* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Answer all the questions Time allowed : 49 minutes 1. State two
DNA paternity testing wikipedia , lookup
Comparative genomic hybridization wikipedia , lookup
DNA barcoding wikipedia , lookup
Genomic library wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Mitochondrial DNA wikipedia , lookup
DNA profiling wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
DNA polymerase wikipedia , lookup
Primary transcript wikipedia , lookup
DNA vaccination wikipedia , lookup
Koinophilia wikipedia , lookup
Bisulfite sequencing wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
DNA damage theory of aging wikipedia , lookup
Epigenomics wikipedia , lookup
SNP genotyping wikipedia , lookup
Non-coding DNA wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Molecular cloning wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
Microsatellite wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Point mutation wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Genealogical DNA test wikipedia , lookup
Cell-free fetal DNA wikipedia , lookup
History of genetic engineering wikipedia , lookup
Helitron (biology) wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
DNA supercoil wikipedia , lookup
Microevolution wikipedia , lookup
Nucleic acid double helix wikipedia , lookup
Buddhist Chi Hong Chi Lam Memorial College P. 1 A. L. Bio. Revision Test ---- Genetics & Evolution Answer all the questions Time allowed : 49 minutes 1. State two factors other than genotype which could affect the characteristics of an offspring ? [2 marks] 2. DNA is an excellent medium to carry hereditary information as it is stable but changeable. (a) What is the advantage of DNA being stable ? [2 marks] (b) Describe the structure of DNA and how the structure confers stability to the molecule. [7 marks] (c) What mechanisms may be involved in changing the DNA molecule ? [4 marks] 3. Deep sea animals usually have degenerated vision. Explain this in terms of the modern theory of evolution. [6 marks] 4. The diagram shows the inheritance of Huntingdon’s chorea in a family. Symptoms of Huntingdon’s chorea usually develop between the ages of 35 and 40. What is the chance that individuals G and H will develop Huntingdon’s chorea whereas this is an dominant disease. Explain the reasons for your answer as fully as you can. You may use genetic diagrams if you wish. [6 marks] Total : 27 marks ------ THE END ------ Buddhist Chi Hong Chi Lam Memorial College P. 2 A. L. Bio. Revision Test ---- Genetics & Evolution Quest. 1. Suggested solution Marks Nutritional status of mother during pregnancy / Radiation e.g. X-rays / Drugs e.g. alcohol, tobacco < any 2 or other reasonable examples > 1x2 Sub-total : 2(a) 2(b) 2(c) Individual cells of a multicellular organism can work in a co-ordinated manner. Any change in the DNA constituent upsets this harmony. The stable nature of DNA enables the perpetuation of a species. Each DNA molecule is formed from two complementary polynucleotide chains running anti-parallel to each other. In a polynucleotide chain, adjacent nucleotides are joined together by phosphodiester bridges . A phosphate gro up, a deoxyribose and a nitrogenous base join together to form a nucleotide. Projecting out from each deoxyribose molecule is a nitrogenous base. The nitrogen base of one polynucleotide pairs with a complementary base on the opposite strand. Purines always bond to pyrimidines, e.g. G to C and A to T. Features contributing to DNA stability : Adjacent nucleotides are liked by phosphodiester bonds which are strong covalent bonds. The total attractive force which results from hydrogen bonding between the paired bases of two polynucleotide chains is strong and holds the two chains together. The two chains are helically coiled around each other. max.: Mutation may occur spontaneously, or be induced by chemicals (e.g. colchicines ), radiations (e.g. X-rays and UV) and biological factors (e.g. viruses). <any 1> Mutation may involve change in the number of chromosomes, e.g. polyploidy changes in chromosome structure, changes in DNA structure Sub-total : 3. 4. . Variation in a species can arise through gene mutation, random assortment and crossing over at meiosis. Thus in a deep sea environment fish may have good vision, degenerated vision but with alternative forms of sense. More offspring are produced than the environment can support, which lead to struggle for existence among different varieties. The environmental pressure selects for those individuals that exhibit alternative forms of sense other than vision and against those that have good vision which is useless in the dark environment, i.e. natural selection. Individuals that have more adaptive features (degenerated vision but with alternative sense organs ) are able to survive the environment and pass on their characters to their offspring, i.e. survival of the fittest. Therefore deep sea organisms tend to have degenerated vision. 2 1 1 1* 1* 1* ½* ½* 1* 1* 1* 1* 7 ½ ½ 1 1 1 13 1* 1½ * ½* 1* ½* 1* ½* 1* Sub-total : 6 Sub-total : ½ ,½ 1 1 1 1 1 6 G : 50 % ; H : 0% Since Huntingdon’s chorea is dominant, so C must be homozygous recessive. Then D must be heterozygous since his father is normal. Therefore G have ½ chance to be heterozygous. Both parents of H are homozygous recessive, therefore H must also be homozygous recessive.