Chromosomal Mutations and Karyotypes

Chromosomes Humans have 46 chromosomes (diploid =2N) 2 of them are sex chromosomes (the last pair) X and Y they determine what sex you are XX = female XY = male 44 of them are autosomes they do not determine the sex of an individual. they code for everything else

Chromosomes  Males (Xy) Females (XX) 

Differences among species Each organism has a characteristic number of chromosomes The number is constant with the species Potatoes, plums, and chimpanzees all have 48 chromosomes

Differences among species Oats, Raccoon Dogs, Rats, Wheat and Wolverines all have 42 chromosomes

Differences in Species If multiple organisms can have the same number of chromosomes, why do they look so different? The order of the DNA nucleotides found on their chromosomes determines an organism’s traits The number of chromosomes does NOT determine intelligence Some plants, for example can have over 100 chromosomes- this doesn’t mean they are more intelligent than an organism with 46 chromosomes

Karyotypes Female A karyotype is a picture of an organisms chromosomes We can determine the sex of an organism as well as determine if it has mutations or nondisjunction What is the sex of this organism? Female

Karyotypes During mitosis, a picture of a cell is taken The chromosomes are sorted into identical pairs and arranged from biggest to smallest The 2 sex chromosomes are put at the end (pair 23)

Chromosomal Mutations Mutations are changes made to an organism’s genetic material These changes may be due to errors in DNA replication or during transcription, radiation, viruses and many other things Mutations can occur within a specific gene (small scale) as well as to the chromosome as a whole (large scale)

Chromosomal Mutations In protein synthesis we talked about SMALL scale mutations that involved changes in nucleotides There are also LARGE scale mutations that can change entire segments of a chromosome Deletions Duplication Inversion Translocation

Chromosomal Mutations Original Chromosome: Deletion- when a piece of chromosome breaks off completely Duplication- occurs when a segment of a chromosome is doubled 1 2 3 4 1 2 4 1 2 3 4

Chromosomal Mutations Inversion- when a piece of DNA is removed from the chromosome, inverted/flipped and then placed back into the chromosome Translocation- when the chromosome piece attaches to a nonhomologous chromosome 1 2 3 4 1 2 4 3 9

Chromosomal Mutations

Nondisjunction Sometimes during meiosis, the chromosomes fail to separate correctly during anaphase I or anaphase II. This is called nondisjunction

Nondisjunction When a gamete has only 1 copy of the affected chromosome it is called monosomy When the other gamete has 3 copies of one chromosome it is called trisomy

Nondisjunction Common Disorders Klinefelter’s syndrome: One to several extra sex chromosomes Presence of a Y  male Ex. XXY or XXXY

Turner’s syndrome: Only one sex chromosome Absense of Y develops into female Ex. XO

Downs Syndrome: Autosomal Trisomy 21 Most common birth defect

Patau Syndrome: Autosomal Trisomy 13 Rarely live past infancy Neurological problems, polydactyl and facial defects

Edwards Syndrome: Autosomal Trisomy 18 30% of babies die by 1 month Learning disabilities, congenital heart defects and malformations of digestive tract, urinary tract and genitals