Recording-2025-02-24T00_42_23.193Z

Meiosis and Inheritance

• During meiosis, each parent contributes one gene for each trait.

• Law of Independent Assortment: Different traits assort independently during gamete formation, meaning traits such as plant height and seed color segregate independently.

• Chromosomal Theory of Inheritance: Genes are located on chromosomes, and chromosomes' behavior during meiosis explains inheritance patterns.

Behavior of Chromosomes During Meiosis

• Meiosis leads to the production of four genetically unique haploid daughter cells, each with half the chromosome number of the parent (diploid cells).

• This relates to Mendel's laws, specifically the Law of Segregation: Each parent can pass on only one gene for each trait to their offspring.

Metaphase and Independent Assortment

• During Metaphase I of meiosis, homologous chromosomes randomly align at the cell's center.

• The random alignment of these chromosomes accounts for the law of independent assortment, as it determines which chromosome goes to which daughter cell during Anaphase I.

Exceptions to Mendel's Laws

• Some alleles are neither dominant nor recessive, and multiple alleles or genes can control traits.

• Examples of traits that do not fit Mendelian genetics: hair color, eye color, height, and certain genetic conditions.

Incomplete Dominance and Codominance

• Incomplete Dominance: The heterozygous phenotype is a blend of the two homozygous phenotypes (e.g., red and white flowers producing pink flowers).

• Codominance: Both alleles are fully expressed in the phenotype (e.g., AB blood type).

• Example: Curly hair (HH) is incompletely dominant to straight hair (h'h'), leading to wavy hair (Hh).

Punnett Squares in Genetic Crosses

• Creating Punnett squares for crosses involving incomplete dominance and codominance to determine genotypic and phenotypic ratios.

• Example: Cross of wavy hair individuals results in a genotypic ratio of 1:2:1 (HH:Hh:h'h') and a phenotypic ratio of 1:2:1 (curly:wavy:straight).

Blood Types and Multiple Alleles

• Blood types illustrate both codominance and multiple alleles.

• Blood type A (IAi) and B (IBi) can produce types A, B, AB, or O in children.

• Agglutinogens on red blood cells determine compatibility in blood transfusions.

• Important to note that O blood has no agglutinogens, and AB blood has both.

Sex-Linked Traits and Linked Genes

• Sex chromosomes: Males (XY) and females (XX); the Y chromosome has fewer genes.

• X-linked traits can be expressed in males with one recessive allele, whereas females require two recessive alleles to express the trait.

• Ex: Color blindness is a common practice example for X-linked inheritance.

Practical Applications

• Understanding blood types to determine potential parent-child relationships in case of mix-ups (e.g., hospital scenarios).

• Utilize Punnett squares to analyze genetic crosses.

• Recognize linked traits that tend to be inherited together, such as hair and eye color.