Are homologous chromosomes present in mitosis?

[Wererew]

Are they only present in meiosis?

Homologous chromosomes do not cross over during mitosis, but wouldn't they still be called homologous chromosomes?

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[rufflev]

Are they only present in meiosis?

Homologous chromosomes do not cross over during mitosis, but wouldn't they still be called homologous chromosomes?

Homologous chromosomes are NOT present in mitosis, rather only in meiosis. In mitosis you have sister chromatids; homologous chromosomes are chromosome pairs, each coming from one parent.

 

[Wererew]

Homologous chromosomes are NOT present in mitosis, rather only in meiosis. In mitosis you have sister chromatids; homologous chromosomes are chromosome pairs, each coming from one parent.

Oh okay.. so it is always references in terms of homologous chromosome pairs, (in a picture, we would see 4 chromatids present? )

 

[FeralisExtremum]

I disagree, homologous chromosomes are present in both mitosis and meiosis (before the homologous pairs get split up). They don't need to be physically paired to be considered homologous chromosomes.

 

[rufflev]

I disagree, homologous chromosomes are present in both mitosis and meiosis (before the homologous pairs get split up). They don't need to be physically paired to be considered homologous chromosomes.

Homologous chromosomes are present in both mitosis and meiosis, but they don't form pairs in mitosis. Rather they will form homologous chromosome pairs during meiosis, which allows for crossing over to occur.

Oh okay.. so it is always references in terms of homologous chromosome pairs, (in a picture, we would see 4 chromatids present? )

If it's referring to a homologous chromosome pair, you know it's referring to meiosis. The number of chromatids is determined by 2 x # chromosome pairs.

 

[FeralisExtremum]

Homologous chromosomes are present in both mitosis and meiosis, but they don't form pairs in mitosis. Rather they will form homologous chromosome pairs during meiosis, which allows for crossing over to occur.

If it's referring to a homologous chromosome pair, you know it's referring to meiosis. The number of chromatids is determined by 2 x # chromosome pairs.

I'm not sure where the specification about pairs is coming from though - OP's original question doesn't mention the word, they only asked about homologous chromosomes in general.

 

[Wererew]

So if the term is "homologous chromosomes", it is referring to many, two sister chromatids with a centromere?

 

[FeralisExtremum]

So if the term is "homologous chromosomes", it is referring to many, two sister chromatids with a centromere?

Homologous chromosomes just means you have a set of both a maternal and paternal chromosome. You can tell if two chromosomes are homologous because they will pair up during meiosis and crossover. But you always (except when producing gametes, or in the rare cases of monosomies) have homologous chromosomes. It's not referring to a physical structure but the dual set of your chromosomes. For example, you have 23 chromosomes (inherited from your mother) and 23 chromosomes (inherited from your father). 22 of these from each parent are always homologous - they carry carry the same genes (but not necessarily the same alleles) in the same locations - thus you always have at least 22 homologous chromosome pairs. The sex chromosomes are not homologous in men, for obvious reasons.

 

[WinstonsDad]

Homologous chromosomes having similar genes and loci, but possibly different alleles. This comes from one being paternal and one being maternal. Homologous chromosomes are present in both Mitosis AND Meiosis, but their arrangement differs. Let's explain how.

In humans we have 22 homologous autosomal pairs, (and 2 sex chromosomes) for a total of 46 chromosomes. We simply the chromosomes to look like an "X". Each "X" is one chromosome, made of two sister chromatids ( exact copies of the chromosome) connected at a common centromere.

In mitosis the chromosomes line up in a straight line in metaphase and are pulled apart in anaphase. Since homologous chromosomes do not arrange in pairs during mitosis, in a human we see 46 chromosomes lined up in mitosis metaphase, making it diploid. After anaphase each of the 2 progeny have 46 chromatids (each identical, still diploid). Homologous chromosomes are present in mitosis but they arrange differently in meiosis.

