Genetics

• How do we inherit characteristics:

  23 chromosomes from the egg (girl) and 23 chromosomes from the sperm (boy)

  Fertilizations 46 chromosomes in 23 pairs in the embryo
• The resemblance of children to their parents is the result of genetic information passed on in gametes
• DNA: Molecules which contain genes, a gene is a section of DNA found in a chromosome, they carry genetic info
• Genes carry instructions for some of our characteristics: genetic variation
• Genes code for a specific order of amino acids for proteins
• DNA is made up of 4 different bases, 3 bases make one amino acid, a gene is made up of 100's of bases, order of bases code to make specific proteins.

  A mutation can change the structure of a protein
• Alleles: Different versions of a gene that can lead to different traits, like various eye colors in individuals.
• Dominant and recessive allele:

  Dominant: an allele which is always expressed when it is present, it cannot be masked by another allele

  Recessive: an allele which can be masked by another allele, it is only expressed when 2 copies are present
• dominant alleles: B (Brown eyes)
• Recessive Alleles: b (blue eyes)
• Genotype: The combination of alleles you carry for a specific gene
• Homozygous: When both alleles are identical
• Heterozygous: When there are two different alleles
• Phenotype: Peoples physical appearance due to their genes
• Punnet squares: A diagram used to show the probability of offspring from a cross.
• A karyotype is an individual's collection of chromosomes.
• A karyogram is a photograph of the chromosomes of a cell, arranged in homologous pairs + in a numbered sequence
• The sperm determines whether a boy or girl will be born
• Men have an Xy chromosome and women have an XX chromosome
• Which one

  A) Female

  B) Male

  
• Sex determination in humans:

  • Chromosomal sex is determined at fertilization
  • Sexual differences begin in the 7th week
  • Sex is influenced by genetic and environmental factors
• SRY: Sex determining region Y
• What is SRY: Sex determining region of the Y chromosome, it is the master switch that triggers the events that converts the embryo into a male, without this you would get a female
• Mutations which alter phenotypic sex:

  • Hermaphrodites
  • Have both male and female gonads
  • Androgen insensitivity
  • XY males become phenotypic females
  • Pseudo hermaphroditism
  • XY males at birth are phenotypically female; at puberty develop a male phenotype
• Women are much less likely to have a sex-linked recessive trait:

  • The notation for sex-linked traits e.g. XHXh or XhY
  • much less likely to have a sex-linked recessive trait because they will have another X chromosome carrying the dominant allele
• Hemophilia is a group of diseases in which blood does not clot normally.
• conditions such as down-syndrome are affected by the extra chromosome on the 21st chromosome, while conditions such as Turner's syndrome lack a chromosome
• Heterozygous means that the individual has two different letters, --> Aa, Bb, Dd.  Homozygous means that the individual has two same letters -->  AA, bb, DD, ee
• SRY - Sex determining region of Y chromosome. It is a gene that determines the sex of an individual. If you possess it you are a boy
• Stages of Meiosis

  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. Telophase I
  5. Prophase II
  6. Metaphase II
  7. Anaphase II
  8. Telophase II
• stages of mitosis

  PMAT
• PMAT stands for --> Prophase, metaphase, anaphase, telophase
• Interphase:

  G1 Phase: Cell growth and normal functions occur.

  S Phase: DNA replication takes place, doubling the chromosomes.

  G2 Phase: Additional growth and preparation for mitosis happen.

  Mitosis is the process of cell division where a single cell divides into two genetically identical daughter cells, each containing the same number of chromosomes as the parent cell.

  Cytokinesis: Division of the cytoplasm occurs, resulting in the formation of two daughter cells, each with a complete set of chromosomes.
• Stages of the mitosis

  Prophase:

  • Nuclear membrane dissolves.
  • DNA condenses into visible chromosomes.
  • Centrioles migrate to opposite poles.
  • Spindle fibers form and extend.

  Metaphase:

  • Chromosomes align along the cell's middle.
  • Spindle fibers attach to chromosomes.

  Anaphase:

  • Sister chromatids separate and move to opposite poles.

  Telophase:

  • Chromosomes decondense.
  • Nuclear envelopes reform.
  • Spindle fibers disassemble.
  • Cytokinesis starts.
• Chromosome

  A) Centromere

  B) Chromatid

  C) Chromatid

  
• Mitosis:

  • Purpose: Produces two identical daughter cells.
  • Occurrence: Occurs in non-reproductive cells.
  • Stages: Consists of one round of division PMAT
  • Result: Maintains the same chromosome number as the parent cell (diploid).

  Meiosis:

  • Purpose: Produces four genetically diverse daughter cells.
  • Occurrence: Occurs in gametes cells.
  • Stages: Consists of two rounds of division (meiosis I and meiosis II), each with PMAT
  • Result: Halves the chromosome number (haploid) and introduces genetic variation through crossing over + random assortment.
• Genotype:

  • A genotype is the genetic makeup of an organism, the specific alleles present in its DNA.
• genotype example; BB homozygous dominant
• Meiosis gives rise to four different daughter cells, each of which has half the number of chromosomes as the parent cell.
• Haploid

  presence of a single set of chromosomes in an organism's cells