promoter region in DNA?

Answer 20

A promoter is a DNA sequence located upstream of a gene that provides a binding site for RNA polymerase to initiate transcription.

Question 21

What is the role of transcription factors?

Answer 21

Transcription factors are proteins that bind to specific DNA sequences, enhancing or inhibiting the binding of RNA polymerase and thereby regulating gene expression.

Question 22

What is recombinant DNA technology?

Answer 22

Recombinant DNA technology involves combining DNA from different sources, often using restriction enzymes and ligase, to create genetically modified organisms (GMOs) or produce useful products like insulin.

Question 23

What are restriction enzymes?

Answer 23

Restriction enzymes are proteins that cut DNA at specific sequences, creating sticky or blunt ends that can be used to join DNA fragments from different organisms.

Question 24

What is a vector in genetic engineering?

Answer 24

A vector is a vehicle, such as a plasmid or a virus, used to transfer foreign genetic material into a host cell.

Question 25

What is transformation in genetic engineering?

Answer 25

Transformation is the process by which foreign DNA is introduced into a cell, typically using a vector like a plasmid.

Question 26

What is polymerase chain reaction (PCR)?

Answer 26

PCR is a technique used to amplify small amounts of DNA, producing millions of copies of a specific DNA sequence for analysis.

Question 27

What is gel electrophoresis?

Answer 27

Gel electrophoresis is a technique used to separate DNA fragments based on size, allowing for analysis of the DNA after it has been cut by restriction enzymes.

Question 28

What are gene probes, and how are they used?

Answer 28

Gene probes are short, single-stranded DNA or RNA sequences labelled with a fluorescent or radioactive marker, used to detect specific DNA sequences by hybridising with complementary sequences.

Question 29

What is gene therapy?

Answer 29

Gene therapy involves introducing functional genes into cells to correct or replace defective genes, potentially treating genetic disorders.

Question 30

What is an oncogene?

Answer 30

An oncogene is a mutated or overactive form of a proto-oncogene that causes uncontrolled cell division, contributing to cancer development.

Question 31

What is a tumour suppressor gene?

Answer 31

A tumour suppressor gene encodes proteins that regulate cell growth and division. Mutations that inactivate these genes can lead to cancer.

Question 32

What is the difference between benign and malignant tumours?

Answer 32

Benign tumors are non-cancerous, encapsulated in fibrous tissue, slow growing, normal nucleus appearance, have well differentiated cells and do not invade other tissues, while malignant tumours are cancerous, invade surrounding tissues, are not encapsulated, grow quickly, have large and dark nuclei, have undifferentiated cells and can spread (metastasize) to other parts of the body.

Question 33

What is metastasis?

Answer 33

Metastasis is the spread of cancer cells from the original tumor to other parts of the body, forming secondary tumors.

Question 34

What are monoclonal antibodies, and how are they used in cancer treatment?

Answer 34

Monoclonal antibodies are identical antibodies produced from a single clone of B cells. They can be designed to target specific cancer cells, either by delivering toxins or marking the cells for destruction by the immune system.

Question 35

What is genetic fingerprinting?

Answer 35

Genetic fingerprinting is a technique that uses unique patterns in an individual’s DNA (e.g., short tandem repeats) for identification, commonly used in forensics and paternity testing.

Question 36

What is genome sequencing?

Answer 36

Genome sequencing is the process of determining the complete DNA sequence of an organism’s genome, providing information about all its genes and genetic variations.