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Pedigrees & Karyotypes

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Presentation on theme: "Pedigrees & Karyotypes"— Presentation transcript:

1 Pedigrees & Karyotypes

2 Pedigrees Used to explore human genetics Circles = Female
Squares = Male Traits: Not Shaded = Do not have ½ Shaded = Carrier Full Shade = Have

3 Hyperlink to PI Investigator in picture

4 Modes of Inheritance Autosomal or Sex-Linked Dominant or Recessive
Autosomal –chromosomes other than sex chromos. Sex linked – X or Y Dominant or Recessive

5 Autosomal Recessive ~equal in males & females Often skips generations
May show carriers (half shaded) but not always!

6 Autosomal Dominant Does not skip generations
Affect crossed with unaffected = 50% of offspring are typically affected

7 Sex-Linked Traits Mostly males
Mother of affected male is a carrier or affected. No male carriers, but can have female carriers

8 Pedigree Flowchart How many males & females are affected? More Males
Males = Affected Females Autosomal More Males Sex Linked Trait No male carriers? No: Does the trait skip a generation? Are carriers present? Yes: Recessive No: Dominant Yes: Recessive 8

9 Human Karyotypes Diploid organisms 46 Chromosomes 23 homologous pairs
2 sex chromos. Used to detected aneuploidy associated disorders

10 Nondisjunction Not coming apart Abnormal chromosome #s in gametes
Causes: Aneuploidy

11 Down Syndrome Trisomy Chromosome 21 1/800 US births Mild – severe
Three bodies Chromosome 21 autosomal 1/800 US births Mild – severe

12 Sex Chromosomes Disorder
Turner’s Syndrome Female with only one X XO Causes Sterility = no sex organ development at puberty Short stature Webbed neck common feature of Turner syndrome is short stature, which becomes evident by about age 5. An early loss of ovarian function (ovarian hypofunction or premature ovarian failure) is also very common. Many affected girls do not undergo puberty unless they receive hormone therapy, and most are unable to conceive (infertile) About 30 percent of females with Turner syndrome have extra folds of skin on the neck (webbed neck), a low hairline at the back of the neck, puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, or kidney problems. One third to one half of individuals with Turner syndrome are born with a heart defect, such as a narrowing of the large artery leaving the heart (coarctation of the aorta) or abnormalities of the valve that connects the aorta with the heart (the aortic valve).

13 Klinefelter’s Syndrome
Males with an extra X Reduced fertility Less testosterone 1/1000 males XYY Normal reproduction Delay motor skills temper Klinefelters do not produce as much testosterone as usual shortage of testosterone can lead to delayed or incomplete puberty, breast enlargement (gynecomastia), reduced facial and body hair, and an inability to have biological children (infertility Older children and adults with Klinefelter syndrome tend to be taller than their peers. Compared with unaffected men, adults with Klinefelter syndrome have an increased risk of developing breast cancer and a chronic inflammatory disease called systemic lupus erythematosus. Their chance of developing these disorders is similar to that of women in the general population. Children with Klinefelter syndrome may have learning disabilities and delayed speech and language development. They tend to be quiet, sensitive, and unassertive, but personality characteristics vary among affected individuals. XYY Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most males with 47,XYY syndrome have normal sexual development and are able to father children. 47,XYY syndrome is associated with an increased risk of learning disabilities and delayed development of speech and language skills. Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), hand tremors or other involuntary movements (motor tics), and behavioral and emotional difficulties are also possible. These characteristics vary widely among affected boys and men.

14 X Chromosome No cases of babies born without an X chromosome
X is vital for normal development

15 Y Chromosome Important role in sex determination
Y presence creates a male no matter how many extra Xs Exception : Swyer syndrome SRY gene mutations that cause Swyer syndrome prevent production of the sex-determining region Y protein or result in the production of a nonfunctioning protein. A fetus whose cells do not produce functional sex-determining region Y protein will develop as a female despite having a Y chromosome.



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