Biology~Genetics

• Learning Targets:

  • Predict genotypes and phenotypes of parents and offspring using the laws of inheritance
  • Explain sex linkage and recombination
  • Describe modifications to Mendel’s classic ratios (gene interaction)
  • Illustrate the molecular structure of DNA, RNA, and proteins
  • Diagram the steps in DNA replication and protein synthesis
  • Outline the processes involved in genetic engineering
  • Discuss the applications of recombinant DNA
• The flow of genetic information in the cell: DNA → RNA → protein
• DNA replication involves the following steps:

  • Transcription
  • Sense vs antisense strand
  • Translation
  • Reading frames
  • The genetic code
• Research on E. coli revealed a sexual mechanism that can combine genes from two different cells, leading to the development of recombinant DNA technology
• Bacteria can transfer DNA in three ways:

  • Transformation
  • Transduction
  • Conjugation
• Restriction enzymes cut DNA at specific points, DNA ligase "pastes" the DNA fragments together, resulting in recombinant DNA
• Plasmids are key tools for DNA technology, used to insert genes into bacteria and customize them
• Genetic engineering involves changing the DNA in living organisms to create genetically modified organisms (GMOs)
• Artificial selection in genetic engineering involves breeders choosing which organisms to mate to produce offspring with desired traits
• Three types of artificial selection:

  A. Selective breeding: when animals with desired characteristics are mated to produce offspring with those desired traits, passing important genes to the next generation

  • Example: Champion race horses, cows with tender meat, large juicy oranges on a tree
  • Selective breeding occurs when you choose the best male and female to breed, allowing fine-tuning and control of traits
• Examples of selective breeding:

  • Angus cows are bred to increase muscle mass for more meat
  • Egg-Laying Hen produces more eggs than the average hen
• B. Hybridization: two individuals with unlike characteristics are crossed to produce the best in both organisms

  • Example: Luther Burbank created a disease-resistant potato called the Burbank potato by crossing a disease-resistant plant with one that had a large food-producing capacity
• C. Inbreeding: breeding genetically similar organisms to maintain desired traits

  • Example: Dogs breeds are kept pure this way, keeping each breed unique from others
  • Risk: higher chance of recessive genetic disorders like blindness and joint deformities
• Variation: differences between individuals of a species, seen in physical traits due to genetic differences

  • Inbreeding decreases variations
• Cloning: creating an organism that is an exact genetic copy of another

  • Identical twins are naturally created clones
  • Researchers clone animals by nuclear transplantation, replacing the nucleus of an egg cell with the nucleus of a somatic cell from an adult
• Risks of cloning:

  • Decreases genetic diversity
  • Inefficient with a high failure rate (90%+)
  • Expensive
• Gene splicing: DNA is cut out of one organism and put into another to transfer a trait

  • For example, the human insulin gene can be put into a bacterial cell to produce human insulin
• Genetic engineering risks:

  • Possible ecological damage from pollen transfer between GM and wild crops
  • Risks and ethical questions regarding harm to human health or the environment
• Learning Targets:

  1. Predict genotypes and phenotypes of parents and offspring using the laws of inheritance

  2. Explain sex linkage and recombination, describe modifications to Mendel’s classic ratios (gene interaction)

  3. Illustrate the molecular structure of DNA, RNA, and proteins

  4. Diagram the steps in DNA replication and protein synthesis

  5. Outline the processes involved in genetic engineering

  6. Discuss the applications of recombinant DNA
• Nucleolus - site of ribosome synthesis
• The nucleus is the control center of the cell.
• gene


  a section of DNA on a chromosome that codes for a protein.

  
• alleles


  one version of a gene. You have one on a chromosome from Mom, the other on the chromosome from Dad. They are represented by capital or lower case letters.

  
• dominant allele


  A version of a gene where you only need one copy in order to express that trait. Represented by a capital letter

  
• recessive allele


  A version of a gene that is not expressed if paired with a different type of allele. Represented by a lowercase letter.

  
• homozygous


  two of the same alleles. If it is two upper case, the trait is dominant, if it is two lower case, the trait is recessive; (RR/rr)

  
• heterozygous


  A genotype with two different alleles. One capital next to a lower letter; the capital is dominant and is next to a recessive allele; (Rr)

  
• complete dominance


  the dominant allele will take over the appearance of the recessive allele when there is an uppercase and a lower case together

  
• homozygous recessive


  Two copies of the recessive allele make up the genotype. When there are two lower case letters together

  
• homozygous dominant


  Two copies of the dominant allele makes up the genotype. There are two upper case letters.

  
• genotype


  The genetic makeup-- the alleles a person has.

  
• phenotype


  How the genotype is expressed in the individual.

  
• Punnet Square


  A tool that is used to determine the likelihood of offspring traits.

  
• Genotypic ratio


  count the number of squares that have the same letter combination

  
• Phenotypic ratio


  count the number of squares that have different physical appearances

  
• homozygous x homozygous


  no ratio; 100% have the same genotype and phenotype

  
• Karyotype


  the number and visual appearance of the chromosomes in the cell nuclei of an organism or species-- used to identify chromosomal abnormalities.

  
• Trisomy


  a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities

  
• incomplete dominance


  two alleles blend together, giving a heterozygote a blended phenotype

  
• codominance


  two alleles share dominance by both expressing themselves