Bio Questions from Destroyer

[tawaqul]

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1) On #57 it says that birds have a long loop of henle and thus have concentrated urine. Why is this? I know that as the urine descends the loop, it becomes more concentrated and as it ascends, it becomes diluted, and Cliffs says at the end of the loop, the filtrate is NOT more concentrated (p.191). So why would this be?

2) On #127, it says that differentiation will arise as a result of selective gene expression. What does that mean? I don't even understand the statement...

3) On #158, it says that an egg cell has 23 chromosomes and 23 chromatids. I understand the egg cell is haploid, which makes it have 23 chromosomes, but why doesn't have double the chromatids?

4) On #160, it says, "The frequency for the allele for cystic fibrosis, an autosomal recessive trait is 1/2500 among white americans. What is the heterozygote frequency? The answer is 4%.

What I don't understand here, is usually when they give you the frequency of an allele, they are giving you p or q. When they give you a phenotypic percentage, they are giving you p^2 or q^2. That's how I've done all the other problems correctly. Here, however, they use 1/2500 as equal to q^2 which confuses me...shouldn't it just be q-- the recessive allele frequency?

5) How can a male be heterozygous? All there is is an X and Y and the X is the only one with any allele on it...

Thanks in advance, I didn't want to post 5 threads.

 

[ksksks]

1) On #57 it says that birds have a long loop of henle and thus have concentrated urine. Why is this? I know that as the urine descends the loop, it becomes more concentrated and as it ascends, it becomes diluted, and Cliffs says at the end of the loop, the filtrate is NOT more concentrated (p.191). So why would this be?

2) On #127, it says that differentiation will arise as a result of selective gene expression. What does that mean? I don't even understand the statement...

3) On #158, it says that an egg cell has 23 chromosomes and 23 chromatids. I understand the egg cell is haploid, which makes it have 23 chromosomes, but why doesn't have double the chromatids?

4) On #160, it says, "The frequency for the allele for cystic fibrosis, an autosomal recessive trait is 1/2500 among white americans. What is the heterozygote frequency? The answer is 4%.

What I don't understand here, is usually when they give you the frequency of an allele, they are giving you p or q. When they give you a phenotypic percentage, they are giving you p^2 or q^2. That's how I've done all the other problems correctly. Here, however, they use 1/2500 as equal to q^2 which confuses me...shouldn't it just be q-- the recessive allele frequency?

5) How can a male be heterozygous? All there is is an X and Y and the X is the only one with any allele on it...

Thanks in advance, I didn't want to post 5 threads.

A1) You know that as you get deeper inside the cortex, the level of concentration of ions increase right? Therefore, if the loop of Henle is long, you get deeper into the cortex, hence the concentrated urine.

A2) Selective gene expression is a function where body goes through in the beginning to allow transcription to occur in order for baseline cells to become different organs, tissues, etc (this is differentiation). It is selective to allow consistency in development (example: the sequence of organ development)

A3) Because it has not replicated yet. A replicated chromosome will have x2 the chromatids

A4) Yes you are right. But it's asking for heterozygous frequency 2pq

A5) Check the definition of heterozygous...I can't really explain this one...Its just something that you know...

 

[tawaqul]

thanks--but if you calculate the heterozygote frequency (2pq) with the way I think it should be done, you don't get the correct answer.....?

 

[tawaqul]

still not understanding 4), anyone?

 

[Gbrando2]

I don't get #4 either, but as for #5 men cannot be heterozygous for sex-linked traits since they only have 1 X. However, for normal autosomal traits males can be heterozygous just as much as women ie Gg Nn Rr etc.

 

[tawaqul]

I don't get #4 either, but as for #5 men cannot be heterozygous for sex-linked traits since they only have 1 X. However, for normal autosomal traits males can be heterozygous just as much as women ie Gg Nn Rr etc.

But on #107 in Destroyer the question talks about a heterozygous brown-eyed man and a green-eyed woman...so here, a man is heterozy for a sex linked trait...right?

 

[Gbrando2]

But on #107 in Destroyer the question talks about a heterozygous brown-eyed man and a green-eyed woman...so here, a man is heterozy for a sex linked trait...right?

Is eye color sex linked? I know colorblindess is, but not sure about eye color. I always thought it was several alleles that determined eye color

 

[tawaqul]

so you're saying I could just do this problem without X's and Y's, and just use Bb for the man or something? I feel like this should be so basic, why am I confused!! lol

 

[Gbrando2]

so you're saying I could just do this problem without X's and Y's, and just use Bb for the man or something? I feel like this should be so basic, why am I confused!! lol

Yes, unless someone else can correct me, eye color isn't sex linked (which would make it impossible for the man to be heterozygous) so you can just use Bb

 

[tranv117]

1) On #57 it says that birds have a long loop of henle and thus have concentrated urine. Why is this? I know that as the urine descends the loop, it becomes more concentrated and as it ascends, it becomes diluted, and Cliffs says at the end of the loop, the filtrate is NOT more concentrated (p.191). So why would this be?

2) On #127, it says that differentiation will arise as a result of selective gene expression. What does that mean? I don't even understand the statement...

3) On #158, it says that an egg cell has 23 chromosomes and 23 chromatids. I understand the egg cell is haploid, which makes it have 23 chromosomes, but why doesn't have double the chromatids?

4) On #160, it says, "The frequency for the allele for cystic fibrosis, an autosomal recessive trait is 1/2500 among white americans. What is the heterozygote frequency? The answer is 4%.

What I don't understand here, is usually when they give you the frequency of an allele, they are giving you p or q. When they give you a phenotypic percentage, they are giving you p^2 or q^2. That's how I've done all the other problems correctly. Here, however, they use 1/2500 as equal to q^2 which confuses me...shouldn't it just be q-- the recessive allele frequency?

5) How can a male be heterozygous? All there is is an X and Y and the X is the only one with any allele on it...

Thanks in advance, I didn't want to post 5 threads.

1) Someone mentioned that the Loop of Henle extends into the cortex, but actually it extends into the medulla. Basically, the descending Loop of Henle is very permeable to water making urine more concentrated while the thick ascending Loop of Henle is practically impermeable to water. So the longer the LOH, the more water is reabsorbed making for more concentrated urine.

2) Selective gene expression... Basically somatic cell in your body contains the exact same DNA makeup. So what makes an eye cell into an eye and what makes skin cells into skin? Differentially regulating genes in different cells will bring about different cell characters.

3) I think that chromatids are just the copied chromosomes after S phase or during cell division. After division, the # of chromosomes and chromatids are equal. But during division when you have twice the amount of Chromosomes due to replication, chromatids = twice the amount of chromosomes.

4) P^2 + 2PQ + Q^2 is the genotypic frequency and not the phenotypic frequency. ie. Homozygous dominant, heterozygous, and homozygous recessive. If you're talking about phenotype, theres only two phenotypes...unless you're talking about for example Codominance such as in blood type.

5) Heterozygous for an autosomal trait.