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.

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 For example, some plants can have over 100 chromosomes—this doesn’t mean they are more intelligent than an organism with 46 chromosomes.

Karyotypes A karyotype is a picture of an organisms chromosomes 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)

Karyotypes We can determine the sex of an organism as well as determine if it has mutations or nondisjunction Karyotypes from a somatic cell will show 2 of each chromosome since they are diploid. Karyotypes from a gamete will show only 1 of each chromosome since they are haploid.

Karyotypes 1.What is the sex/gender of this organism? 2.How many total chromosomes? 3.How many autosomes? How many sex chromosomes? HINT: Autosomes + sex chromosomes = total chromosomes. 4. Is this from a somatic cell or gamete? _female_ _46__ _44__ _2__ _somatic___

This is an example of what a karyotype from a gamete (egg or sperm) would look like. Notice there is a haploid number of chromosomes (one of each).

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 – Deletion – 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

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

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 Y = MALE Ex. XXY or XXXY

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

Down Syndrome: – Autosomal – Trisomy 21 – Most common birth “defect” – Learning disabilities, heart defects, hypotonia, characteristic facial features

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

Practice 1 1.Number of autosomes ________ 2.Number of sex chromosomes ________ 3.Total number of chromosomes ________ 4.Sex of the individual ________ 5.Position (chromosome number) where disorder is located __________, Monosomy / Trisomy (circle one) 6.Specific Name of disorder __________________________ Female 13 Pautau

Practice 2 1.Number of autosomes ________ 2.Number of sex chromosomes ________ 3.Total number of chromosomes ________ 4.Sex of the individual ________ 5.Position (chromosome number) where disorder is located __________, Monosomy / Trisomy (circle one) 6.Specific Name of disorder __________________________ male 21 Down syndrome

Practice 3 1.Number of autosomes ________ 2.Number of sex chromosomes ________ 3.Total number of chromosomes ________ 4.Sex of the individual ________ 5.Position (chromosome number) where disorder is located __________, Monosomy / Trisomy (circle one) 6.Specific Name of disorder __________________________ Female 23 Turner

Practice 4 1.Number of autosomes ________ 2.Number of sex chromosomes ________ 3.Total number of chromosomes ________ 4.Sex of the individual ________ 5.Position (chromosome number) where disorder is located __________, Monosomy / Trisomy (circle one) 6.Specific Name of disorder __________________________ male 23 Klinefelter’s