Crossing-over occurs between a. sister chromatids of the same chromosome. b. chromatids of nonho

step 1 Let's quickly review the parts of a chromosome. So we have these two chromatids, this chromatid

Crossing-over occurs between a. sister chromatids of the...

Key Concepts

Meiosis

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in the formation of haploid gametes. It includes stages such as homologous chromosome pairing and crossing-over, which are essential for generating genetic diversity in sexually reproducing organisms.

Nonsister Chromatids

Nonsister chromatids are the chromatids of homologous chromosomes that are not identical to each other. During crossing-over in meiosis, these chromatids exchange segments of DNA, making them a key element in the genetic recombination process that introduces variability among gametes.

Crossing-Over

Crossing-over is a process that occurs during meiosis where segments of homologous chromosomes are exchanged between non-sister chromatids. This genetic recombination is crucial for increasing genetic diversity in offspring by shuffling alleles between paired chromosomes.

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes, one inherited from each parent, that carry the same types of genes in the same order. They align during meiosis, allowing for the possibility of exchange of genetic material through crossing-over, which contributes to genetic variation.

Transcript

00:01 Let's quickly review the parts of a chromosome.

00:04 So we have these two chromatids, this chromatid and this chromatid, attach at the centromere, which makes them sister chromatids.

00:17 And this whole thing is a duplicated chromosome.

00:25 So if a cell is going to undergo myosis, it has to be diphoid, which means it has two copies of every gene and two copies of every chromosome.

00:36 So let's say it has this is one copy of one chromatome.

00:40 Chromosome and now it has two.

00:46 So these two chromosomes are the same in that they code for the same genes and each gene codes for the same thing.

00:54 But they have different alleles or they could have different alleles.

00:57 They might not.

00:58 So for example, this gene could code for hair color with one having a dominant and one having recessive allele.

01:06 So before myosis, the dna will be duplicated, which creates our duplicated chromosome.

01:24 So now, and now we have, again, we still have the dominant alleles on both of these now and recessive on both of the green ones.

01:34 Now this whole thing is called a homologous pair.

01:44 In a process called synapsis, this homologous pair will be forming a tetrae, which is a structure made of these two chromosomes.

01:54 And this is when crossing over can occur.

01:59 So here you can see what crossing over looks like...

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