CSET: Genetics

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CSET: Genetics
2012-12-30 00:17:59

Biology CSET
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  1. Explain the inheritance of traits which are determined by one or more genes, including dominance, recessive, sex linkage, phenotypes, genotypes and incomplete dominance
    • dominance - if two alleles of an inherited pair differ, determines the organism's appearance
    • recessive - has no noticeable effect on the organism's appearance
    • phenotype - physical traits
    • genotype - genetic makeup
    • sex linkage - a gene located on a sex chromosome
    • incomplete dominance - an appearance between the phenotypes of the two parents
  2. Solve problems that illustrate monohybrid and dihybrid crosses
    • monohybrid - a mating of individuals differing at one genetic locus
    • dihybrid - a mating of individuals differing at two genetic loci
  3. Compare sexual and asexual reproduction
    • sexual:
    • creation of offspring by the fusion of gametes
    • increases genetic variability

    • asexual: offspring are genetically identical to lone parent
    • no need for mate
    • quicker and less energy in the production of gametes
    • produces genetically uniform populations
  4. Explain how the coding of DNA controls the expression of traits by genes
    • the sequence of nucleotide bases in DNA contains 3-base codons that code for amino acids for protein synthesis
    • traits arise from the actions of a wide variety of proteins
  5. Define mutations and explain their causes
    • any change in the nucleotide sequence of DNA
    • caused by errors during DNA replication or recombination
    • chemical or physical mutagens
  6. Explain the process of DNA replication
    • begins at origins of replication
    • semi-conservative - two strands of parental DNA separate and each becomes a template for the assembly of a complementary strand from a supply of free nucleotides
    • the nucleotides are lined up one at a time along the template strand in accordance to base pairing rules
    • enzymes link the nucleotides to form the new DNA strands
  7. Relate the structure and function of DNA, RNA and proteins to the concept of variation in organisms
    • DNA is a double helix and stores information
    • RNA is single stranded and carries the information or acts as a messenger
    • the information is transformed into proteins which perform most of the functions of cells, proteins come in many different structures according to their function
  8. Describe chromosome structure as a sequence of genes each with a specific locus
    a locus is the specific location of a gene on a chromosome
  9. Explain the necessity of both meiosis and fertilization in promoting variation
    • independent assortment - large number of possible arrangements of chromosome pairs at metaphase of meiosis I leads to many different combinations of chromosomes in gametes
    • random fertilization of gametes greatly increases variation
    • crossing over during prophase of meiosis I also increases variation
  10. Describe the role of chromosomes in determining phenotypes (eg sex determination, chromosomal aberrations)
    • one chromosome comes from each parent and the genes on those chromosomes determine phenotype
    • chromosomal abberations occur when there is an abnormal number of chromosomes or abnormality in a chromosome, usually occur from errors in mitosis or meiosis
  11. Predict the probable outcome of phenotypes in a genetic cross from the genotypes of the parents and mode of inheritance (eg autosomal or X-linked, dominant or recessive, co-dominance)
    • autosomal - gene is on any chromosome that is not a sex chromosome
    • X-linked - gene is located on X chromosome, if gene is recessive females will only have trait if they carry two copies of allele, males only need to carry a single copy of the recessive allele to show trait
    • dominant or recessive - dominant phenotype in heterozygote
    • co-dominance - both dominant alleles are expressed in heterozygote
  12. Explain the genetic and cellular bases for Mendel's laws of dominance, segregation and independent assortment
    • segregation - a sperm or egg carries only one allele for each inherited character because the two members of an allele segregate from each other during the production of gametes
    • independent assortment - each pair of alleles assorts independently of the other pairs of alleles during gamete formation
  13. Explain how random chromosome segregation explains the probability that a particular allele will be in a gamete
    • chromosomes are randomly segregated into 4 gametes during meiosis
    • there is a 1/4 chance that a particular allele will be in a gamete
  14. Recognize that specialization of cells in multicellular organisms is usually due to different patterns of gene expression rather than to differences among the genes themselves
    gene regulation turns on certain genes in cells which allows them to develop into cells ith different structures and functions
  15. Describe how alleles that are lethal in a homozygous individual may be carried in a heterozygote and thus maintained in a gene pool
    allele may be recessive and so is not lethal in individuals that are heterozygous
  16. Distinguish when and why mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino acids in an encoded protein
    • silent mutation - because of redundancy of genetic code, some substitution mutations have no effect if the base change results in the same amino acid being made
    • missense mutation - change of single base changes the amino acid codon
    • nonsense mutation - base substitution changes the amino acid codon to a stop codon
    • insertion or deletion of bases can cause all downstream bases to be read incorrectly
  17. Recognize how genetic engineering (biotechnology) produces biomedical and agricultural products
    • genetic engineering is the direct manipulation of genes for practical purposes
    • by transferring the gene for a desired protein into a bacterium or other kind of cell that is easy to grow in culture, scientists can produce large quantities of proteins that are present naturally in only small amounts
    • in agriculture scientists have produced GMOs that have acquired new genes by artificial means to improve the productivity of important plants and animals
  18. Describe the construction of recombinant DNA molecules by basic DNA technology including restriction digestion by endonucleases, gel electrophoresis, ligation and transformation
    • perform restriction digestion by endonucleases to cut DNA into fragments
    • verify success of digestion by seaparating the different DNA fragments using gel electrophoresis
    • combine DNA fragments using ligation enzyme
    • prepare for transformation to incorporate recombined DNA
  19. Discuss issues of bioethics including genetic engineering, cloning, the human genome project, gene therapy and medical implications
    • Along with new DNA technology comes new potential dangers
    • children with SCID were cured using gene therapy, but 4 children developed leukemia from the treatment
    • concerns about creating new dangerous disease causing organisms
    • guidelines and safety precautions are taken
    • controversy over the safety of GMOs, may be harmful to environment or humans
    • legeal and ethical questions are raised, privacy issues
    • information about disease associated genes could be abused and lead to discrimination