2 What is a karyotype?A karyotype is a picture of chromosomes found in a typical human body cell.The karyotype is the result of a haploid sperm cell, carrying 23 chromosomes fertilizing a haploid egg cell, carrying 23 chromosomes.
3 A Normal Human Karyotype The chromosomes in a human karyotype are arranged in homologous pairs.The first 22 pairs of chromosomes are called autosomes.The 23rd pair of chromosomes are known as the sex chromosomes.
4 Chromosomal MutationB. Chromosomal mutations involve changes in the number or structure of chromosomes. Such mutations may change the locations of genes on chromosomes, and may even change the number of copies of some genes.
5 Chromosomal mutations occur during crossing over. The exchange of genetic material between homologous pairs of chromosomes
6 IV. Chromosomal Mutation C. Four types of chromosomal mutations:DeletionDuplicationInversionTranslocation
11 IV. Chromosomal Mutation D. Deletions involve the loss of all or part of a chromosomeE. Duplications produce extra copies of all or part of a chromosomeF. Inversions reverse the direction of parts of chromosomesG. Translocations occur when part of a chromosome break off and attach to another chromosome.
13 IV. Chromosomal Mutation H. Most mutations are neutral – they do not change the expression of genes or proteins.I. Some are harmful, some are beneficial.
14 NondisjunctionJ. Nondisjunction occurs during meiosis when homologous chromosomes fail to separate.Nondisjunction means “not coming apart”.When it occurs, abnormal numbers of chromosomes may find their way into gametes (sperm or egg), and a disorder of chomosome numbers may result.
17 Down’s SyndromeDefect – autosomal disorder (extra copy of chromosome 21)Symptoms:Have delayed mental and social development.Common problems may include:Impulsive behaviorPoor judgmentShort attention spanSlow learning
18 Down’s Syndrome Neither! Due to nondisjunction. Disorder is also called trisomy 21. Have an extra 21st chromosome.Dominant or Recessive?Neither! Due to nondisjunction.
19 Down’s Syndrome Interesting Facts: It is usually the egg that provides the extra copies of chromosome 21The older the mother, the chances of having a baby with Down’s Syndrome increasesAge 20, 1 in 1500Age 40, 1 in 60
20 Patau Syndrome- Trisomy 13 SymptomsCleft lip or palateClenched hands (with outer fingers on top of the inner fingers)Close-set eyes -- eyes may actually fuse together into oneDecreased muscle toneExtra fingers or toes (polydactyly)Low-set earsScalp defects (missing skin)SeizuresSkeletal (limb) abnormalitiesIntellectually Disabled
21 Turner’s Syndrome- XO Symptoms: May be intellectually disabled, some have normal IQShort statureSterile (cannot have kids)Webbed neckUnderdeveloped breastsand ovariesDefect:XO (missing a sexchromosome)
22 Turner’s Syndrome- XOFrequency: 1 in 2,500 Interesting Fact: Caused by non-disjunction. (Occurs in meiosis when the sister chromatids aren’t pulled apart.
23 Klinefelter’s Syndrome- XXY Symptoms:Underdeveloped testesInability to produce spermMuscle structure, fat and hair distribution similar to that of a femaleBreasts developDefect: XXY-Male with an extra X chromosome in some cells
24 Klinefelter’s syndrome Eggs SpermDominant or recessive – chromosomal mutation XXYFrequency – 1 in 400 malesInteresting fact – often goes undiagnosed. Caused by nondisjunction. Can be treated with male hormones.
25 Double Y syndrome- XYY Signs and symptoms: Often less than average IQ TallHigh levels of male hormonesLarge earsSunken chestDelayed speech and language skillsDefect: Chromosomal mutation - XYY Frequency: 1 in 250 males Interesting fact: Questionable connection to violent tendencies