1st part

• Genetics

  • study of genes and their transmission from one generation to the next
• Genes

  • DNA sequences that contain instructions for building proteins
• Genomes

  • Sum total of all of an organism’s DNA
• Genes - DNA - Chromosomes - Genome - Cell
• Genes

  • A discrete unit of heredity information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)
• Chromosome

  • A cellular structure consisting of one DNA molecule and associated protein molecules
• Genome

  • The complete genetic material of an organism along with its noncoding nucleic acid sequence
• Chromosomes

  • structures within the nucleus, composed of DNA and protein
• The genes are located on the chromosomes
• Humans:

  46 chromosome

  23 pairs
• First 22 pairs - Autosome

  Last 1 pair - Allosome
• Karyotype

  • A composite visual display of all the chromosomes of an individual shows all 23 pairs of chromosomes lined up side-by-side
• Alleles: alternative forms of a gene, Alleles arise from mutation
• Homologous Chromosomes

  • One member of each pair is inherited from each parent
  • Look alike (size, shape, banding pattern)
  • Not identical: may have different alleles of particular gene
• Homozygous

  • two identical alleles at a particular locus
  • Alleles are same
• Heterozygous

  • two different alleles at a particular locus
  • Alleles are different
• Hemizygous

  • only one allele
  • ex.XY
• Dominant allele - A

  • Masks or suppresses the expression of its complementaryallele
  • Always expressed, even if heterozygous
  • Are not always more common than recessive ones; sometimes they may be rare in a population
• Recessive allele - a

  • will not be expressed if paired with a dominant allele (heterozygous)
  • will only be expressed if imdividual is homozygous for the recessive allele
• Genotype

  • an individual’s complete set of alleles
• Phenotype

  • observable physical amd functional traits
• Greogor Mendel - Father of Genetics, studied pea plants, discovered that genes are inherited in discrete units called genes, and that genes are passed from parents to offspring in discrete units
• One-trait cross example

  • A monohybrid cross is one in which both parents are heterozygous (or a hybrid) for a single (mono) trait.
• Two-trait cross example

  • A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits.
• • In complete dominance, only one allele in the genotype is seen in the phenotype.
• • In codominance, both alleles in the genotype are seen in the phenotype.
• • In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype and creates a new phenotype.
• Polygenic Inheritance

  • inheritance of phenotypic traits that depend on many genes
• Linked alleles:

  • physically located on the same chromosome may be inherited together
  • may be “shuffled” during crossing over during meiosis
• Law of independent assortment

  • Genes for different traits are separated from each other independently during meiosis. This applies only if the two genes in questions are on different chromosomes
• Sex-linked inheritance

  sex chromosomes

  • 23rd pair of chromosomes
  • not homologous
  • X and Y chromosomes carry different genes
• • Males;have one X and one Y chromosome
• • Females: have two X chromosomes
• • Male parent determines the gender of offspring
• Genes: encode specific proteins Proteins have specific functions leading to phenotypes
• Down Syndrome

  • 47, 21+
  • Trisomy 21
  • Simian crease
  • characteristically short
  • epicanthic fold in the eye corner
  • mental development are retarded
• Klinefelter Syndrome

  • 47, XXY
  • a taller less muscular body than
  • males there age
  • broader hips and longer legs
  • larger breast
  • weaker bones
  • a lower energy level
  • smaller penis and testicles
  • delay in puberty or go a parcel amount
  • less facial and body hair following puberty
• Turner Syndrome

  • 45,XO
  • Monosomy
  • all or part of one X chromosome is absent
  • short stature, webbed neck, rudimentary ovaries, underdeveloped breasts, broad shield like chest
• Jacob Syndrome

  • 47, XYY
  • Extremely tall
  • no facial and body hair
  • breast development
  • osteoporosis
  • feminine fat distribution
  • small testes
• Cri-du-chat Syndrome

  • severe developmental delay and cognitive deficits and distinctive facial abnormalities
  • Round face low-set ears
  • microcephaly
  • hypoplastic nasal bridge