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Human Chromosomes and Genes. Sanjaya Adikari Department of Anatomy. DNA. DNA is the genetic material DNA is organized into chromosomes. Chromosomes. DNA histone proteins non-histone proteins. chromatin. chromosome. chromatids. short arm (p). cell division. centromere. long arm (q).
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Human Chromosomes and Genes SanjayaAdikari Department of Anatomy
DNA • DNA is the genetic material • DNA is organized into chromosomes
Chromosomes DNA histone proteins non-histone proteins chromatin chromosome
chromatids short arm (p) cell division centromere long arm (q) telomere Chromosomes….
Autosomes and sex chromosomes • Total of 46 chromosomes • 23 pairs of chromosomes • 22 pairs of autosomes • 1 pair of sex chromosomes, XX or XY
Karyotype • Chromosome constitution of a cell • Normal male 46,XY • Normal female 46,XX
Karyograph Karyotyping
Homologous pair Karyograph
1 2 3 4 5 6 diploid haploid Haploid and diploid
in meiosis, gametes Somatic cell diploid haploid
Genes • Gene is a sequence of DNA coding for a polypeptide
Exon 1 Intron 1 genes Exon 2 non coding regions Intron 2 Exon 3 Intron 3 Exon 4 Gene chromosome
Homologous pair Genes residing at the same level of the homologous pair of chromosomes are called alleles Alleles are in the same locus Locus A A Locus and alleles
Homozygous and heterozygous AA aa Homozygous Aa AB Heterozygous
Recessive and dominant characters Dominant characters are expressed in the heterozygote* Recessive characters are expressed only in the homozygote# T t * heterozygote=person with heterozygous genotype #homozygote=person with homozygous genotype
TT => tall Tt => tall tt => short ‘Tall’ is the dominant character ‘Short’ is the recessive character
Blood groups ABO group-A group- B group-AB group-O AA AO BB BO AB OO Locus A A Genetic polymorphism
References • Emery’s Elements of Medical genetics. Robert F. Mueller and Ian D. Young Medical Library Class No. 616.042 • Medical Genetics: An illustrated outline. Andrew Read Medical Library Class No. 616.042 • Web sites http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Chromosomes.html http://www.csu.edu.au/faculty/health/biomed/subjects/molbol/DNAstruc.htm http://gslc.genetics.utah.edu/units/disorders/karyotype/karyotype.cfm http://homepages.which.net/~gk.sherman/baaaaabz.htm http://www.eurekah.com/abstract.php?chapid=1777&bookid=118&catid=19