Loci and the Human Karyotype Biology Unit 6

Loci and the Human Karyotype Biology Unit 6 2014 -2015

Chromosomes Karyotype: ◦ ordered display of an individual’s chromosomes. ◦ Collection of chromosomes from mitotic cells. ◦ Staining can reveal visible band patterns, gross anomalies.

Karyotyping Meiosis KM 3

Karyotypes arrange chromosomes in order by size: Largest to smallest

Chromosomes Some large like #1 Some small like #22

Homologous pairs Same Length Centromere in same location Same bands (genes)

Centromere Position The centromere is not exactly in the center of the chromosome “p” arm: (p=petite) the shorter arm of the chromosome “q” arm: the longer arm of the chromosome

Locus (plural=loci) The position that a given gene occupies on a chromosome. (Its like an address for your genes) Written like this: 15 p 23

Example: 15 p 23=Chrom 15 small arm, 23 rd band from the centromere

Trisomy: *Having 3 chromosomes of each kind instead of 2 *Normally trisomy results in death. 1 Example

Down Syndrome: a genetic condition in which the individual has 3 copies of the 21 st chromosome. Genotype: 3 copies of 21 st chromosome

Chrom # 2 Gene Description Skin Color Polygenic Locus 2 p 18 2 q 21 Allele S = Dark s= Light My My Geno. Pheno Lt Ssss Olive SSSS= Dark SSSs= Fairly Dark S s s s SSss= Olive Ssss = Light Olive ssss = Lightest White

Chrom # 4 Gene Description Acne Polygenic Incomplete Dominance Locus 4 p 20 Allele A=Acne a=No Acne AA=Lots Aa=some aa= none My My Geno. Pheno Aa A Some Acne a

Chrom # 4 Gene Description Cleft Chin Regular Dominance Locus 4 p 19 Allele N = Cleft n= no cleft My My Geno. Pheno nn n No Cleft n

Chrom # 7 Gene Description Eye color Incomplete Dominance Locus 7 p 15 Allele B=Brown b=Blue My My Geno. Pheno Bb Light Brown BB=Brown Bb=Light Brown, Hazel, Green bb=blue B b

Chrom # 7 Gene Description Hair Color Incomplete Dominance Locus 7 p 11 Allele My My Geno. Pheno H=Brown/Black Hh h=blonde Light Brown HH=Brown/Black Hh=Light Brown hh=Blonde H h