Genotypes and Phenotypes Quiz

Genotypes: Homozygous and Heterozygous

• Homozygous genotype displays a specific characteristic consistently.
• Heterozygous genotype reveals varying dominance among genes.

Phenotypes

• Dominant genes express themselves in the phenotype even when paired with recessive genes.
• Recessive genes express only when homologous (similar version) is present.
• Genes have different versions called alleles.
• Common recessive traits include red hair, facial dimples, curly hair, normal vision, and dark hair.
• Many traits are polygenic, influenced by multiple genes.
• Incomplete dominance occurs when a dominant gene does not completely suppress a recessive gene.
• Carriers of recessive traits inherit only one recessive gene and remain unaffected.

Heredity: Monozygotic and Dizygotic Twins

• Monozygotic (identical) twins result from the splitting of a single fertilized egg, sharing the same genotype and often similar phenotypes.
• About one-third of twins are monozygotic.
• Dizygotic (fraternal) twins arise from two separate eggs fertilized by different sperm, sharing similar genetic material as siblings born at different times.

Heredity: Genetic Disorders

• Most known genetic disorders are linked to dominant genes, but they typically do not lead to serious health issues.
• Sex-linked disorders often appear due to genes located on the X chromosome, affecting males more severely.
• Common sex-linked disorders include hemophilia, color blindness, and baldness.
• Females require two recessive genes on both X chromosomes to express these disorders, while dominant ones can affect them equally.

Heredity: Chromosomal Abnormalities

• Chromosomal abnormalities occur when a child has too many or too few chromosomes, often linked to maternal age.
• Trisomy 21 (Down syndrome) involves three copies of chromosome 21, resulting in intellectual disabilities and specific physical traits.
• Trisomy 13 (Patau syndrome) is characterized by extra genetic material from chromosome 13 causing various physical and intellectual issues.
• Trisomy 18 (Edwards syndrome) leads to severe developmental issues and is often associated with small size and heart defects.

Heredity: Chromosomal Disorders

• Turner Syndrome affects females, resulting from the loss of all or part of one X chromosome.
• Klinefelter Syndrome occurs in males who have an extra X chromosome.

Heredity: Genetic Counseling

• Genetic counseling helps individuals identify and understand genetic conditions affecting them or their offspring.
• Factors considered include family history, ethnicity, genetic testing results, and parental health issues.

Heredity: Behavioral Genetics

• This field studies how genetic and environmental factors influence behavior, suggesting a bidirectional influence.
• Genotype-environment correlations types:
  • Passive: Children inherit both genes and environments from their family.
  • Evocative: Social environments react to individuals based on genetic traits.
  • Active: Individuals seek environments supporting their genetic tendencies (niche picking).

Heredity: Genetic-Environment Interactions

• Different genetic makeups can respond distinctively to environmental conditions, explaining variability in traits and disease risks.
• Epigenetics studies how gene activity is regulated without changing DNA sequences, influenced by environmental factors, potentially affecting future generations.

Prenatal Development: Germinal Period

• The germinal period lasts about 14 days from conception to implantation.
• Zygote formation combines genetic material from both parents; blastocyst consists of inner (embryonic disk) and outer cells (trophoblast).
• Approximately 50-75% of blastocysts fail to implant, with many zygotes not surviving the first two weeks.

Prenatal Development: Embryonic Period

• After implantation, the organism is termed an embryo, with a placenta forming to provide nourishment.
• Two primary growth directions are:
  • Cephalocaudal development (head to tail).
  • Proximodistal development (midline outward).
• An embryo measures about an inch and weighs around 8 grams by the end of eight weeks.

Prenatal Development: Fetal Period

• The phase from the ninth week until birth, with the organism called a fetus.
• A fetus grows significantly, being about 3 inches and 28 grams by this stage.
• The age of viability, when survival outside the womb is possible, occurs around 24 weeks.

Prenatal Development: Prenatal Brain Development

• Begins in the third gestational week with stem cell differentiation into brain cells.
• The neural plate forms the neural groove and then the neural tube.
• By week eight, the neural tube differentiates into forebrain, midbrain, and hindbrain.
• Neurogenesis is completed after five months, with neural migration primarily finished by 24 weeks.

Teratogens

• Teratology studies factors causing birth defects; teratogens are environmental agents impacting fetal development.
• Influencing factors for prenatal risks include timing and amount of exposure, number of teratogens, genetic makeup, and the sex of the fetus.
• Alcohol consumption during pregnancy can result in lifelong cognitive and behavioral difficulties, categorized under Fetal Alcohol Spectrum Disorders (FASD).
• Tobacco exposure is another significant teratogen; over 7% of pregnant women reported smoking in 2016, affecting fetal development and health.

Test your knowledge on genotypes, phenotypes, and heredity! This quiz covers key concepts such as homozygous and heterozygous characteristics, dominant and recessive genes, and the implications of monozygotic and dizygotic twins. Delve into the complexities of genetic traits and their expressions.