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2 years ago

Predict phenotypes associated with nondisjunction of sex chromosomes.

1 answer:

3 0

Answer: The new daughter cells will have an abnormal amount of genetic material. That is called aneuploidy and it is the presence of an abnormal number of chromosomes. Different clinical conditions are the result of this nondisjunction.

Explanation:

Normal cells are diploids, that means they have two copies of each gene, one of each chromosome. So normal cells have two homologous chromosomes, one from each parent.

During anaphase of cell division, each pair of chromosomes is separated by the mitotic spindle. The separated chromosomes are then pulled by the spindle to opposite poles of the cell, and eventually will end up in the new daughter cells.

Nondisjunction is the failure of homologous chromosomes to separate properly during cell division, so it is the miss segregation of them. The new daughter cells will have an abnormal amount of genetic material. <u>Different clinical conditions are the result of this nondisjunction.</u>

Sex chromosomes participates in sex determination of an individual. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY) So nondisjunction of sex chromosomes could be:

XX: one cell with no chromosome and the other cell with two X chromosomes.
XY: one cell with no chromosomes and the other cell with XY chromosomes.

According to which gametes are fused during fertilization, different phenotypes can be given. For example, if a gamete with one chromosome fuses with another gamete with two chromosomes, the result will be an individual with three chromosomes (it could be XXY, or XXX) called trisomy.

Triple X syndrome is characterized by an extra X chromosome in females. Those affected are often taller than average, but most females have a normal sexual development. Klinefelter syndrome is known XXY individuals, and it causes infertility in males, breast growth, less body hair and weaker muscles.

And if a gamete with no chromosome fuses also with another gamete with no chromosome, the result is a nullisomy. But due to the lack of genetic material, the nullisomic gametes are rendered unviable for fertilization.

And if a gamete with no chromosome fuses with another gamete with one chromosome (normal) the result is a monosomy, the presence of only one chromosome from a pair. The result can be an individual who is X or Y. People with Turner syndrome have one X chromosome and it is the only monosomy that is seen in humans because other cases monosomy are lethal.

Any of those examples is called aneuploidy and it is the presence of an abnormal number of chromosomes.

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In garden peas a pure line that is tall with purple flowers is crossed to another pure line that is short with white flowers. Th

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Answer:

See the explanation

Explanation:

Answer 1.

As given that in F1 all are short and white then it can be said according to Mendel's law that short and white are dominant over tall and purple.

Let S for short s for tall and W for white and w for purple allele.

So the genotype of short purple will be Ssww or SSww. So In first case Ssww self crossed then resultant offsprings will be,

................ Sw .................... sw

Sw ........ SSww ............. Ssww

sw ........ Ssww .............. ssww (tall and purple)

So from this 1/4 will be tall and purple while 3/4 will be short and purple.

In second case SSww only short purple progeny will appear.

Answer 2.

2. a) The female progeny will not show any trait because there are two X chromosome in females , so female offspring can be carrier but not show any trait in case of X- linked trait.

2. b) Half of male offsprings show trait because X is inherited from mother. So the chance of having X-linked recessive allele is 1/2.

2. c) The chance of having X linked affect allele in daughter is 1/2. So the chance of inheriting that X to son will be 1/2 so in total there is chance of 1/4 that son will be affected.

2. d) the chance of first child show this trait will be 1/4 in case of male offspring while 0 in case of female offspring.

Hope this helps!

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Two protein kinases, K1 and K2, function sequentially in an intracellular signaling pathway. If either kinase contains a mutatio

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Answer:

The order must be K2→K1, since the permanently active K1 allele (K1a) is able to propagate the signal onward even when its upstream activator K2 is inactive (K2i). The reverse order would have resulted in a failure to signal (K1a→K2i), since the permanently active K1a kinase would be attempting to activate a dead K2i kinase.

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You characterize a double mutant cell that contains K2 with type I mutation and K1 with type II mutation.
You observe that the response is seen even when no extracellular signal is provided.
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