chap 15

• Colorblindness is more common in males than in females
• Blood groups that are codominant, when paired, they produce the blood type AB
• X chromosome


  Contains 10 times more information than the human Y chromosome
• Males exhibit recessive traits carried on the X chromosome that they inherit from their mothers
• Blood type O


  Considered the universal donor because it produces no antigens
• Phenomenon that occurs in females

  A condensed region in the nucleus called a Barr body binds with a special RNA molecule and keeps it in a condensed state
• Huntington's disease is a disorder that does not appear until later in a person's life
• Sickle cell disease


  Caused by a single amino acid difference in a protein
• Sickle cell disease does not result from nondisjunction in meiosis
• Being heterozygous for sickle cell


  Provides a beneficial resistance to malaria
• CF allele


  Protects a carrier from contracting typhoid by blocking the entry of the typhoid bacterium
• Disorders caused by nondisjunction

  • Down Syndrome (Trisomy of chromosome 21)
  • Turner's disease (Monosomy of X chromosome)
  • Klinefelter's disease (Extra copy of X chromosome)
• Huntington's disease allele


  Causes a long string of bases in which the codon CAG codes for glutamine repeats over and over
• It would be useful for an adopted child to have access to their birth parents' health histories to know if they have any diseases or genetic disorders
• Karyotype


  An image that shows the complete diploid set of chromosomes grouped together in pairs arranged in order of decreasing size
• Human karyotype


  • Contains 46 chromosomes, arranged in 23 pairs
• The first cell of a human is formed when a haploid sperm, carrying 23 chromosomes, fertilizes a haploid egg, also with 23 chromosomes
• Sex chromosomes


  Chromosomes that determine an individual's sex
• Females have two copies of the X chromosome, males have one X chromosome and one Y chromosome
• More than 1400 genes are found on the X chromosome, the Y chromosome contains only about 158 genes
• Autosomal chromosomes


  The remaining 44 human chromosomes, distinct from the sex chromosomes
• The complete human genome consists of 46 chromosomes, including 44 autosomes and 2 sex chromosomes
• Males and females are born in a roughly 50:50 ratio because there is a 50% probability that an egg cell will be fertilized by an X-carrying sperm, and a 50% probability that it will be fertilized by a Y-carrying sperm
• Dominant allele


  An allele that is expressed even when only one copy is present
• Recessive allele


  An allele that is only expressed when two copies are present
• Codominant inheritance


  Both alleles are expressed, producing a combined phenotype
• Codominant inheritance in humans

  • ABO blood group
• Individuals with alleles A and B produce both A and B antigens, making them blood type AB
• Individuals with alleles A or B produce only the A or B antigen, making them blood type A or B
• Individuals homozygous for the i allele produce no antigen and have blood type O
• If a patient has AB-negative blood, it means the individual has A and B alleles from the ABO gene and two Rh alleles from the Rh gene
• Piquo 15-8
• Eye Test
• Ooctors ages
• to l for colondres
• Apa who is blind will prove only
• Sex-Linked Inheritance


  Use the X and Y chromosomes
• Genes located on the Y chromosome are found only in males and are passed directly from father to son
• Genes located in the X chromosome are found in both sexes, but the fact that men have just one X chromosome leads to more common expression of recessive X-linked traits in males
• Humans have three genes responsible for color vision, all located on the X chromosome