Turner syndrome (TS) is a medical disorder that affects about 1 in every 2,500 girls. Although researchers don't know exactly what causes Turner syndrome, they do know that it's the result of a problem with a girl's chromosomes . Girls with Turner syndrome are usually short in height. Those who aren't treated for short stature reach an average height of about 4 feet 7 inches (1.4 meters). The good news is that when Turner syndrome is diagnosed while a girl is still growing, she can be treated with growth hormones to help her grow taller. http://kidshealth.org/teen/diseases_conditions/sexual_health/turner.html Most girls are born with two X chromosomes, but girls with Turner syndrome are born with only one X chromosome or they are missing part of one X chromosome. The effects vary widely among girls with Turner syndrome. It all depends on how many of the body's cells are affected by the changes to the X chromosome. In addition to growth problems, Turner syndrome prevents the ovaries from developing properly, which affects a girl's sexual development and the ability to have children. Because the ovaries are responsible for making the hormones that control breast growth and menstruation, most girls with Turner syndrome will not go through all of the changes associated with puberty unless they get treatment for the condition. Nearly all girls with Turner syndrome will be infertile, or unable to become pregnant on their own.
Klinefelter's syndrome, 47, XXY, or XXY syndrome is a condition in which human males have an extra X chromosome. While females have an XX chromosomal makeup, and males an XY, affected individuals have at least two X chromosomes and at least one Y chromosome.  Because of the extra chromosome, individuals with the condition are usually referred to as "XXY Males", or "47, XXY Males".  This chromosome constitution (karyotype) exists in roughly between 1:500 to 1:1000 live male births  but many of these people may not show symptoms. The physical traits of the syndrome become more apparent after the onset of puberty, if at all.  In humans, 47XXY is the most common sex chromosome aneuploidy in males  and the second most common condition caused by the presence of extra chromosomes. Other mammals also have the XXY syndrome, including mice.  Principal effects include hypogonadism and reduced fertility. A variety of other physical and behavioural differences and problems are common, though severity varies and many XXY boys have few detectable symptoms. Not all XXY boys and men develop the symptoms of Klinefelter syndrome.
Mitosis meiosis mine
HeredityInheritance (transmission) of certain characteristics from one generation to the following one* GENETICS is the branch of Biology that studies heredity* ZYGOTE one cell that contains ALL the inherited genetic information Heredity Mitosis Meiosis* nuclear division which produces * produces haploid gametes that from 1 cell, 2 genetically are genetically different. identical, diploid cells * only in reproductive organs * Produced in all the growing tissues (somatic cells)
Role of Mitosis 1) Faithful copying ofgenes and their transfer to the next generation of nuclei or cells 2) Maintains the correct chromosome number of somatic cells. 3) Formation of a multicellular organism 4) Cell replacement and regeneration
MitosisCHROMOSOMESIN PAIRS 23 PAIRS(1 FROM MUM/1 FROM DAD) 46 chromosomes)
Stages of mitosis Chromosomes appear, nucleus interphase disappearsM prophase Chromatids pulled to polesIT metaphase Chromosomes invisible; DNAO replicatesS anaphase Cytoplasmic divisionIS telophase Chromosomes at equator, spindle forms cytokinesis Chromatids at poles, nucleus reforms
ProphaseThe Cell begins the division process1. The nucleolus disappears,2. The nuclear membrane breaks apart
3. The chromosomes become visible4. The spindle apparatus forms and attaches to the centromeres of the chromosomes
Metaphase The Second Phase of Mitosis1. The Nuclear Membrane is completely gone2. The duplicated chromosomes line up along the cells equator.
