What happens when chromosomes combine?

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What happens to chromosomes when gametes combine?

When the two gametes combine, they merge the two sets of chromossome to create a cell with the total number of chromosomes needed to develop, known as a diploid cell. In humans when the haploid sperm and egg cell join in fertilisation the resulting zygote has a total of 46 chromosomes the correct number to develop.

What do chromosomes combine to form?

During prophase I, the pairs of homologous chromosomes come together to form a tetrad or bivalent, which contains four chromatids. Recombination can occur between any two chromatids within this tetrad structure.

What happens when 2 chromosomes crossover?

Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but to the different end piece. If they break at the same place or locus in the sequence of base pairs, the result is an exchange of genes, called genetic recombination.

What happens when two haploid cells combine?

The gametes must be haploid, signified by N, containing only one allele; so that when two haploid gametes combine, they produce a normal diploid individual. The process where haploid sex cells are created from diploid parents is called meiosis, and it occurs only in the reproductive organs.

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How is meiosis responsible for introducing variation?

During meiosis, homologous chromosomes (1 from each parent) pair along their lengths. The chromosomes cross over at points called chiasma. At each chiasma, the chromosomes break and rejoin, trading some of their genes. This recombination results in genetic variation.

What happens to chromosomes during meiosis?

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is required to produce egg and sperm cells for sexual reproduction.

What is the significance of crossing over?

Crossing over gives the evidence for linear arrangement of linked genes in a chromosome. 2. Crossing over helps in the construction of genetic maps 3. Crossing over results in the production of new combinations of genes & hence the genetic diversity.

Are chromosomes joined together?

Chromosomes are packaged by histone proteins into a condensed structure called chromatin. … The two identical chromosomes that result from DNA replication are referred to as sister chromatids. Sister chromatids are held together by proteins at a region of the chromosome called the centromere.

What does a centrosome look like?

Centrosomes are made up of two, barrel-shaped clusters of microtubules called “centrioles” and a complex of proteins that help additional microtubules to form. This complex is also known as the microtubule-organizing center (MTOC), since it helps organize the spindle fibers during mitosis.

Are chromosome pairs joined?

In prophase I of meiosis I, each chromosome is aligned with its homologous partner and pairs completely. In prophase I, the DNA has already undergone replication so each chromosome consists of two identical chromatids connected by a common centromere.

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