CE 遺傳

tsubasa

Originally posted by alan_given at 2005-3-11 06:34 PM:
colour blindess係o係x chromosome
生出黎既女係
x(from father,normal colour vision)x(from mother,colour blindness)
生出黎既仔係
x(from mo ...

colourblindness 係recessive?
如果唔係既話咁mother有冇機會pass on個normal既allele@@?

alan_given

Originally posted by tsubasa at 2005-3-11 06:43 PM:


colourblindness 係recessive?
如果唔係既話咁mother有冇機會pass on個normal既allele@@?

冇記錯colourblindness係recessive,ce bio好似冇講,但阿sir講過下

alan_given

Originally posted by cmh_2002 at 2005-3-11 06:40 PM:

X唔係隱性咩?

唔明你想講咩

tsubasa

Originally posted by alan_given at 2005-3-11 06:50 PM:


冇記錯colourblindness係recessive,ce bio好似冇講,但阿sir講過下

岩岩搵返書黎睇
colourblindness is caused by a recessive allele located on the X chromosome.

colourblind father will pass the colourblind recessive allele onlyl to their daughter since they give then an X chromosome. If a mother has one normal X chromosome and one colourblind X chromosome(i.e. she is a carrier of the colorblind recessive allele) while a father is normal, their sons will have 50% chance of being colourblind.

所以因為題目話mother係colourblind, 所以一定pass on recessive chromosome, therefore 個仔好唔好彩咁100%有colorblindness, is that correct?

Newcastle Fans

The allele for (red-green) colourblindness is sex-linked and recessive.
Let N be the allele for normal vision and n be that of (red-green) colourblindness.
In B, the father has normal vision, so his genotype is XNY.
The mother has (red-green) colourblindness, so its genotype is XnXn. She is homozygous recessive.
The son has his Y chromosome from his father, and has his X chromosome from his mother. Therefore, his genotype is XnY and he is (red-green) colourblind.
The daughter has one X chromosome from each of her parents. Therefore, she is heterozygous, with genotype of XNXn. As the recessive character is masked by the dominant one, she possesses normal vision.

cmh_2002

Originally posted by alan_given at 2005-3-11 06:50 PM:


冇記錯colourblindness係recessive,ce bio好似冇講,但阿sir講過下

點解唔係a呢?

tsubasa

Originally posted by cmh_2002 at 2005-3-11 07:04 PM:

點解唔係a呢?

好似因為個女有兩個X, 而得一個係COLOURBLIND
但個仔得一個X而呢個X係COLORBLIND, 所以仔係女唔係

alan_given

Originally posted by cmh_2002 at 2005-3-11 07:04 PM:

點解唔係a呢?

colourblindness is caused by a recessive allele located on the X chromosome.
y chromosome 係唔會影響colourblindness

cmh_2002

Originally posted by tsubasa at 2005-3-11 07:07 PM:


好似因為個女有兩個X, 而得一個係COLOURBLIND
但個仔得一個X而呢個X係COLORBLIND, 所以仔係女唔係

x 係recessive嫁啵...

father都有一個colourblind既allele嫁
mather2個x都係colourblind既allele

cmh_2002

Originally posted by alan_given at 2005-3-11 07:07 PM:


colourblindness is caused by a recessive allele located on the X chromosome.
y chromosome 係唔會影響colourblindness

你即係話xy冇colorblind?

Newcastle Fans

A唔岩係因為個仔既genotype係XnY
佢既Y係黎自佢father
佢既Xn係黎自佢mother
mother一定係俾Xn佢係因為mother既genotype係XnXn
所以個仔既genotype係XnY
因為只有recessive allele, 所以就應該係colourblind

tsubasa

好confused
father has normal vision 是否=佢既x chromosome一定係normal?

Newcastle Fans

Originally posted by tsubasa at 2005-3-11 19:16:
好confused
father has normal vision 是否=佢既x chromosome一定係normal?

係
因為佢只有一條X chromosome
佢有normal vision, 所以佢既allele on X chromosome一定係N

cmh_2002

Originally posted by tsubasa at 2005-3-11 07:16 PM:
好confused
father has normal vision 是否=佢既x chromosome一定係normal?

第50題

Referring to question49, which of the following conclusion can be drawn about the genotype of alice's parent

A.her father carries an allele for normal colour vision
B.her father carries an allele for colour blindness
C.her mother is homozygous for normal color vision
D.her mother is homozygous for colour blindness


ANS :B

cmh_2002

Originally posted by cmh_2002 at 2005-3-11 07:20 PM:

第50題

Referring to question49, which of the following conclusion can be drawn about the genotype of alice's parent

A.her father carries an allele for normal colour vision
B.her father ca ...

即係話father果條x=recessive allele

alan_given

Originally posted by tsubasa at 2005-3-11 07:16 PM:
好confused
father has normal vision 是否=佢既x chromosome一定係normal?

male係xy架ma,佢得一個x chromosome,所以呢個case佢既x chromosome一定係normal

cmh_2002

Originally posted by alan_given at 2005-3-11 07:22 PM:


male係xy架ma,佢得一個x chromosome,所以呢個case佢既x chromosome一定係normal

no...睇埋question 50

Newcastle Fans

Originally posted by cmh_2002 at 2005-3-11 19:21:

即係話father果條x=recessive allele

係
因為佢兩條allele都係recessive
而其中一條係黎自佢阿爸
所以佢阿爸既X chromosome上面既allele就係recessive
而佢既Y chromosome上面就冇呢種allele
所以佢阿爸一定係colourblind

alan_given

Originally posted by cmh_2002 at 2005-3-11 07:24 PM:

no...睇埋question 50

你睇清楚第50題先,佢係問alice's parents,alice係colourblindness既female

[ Last edited by alan_given on 11-3-2005 at 07:29 PM ]

cmh_2002

Originally posted by Newcastle Fans at 2005-3-11 07:25 PM:

係
因為佢兩條allele都係recessive
而其中一條係黎自佢阿爸
所以佢阿爸既X chromosome上面既allele就係recessive
而佢既Y chromosome上面就冇呢種allele
所以佢阿爸一定係colourblind

明白了 thx 師父

[ Last edited by cmh_2002 on 11-3-2005 at 07:31 PM ]