Question

1. chromosomes contain millions of genes .true or false?
2. an example of a reduced penetrance trait is syndactyly true or false
3.in fragile X syndrome, male offsprings are carriers and female offsprings are at risk for being affected true or false
4.people with hemophilia bleed more profusely and faster than normal, true or false
5. hemophilia is. a---- trait
6. the karyotype for klinefelters syndrome is-----

Answer 1

1. False. Chromosomes are paired structures in the nucleus comprising tightly coiled DNA around histone proteins. The distance between each base pair in DNA is 0.34 nm; the length of a chromosome is determined by the number of base pairs multiplied by 0.34 nm. Humans who have 23 pairs of chromosomes have about 30,000 genes. Therefore it is simply implausible to imagine a chromosome with millions of genes. A chromosome would have a few hundred to a few thousand genes, not millions.

2. True. Syndactyly is a condition where fusing of the fingers or toes occur as a result of failure of their development during organogenesis. Syndactyly is quite complex as it is classified into at least nine types with sub-divisions, based on the nature of fusion of the digits. According to the journal article on "Syndactyly: Phenotypes, genetics and current classification" by  Malik (2012), most of syndactyly traits are autosomal dominant phenotypes, that show reduced or incomplete penetrance.

3. False. Fragile X syndrome displays a dominant X-linked inheritance pattern where the mutation is located on the X-chromosome and it is enough if it is present in one copy of the gene. Therefore the carriers are female off-springs whereas male off-springs are at risk because they may or may not get the copy of the gene mutation in one of the two parent X chromosomes.

4. True. People with hemophilia lack clotting factors in their blood which makes them bleed profusely. They are classified into A or B types based on the clotting factors they lack due to mutation  in the gene for Factor VIII   and Factor IX respectively.

5. Hemophilia is a X-linked recessive trait. This means that if inherited, it would certainly affect males due to lack of a normal gene as males carry a Y chromosome.

6. The karyotype for klinefelter's syndrome is 47,XXY. It is a condition that results due to the occurrence of two or more X chromosomes in males, instead of a normal single X chromosome.