human chromosomes and genes sanjaya adikari department of anatomy
TRANSCRIPT
Human Chromosomes and
Genes
Sanjaya Adikari
Department of Anatomy
DNA
• DNA is the genetic
material
• DNA is organized into
chromosomes
Chromosomes
DNAhistone proteinsnon-histone proteins
chromatin
chromosome
Chromosomes….
cell division
chromatids
short arm (p)
long arm (q)
centromere
telomere
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
Karyotyping
Karyograph
Homologous pairKaryograph
Haploid and diploid
haploid
diploid
1 2 3 4 5 6
diploid
Somatic cell
haploid
gametesin meiosis,
Genes
• Gene is a sequence of DNA coding for a polypeptide
Exon 1
Intron 1
Exon 2
Intron 2
Intron 3
Exon 3
Exon 4
Gene
genes
non coding regions
chromosome
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
Homozygous and heterozygous
AAaa
Homozygous
AaAB
Heterozygous
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
TT => tall
Tt => tall
tt => short
‘Tall’ is the dominant character
‘Short’ is the recessive character
Genetic polymorphism
LocusA A
Blood groups
ABO
AAAOBBBOABOO
group-A
group- B
group-ABgroup-O
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