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Inheritance Patterns and Human Genetics

Inheritance Patterns and Human Genetics. Sex Chromosomes and Autosomes. Sex Chromosomes contain genes that determine the gender of an individual. Many organisms have the XX & XY chromosomal mechanism to determine the sex of an individual. Sex Chromosomes and Autosomes.

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Inheritance Patterns and Human Genetics

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  1. Inheritance Patterns and Human Genetics

  2. Sex Chromosomes and Autosomes • Sex Chromosomes contain genes that determine the gender of an individual. • Many organisms have the XX & XY chromosomal mechanism to determine the sex of an individual.

  3. Sex Chromosomes and Autosomes • In certain organisms, like chickens and moths, males have two identical chromosomes and females have two different chromosomes.

  4. Sex Determination • In mammals, the male determines the sex of the offspring. • If the sperm contributes an X sex chromosome, a female will be created • If the sperm contributes a Y sex chromosome, a male will be created.

  5. The Y Chromosome • In a male mammal, the Y chromosome contains a gene called SRY (Sex-determining Region Y) • This gene codes for a protein that causes gonads of an embryo to develop as testes.

  6. Sex Linkage • Genes found on the X chromosome are said to be X-linked • Genes found on the Y chromosome are said to be y-linked

  7. Mutations • Change in the nucleotide-base sequence of a gene or DNA molecule

  8. Mutations • Germ-cell mutations occur in an organism’s gametes. • These do not affect the organism itself, but can be passed on to offspring.

  9. Mutations • Somatic-cell mutations take place in an organism’s body cells. • These mutations can affect the organism but are not passed on to offspring

  10. Mutations • Lethal mutations cause death, often before birth. • Some mutations will produce a phenotype that is beneficial to an organism. • Mutations provide the variation upon which natural selection acts.

  11. Chromosome MutationDeletion • Loss of a piece of a chromosome due to breakage

  12. Chromosome MutationInversion • A chromosomal segment breaks off, flips around backward, and reattaches.

  13. Chromosome Mutation Translocation • A piece of one chromosome breaks off and reattaches to a nonhomologous chromosome

  14. Chromosome MutationNondisjunction • A chromosome fails to separate from its homologue during meiosis.

  15. Gene Mutations • The substitution, addition, or removal of a single nucleotide is called a Point Mutation • This image shows a substitution point mutation.

  16. Gene Mutation (Frameshift) • If a nucleotide is deleted (Deletion), this can cause an incorrect grouping of the remaining codons. This is called a frameshift mutation.

  17. Gene Mutation (Frameshift) • If a nucleotide is inserted (insertion mutation), this can cause an incorrect grouping of the remaining codons. This is also called a frameshift mutation. CTTCGAAGTC CTATCGAAGTC

  18. Inheritance of TraitsPedigrees • A diagram that shows how a trait is inherited over several generations.

  19. Can you make sense of this Pedigree?

  20. Polygenic Inheritance • Most human traits are polygenic. • This means they are influenced by several genes. • Often show many degrees of variation. • Eye color, height, hair color and skin color.

  21. Multiple Allele Inheritance • Genes with three or more alleles • The ABO blood types are controlled by 3 alleles. • A, B, i • A & B are dominant to i

  22. Blood Types PhenotypesGenotypes A AA, Ai B BB, Bi AB AB O ii

  23. Rh Factor for Blood • Rh stands for Rhesus Factor • If you are Rh +, you have a blood protein that Rh – people do not have. • Rh+ is dominant to Rh – • 85% of the US population is Rh+

  24. Rh Factor Problems • When a pregnant woman who is Rh - is having a Rh + baby the woman will produce antibodies against the foreign protein.

  25. Rh Factor Problems • The woman’s first child will not be affected. • If the woman has any other children, her antibodies can attack the babies blood causing death to the baby. • There are injections that are given to women today to keep this from being a problem.

  26. X – Linked Traits • Traits and disorders that are found on the X chromosome • For a man to have an X-linked disorder, he only needs the trait on his one X. • For a female to have an X-linked disorder, she needs to have the trait on both of them. (unless it is a dominant X-linked trait)

  27. X – Linked Traits • Color blindness is a recessive X-linked disorder

  28. X – Linked Traits • Hemophilia is also a recessive X-linked disorder

  29. Sex-Influenced Traits • The presence of male or female sex hormones influence the expression of certain human traits

  30. Disorders due to Nondisjunction • Monosomy – when an organism has only one copy of a particular chromosome • Trisomy – when an organism has 3 copies of a particular chromosome

  31. Disorders due to Nondisjunction • Down Syndrome (trisomy 21) • Turner Syndrome (X0) • Klinefelter’s Syndrome (XXY) • Triple X Syndrome (XXX)

  32. Genetic Screening • Amniocentesis – amniotic fluid is removed and a karyotype of the baby is produced.

  33. Genetic Screening • Chorionic Villi Sampling – a sample of the tissue that grows between the mother’s uterus and the placenta is taken. • A karyotype is produced.

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