Chapter 6.1- Cellular Control Flashcards
What is a mutation?
- random change to the genetic material
- some mutations involve changes to the structure or number of chromosomes.
What is a gene mutation?
change to the DNA
What chemicals are described as being mutagenic(physical or chemical agent that changes that changes the genetic material?
- tar in tobacco smoke
- ionising radiation such as UV light, X-rays and gamma rays
What type of mutations are not passed onto offspring and give an example?
- mutations associated with mitotic divisions which are somatic (any cell other than reproductive cells) mutations
- development of cancerous tumours
What type of mutations are passed onto offspring?
-mutations involved with meiosis and gamete formation may be inherited by offspring
What are point mutations?
one base pair replaces(is substituted) for another
What are insertion or deletion (indeed) mutations?
one or more nucleotides are inserted or deleted from a length of DNA. They may cause a frameshift
What are the three types of point mutation?
- silent
- missense
- nonsense
What is a silent mutation?
- this is where there is a change to the base triplet, where that triplet still codes for the same amino acid
- the primary structure of the proteins and therefore the secondary and tertiary structure, is not altered.
What is a missense mutation?
- a change to the base triplet sequence that leads to a change in the amino acid sequence
- this may have a significant effect on the protein produced. The alteration to the primary structure leads to a change to the tertiary structure of the protein, altering its shape and preventing it from carrying out its usual function
What disease arises from a missense mutation?
Sickle cell anaemia as the sixth base triplet of the gene for the beta-polypeptide chains of haemoglobin:the amino acid valine, instead of glutamic acid, is inserted at this position. This results in deoxygenated haemoglobin crystallising within erythrocytes, causing them to become sickle shaped, blocking capillaries and depriving tissues of oxygen
What is a nonsense mutation?
- A point mutation that becomes a termination(stop) triplet.
- this particularly disruptive point mutation results in a truncated protein that will not function. This abnormal protein will most likely be degraded within the cell
What genetic disease arises from a nonsense mutation?
Duchenne muscular dystrophy
What are insertion and deletion mutations(indel)?
when nucleotide bases, not in multiple threes, are inserted in the gene or deleted from the gene, because the code is non-overlapping and read in groups of three bases, all the subsequent base triplets are altered. This is known as a frameshift.
-the primary structure of the protein, and subsequently the tertiary structure, is much altered.
What disorder is caused by a insertion or deletion(indeed) mutation?
some forms of thalassaemia, a haemoglobin disorder, results from frameshift due to deletions of nucleotide bases
What type of insertion and deletion (indeed) mutations do not cause a frameshift and degradation of the protein?
insertion or deletions of a triplet of base pairs results in the addition or loss of an amino acid
What are expanding triple nucleotide repeats?
the number of the same triplet increases at meiosis and again from generation to generation, such as -CAG CAG CAG
What disease is caused by expanding nucleotide repeats?
- Huntington’s disease
- if the number of CAG sequences goes above a certain critical number, then the person with that genotype will develop the symptoms of Huntington’s disease later in life
