something about genetic (CE)

Benny Cheng Chi Fai

2010-03-26 11:08 pm

I would like to ask about some special terms in genetic.

1. What is the difference and definition of chromosome and chromatids?

Human cells have 23pairs of chromosome, then how many number of
chromatids do we have ?

2. What is the meaning of homologus chromosomes?
Is the 23pairs of chromosome in our cells are all pairs of
homologus chromosomes?

Also, during mitotic coll division, the chromosome replicate into two chromatids
(my teacher tell me) then can i say it is a pair of homologus chromosome or
just simply call a chromosome or none of the above two?

genetic d term 好亂

希望大家幫下手而家o係genetic e 課到卡住左...

回答 (1)

[匿名]

2010-03-27 3:47 am

✔ 最佳答案

1 pair of chromosomes = 2 chromatids
23 pairs of chromosomes = 46 chromosomes

chromosomes contain genes (which made up of DNA) which alter your characteristic, normally occuring as single strand, unless replication occure which become double strands structure and chromatid is the half the chromosome after replication, so instead of the chromosomes having X structure, it has l l structure in the chromosome.

homologous chromosomes are chromosomes that alter the same features in the pair, which means that for both the chromosomes in the pair, they contain the genes for the same features/characteristic. basically all 22 pairs of chromosomes are homologus, except for the sex chromosomes X and Y, this is because the X chromosome in the sex chromosomes contain informations that doesn't contain in the Y, e.g colour blindness genes.

You can't say that the two chromatids is a pair of homologous chromosomes, because it is not a pair of chromosomes, it is just a single chromosome with 2 strands after replication.

2010-03-26 20:07:06 補充：
ignore the first line: 1 pair of chromosomes = 2 chromatids

參考: heinemann biology textbook, wikipedia

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