week 4

Page 1: Sex-Linked Traits

• Sex-Linked Recessive Trait Inheritance

  • Normal Female, Normal Male, Carrier Female, Hemophiliac Male.

  • Relationships involving historical figures: Victoria, Edward, Alice, Louis IV, Leopold, Beatrice, Helena, Alix, Nicholas II, Mary, Olga, Marie, Alexis, Tatiana, Anastasia, Victoria, Edward VII, Juan Carlos, Irene, Alexandra, George V, Charles, George VI, Philip, Elizabeth II, Diana, Margaret, Andrew, William, Harry.

Page 2: Extranuclear DNA Inheritance

• Mitochondrial DNA (mtDNA) Inheritance

  • Descendants chart: Male inherits mtDNA from the mother.

  • Maternal inheritance of mtDNA as it provides the cytoplasm to the zygote.

Page 3: Extranuclear Inheritance Overview

• Chapter 9 – Extranuclear Inheritance

  • Most DNA in the nucleus but considerable DNA exists in mitochondria and chloroplasts.

  • Traits can influence phenotype through proteins produced by organellar DNA.

  • Extranuclear traits inherited maternally; mitochondrial and chloroplast genotypes from female gametes.

  • Maternal effect vs. Extranuclear inheritance: Temporary influence of maternal genotype, not genetic transmission.

Page 4: Fertilization and Extra-Nuclear Inheritance

• Fertilization Dynamics

  • Female gametes are larger, carry cytoplasmic organelles.

  • Zygote contains equal nuclear contributions; however, cytoplasmic organelles like mitochondria are nearly all from the female parent.

  • Traits encoded in mtDNA do not follow Mendelian inheritance laws.

Page 5: The Extranuclear Genome

• Genomic Characteristics

  • Mitochondria and chloroplasts possess their own DNA.

  • Each organelle contains a single circular chromosome, replicated independently.

  • Nuclear and mitochondrial genes can interact in protein synthesis, e.g., Rubisco involved in photosynthesis.

Page 6: Maternal Effect Definition

• Understanding Maternal Effects

  • Maternal cytoplasmic inheritance vs. maternal effect: influence of maternal genes on offspring traits.

  • Temporary states affecting seed traits (e.g., oil content influenced by maternal genotype).

  • Selection for breeding may overlook differences in inherited phenotypic traits not indicative of seed genotype.

Page 7: Maternal Influence on Traits

• Impacts of Maternal Effect

  • Birth weight and weaning weight in animals highly influenced by maternal capability.

  • Maternal effects can lead to misleading assumptions about inheritance if solely considering offspring genotype.

Page 8: Determining Inheritance Mode

• Investigating Trait Inheritance Through Crosses

  • Analyze F1 and F2 generations of reciprocal crosses to understand inheritance modes.

  • F1 similarities indicate nuclear inheritance; F1 differences indicate possible extranuclear or maternal inheritance.

Page 9: Chromosomal Mutations Overview

• Chapter 10 – Chromosomal Mutations

  • Mutations categorized as gene mutations (point mutations) or chromosomal mutations affecting larger segments.

  • Structural and numerical mutations are the two major types of chromosomal mutations.

Page 10: Types of Chromosomal Mutations

• Identifying Chromosomal Mutation Types

  • Structural mutations involve damage and rearrangement to chromosome regions.

  • Numerical mutations refer to changes in chromosome counts (aneuploidy, euploidy).

Page 11: Structural Chromosomal Mutations Details

• Mechanisms of Structural Mutations

  • Breakage during meiotic division can result in deficiencies, duplications, inversions, and translocations.

Page 12: Consequences of Chromosomal Mutations

• Impact of Structural Changes

  • Severity of mutations depends on the genes affected by breakage.

  • Non-viable gametes may result due to improper alignment during meiosis.

Page 13: Numerical Mutations Defined

• Aneuploidy vs. Euploidy

  • Numerical mutations involve basic genetic changes, affecting overall fertility.

  • Types include monosomic, trisomic, and nullisomic; primarily from nondisjunction errors.

Page 14: Changes in Chromosomal Counts

• Understanding Polyploidy

  • Polyploidy involves multiple sets of chromosomes, affecting organism characteristics.

  • Autopolyploid vs. allopolyploid distinctions based on genetic origins.

  • Triticale as an example of an artificial polyploid resulting from wheat and rye hybridization.

Page 15: Origin of Ploidy Levels

• Causes of Various Ploidy Levels

  • Autotriploid and allotetraploid origins explained through gamete contributions from different parental species.

  • Implications for traits in crops, emphasizing both agricultural advantages and fertility challenges.