CHAPTER 12

Alleles are different forms of the same gene, and are carried in the same homologous chromosome. The offspring of the parents will inherit their alleles which allows them to combine traits. Genes in DNA sequences on the same homologous chromosome may become alleles from mutation. They allow for differences to be shown in the same trait. They also allow for combinations that form new traits.

Homologous chromosomes are the two different sets of chromosomes in every cell, with one from the father and one from the mother. However, they do differ in their alleles who may carry different genes. Genes are formed on the homologous chromosomes but their alleles will make theme different.

A gene is a sequence of nucleotides that make up a chromosome. They are passed down from both parental cells in each homologous chromosomes. This allows for the offspring to take in some of the prominent features as its mother or father. Genes occur in pairs on homologous chromosomes, and they can be very similar or different depending on alleles.

Every single gamete is a haploid but they all differ in some detail among species. They are formed from meiosis and are single stranded chromosomes not in pairs like diploids. Gametes are formed when haploid divide. So the haploid form the cells necessary to have sex because diploids are cut in half and from haploids, who form gametes. In meiosis diploid chromosomes are made into 4 haploid nuclei that allow for the gametes to form. The two haploid gametes then form a zygote which starts human life.

It starts with prophase I which homologous chromosomes condones and cross over, along with spindle fibers forming and the nucleus beginning to break down.

Then in Metaphase I the chromosomes meet up in the middle of the cell before they start to drift away from one another.

Next in Anapahse I the chromosomes separate and start heading toward the opposite poles.

After that in Telopahse I the chromosomes reach the poles and nuclei form around two haploid chromosomes.

Following that those nuclei begin to break, the chromosomes condense, and spindle fibers form in prophase II.

Then in metaphase II, the duplicated chromosomes line up in the middle again.

Next in Anapase II, everything breaks up and heads toward the poles.

Finally, in Telophase II all of the chromosome clusters arrive at the poles, the nuclear envelope encloses those chromosomes and now four haploid chromosomes form.

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