AnaphaseThe third phase ofMitosisDiploid sets of daughterchromosomes separateThey are pushed andpulled toward oppositepoles of the cell by thespindle fibers
The Cell Platebegins to formThe Cellprepares forfinial division
Cytokinesis – The final stage of MitosisThe cytoplasm, organelles, and nuclearmaterial are evenly split and two newcells are formed.CellPlate
Chromosome A threadlike structure within the cell that carries the genetic material as a linear strand of DNA bonded to various proteins (gene) in the nucleus of eukaryotic cells.The chromosomes are always in pairs becauseone of them is derived from the male parent andthe other from the female parentDifferent species have different numbersand shapes of chromosomesMembers of the same species haveidentical sets of chromosomes
Genes * are the chemical component of the chromosomes •Control the development of a particular characteristic in a living organisms • provide the ”instructions” •Genes are in pairs so the genes they carry are also in pairs Genes controlling the same characteristics occupy identical positions on corresponding chromosomes Each member of a pair of genes comes A a from either the male or the female B b parent just as the chromosomes do C c D d The individual genes of a pair, control E e the same characteristic (ALLELES), e.g. B F f and b could control eye colour; G and g could G g control hair colour (they only carry out H h their function in the correct situation) I I The gene is EXPRESSED
Why do we need meiosis?It is the fundamental basis of sex. What is the purpose of sex?- to bring two haploidgametes together toform a diploid zygote. n (mom) + n (dad) = 2n (offspring)
Meiosisensures that all living organismswill maintainboth GeneticDiversity and Genetic Integrity
Why form gametes?• Goal: Reduce genetic material by halffrom mom from dad child too much! meiosis reduces genetic content
Meioisis vs. Mitosis Mitosis Meiosis Number of 2 1 divisions Number of 2 4daughter cells Genetically Yes No identical?Chromosome # Same as parent Half of parent Where Somatic cells Germline cells When Throughout life At sexual maturity Growth and Sexual Role repair reproduction
• Start with 46 double stranded chromosomes (2n) – After 1st division - 23 double stranded chromosomes (n) – After 2nd division - 23 single stranded chromosomes (n)• Occurs in our germ cells – cells that produce our gametes – egg and sperm
A form of cell division happening in sexually reproducingorganisms by which two consecutive nuclear divisions occurwithout the chromosomal replication in between, leading to theproduction of four haploid gametes (sex cells) Meiosis 1 Meiosis 2
During Meiosis gamete (sex) cells undergo a“double division”, maintaining the DNA, butreducing the chromosomal count to 23 + =Sperm (23) + Egg (23) = Fertilized Cell (46)
Gene Structure Formed by DNA Group of molecules A DOUBLE chain of NUCLEOTIDS in the form of a helix Phosphate 5-carbon group Organic sugar molecule baseJoins the nucleotidsto form a long chain Adenine Thymine Cytosine Guanine
A+T C+GHELICASE unwinds the 2 strands of DNAOther enzymes bring nucleotides to join them to the unzipped DNAThe new nucleotides join up to form a chain attached to the exposedstrand the double helix is REPLICATED
MUTATION Any spontaneous change in the DNA sequence (in a gene or a chromosome) of an organism 1 or more are •Damage or loss of a During mitosis or not replicated correctly part meiosis • gain of extra chromosome or part – a mutation that occurs in many genes and affects many traits atEye color, Sickle cell once.Anemia, Hemophilia Ex: Down Syndrome (an extra 21st chromosome)
* Body cell mutations (during MITOSIS) can causecancer. only the individual is affected.* Gamete cell mutations (during MEIOSIS) affect theegg and the sperm. all offspring of the individualcan be affected.
MUTATION It results in a defective enzyme disrupts the reactions in the cell • Most are neutral • Some are harmful • Some are beneficial – Polyploidy plants are larger and stronger – Mutations lead to evolution in living organisms Origin/Cause of Mutation• Spontaneous: due to errors in the genetic machinery during DNA replication• Induced: arising from exposure to mutagenic agents (tobacco/X-rays/Ultraviolet radiation)
Only 3% of DNA consists of GENESThe rest is a repeated sequences ofnucleotides that don’t code for proteinsIf mutations occur there, they are unlikely tohave any effect on the organism Neutral mutation
Example of Genetic disorder1) Down syndrome • 47, trisomic 21 CHROMOSOME MUTATION • During MEIOSIS one of the chromosomes fails to separate from the homologous partnersOvum carries 24 chromosomes
Example of Genetic disorder 2) Turner syndrome • 45 chromosome, xo
Example of Genetic disorder 3) Klinefelter syndrome – 47, XXY