Tuesday, October 31, 2006

Why you and your little sister look different...

Hey, that was fun! I got quick and correct responses back from Chelsea, Jackie, and Stephanie. The answer to the question below is indeed c: there are 8 homologous pairs.

Here's your next question -- this one is short answer, and you have to explain your answer.
  • There are three ways genetic variablility is generated in the offspring of sexually reproducing organisms like most animals. What are they?
  • For extra brain stretching, think about organisms like plants, lizards and insects that reproduce asexually. What kind of variablility would their offspring still have?


catherine nguyen said...
This comment has been removed by a blog administrator.
Anonymous said...

Dr. Williams, in the second point of the previous post, did you mean to say humans have 46 (instead of 42) chromosomes?


Adrienne Williams said...

Yes, thanks Catherine! It's fixed now.

Anonymous said...

That picture of those lovely ladies distracted me.
So what was the question about? And even more important who are those lovely ladies?

Adrienne Williams said...

Catherine had the right answer above. I've hidden it to encourage other answers.
And I'm afraid the women in the photo are from a random flickr shot. Sorry, no introductions possible. Try to focus... :)

Gwyneth said...

Question 1: 3 sources of genetic variability:
1- In the interphase of Meiosis, the process of crossing over occurs. It happens randomly. Thus, the possibility from different crossing over creates variability.
2-Independent alignment of Homologous Chromosome during Prophase I in Meiosis.
3- The law of segregation also states that "the two alleles for a heritable character segregate during gamete formation and end up in different gametes". It means if the allele is heterozygous, then "50% of the gametes receive the dominant allele and 50% receive the recessive allele". Therefore, it creates variability when each parent randomly "give" gametes in fertilization.

Question 2: Variability in Asexual reproduction
- DNA can be replicated wrongly during the S phase of Mitosis (which may lead to mutation).Thus it creates variability. When the environment changes, some mutation can become advantages. Thus, there's variability.

Gwyneth L
Fri 1

Lindy G said...

i know i know..

1. crossing over
2. independent assortment
3. law of segregation

then the second question answer is the changes of DNA, or mutation

Robert Lin said...

1. saw of segregation
2. crossing over
3. independant assortment

The only variability in asexual reproduction is during the replication of DNA.