Mutations, Gene expression and cancer Flashcards
What does degenerate mean? (1)
More than one codon can code for the same amino acid
What does non-overlapping mean? (1)
Each base is read once in a triplet
What does universal mean? (1)
The same 3 bases on mRNA codon/DNA triplets code for the same amino acid in all organisms
What is a mutation? (1)
Any change to the DNA base sequence
What is a gene mutation? (1)
Change to a single base in the DNA base sequence of a gene.
What is cell differentiation? (1)
The process which cells undergo to become specialised
What are totipotent stem cells and where do they occur? (2)
Divide by mitosis to produce genetically identical daughter cells and can produce any type of body cells
Occur only for a limited time in the earliest stage of mammalian embryo development
Why can totipotent cells produce any type of body cells? (1)
They translate only part of their DNA so that only some genes are switched on, in order to differentiate the cell into a specific type and producing specific proteins that lead to cell specialisation
What is gene expression? (1)
The ability to translate a specific gene
What are pluripotent stem cells? (2)
Divide by mitosis and begin to differentiate into the vast majority of specialised cells that make up tissue in the mammalian foetus
Only translate part of its DNA
What is a fertilised egg cell (zygote) made of?
Totipotent stem cells
What are multipotent stem cells and where are they found? (1)
Retain the ability to differentiate into a limited number of different cell types
Bone marrow
What are unipotent stem cells? (1)
Capable of giving rise to only one cell type
What do unipotent stem cells differentiate into in the heart? (1)
Cardiomyocytes
What are multipotent and unipotent stem cells vital for? (1)
Repair and growth of damaged tissue
Differentiation of stem cells is determined by what? (1)
Gene expression - only certain parts of the DNA are expressed whereas other genes are inactive
Uses and limitations of stem cells (4)
Uses:
Medical therapies - bone marrow transplant and treating blood disorders
Drug testing - on artificially grown tissue
Research - on formation of organs and embryos
Limitations:
Stem cells can divide out of control by mitosis and lead to the formation of tumours
How are induced pluripotent cells produced? (1)
Laboratory grown pluripotent cells which are produced from human somatic cells using certain protein transcription factors
Why are induced pluripotent cells used in medical research? (2)
Capable of self-renewal and provide a limitless supply in medical research
Removes the ethical issue of using embryonic stem cells in medical research
What are promoter regions? (1)
One or more base sequences found upstream of a gene that control the expression of that gene
What are transcription factors? (1)
Proteins which control the transcription of genes so that only certain parts of the DNA are expressed
What is oestrogen? (1)
Lipid soluble steroid hormone
What is the role of oestrogen in initiating transcription? (7)
Oestrogen diffuses through the phospholipid cell membrane
Diffuses through nuclear envelope
Binds to the oestrogen receptor
Changes the tertiary structure
This causes the release of the transcription factor
Transcription factor binds to the DNA at the promoter region
Stimulates RNA polymerase to transcribe the gene
What is done to stop the production of a specific polypeptide? (1)
Short regulatory RNA molecules are transcribed from a cell’s DNA
What are the two types of short regulatory RNA molecules?
microRNA (miRNA)
small interfering RNA (siRNA)
How is an RNA-induced silencing complex (RISC) formed?
A single strand of miRNA or siRNA binds to a enzyme in the cytoplasm to form a complex
How does RISC inhibit gene expression? (2)
Binds to the complementary mRNA and it either
- hydrolyses the mRNA by an enzyme
or
- inhibits the initiation of ribosomal translation as the ribosome is prevented from attaching to the mRNA.
What is epigenetics? (1)
Heritable changes in gene expression without changes to the DNA base sequence
How do inheritable changes inhibit transcription? (2)
Increased methylation of DNA
Decreased acetylation of histones
What is methylation of DNA? (3)
A methyl group is added to carbon 5 of a cytosine base
Prevents transcription factors from binding to the promoter region
Prevents activation of RNA polymerase and inhibits transcription
What enzyme catalyses methylation reaction?
Methyltransferase
What is acetylation of histones? (3)
Acetylation of histones results in them being loosely packed/DNA is less condensed
When unwound the promoter region is exposed and transcription factors can bind.
This allows RNA polymerase to bind and the target gene can be transcribed
What are the two types of tumours?
Malignant and Benign
What is cancer?
Uncontrolled division of cells
What are malignant tumours? (3)
Tumours that are fast growing, non-capsulated and they do metastasise
What are benign tumours? (3)
Slow growing tumours, surrounded by a capsule and do not metastasise
What does metastasise mean?
Can spread
What two types of genes control the rate of cell division?
Proto-oncogenes and tumour suppressor genes
What are proto-oncogenes?
Stimulate cell division
What are tumour suppressor genes?
Slow cell division
What happens if a mutation occurs in the proto-oncogene? (3)
Alters to become oncogene.
Results in over-stimulation of cell division so that it is permanently switched on.
Resulting in a mass of cells known as tumours
What happens if a mutation occurs in the tumour suppressor genes? (2)
Gene becomes inactivated so it stops inhibiting cell division
Rate of cell division increases
What happens if there is increased methylation of tumour suppressor gene?
Rate of cell division increases
What happens if there is increased acetylation of tumour suppressor gene?
Rate of cell division decreases
What happens if there is decreased methylation of oncogene?
Rate of cell division increases
What happens if there is decreased acetylation of oncogene?
Rate of cell division decreases
What is a stem cell? (1)
Undifferentiated cell, that can continually divide by mitosis and become specialised
Give a unique feature of pluripotent cells and the use of this feature (3)
Divide in unlimited numbers
Can be used to treat human disorders
Can therefore be used to repair or replace damaged tissues
Explain how oestrogen could be involved in developing breast cancer (2)
High concentration of oestrogen in some areas
Leads to uncontrolled cell division
