[BOTLEC] M4 - Mendelian Genetics

• What was the prevailing explanation for heredity in the 1800s?

  Blending hypothesis
• What was Gregor Mendel's hypothesis?

  Parents pass on discrete heritable units in the form of genes.
• What is character?

  A eritable feature that varies among individuals (e.g. petal color)
• Why were peas used by Mendel in his experiments?

  Peas have a short generation time and create large numbers of offspring. Mendel could also control their mating.
• What is true-breeding?

  It is when offspring exhibit parental traits for many generations.
• What is hybridization?


  It is a mix of two contrasting, true-breeding varieties such that some of the F2 generation shows traits different from the P generation.
• What did Mendel's Model consist of?

  1.) Alternative versions of genes (alleles) account for variations

  2.) Each gene resides at a specific locus on a specific chromosome

  3.) For each character, an organism inherits one allele from each parent

  4.) The dominant allele determines the organism’s appearance; the recessive allele is masked

  5.) Law of Segregation.
• What is the law of segregation?

  The two alleles separate during gamete formation and end up in different gametes, so each sperm or egg only gets one of the two alleles present in the organism.
• What is a testcross?

  It crosses a dominant phenotype with a homozygous recessive individual to determine whether the parent is homozygous or heterozygous for the dominant trait.
• What is the model organism for plants?

  Arabidopsis sp.
• What are monohybrids and dihybrids?

  Monohybrids: heterozygous for one particular character being traced

  Dihybrids: heterozygous for two characters being traced
• What is the law of independent assortment?

  Each pair of alleles segregates independently of other allele pairs during gamete formation. It applies only to genes on different, nonhomologous chromosomes or those far apart on the same chromosome.
• What do Mendel's laws of segregation and independent assortment reflect?

  It reflects the rules of probability.
• When do inheritance of characters deviate from Mendelian patterns?

  1.) When alleles are not completely dominant or recessive

  2.) When a gene has more than 2 alleles

  3.) When a gene produces multiple phenotypes
• What is complete dominance?

  The phenotypes of the heterozygote and dominant homozygote are identical.

  Ex. Red and white flowers breed and produce 3 reds & 1 white.
• What is incomplete dominance?


  The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties.
• What is the codominance?


  Two dominant alleles affect the phenotype in separate, distinguishable ways

  Ex. A flower having pink and white petals.
• Which genes have more than two alleles?

  For blood type.
• What is pleiotropy?


  One gene affects many phenotypic characters (e.g. cystic fibrosis, sickle cell disease)
• What is epistasis?


  The phenotypic expression of one gene at one locus alters that of a gene at a second locus (e.g. labrador hair color expression)
• What is polygenic inheritance?


  Many genes affect one phenotypic character as a result of quantitative characters expressed in gradations along a continuum (e.g. human skin color, height).
• How can you say that an allele is dominant?

  An allele is dominant because they are seen in the phenotype, not because they subdue the recessive allele.
• What are multifactorial traits?


  They are traits that depend on multiple genes combined with environmental influences.
• True or False: Genes can be turned off and on.

  True. They can be promoted or repressed.
• What is epigenetics?


  The study of how your behaviors and environment can cause changes that affect the way your genes work.
• What is the difference between genetic and epigenetic changes?

  Epigenetic changes are reversible and do nat change your DNA sequence, ut they can change how your body reads a DNA sequence.
• What is reflected in an organism's phenotype?


  An organism’s phenotype includes its physical appearance, internal anatomy, physiology, and behavior. It reflects its overall genotype and unique environmental history.