In Meiosis, homologous pairs form tetrads. Tetrads, containing tetra (4), refers to the pairing of homologous chromosomes (which have 4 sisters chromatids between the homologous pair). Unlike mitosis where the chromosomes are unpaired in their metaphase (46 total in "single file"), in metaphase 1 of meiosis 23 tetrads are formed (23 in "double file"). Immediately after anaphase 1 each of the progeny is now haploid, containing 23 chromosomes, rather than 23 pairs. Another cycle of meiosis occurs yielding four haploid progeny with 23 chromatids. (see picture below, 2n=4 for picture instead of 2n=46 for humans)

Homologous pairs ARE PRESENT in both MITOSIS AND MEIOSIS, but the arrangement of the homologous pairs determines its diploid or haploid future. Recapping mitosis, the chromosomes lines up, not paired with their homologue, and yield a diploid progeny. Recapping meiosis, the chromosomes line up with homologous pairs, forming tetrads, and yield haploid progeny after 2 cycles. You are right about crossing over in meiosis, but that doesn't change the fact that homologous chromosomes are present in both mitosis and meiosis. Inbox any more questions, hope it helps!

 

[Wererew]

Homologous chromosomes having similar genes and loci, but possibly different alleles. This comes from one being paternal and one being maternal. Homologous chromosomes are present in both Mitosis AND Meiosis, but their arrangement differs. Let's explain how.

In humans we have 22 homologous autosomal pairs, (and 2 sex chromosomes) for a total of 46 chromosomes. We simply the chromosomes to look like an "X". Each "X" is one chromosome, made of two sister chromatids ( exact copies of the chromosome) connected at a common centromere.

In mitosis the chromosomes line up in a straight line in metaphase and are pulled apart in anaphase. Since homologous chromosomes do not arrange in pairs during mitosis, in a human we see 46 chromosomes lined up in mitosis metaphase, making it diploid. After anaphase each of the 2 progeny have 46 chromatids (each identical, still diploid). Homologous chromosomes are present in mitosis but they arrange differently in meiosis.

In Meiosis, homologous pairs form tetrads. Tetrads, containing tetra (4), refers to the pairing of homologous chromosomes (which have 4 sisters chromatids between the homologous pair). Unlike mitosis where the chromosomes are unpaired in their metaphase (46 total in "single file"), in metaphase 1 of meiosis 23 tetrads are formed (23 in "double file"). Immediately after anaphase 1 each of the progeny is now haploid, containing 23 chromosomes, rather than 23 pairs. Another cycle of meiosis occurs yielding four haploid progeny with 23 chromatids. (see picture below, 2n=4 for picture instead of 2n=46 for humans)

Homologous pairs ARE PRESENT in both MITOSIS AND MEIOSIS, but the arrangement of the homologous pairs determines its diploid or haploid future. Recapping mitosis, the chromosomes lines up, not paired with their homologue, and yield a diploid progeny. Recapping meiosis, the chromosomes line up with homologous pairs, forming tetrads, and yield haploid progeny after 2 cycles. You are right about crossing over in meiosis, but that doesn't change the fact that homologous chromosomes are present in both mitosis and meiosis. Inbox any more questions, hope it helps!

Homologous chromosomes just means you have a set of both a maternal and paternal chromosome. You can tell if two chromosomes are homologous because they will pair up during meiosis and crossover. But you always (except when producing gametes, or in the rare cases of monosomies) have homologous chromosomes. It's not referring to a physical structure but the dual set of your chromosomes. For example, you have 23 chromosomes (inherited from your mother) and 23 chromosomes (inherited from your father). 22 of these from each parent are always homologous - they carry carry the same genes (but not necessarily the same alleles) in the same locations - thus you always have at least 22 homologous chromosome pairs. The sex chromosomes are not homologous in men, for obvious reasons.

Thanks for the replies. I was taking an online practice quiz and came across an explanation saying that "homologous chromosomes are not present in mitosis", which tripped me up..

Also, I am now really confused:
Isnt NAD reduced to NADH? I picked the first choice but shouldn't it be reduced to NADH? Ahh..

 

[FeralisExtremum]

Thanks for the replies. I was taking an online practice quiz and came across an explanation saying that "homologous chromosomes are not present in mitosis", which tripped me up..

Also, I am now really confused:
Isnt NAD reduced to NADH? I picked the first choice but shouldn't it be reduced to NADH? Ahh..

Where's this practice quiz from? Both the original explanation and the NAD explanation they provided are incorrect. NAD is reduced to NADH, NADH is oxidized to NAD.

 

[caffeine jitters]

I would suggest you stop using this resource lol