Mendelian Genetics and Traits

Phenotype and Genotype

• Phenotype refers to observable traits.
• Genotype refers to an organism's genetic makeup.

Dominant and Recessive Traits

• Dominant traits are expressed even with only one allele.
• Recessive traits are masked by dominant traits; expressed only with two recessive alleles.

Homozygous and Heterozygous

• Homozygous: having two identical alleles (e.g., BB or bb).
• Heterozygous: having two different alleles (e.g., Bb).

Mendelian Genetics and Punnett Squares

• Punnett squares predict offspring trait probabilities.
• Example: Crossing homozygous black (BB) and homozygous white (bb) guinea pigs produces 100% black offspring (Bb).
• First-generation offspring result from combining parental traits; recessive traits may "recede."
• Probability is crucial in genetic predictions.

DNA and Protein Synthesis: Base Pairing

• Adenine (A) pairs with Thymine (T).
• Cytosine (C) pairs with Guanine (G).
• Codons are three-base sequences in DNA, coding for amino acids.
• Example: ACCTAGTTG codes for specific amino acids.

Inheritance Patterns: Beyond Simple Dominance

• Incomplete dominance: Traits blend (e.g., red + white snapdragons = pink).
• Codominance: Both traits are fully expressed (e.g., black and white feathered chickens).
• Multiple alleles: More than two options exist, but individuals inherit two (e.g., blood types A, B, O).
• Polygenic traits: Multiple genes influence a trait (e.g., human height).

Genetic Disorders and Mutations

• Mutations are DNA sequence changes.
• Substitution mutation: One base replaces another.
• Mutations in sex cells can be passed to offspring.
• Genetic disorders result from mutations or chromosomal abnormalities.
• Karyotype: Visual representation of chromosomes to detect abnormalities.

Applications of Genetics: Blood Typing

• Blood types (A, B, AB, O) depend on inherited alleles.
• Type A and Type B parents can have offspring of any blood type.
• Pedigrees chart trait inheritance through generations.

Environmental Influence and Sex Chromosomes

• Environment influences some traits like height.
• Males have XY chromosomes; females have XX.

Practice Questions Answers (based on provided text):

• Complementary DNA strand for ACCTAGTTG: TGGATCAAC
• Tt x tt pea plant cross: 50% tall offspring and 50% short offspring.
• Difference between Incomplete Dominance and Codominance: Incomplete dominance produces a blended trait; codominance expresses both traits fully.

Explore the fundamentals of Mendelian genetics through this quiz. Test your knowledge on phenotypes, genotypes, dominant and recessive traits, as well as Punnett squares for predicting offspring traits. Delve into the concepts of homozygous and heterozygous alleles for a comprehensive understanding of heredity.