Heredity and Reproduction

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Heredity and Reproduction

• The Nature of Heredity

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Genetic Material

• Genetics is the study of heredity and variation.
• Chromosomes are made of DNA (deoxyribonucleic
  acid)
• A gene is a segment of a DNA molecule that codes
  for a specific trait and is always found at the
  same spot (locus) on a chromosome.

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Asexual Reproduction

• A new individual is created from a single parent
  by cell division.
• Genes are identical to parent.
• Advantages parent does not have to find a mate,
  no specialized mating behaviours, no need for
  complex anatomy.

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Types of Asexual Reproduction

• Runners above ground stems that extend and
  produce a new plant
• Budding a new individual is an outgrowth of the
  parent before it buds off and becomes its own
  body.
• Binary fission parent splits into two
• Fragmentation fungi do this a fragment of the
  parent develops into a mature individual.

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Cell Division

• Mitosis happens for growth and development,
• tissue repair
• replacing cells that have aged
• Cell division happens at different rates
  depending on where the cell is located in the
  body, the age of the organism and even which
  organism it is.
• Mitosis occurs when a parent cell divides into 2
  daughter cells (which are genetically identical
  to each other and the parent cell)

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• Because the genetic material is the same, we call
  it genetic continuity.
• DNA --gt chromatin (DNA protein)--gt chromosome
  (condensed and folded)
• Occurs in all of our body cells somatic cells
• Each human cell has 46 chromosomes, which we call
  the diploid number.
• After Mitosis cells will go through
  differentiation where they will specialize and
  have different forms and functions within the
  organism.
• Mitosis and Cancer cancer is basically mitosis
  gone out of control. There are many types of
  therapy to help combat cancer.

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Cloning

• Is the process of producing one individual that
  is genetically identical to another using a
  single cell or tissue.
• Biotechnology is the use of organisms for
  applications in engineering, industry, and
  medicine.
• Cloning of plants is widely used today.
• In 1996, the worlds most famous sheep, Dolly
  was born. She was the first mammal cloned from
  an adult body cell.

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Applications of Cloning

• Mass production of livestock and crop plants
• Improve livestock and crop production
• May be very expensive
• Unnatural/unethical
• Vulnerability to disease
• Clone genetically modified organisms (GMOs)
• Commercial insulin
• GM bananas have genes for hepatitis vaccine
• GM pigs production of omega-3 fatty acids
• Cloning endangered species
• Genetic variability is still a problem

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Sexual Reproduction

• Individuals are produced from the fusion of two
  cells.
• Sex cells usually come from two different
  parents.
• Offspring are genetically different from parents.

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Meiosis

• A two-stage cell division in which the resulting
  daughter cells have half the number of
  chromosomes as the parent cell results in the
  formation of gametes or spores.
• The number of chromosomes in somatic (body) cells
  any organism has is referred to as the diploid
  number (2n).
• We have 23 pairs of homologous chromosomes making
  46 chromosomes in total. We have 23 chromosomes
  from our mother, and 23 from our father.
• Each gene has its own specific position on the
  DNA strand, this is called its locus.

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• Because we have homologous pairs of chromosomes,
  the genes will be found at the same locus on each
  of the pairs.
• Sometimes both chromosomes will not have the
  identical genes on them, when they have these
  differences they are called alleles.
• Meiosis produces gametes that contain one of each
  of the homologous pairs of chromosomes and
  therefore will have only 23 chromosomes in a
  gamete. This is called the haploid number. (n)
• When fertilization happens, the male gamete (the
  sperm that is made by the spermatogonia in the
  testes) and the female gamete (the egg that is
  made by oogonia in the ovaries) join together,
  resulting in a diploid cell called the zygote.

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• Meiosis produces genetic variability in two ways
  
• By random assortment of the maternal and paternal
  sets of chromosomes during Metaphase I.
• By the crossing over during Prophase I.

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Prophase I
Metaphase I
Anaphase I
Interphase





Telophase I
Metaphase II
Telophase II
Prophase II
Anaphase II
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Random Assortment

• During meiosis I, homologous pairs line up in
  pairs and separate. The number of possible
  combinations depends on the number of chromosome
  pairs.
• For the same couple mating, with only three
  chromosome pairs it would be 23 8 different
  possibilities. Since we have 23 pairs, it would
  be 223 8 388 608 different possibilities!!
• This variation doesnt even include crossing
  over! Thats why we look so different!

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Female Meiosis

• The formation of egg cells is a bit different
  because only one egg is made each month, but more
  energy goes into making that egg.
• Telophase I the cytoplasm does not divide
  equally and the parent cell (primary oocyte)
  divides into one large haploid cell and one small
  haploid cell.
• larger cell secondary oocyte the smaller cell
  polar body.
• Meiosis II large cell divides unequally again,
  making a larger cell (egg or ovum) and a smaller
  cell (polar body.)
• The polar body produced after meiosis I may also
  divide and make two small polar bodies or it may
  just deteriorate.
• End result only 1 functional cell, but it has a
  lot more cytoplasm and nutrients. Hence the
  difference in size between the egg and sperm.

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Karyotypes

• The chromosomes of an individual that have been
  sorted and arranged according to size and type.

Numbers 1 to 22 are autosomal chromosomes
Number 23 are the sex chromosomes (XX or XY)