Lecture Notes Review: Genetics and Gene Expression

It serves to determine the pattern of inheritance of traits in humans and animals.
Predict possible genotypes and phenotypes (diseases or disorders) of future offspring.
More common in human studies due to ethical constraints regarding experimental matings.

Male: Represented by a square (□)
Female: Represented by a circle (○)
Affected individuals: Those showing the phenotype are filled (●).
Marriage: Connected by a horizontal line.
Offspring: Listed in order from left to right (first-born leftmost).
Consanguineous marriage: Related parents indicated.
Identical twins: Shown by connecting two circles or squares.
Fraternal twins: Shown by two adjacent circles or squares without a connecting line.
Proband: The first individual diagnosed, usually, indicated by an arrow.
Deceased individuals: Shown with a diagonal line through the symbol.
Symbols also indicate whether the individual is affected or a carrier.

Example: Widow's peak phenotype defined as inheriting a pointed hairline contour.
Probability calculations:
- For two heterozygous individuals (Ww x Ww), probability of a child with a widow's peak (WW or Ww):
  P(WW \text{ or } Ww) = \frac{1}{4} + \frac{1}{2} = \frac{3}{4} = 75 \text{%}

Example: PTC tasting ability; inability to taste is due to a recessive gene (tt).
Probability calculations when two heterozygous individuals have a child:
- P(tt) = \frac{1}{2} \times \frac{1}{2} = \frac{1}{4} = 25 \text{%}

Analysis predicting likelihood of traits:
Probability of a child having a widow's peak and inability to taste PTC:
- P[(WW \text{ or } Ww) \text{ and } (tt)] = \frac{3}{4} \times \frac{1}{4} = \frac{3}{16} = 18.75 \text{%}

Dominant Trait Example: Achondroplasia (dwarfism)
Offspring probabilities: If one parent is heterozygous, about 50% of offspring will be affected, and there are no skips in generations.
Recessive Trait Example: Albinism
Carriers (Aa) may produce affected offspring (aa) if both are carriers, about a 25% chance.

Example: Red-green color-blindness.
Note: The trait does not pass from father to son. Males are affected more due to only having one X chromosome (hemizygous).

Example: Hypophosphatemia.
Does not skip generations.
Males and females are equally likely to be affected, and affected sons must have affected mothers.

Transcription occurs in the nucleus, synthesizing pre-mRNA from a DNA template.
Template strand is used for complementary base pairing for mRNA synthesis.
RNA polymerase catalyzes RNA synthesis, running in a 5’ to 3’ direction, and recognizing the promoter region to initiate transcription.
Regulation involves transcription factors interacting with promoter and enhancer regions.

Elongation and Termination

Elongation: RNA polymerase unwinds DNA and adds nucleotides to the growing RNA strand; the DNA helix reforms behind the polymerase.
Termination: Signaled by specific sequences on the DNA, releasing RNA polymerase and the newly synthesized RNA.

Pre-mRNA undergoes modifications:
- 5’ cap addition for protection and ease of ribosome binding.
- Poly-A tail for mRNA lifespan extension in cytoplasm.
- Introns are spliced out, leaving only exons in mature mRNA.

DNA sequencing: Enables reading nucleotide sequences of genomes.
Gene cloning: Involves inserting DNA into plasmids to create recombinant DNA, then amplifying it.
PCR: Generates billions of copies of DNA segments and is critical for studying gene expression.

Utilize approaches like CRISPR for gene editing, tackle genetic disorders, and develop genetically modified organisms for agriculture or medicine.

Composed of coding and noncoding regions, showcasing complexities beyond simple DNA sequences.
Eukaryotic genomes often have repetitive DNA, transposable elements, and introns that contribute to diversity and function.

Studying genomic differences (e.g., humans vs. chimpanzees) highlights evolutionary processes and adaptive changes over time.