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• Karyotype


  A picture of a person's chromosomes arranged in homologous pairs (matching pairs)
• Human chromosomes


  • 22 pairs of autosomes (non-sex chromosomes)
  • 1 pair of sex chromosomes (XX for females, XY for males)
• Chromosomal abnormalities


  Errors during cell division (meiosis) called "nondisjunction"
• Nondisjunction


  1. Homologous chromosomes fail to separate properly

  2. Results in one gamete (sex cell) having an extra chromosome (trisomy) or missing a chromosome (monosomy)
• Things geneticists look for when analyzing karyotypes

  • Correct number of chromosomes (46)
  • Two copies of each autosome and the correct sex chromosomes (XX or XY)
  • Missing chromosome pieces or rearrangements
• Karyotypes don't show individual DNA strands or genes, the order of DNA bases (DNA sequence), the number of genes on a chromosome, or gene mutations
• Down Syndrome (Trisomy 21)


  Caused by an extra copy of chromosome 21. It's one of the few trisomies where a child can live to adulthood, though they may have characteristic features, short stature, intellectual disability, and a reduced lifespan.
• Edward's Syndrome (Trisomy 18)

  Trisomy 18, also called Edwards syndrome, is a chromosomal condition associated with abnormalities in many parts of the body. Individuals with trisomy 18 often have slow growth before birth (intrauterine growth retardation) and a low birth weight.
• Patau's Syndrome (Trisomy 13)


  Affects the development of the face, brain, and heart, along with physical growth abnormalities throughout a child's body.
• Klinefelter Syndrome (XXY)

  Males with an extra X chromosome. They may be taller than average, have low testosterone, and be sterile. Often they don't know they have it unless tested.
• Jacob's Syndrome (XYY)

  Males with extra Y 47 chromosomes. Taller than average. Normal development – never know they have it unless tested. May have sterility problems.
• Trisomy X (XXX)


  Females with extra X 47 chromosomes. Taller than average. Normal development – never know they have it unless tested. May have sterility problems.
• Turner Syndrome (XO/Monosomy X)


  Females missing one sex chromosome (X). This is the only monosomy compatible with life. They may be shorter than average, sterile, and have other characteristic symptoms.
• Polygenic traits


  Controlled by two or more genes. The different combinations of alleles in these genes can produce a wide range of phenotypes.
• Polygenic traits


  • Height, hair color, eye color, and weight
• Sex-linked inheritance


  Genes located on sex chromosomes (X and Y) can lead to inheritance patterns differing in males and females. Examples include colorblindness and hemophilia.
• Epistasis


  A type of gene interaction in which the expression of one unrelated gene affects the expression of another gene.
• Heredity


  The passing of traits from parents to offspring
• DNA


  The genetic material that codes for these traits. Found in almost all the cells of an organism.
• DNA structure


  DNA is a type of nucleic acid made up of building blocks called nucleotides. Each nucleotide has three parts: a sugar (deoxyribose), a phosphate group, and a nitrogenous base. There are four types of nitrogenous bases in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair up specifically: A with T and C with G. The two strands of DNA are twisted in a double helix shape.
• Genes


  Portions of DNA that code for proteins or RNA molecules. Proteins play a crucial role in expressing traits, such as eye color. Not all DNA codes for proteins; some DNA is non-coding.
• Chromosomes

  Tightly packed structures of DNA wrapped around proteins. Humans have 46 chromosomes (23 from each parent). Sperm and egg cells have 23 chromosomes each.
• Locus


  A particular location of a chromosome.
• DNA structure

  • Double helix structure proposed by Watson and Crick
  • Antiparallel backbones
  • Complementary base pairing: A-T, C-G
• Chromosomes vs Genes


  Chromosomes: Composition - DNA molecule + proteins (histones), Structure - Supercoiled DNA in nucleosomes, Human chromosome count - 46 (44 somatic chromosomes, 2 sex chromosomes)

  Genes: Distinct regions on chromosomes, Code for protein products, DNA → RNA → protein
• DNA Replication


  1. Occurs during the cell cycle

  2. Each chromosome makes a copy of itself

  3. Necessary for cell division and daughter cells to receive complete sets
• Cell Cycle


  • DNA replication during this phase
  • Cytoplasmic contents also duplicate
  • Formation of spindle tubules for cell division: Mitosis in body cells, Meiosis in sex cells
• Genetics


  The study of heredity, which is how characteristics are passed down from parents to offspring. These characteristics are determined by genes, which are found on chromosomes in the cell nucleus.
• Gregor Mendel and His Peas


  Gregor Mendel was a scientist who experimented with pea plants in the mid-1800s. He used true-breeding pea plants, which means they always produced offspring identical to themselves when self-pollinated (pollinated with pollen from the same plant). Mendel then performed cross-pollination experiments, where he joined male and female reproductive cells from two different pea plants with contrasting traits (like tall vs. short). This allowed him to study how these traits were inherited.
• Genes and Dominance


  Traits are specific characteristics, such as flower color or pea plant height. Traits are controlled by genes, which come in different forms called alleles. In some cases, one allele (the dominant allele) is fully expressed when paired with another allele (the recessive allele). The recessive allele is only expressed when paired with another recessive allele.
• Recessive alleles do not disappear. Even though they may not be expressed in an organism with one dominant allele, they can still be passed on to offspring.
• The F2(Second Filial) Cross

  The F2 generation refers to the offspring of the F1 generation (the first generation resulting from a cross between parents with contrasting traits). During the formation of sex cells (gametes) in the F1 plants, the alleles segregate, or separate from each other. This means each gamete only carries one copy of each gene. When F1 plants self-pollinate (F2 generation), there is a possibility that the offspring will inherit two recessive alleles, allowing the recessive trait to be expressed again.
• Genetics and Probability


  Probability is the likelihood that an event will occur. Scientists use probability to predict the outcomes of genetic crosses.
• Punnett Squares


  A visual tool used to predict the possible gene combinations that result from a genetic cross. The parent alleles are shown on the top and side of the square, and the possible offspring genotypes are displayed in the boxes.
• Homozygous and Heterozygous


  Homozygous refers to having two identical alleles for a particular gene (e.g., TT for tall pea plants).