Human Heredity

• Humans have 46 chromosomes– 22 pairs of Autosomes

(body cells)– 1 pair of Sex chromosomes

(XX or XY)• Chromosomes can be cut up

and arranged in a Karyotype.– Females are XX– Males are XY

• There is a 50% chance of having a boy or 50% chance of having a girl.

• Humans with more or less than 46 chromosomes tend to have serious disorders.– Called chromosomal disorders

What is a Karyotype?

• A cell is photographed in mitosis when chromosomes are fully condensed and easier to see.

• They are cut from photographs and arranged into pairs.

• This is called a karyotype.

Chromosomal Disorders• Due to a failure in

meiosis, homologous chromosomes will fail to separate properly.

• Called Nondisjunction.

• Therefore, abnormal (+ or -) numbers of chromosomes will end up in the gametes.

http://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20I.htm

http://www.mtholyoke.edu/courses/rfink/Videopages/video8.htm

Chromosomal Disorders

• http://www.biology.iupui.edu/biocourses/N100/2k2humancsomaldisorders.html

• Disorders can be within the chromosome as well:– Deletion - a portion of one chromosome is

lost during cell division.• Example: Cri Du Chat

– Duplication – if the fragment joins the homologous chromosome, then that region is repeated.

• Example: Fragile X– Inversion – if part of a fragment flips 180

degrees on the same chromosome.• Example: Hemophilia A

– Translocation –a fragment of a chromosome is moved ("trans-located") from one chromosome to another and joins a non-homologous chromosome.

• Example: Acute Myelogenous Leukemia

Diseases/Disorders you should know!

• Chromosomal Disorders– Down Syndrome or Trisomy 21 (47,+21) –birth

defects, mild to severe mental retardation, deformed facial features (1:800 babies)

– Turner’s Syndrome (45,X0) – Sterile, sex organs do not develop at puberty (1:2500 females)

– Klinefelter’s Syndrome (47,XXY) – sterile, subject tends to have both stunted male yet feminine features (1:750 males)

• Note: A single Y will cause male development

Down Syndrome (Trisomy 21)

http://www.ndss.org/index.php?option=com_content&view=article&id=59&Itemid=76

Turner’s Syndromehttp://vodpod.com/watch/74840-turners-syndrome

Klinefelter’s Syndrome

http://www.nichd.nih.gov/health/topics/klinefelter_syndrome.cfm

Diseases/Disorders you should know!

• Recessive Disorders: Autosomal– Cystic Fibrosis –Mucus clogs airways and ducts in lungs,

and other organs. Life expectancy is 30 years. (1:3500) – Albinism –lack of pigment (melanin) in skin, hair, eyes,

extremes case deafness. (1:17000) – Phenylketonuria (PKU) –missing the enzyme to process

the amino acid phenylalanine, builds in the body and causes mental retardation. (1:15000)

• Very easily treatable with dietary restrictions.– Tay-Sachs disease –Lipid accumulation in the brain due to

abnormal lysosomes. Causes mental retardation, blindness, early death before age 5. (1:5000) where (1:300 carrier)

• Occurs mainly in eastern European Jews (1:27 carrier)

Cystic Fibrosishttp://www.ygyh.org/cf/whatisit.htm

Albinism

PKU

Tay-Sachs

Diseases/Disorders you should know!

• Recessive Disorders: Sex-linked– Colorblindness – the disability to perceive colors in the

cones of the eyes. red/green (1:10 males) & (1:100 females)

– Hemophilia – blood fails to clot after injury (1:10000 males)• Hemophilia figured prominently in the history of European royalty in the 19th

and 20th centuries. Queen Victoria, through two of her five daughters passed the mutation to various royal houses across the continent, including the royal families of Spain, Germany and Russia. Victoria's son Leopold suffered from the disease. For this reason, hemophilia was once popularly called "the royal disease".

– Duchenne Muscular Dystrophy –weakening and loss of skeletal tissue (1:3500 boys)

Colorblindness

Interactive Colorblindness Test: http://micro.magnet.fsu.edu/primer/java/humanvision/colorblindness/index.html

Hemophilia

Duchenne Muscular DystrophyMuscles are made up of bundles of fibers (cells). A group of interdependent proteins along the membrane surrounding each fiber helps to keep muscle cells working properly. When one of these proteins, dystrophin, is absent, the result is Duchenne muscular dystrophy; poor or inadequate dystrophin results in Becker muscular dystrophy.

Diseases/Disorders you should know!

• Dominant Disorders: Autosomal– Achondroplasia – A genetic form of Dwarfism (1:30000) – Huntington’s Disease –A wasting away of brain tissue,

causes uncontrolled movements, emotional disturbances and mental deterioration. Is fatal (8:100000)

• Huge problem in passing to children without even knowing! Tested for often.

• CoDominant Disorders: Autosomal– Sickle Cell Anemia – Misshapen red blood cells due to a

mutation in hemoglobin, the protein that carries oxygen in the blood. Causes pain and damage to tissues (72,000 US, 1:500 African-American births, 1:1200 Hispanic births)

• Heterozygous condition: malaria immunity

Achrondroplasia

Huntington’s Disease

Sickle Cell Anemia