Heredity

• Gene


  Section of DNA that provides the instructions for making a protein
• Alleles


  Different versions of the same gene
• Homologous chromosomes


  The matching chromosomes from your mom and dad
• Homozygous


  2 of the same alleles
• Heterozygous


  2 different alleles
• Dominant


  Allele that will always have that trait expressed, if present
• Recessive


  Allele that will only have the trait expressed when the dominant allele is NOT present
• Genotype


  The actual alleles inherited for a gene
• Phenotype


  The physical traits/characteristics seen in an organism
• Punnett square


  Diagram that shows the probability of inheriting traits from parents with certain genes
• Monohybrid cross


  A cross between two organisms looking at one trait
• Dihybrid cross


  A cross when looking at the likelihood of inheriting two
• Mendel used purebred pea plants that he could intentionally breed to investigate either-or traits to determine inheritance patterns
• Law of Dominance


  A dominant allele will express itself over a recessive allele
• Law of Segregation


  When chromosomes separate in meiosis, only one from each pair should end up in each gamete
• Law of Independent Assortment


  When chromosomes line up and separate in meiosis, it happens completely randomly (think, they "assort" themselves "independently")
• Chromosome Theory of Inheritance


  Since genes are located on chromosomes, how the chromosomes behave during meiosis will determine inheritance patterns
• Epistasis


  When one gene overshadows all others
• Carrier


  Someone who carries a recessive allele but doesn't show the trait due to having a dominant allele to mask over it
• Incomplete dominance


  Heterozygous genotype yields a phenotype that is a blend of the other two traits
• Codominance


  Heterozygous genotype yields a phenotype that shows both of the other traits fully and separately
• Incomplete dominance


  • Red and white flowers would make pink flowers
• Codominance


  • Red and white flowers would make red and white speckled flowers
• Multiple alleles


  More than 2 versions of 1 gene
• Polygenic inheritance


  More than 1 gene determines a trait
• Blood type


  • Example of codominance because the AB blood type is fully A and fully B
  • Example of multiple alleles because it has 3 alleles to determine the genotype = A, B, i
• Linked genes


  Genes that are physically located close together on the same chromosome are often inherited together
• Linked genes


  • Red hair and freckles
• Sex-linked traits


  Genes for traits located on sex chromosomes; if on the X (most likely), males only get 1 copy and females get 2
• Sex-linked traits


  • Colorblindness
• Traits inherited on autosomes are equally as likely to occur in males and females
• The X chromosome carries MANY genes. These genes are inherited differently in males vs. females because males only have 1 X and females have 2
• Because of this, females inherit these traits like they would traits on their autosomes. Males, however, only need 1 copy of the trait to show it since they only have 1 X
• Mutation


  Any change in DNA
• Mutagen


  Chemical that can cause a mutation in DNA
• Duplication


  A chromosome mutation that changes the size of chromosomes and results in multiple copies of a gene
• Translocation


  A chromosome mutation that results when pieces of non-homologous chromosomes exchange segments during crossing over
• Nondisjunction


  A chromosome mutation that results from chromosomes not separating correctly during anaphase, causing the wrong number
• A mutation in a somatic cell is passed on via mitosis and can result in cancer
• A mutation in a gamete was passed on via meiosis and could result in an offspring with the mutation, if the gamete is fertilized