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Glossary. sex-linked trait. traits carried by genes located on the X or Y sex chromosomes genetically normal females: XX genetically normal males: XY. Glossary. sex-linked trait. most X-linked characteristics are recessive in females
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Glossary sex-linked trait traits carried by genes located on the X or Y sex chromosomes genetically normal females: XX genetically normal males: XY
Glossary sex-linked trait • most X-linked characteristics are recessive in females • which means that unless they are present on both X chromosomes of a female, the trait is carried but not expressed
Glossary sex-linked trait • males, with only one X chromosome, more commonly exhibit such traits phenotypically • e.g. hemophilia • e.g. red-green color blindness
Sex-linked Punnet Square:Hemophilia carrierXHXhxXHY Hemophilia!
Human Geneticsand Meiosis The study of inheritance patterns in humans Oculocutaneous albinism http://www.foxnews.com/slideshow/health/2009/10/19/celebrities-different-color-eyes/#slide=1
Karyotype: A photomicrograph of chromosomes arranged according to a standard classification
In other words… • Chromosomes are digitally arranged so that they are matched with their homologue or “partner” chromosome. • Homologue chromosomes are the same size, shape, and carry the same genes, and one is inherited from each parent. • They are numbered according to size.
Sex determination with karyotype • This karyotype has 23 exact pairs, which means the person is female. • Note that #23 chromosomes are both X.
Normal human male • Note that #23 chromosomes are X and Y.
Trisomy 21 • Abnormality shown in karyotype • Note that there are three copies of #21 chromosome. • This person has Down Syndrome.
Photos of Down Syndrome patients from the National Down Syndrome Society
Monosomy X • Abnormality shown in karyotype • Note this person only has 1 copy of the X chromosome. • This female has Turner’s syndrome.
Amniocentesis: obtaining amniotic fluid which has cells from the fetus
Chorionic villi sampling: removing cells from the chorion with fetal tissue
If there are chromosomal number abnormalities, how do they form? • Meiosis: the process of creating sperm or egg from a diploid cell • If there is a mistake when chromosomes are separating, then the resulting sperm or egg will have too many or too few chromosomes.
How can siblings look alike but not exactly the same if they come from the same parents?
Crossing over • The chromosomes during prophase I undergo crossing over, where parts of the homologues randomly switch places.
Importance of crossing over • The gene combinations that a person gets from his or her parents will be different, to varying degrees, than the combination a sibling may get.
What other chromosomal disorders can arise? • Deletion • Inversion • Translocation* • Duplication *Don’t worry about this one.
Chromosomal mutations Deletion Duplication Inversion Translocation
Problems with chromosomes • Duplication: copied parts of chromosome A B C D A B B B C D
Problems with chromosomes • Deletion: missing parts of chromosome A B C D A D
Problems with chromosomes • Inversion: parts of chromosome tched A B C D A C B D
Human genetic disorders from deleterious genes • Sometimes the alleles inherited contribute to disorders and not from the number or shape of the chromosomes. • Sex-linked: genes found on X or Y chromosome • Recessive: requires 2 allele copies to express disorder • Dominant: requires only 1 allele copy to express disorder
Are you red-green color blind? • Yes, if you have a difficult time distinguishing a number from this picture
Pedigrees: a chart which can show trait inheritance through several generations Albinism
Symbols marriage Male Female
