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KEY CONCEPT A combination of methods is used to study human genetics.

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Presentation on theme: "KEY CONCEPT A combination of methods is used to study human genetics."— Presentation transcript:

1 KEY CONCEPT A combination of methods is used to study human genetics.

2 Human genetics follows the patterns seen in other organisms.
The basic principles of genetics are the same in all sexually reproducing organisms. Inheritance of many human traits is complex. Single-gene traits are important in understanding human genetics. Widow’s Peak 

3 Females can carry sex-linked genetic disorders.
Males (XY) express all of their sex linked genes. No second X chromosome to mask the X present Expression of the disorder depends on which parent carries the allele and the sex of the child. X Y

4 Females can only show the trait if both alleles are recessive ( Xh Xh )
Females can be a carrier if heterozygous ( XH Xh )

5 A pedigree is a chart for tracing genes in a family.
Phenotypes are used to infer genotypes on a pedigree. Autosomal genes show different patterns on a pedigree than sex-linked genes.

6 Tracing Autosomal Genes
Equal numbers of males and females If the recessive phenotype shows, it must be homozygous The dominant phenotype can be either homozygous or heterozygous

7 If the phenotype is more common in males, the gene is likely sex-linked.

8 Tracing Sex-Linked Genes
More males than females show the trait Females must inherit 2 recessive alleles to show up, males need only 1 allele Heterozygous females are carriers Female carriers can pass on the recessive allele to either males or females Males can pass the recessive allele only to female offspring

9 Queen Victoria – Hemophilia
Sex-Linked recessive

10 Several methods help map human chromosomes.
A karyotype is a picture of all chromosomes in a cell. X Y

11 Karyotypes can show changes in chromosomes.
deletion of part of a chromosome or loss of a chromosome large changes in chromosomes extra chromosomes or duplication of part of a chromosome Trisomy: three of one chromosome


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