Genetics System Review

Genetics System Review

• DNA structure is a double helix composed of nucleotides.
• Nucleotides consist of a sugar, phosphate group, and a nitrogenous base (adenine, thymine, guanine, or cytosine).
• Cytosine bonds with guanine via two hydrogen bonds, and adenine bonds with thymine via three hydrogen bonds.
• Chargaff's rule: A=T and G=C, meaning the amount of adenine equals thymine, and the amount of guanine equals cytosine.

DNA Study Facts & Review

• Genes in DNA determine organism characteristics.
• Mutations are alterations in DNA caused by chemicals, natural processes, or radiation.
• Mutations can happen during DNA replication.
• A chromosome has telomeres (chromosome ends), a centromere (chromosome middle), and chromatids (chromosome halves).

DNA Replication Notes

• DNA has a structure that allows for easy copying.
• The DNA molecule unzips and each side becomes a template for a new complementary half.
• The resulting two DNA molecules are identical.

Cell Division Review

• DNA must replicate for new cells to receive complete genetic information.
• Cells divide for asexual reproduction, growth, and repair.
• Mitosis creates identical daughter cells.
• Mitosis involves division of the nuclear material (cytokinesis) and cytoplasm.
• Interphase is the main stage of cell cycle with three stages first being G1 which is cell growth, S phase which is DNA replication, and G2 which is cell preparation for mitosis.
• Prophase: Centrioles move to opposite cell poles, chromatin condenses into chromosomes, dissolution of nuclear membrane and spindle fibers.
• Metaphase: Chromosomes line up across cell equator, spindle fibers attach to the centromeres.
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase: Chromosomes decondense, nuclear envelopes reform, cytokinesis occurs – cell membrane pinches inward.

Asexual vs Sexual Reproduction

• Mitosis maintains chromosome numbers and is for asexual reproduction and growth.
• Meiosis produces gametes with half the chromosome count for sexual reproduction.
• Asexual reproduction involves single parent, creating identical offspring (clones).

Meiosis & Mitosis Reproduction

• Meiosis involves two divisions (meiosis I and meiosis II) to reduce chromosome number.
• Meiosis produces four daughter cells.
• Meiosis includes prophase I, metaphase I, anaphase I, and telophase I/cytokinesis.
• Mitosis produces two identical daughter cells to maintain the number of the chromosomes.
• Meiosis involves interphase and meiosis I and II each following the PMAT stages.

Karyotype Practice Study Questions

• A karyotype is a genetic test examining chromosome structure, size, and number.
• A normal human has 46 chromosomes (23 pairs).
• Karyotypes assess for missing, extra, or structurally altered chromosomes.
• Karyotypes are used to detect genetic disorders or birth defects.

How to Remember It All

• Homozygous: "same" as matching pairs
• Heterozygous: "different" with unmatching pairs
• Genotype: Genetic makeup (letters, e.g., TT)
• Phenotype: Physical traits (appearance, e.g., tall)

Punnett Squares: Predicting Traits Like a Pro!

• Punnett squares are a tool to predict genetic outcomes.
• It involves mixing parental genes to calculate possible offspring genotypes and phenotypes.

Dihybrid Crosses: In-Depth Study Notes

• Dihybrid cross involves two traits.
• Mendel's second law (independent assortment) states genes for different traits are inherited independently. This explains how combinations of traits emerge in offspring

Blood Cells Genetics Review

• Blood types (A, B, AB, O) are determined by alleles (IA, IB, i).
• IA and IB are co-dominant, and i is recessive.
• Blood type compatibility is determined by the antigens on red blood cells.
• Rh factor is another protein on red blood cells.

Mendelian Genetics: The Blueprint of Heredity

• Law of Segregation: Each organism carries two alleles for each trait, that segregate during gamete formation.
• Law of Independent Assortment: Genes for different traits are inherited independently ,assuming they're located on different chromosomes.
• Law of Dominance: In a pair of alleles, one may mask the expression of the other (dominant allele).

Non-Mendelian Genetics: The Rainbow Beyond Dominance

• Incomplete dominance: A blended phenotype; neither allele is completely dominant (e.g., red x white snapdragon = pink).
• Codominance: Both alleles are fully expressed in the phenotype (e.g., speckled chickens show both black and white feathers without blending).

Sex Linked Inheritance Notes

• Sex chromosomes (X and Y) differ in size and carry different information.
• X-linked traits are more common in males because they have only one X chromosome.
• Sex-linked traits are carried on the X chromosome.

Chromosomal Mutations Notes

• Karyotype: A visual display of an organism's chromosomes, used to detect abnormalities.
• Mistakes in meiosis (nondisjunction), or failure of homologous chromosomes or sister chromatids to separate, can result in an abnormal chromosome number.
• Errors in crossing over can cause chromosomal mutations like duplication, deletion, inversion, or translocation.

X-Linked / Sex Linked Disorders

• X-linked disorders are genetic conditions caused by mutations in genes located on the X-chromosome.
• Males are more commonly affected because they have only one X-chromosome, so the affected allele on the X-chromosome expresses itself.