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Karyotypes

Karyotypes. SBI3U. Key terminology. A karyotype is a picture of the particular set of chromosomes that an individual has. A karyotype can be used to diagnose specific genetic disorders. Gene - part of a chromosome that controls the expression of a particular trait.

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Karyotypes

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  1. Karyotypes SBI3U

  2. Key terminology • A karyotype is a picture of the particular set of chromosomes that an individual has. • A karyotype can be used to diagnose specific genetic disorders. • Gene - part of a chromosome that controls the expression of a particular trait. • Allele - is a variation of a gene • Examples of hair colour alleles include black, brown, blond and red.

  3. Alleles on Homologous Chromosomes • The gene for hair colour has 4 alleles and this person inherited a blond allele and a brown allele • Homologous chromosomes are pair of chromosomes that are identical in their length, centromere location and banding pattern. • Alleles are always found on the same gene of homologous chromosomes.

  4. Karyotype – Somatic Cell Example 1 • Found in somatic cells at the beginning of interphase • Chromosomes are diploid, unreplicated • The first 22 pairs of homologous chromosomes are called autosomes • The 23rd pair of chromosomes are the sex chromosomes • The sex chromosomes are only homologous in females

  5. Karyotype – Somatic Cells Example 2 • These chromosomes are diploid, replicated • This occurs in somatic cells during prophase • Also found in the precursor cells required to make gametes in testes (spermatogonium) and ovary (oogonium)

  6. Karyotype of gamete • Chromosomes are haploid and unreplicated • After fertilization occurs the zygote will have a diploid number of chromosomes

  7. Summary Diploid, unreplicated (2n) Haploid, unreplicated (n) • n indicates the number of haploid chromosomes in a organism • Fruit flies have n=4 • A dove has n = 39 Diploid, Replicated (4n)

  8. Karyotype Charts • A karyotype is an organized profile of a person's chromosomes. • Chromosomes are arranged and numbered by size, from largest to smallest. • This arrangement helps scientists quickly identify chromosomal alterations that may result in a genetic disorder. • To make a karyotype, scientists take a picture of someone's chromosomes, cut them out and match them up using size, banding pattern and centromere position as guides. • Now you try your hand: • http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html

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