AQA Bio A Level Unit 8 Flashcards
What is a gene mutation?
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.
What are the two main types of gene mutations?
The two main types are point mutations (e.g., substitution, deletion, insertion) and frameshift mutations, which alter the reading frame of the gene.
How can mutations be beneficial?
Beneficial mutations can lead to genetic variation, which may result in traits that provide an evolutionary advantage, increasing an organism’s fitness.
What is a mutagen?
A mutagen is an agent (e.g., chemicals, radiation) that increases the frequency of mutations in DNA.
How can mutations lead to cancer?
Mutations in proto-oncogenes or tumor suppressor genes can lead to uncontrolled cell division, which may result in cancer.
What is epigenetics?
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.
What is DNA methylation, and how does it affect gene expression?
DNA methylation involves adding a methyl group to cytosine bases, and preventing the binding of transcription factors.
What is histone acetylation?
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.
What is siRNA, and how does it affect gene expression?
Small interfering RNA (siRNA) binds to mRNA, causing its degradation and preventing translation, effectively silencing gene expression.
What is a stem cell?
A stem cell is an undifferentiated cell that can divide and differentiate into various specialised cell types.
What are totipotent stem cells?
Totipotent stem cells can differentiate into any type of cell, including embryonic and placental cells, and are found in early embryos.
What are pluripotent stem cells?
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)
What are multipotent stem cells?
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).
What are induced pluripotent stem cells (iPSCs)?
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.
What is gene expression?
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.