Genetics

• Gregor Mendel - Father of classical genetics
• His experiments on breeding pea plants made a breakthrough in understanding genetics and heredity
• Also discovered the laws of inheritance or Mendelian inheritance
• Genetics

  • is the branch of biology concerned with the study of the DNA of organisms, how theiR DNA manifests as genes, and how those genes are inherited by offspring.
• Genes are passed to offspring in both sexual and asexual reproduction, and over time natural selection can accumulate variations amongst individuals on the group level, in the process known as evolution.
• Allele

  • An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome.
• Humans are diploid organisms because they have two alleles inherited from each parent
• Alleles contribute to the organism's phenotype, which is the outward appearance of the organism.
• Homozygous - two identical alleles

  Heterozygous - one dominant and one recessive allele, the dominant will always be expressed
• Genotype

  • a gene is a section of DNA that encodes a trait. The precise arrangement of nucleotides (each composed of a phosphate group, sugar and a base) in a gene can differ between copies of the same gene.
• Locus - exact fixed position on the chromosome that contains a particular gene
• Phenotype

  • The sum of an organism’s observable characteristics is their phenotype. A key difference between phenotype and genotype is that, whilst genotype is inherited from an organism’s parents, the phenotype is not.
• Difference of genotype and phenotype:

  • An individual’s phenotype is the combination of their observable characteristics or traits. While an organism’s genotype is directly inherited from its parents, phenotype is merely influenced by genotype. Environmental factors can also affect phenotype.
• Heterozygous

  • refers to having different alleles for a particular trait. If the two versions are different, you have a heterozygous genotype for that gene.
• Homozygous

  • In genetics, the definition of homozygous is when you inherit the same DNA sequence for a specific gene from each of your biological parents.
• What’s the difference between heterozygous and homozygous?

  • Homozygous means you’ve inherited the same alleles of a gene from each of your parents. In contrast, heterozygous means you’ve inherited different alleles of a gene from each of your parents.
• Four types of hereditary characters:

  1. Dominant
  2. Recessive
  3. Co-dominant/Codominance
  4. Intermediate/Incomplete Dominance
• Dominant Character Examples:

  • AB type blood group

  ● Male baldness

  ● Right handedness

  ● Broad lips and nose

  ● High blood pressure

  ● White Hairstreak

  ● Hazel or green eyes
• Recessive character examples:

  • O type blood group

  ● Straight hairlines

  ● Attached earlobes

  ● Left-handedness

  ● Thin lips
• Codominance Example:

  • AB blood type, have one A allele and one B allele. Because both alleles are expressed at the same time, their blood type is AB.
• Incomplete dominance example:

  • These characters are said to present an INCOMPLETE OR PARTIAL DOMINANCE, for instance if we cross-breed white flowers with red flowers, the descendants will have pink flowers. The pink flowers are the result of mixing up both pigments.
• Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms
• Epistasis

  • A certain combination of genotypes from two traits masks the expression of a combination of a certain phenotype that is expected from the two genotypes of the parents resulting in a new phenotype trait
• Sex Linked Inheritance

  • A type of inheritance pattern wherein a trait is expressed on the alleles that reside on the sex chromosome of the parents a.e (X and Y chromosomes)
• Sex linked Inheritance

  • The traits expressed in the phenotypes of the offspring are determined by what type of chromosome they inherit from their parents
• Most sex-link traits are X-linked
• X-LINKED DOMINANT INHERITANCE

  • A type of inheritance pattern wherein it only requires one affected chromosome to affect both male and female offspring.
  • A paternal genotype that has the affected allele will affect all of the daughters
• X-LINKED RECESSIVE INHERITANCE

  • A type of inheritance pattern wherein a recessive allele is carried by the X chromosome This type of inheritance pattern can affect both male and female offspring.