Genetic Change DOT Point Distinguish between mutations of chromosomes distinguisg

Rearrangements The are 4 types of rearrangement: 1. Deletion – where part of a chromosome breaks off and a gene is lost from the chromosome, e.g. Chit-du-Chat syndrome where a deletion from Chromosome 5 occurs 2. Duplication – where the same section of a chromosome is copied or occurs twice. May be copied on to the homologous chromosome 3. Inversion – order of genes is reversed. Occurs due to breaking and re-joining in opposite directions 4. Translocation – part of the chromosome breaks off and attaches to another, e.g. breakages in 21 can cause down syndrome

Changes in chromosome number This can occur during meiosis if homologous chromosomes don’t separate. It is called non-disjunction and results in some gametes with extra or less chromosomes. Trisomy or triplication – There is an extra copy of one chromosome, e.g. Down syndrome is caused by trisomy-21where there are 3 number 21 chromosomes. Polyploidy – When meiosis fails completely in one parent and an offspring inherits a full extra set of chromosomes (3n). This is common in plants, but fatal to humans

Mutations of genes There are 2 types of mutagens: 1. High energy radiation e.g. gamma, x-rays and UV 2. Chemical mutagens e.g. hydrocarbons in cigarette smoke and many industrial chemicals

Mutations of genes Base substitution – Occurs when one base is replaced by another. The polypeptide will have one wrong amino acid. Frame Shift – Extra bases are added or deleted from a gene and will affect the whole base sequence, making a completely different and usually non-functional polypeptide.

Process and analyse information from secondary sources to describe the effect on one named and described genetic mutation on human health The cause of Down Syndrome trisomy-21 when there is an additional copy of number 21 chromosome in the individual can be result of non-disjunction when a gamete with two copies of number 21 chromosome (since homologous chromosome pair did not separate during meiosis) fuses with a normal gamete can be result of translocation of part of chromosome 21 to another chromosome, usually chromosome 14 or 15

Process and analyse information from secondary sources to describe the effect on one named and described genetic mutation on human health The effect of Down Syndrome lower than average mental ability almond shaped eyes, shorter limbs, speech impairment, enlarged tongue, high risk of heart failure

Process and analyse information from secondary sources to describe the effect on one named and described genetic mutation on human health The impact of Down Syndrome reduced mental capacity may be a limiting factor on development on individual in respect to social development, schooling and workforce - restrict opportunities physiotherapy needed as they have weakened muscles, shorter arms and legs increased risk of several diseases such as cardiovascular failure

Outline the ability of DNA to repair itself Mutations are quite common - caused by chemical mutagens, radiation and other mutagens - and so DNA needs to be able to repair itself to ensure no abnormal proteins are produced. Over 130 genes are responsible for repairing DNA Copying errors are repaired by enzymes such as DNA polymerase which fixes incorrect bases based on the undamaged strand. DNA repair genes stop the cell cycle while enzymes replace and repair damaged regions or bases

Outline the ability of DNA to repair itself The DNA can be repaired in three main ways: Damage reversal – Enzymes restore structure without breaking backbone2) Damage removal – who damaged section is cut out (e.g. by glycosylase enzymes) and the correct bases are put back in Damage tolerance – where a method is found to cope with the damage, e.g. leaving a gap where the damage is when replicating, although this can be dangerous if the cell divides Not fixing damaged genes would lead to permanent mutations that can cause cancer and malfunction of cells

Describe the way in which transposable genetic elements operate and discuss their impact on the genome Transposable genetic elements/transposons/jumping genes are sections of DNA that are not fixed and can move around among chromosomes. Code for an enzyme that allows the movement or ‘jumping’ between chromosomes In bacteria, transposons within plasmids can move between bacteria. This means that antibiotic resistance is not simply transferred by asexual reproduction, but it can spread to the genome of other bacteria The impact on humans is not yet clear, although transposons could be inserted into another gene, causing mutation

Distinguish between germ line and somatic mutations in terms of their effect on species Germ line – cells which produce gametes Mutations which affect sperm or ova Passed onto offspring Can have an effect on whole populations are it is passed on. Provides a source of variation which can either be continued due to natural selection

Distinguish between germ line and somatic mutations in terms of their effect on species Somatic – body cells When mutation occurs, DNA is altered as with germ line cells and so gene expression is altered The different is somatic cells are not passed on to the next generation so affect only one organism