Presentation on theme: "I LOVE PEAS MAN!. Photo courtesy of : Alex Reinke."— Presentation transcript:
I LOVE PEAS MAN!
Photo courtesy of : Alex Reinke
Two types of chromosomes are autosomes and sex chromosomes. Autosomes (#’s total) are chromosomes not involved sex determination. Sex chromosomes (23rd pair) either XX or XY directly involved in sex determination
Sex linked traits refers to traits that are carried on the sex chromosomes. Typically sex linked traits are carried on the X chromosome.
H = no hemophilia h = hemophilia
X-inactivation Female mammals inherit 2 X chromosomes –one X becomes inactivated during embryonic development condenses into compact object = Barr body which X becomes Barr body is random –patchwork trait = “mosaic” XHXH XhXh XHXhXHXh patches of black patches of orange tricolor cats can only be female
Multiple allele traits Traits that are controlled by 3 or more alleles of the same gene (blood grouping is controlled by A, B or O alleles
Polygenic traits Traits that are controlled by several genes (skin, eye, hair color) AaAAaaAa = 4 genes but 2 alleles (A or a) polygenic has several genes influencing a trait, multiple allele has several alleles influencing a trait.
Autosomal DOMINANT disorder Disorders carried on the autosomes, controlled by a dominant allele (therefore you only need one dominant allele to show the disorder)
Autosomal recessive disorder Disorders carried on the autosomes, controlled by a recessive allele (therefore you need two recessive alleles to show the disorder)
Chromosomal Abnormalities Nondisjunction chromosomes don’t separate properly during meiosis Chromosomal Mutations deletion duplication inversion translocation
Changes in chromosome structure deletion –loss of a chromosomal segment duplication –repeat a segment inversion –reverses a segment translocation –move segment from one chromosome to another error of replication error of crossing over
Autosomal Disorders Dominant –Acondroplasia Dwarfism Lethal in homozygous cond. –Acromegaly Gigantism Overactive pituitary –Huntington’s Degeneration of nervous system Manifests around 40 years of age Recessive –Albinism Melanin pathway mutated photosensitivity –Phenylketoneuria Cannot break down phenylalanine Lead to mental retardation –Cystic fibrosis Cl - channel problem Mucus buildup Death around 40
trisomy 2n+1 Nondisjunction Cause of aneuploidy (wrong chromosome #) –trisomy cells have 3 copies of a chromosome –monosomy cells have only 1 copy of a chromosome n+1 n monosomy 2n-1 n-1 n
Down syndrome Trisomy 21 –3 copies of chromosome 21 –1 in 700 children born in U.S. Chromosome 21 is the smallest human chromosome –but still severe effects Frequency of Down syndrome correlates with the age of the mother
Down syndrome & age of mother Mother’s age Incidence of Down Syndrome Under 30<1 in in in in in in in in in in in in in 12
Sex Chromosomes Abnormalities Human development more tolerant of wrong numbers in sex chromosome –Cause is nondisjunction But produces a variety of distinct syndromes in humans –XXY = Klinefelter’s syndrome male –XXX = Trisomy X female –XYY = Jacob’s syndrome male –XO = Turner syndrome female
Non-disjunction – failure of homologous chromosomes to separate during meiosis. Results in an aneuploidy Karyotype – Picture of a person’s chromosomes in a somatic cell. Used to detect genetic disorders. Amniocentesis – removal of amniotic fluid and analyze the chromosomes in the cells
Rate of miscarriage due to amniocentesis: 1970s data 0.5%, or 1 in 200 pregnancies 2006 data <0.1%, or 1 in 1600 pregnancies
Pedigree Analysis A pedigree is a family tree that describes the interrelationships of parents and children across generations Inheritance patterns of particular traits can be traced and described using pedigrees
Earlobes E = Free earlobes e = attached earlobes