Chromosomal Mutations and Karyotypes Chromosomes Humans have 46

Chromosomal Mutations and Karyotypes

Chromosomes • Humans have 46 chromosomes (diploid =2 N) • 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? _female_ 2. How many total chromosomes? _46__ 3. How many autosomes? _44__ How many sex chromosomes? HINT: Autosomes + sex chromosomes = total _2__ chromosomes. 4. Is this from a somatic cell or gamete? _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 also LARGE scale mutations that can change entire segments of a chromosome – Deletion – Duplication – Inversion – Translocation

Chromosomal Mutations Original Chromosome: 1 2 3 4 Deletion- when a piece of chromosome breaks off completely 1 2 3 Duplication- occurs when a segment of a chromosome is doubled 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 1 3 4 • Translocation- when the chromosome piece attaches to a nonhomologous chromosome 1 2 3 4 9 2

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 45 1. Number of autosomes ____ 2. Number of sex chromosomes 2 ____ 3. Total number of chromosomes 47 ____ Female 4. Sex of the individual ____ 5. Position (chromosome number) where disorder is 13 located _____, Monosomy / Trisomy (circle one) 6. Specific Name of disorder Pautau _____________

Practice 2 45 1. Number of autosomes ____ 2. Number of sex chromosomes 2 ____ 3. Total number of chromosomes 47 ____ male 4. Sex of the individual ____ 5. Position (chromosome number) where disorder is 21 located _____, Monosomy / Trisomy (circle one) 6. Specific Name of disorder Down syndrome _____________

Practice 3 44 1. Number of autosomes ____ 2. Number of sex chromosomes 1 ____ 3. Total number of chromosomes 45 ____ Female 4. Sex of the individual ____ 5. Position (chromosome number) where disorder is 23 located _____, Monosomy / Trisomy (circle one) 6. Specific Name of disorder Turner _____________

Practice 4 44 1. Number of autosomes ____ 2. Number of sex chromosomes 3 ____ 3. Total number of chromosomes 47 ____ male 4. Sex of the individual ____ 5. Position (chromosome number) where disorder is 23 located _____, Monosomy / Trisomy (circle one) 6. Specific Name of disorder Klinefelter’s _____________