Q. what is the difference between Law of independent assortment and law of segregation?
The law of independent assortment states alleles in non-homologous chromosomes separate during gametogenesis, while the law of segregation states alleles in homologous chromosomes separate during gametogenesis.
Q. what kind of system of sex determination do mammals belong to?
The X-Y system
Q. what are genetic map and linkage map?
genetic map is an ordered list of the genetic loci along a particular chromosomes, while a linkage map is a genetic map based on recombination frequenciesfive facts
1.chromosomes are structures made of chromatin, which is a mixture of DNA and a specific family of proteins called histones.
2.Chromosomes are not uniform, however. Some regions of the chromosome consist of chromatin that is always highly condensed, even during interphase.
3.Further work led to the identification of other genes that were transmitted along with the X chromosome, and genes that were transmitted along with particular autosomes.
4.The X chromosome contains a significant number of genes. In contrast, the Y chromosome contains very few.
5.Because females have twice as many copies of X-linked genes as males, one copy of each must be turned off. This occurs by inactivating one X chromosome in every cell of a female.
diagram
meiotic nondisjunction : gamets with an abnormal chromosome number can arise by nondisjunction in either meiosis 1 and meiosis 2. In which the members of a pair of homologous chromosomes do not move apart properly during meiosis 1 or sister chromatids fail to separate during meiosis 2. In these case, one gamete receives two of the same type of chromosomes and another gamete receives no copy.
video
http://www.youtube.com/watch?v=Q77t8kc4O34summary
Compare Mendel's laws of heredity with the chromosomal basis of heredity. Reflect on why comparing Mendel's work with the chromosomal basis of heredity suggests that the work of science is cumulative.Mendel’s law of inheritance explains how factors control phenotypes and is transmitted to the succeeding generations. Mendel's laws of equal segregation and independent assortment are based on the separation in meiosis of members of each chromosome pair and on the independent meiotic behavior of different chromosome pairs. A parallelism can be drawn between Mendel’s law of heredity and chromosomal basis of inheritance.
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