human chromosomes and genes sanjaya adikari department of anatomy
TRANSCRIPT
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Human Chromosomes and
Genes
Sanjaya Adikari
Department of Anatomy
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DNA
• DNA is the genetic
material
• DNA is organized into
chromosomes
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Chromosomes
DNAhistone proteinsnon-histone proteins
chromatin
chromosome
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Chromosomes….
cell division
chromatids
short arm (p)
long arm (q)
centromere
telomere
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Autosomes and sex chromosomes
• Total of 46 chromosomes
• 23 pairs of chromosomes
• 22 pairs of autosomes
• 1 pair of sex chromosomes, XX or
XY
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Karyotype
• Chromosome constitution of a cell
• Normal male 46,XY
• Normal female 46,XX
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Karyotyping
Karyograph
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Homologous pairKaryograph
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Haploid and diploid
haploid
diploid
1 2 3 4 5 6
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diploid
Somatic cell
haploid
gametesin meiosis,
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Genes
• Gene is a sequence of DNA coding for a polypeptide
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Exon 1
Intron 1
Exon 2
Intron 2
Intron 3
Exon 3
Exon 4
Gene
genes
non coding regions
chromosome
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Locus and alleles
A A
Genes residing at the same level of the homologous pair of chromosomes are called alleles
Homologous pair
Locus
Alleles are in the same locus
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Homozygous and heterozygous
AAaa
Homozygous
AaAB
Heterozygous
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Recessive and dominant characters
T t
Dominant characters are expressed in the heterozygote*
Recessive characters are expressed only in the homozygote#
* heterozygote=person with heterozygous genotype#
homozygote=person with homozygous genotype
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TT => tall
Tt => tall
tt => short
‘Tall’ is the dominant character
‘Short’ is the recessive character
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Genetic polymorphism
LocusA A
Blood groups
ABO
AAAOBBBOABOO
group-A
group- B
group-ABgroup-O
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References• Emery’s Elements of Medical genetics. Robert F. Mueller
and Ian D. YoungMedical Library Class No. 616.042
• Medical Genetics: An illustrated outline. Andrew Read Medical Library Class No. 616.042
• Web siteshttp://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