Bio Exam

• What is a gene


  A length of DNA on a chromosome that codes for the production of a specific protein.
• What is an allele


  form of gene
• What is a genotype


  The complete genetic makeup of an organism
• What is a genome


  Organisms genetic composition, describes all alleles.
• Define heterozygous


  Two different alleles of a gene: Hh (always one dom one rec)
• Define homozygous


  having two identical alleles of a gene (eg. GG or gg).
• What is a phenotype


  physical characteristics of an organism
• What is recessive


  A gene that can is only expressed when dom is not present. only expressed phenotypically when both gene in pair are recessive. (hh)
• What is dominant allele


  an allele that is fully expressed in the phenotype of a heterozygote (HH or Hh)
• What is codominance?


  When both alleles contribute to the phenotype in heterozygous organism
• What is a chromosome


  a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

  
• What is DNA


  A double stranded polymer wound to form a double helix, that carried the genetic code.

  
• What is monohybrid inheritance


  The inheritance of a single gene
• What is mRNA


  A polymer of nucleotides that carried genetic information from the nucleas to the ribosomes during protein synthesis. (single helix and uses U instead of T)

  
• What are multiple alleles.


  The existence of more than two alleles of a gene e.g ABO blood groups controlled by three alleles Ia, Ib, Io
• What is a mutation


  A random change in the base sequence of DNA which may result in genetic variants.
• What is non coding DNA


  DNA which does not code for a protein but instead controls gene expression by influencing the binding of RNA polymerase to DNA
• What is a nucleotide?


  The monomers of DNA consisting of a common sugar, a phosphate and one of four chemical bases (A,T,C,G) attached to the sugar.

  
• What is a protein

  A large molecule that is synthesised from amino acids.
• What is a ribosome?


  Sub-cellular structure that is the side of protein synthesis.

  
• What is RNA polymerase?


  An enzyme involved in transcription that binds to a region of non-coding DNA, unzips the DNA strands and joins free RNA nucleotides to complementary bases on the coding DNA strand.
• What is transcription?


  The first stage of protein synthesis in which mRNA is formed from DNA template.
• What is translation?


  The second stage of protein synthesis that takes place in ribosomes. Amino acids ar ejoined in a specific order dictated by mRNA to form a protein.
• what is tRNA


  tRNA is transfer RNA. It carries amino acids around during translation.
• What is variation?


  Differences in the characteristics of individuals in a population
• What are the blood groups?


  classification of blood type as A, B or O based on surface antigens on red blood cells and the presence of certain antibodies in the plasma.
• Advantages of sexual reproduction and what is it.


  Involves joining of male and female gametes, each with egentic information. Gametes formed with 23 pairs of chromosomes. Offspring has variation. due to mixing of genetic information during fertilisation from chromosomes.

  Allows selelctive breedingg.
• what is asexual reproduction and what are the benefits?


  Involves one parent with no gametes. Happens with mitosis. No mixing of genetic information. Leads to clones.

  - Only one parent needed.

  - less energy used
• What is the DNA made up of

  made of small parts called nucleotides.

  Each nucleotide is made up of one sugar molecule, one phosphate molecule and one organic base (A,C,T,G)

  
• What is the genetic code order?

  A,G,T,T,C,A,A
• What is evolution


  Evolution is the gradual change of inherited characteristics of biological populations over time.
• What is speciation


  when two average phenotypes of two populations have diverged so. much that the two populations can no longer breed to produce fertile offspring.

  - Two different species have been formed.
• How can mutations lead to human evolution ?


  Most mutations (permanent changes in nucleotide sequences of DNA) do not affect the phenotype.

  But if a mutation creates a new phenotype that is better adapted to environmental changes (than the rest of the population), the mutation is likely to spread throughout the population over a small number of generations.

  For example, over time the size of the human brain has increased, as those born with a bigger brain were found to be at a survival advantage.
• Why does speciation happen?


  As a result of evolution.

  Natural mutations can create new alleles and two populations can begin to diverge.
• What is genetic variation (natural selection)?

  Within a biological population, different individuals have genetic variation.
• What is the theory of survival of the fittest?

  Individuals possessing genes that make better adapted to the environment will have a greater chance of survival.
• What is breeding


  Individuals with thee best chance of survival have the most chance to breed successfully.
• What is a mutation


  Most mutations (permentant changes in nucleotide sequences of DNA) do not affect the phenotype. Of the small number that do affect the phenotype, it is rare that phenotypic change gives a significant survival advantage.
• Survival advantage


  if a mutation creates a new phenotype that is better adapted to environmental changes, the mutation is likely to spread throughout the population over a small number of generations.
• What is selective breeding?


  Selective breeding (artificial selection) happens when humans choose animals and crops to breed, based on their genetic characteristics.