Mutations Flashcards
1
Q
Examples of gene and chromosomal mutations
A
Gene: Sickle cell anaemia, PKU.
Chromosomal: Trisomy-21, Klinefelters.
2
Q
Harmful mutations
A
- Any mutation which decreases the quality of life.
- E.g. Tay-Sachs disease, PKU.
3
Q
Neutral mutations
A
- Mutations which occur in the non-coding sections of DNA.
- Therefore, don’t affect protein synthesis and often remain unknown.
4
Q
Beneficial mutations
A
- Any mutation which increases the quality of life.
- E.g. The apoA-1 Milano mutation allows Italian people to withstand high cholesterol levels.
5
Q
Causes of mutations
A
- Caused by mutagens (mutation inducing substances).
- Chemicals and high energy radiation.
- Environmental factors e.g. sunlight.
- Microorganisms and viruses.
6
Q
Causes of variation
A
- Crossing Over - when chromatids share genetic info and recombine.
- Law of Segregation - the determination of where each allele goes after being separated in anaphase.
- Independent Assortment - random separation of chromatids in metaphase.
- Non-Disjunction - the failure of a normal pair of chromosomes to separate during M1.
- Random Fertilisation - sperm randomly fuse with eggs.
- Mutations.
7
Q
Point mutations
A
- Changes in a single nucleotide.
- Nucleotide can either be inserted, substituted, or deleted.
- E.g. Sickle cell anaemia, albinism.
8
Q
Frameshift mutation
A
Occurs when bases have been added or removed to a sequence of DNA which pushes the three-amino acid coding sequence to start at another base. This throws the DNA sequence off and fails to code for the missed protein.
- Insertion or deletion.
9
Q
Chromosomal mutations
A
- Duplication - a section of a chromosome occurs twice.
- Inversion - a section of a chromosome is inverted.
- Translocation - a section of a chromosome breaks off and rejoins itself to another chromosome.
- Insertion/deletion/substitution
10
Q
Lethal recessive
A
- An allele that causes death to an organism either pre-natally or later in the organism’s life.
11
Q
Phenylketonuria (PKU)
A
- The ‘fish one’.
- Autosomal recessive.
- Germ-line mutation.
- Gene mutation.
- Affects the gene that helps create the enzyme needed to breakdown phenylalanine hydroxylase.
- These people can’t break down Phe well, so toxic levels of it build up in their bodies.
- Those affected must refrain from eating proteins and must maintain a vegetable-based diet.
- Amino acids build up in the blood and body tissue, which results in mental retardation and disruptions to brain development.
12
Q
Duchenne muscular dystrophy
A
- Sex-linked recessive.
- LR
- Only occurs in boys.
- Results in muscle weakness and wastage which causes a short life span of 20-25 years.
13
Q
Cystic fibrosis
A
- Gene mutation (on chrom. 7).
- LR
- If one protein is incorrect, then the passage of chloride ions across the membrane is affected.
- Results in lung congestion and infection, malabsorption of nutrients by the pancreas, coughing, salty skin, wheezing, pneumonia.
14
Q
Tay-Sachs disease
A
- Autosomal recessive.
- LR
- Caused by the enzyme for lipid metabolism being missed due to a chromosomal mutation in the HEXA gene.
- The nervous system then accumulates fat which then causes physical and mental difficulties.
- Death usally occurs in early childhood.
15
Q
Sickle cell anaemia
A
- Gene mutation.
- LR
- Autosomal recessive.
- Gene responsible for haemoglobin production is affected.
- Anaemia causes death (as cells become sickled) whereas the trait provides resistance against malaria.
- Results in the reduced ability for oxygen to be carried in the blood.
