gamete formation.... variability of offspring (1 Viewer)

[valentino]

hey does any one have an info or answere to this dot point, coz for some reason my book is crap at explaining it

•explain the role of gamete formation and sexual reproduction in variability of offspring

valentino: stop posting threads with stupid titles. make the titles relevant. i'm sick of opening your threads and finding stuff that's already been covered. consider this a first warning. - babydoll_

 

[Tommy_Lamp]

Gamete formation results in the halving of the chromosome number (haploid) and sexual reproduction results in combining gametes to produce a diploid organism (2n). The processes involved in this result in variability of the offspring.
Gametes are formed during the process of meiosis. In meiosis there are two stages that lead to variability. These are the random segregation of genes and the process of crossing over.
In sexual reproduction each female or male cell produces 4 sex cells from the process of meiosis. Each of these sex cells has half the normal chromosome number and has a random assortment of genes from the parent. The alleles are separated and the sex cells have a random assortment of dominant and recessive genes. More variability is introduced depending on which sex cell is successful in fertilisation. The resulting embryo has a completely different set of genes from either of the parents.

 

[silvermoon]

sorry, just to clarify tommy_lamp (not that ur explanation isnt great, but bio confuses me ):
Is it the two stages in meiosis (crossing over and random segregation) that allows for the variability in sexual reproduction - ie. the random assortment of parental genes? sorry, this probably such a stupid and obvious question, im just really bad at this topic. any help much appreciated.

 

[babydoll_]

Yes - the random assortment of parental genes allows for the variability in sexual reproduction. Basically, some genes swap around, which allows for variation

 

[xiao1985]

doesn't random segregation happen at the site of crossin over tho??? @@

 

[malkin86]

there's both I think.. random assortment and crossing over...

 

[xiao1985]

there's both I think.. random assortment and crossing over...

hwo does random assortment happen[edit] if [/edit] there's no crossin over??

 

[iambored]

from what i understand -
CROSSING OVER
crossing over is when parts of the chromosomes swap, so the offspring don't get the same identical chromosomes as their parents

RANDOM ASSORTMENT
all people have 2 of each type of chromosomes. random assortment is when get one or the other of the chromosome. for example:

your mother's chromosomes: (lower case = maternal (from her mother), upper case = paternal (from her father)

aA
bB
cC
dD

can make combinations of:
ABCD
abcd
AbCD
abCd
ABcD
etc.

none of the above would be identical cells, they all have different chromosomes




random assortment can happen if there's no crossing over because it's just to do with whole chromosomes.

combine random assortment with the (almost infinite?) number of chromosomes that can be made by crossing over and you get VERY varied cells.

 

[xiao1985]

iambored: point taken, but may i draw ur attention to sutton's contribution to blueprint of life: observed similarities between the behavior of chromosomes during meiosis (crossing over) and mendel's law of random assortment (random assortment)...

 

[t-i-m-m-y]

xaio: how do you find to time to post on BOS so much you've overtaken my post count
babydoll_: harsh hey okay enough spamming else i'll get banned


valentino: basically gamete formation=meiosis
sexual reproduction=fertilisation

Your questions have been answered, but I think its easier to spearate gamete formation and sexual reproduction.

Gamete formation- the gametes formed in meiosis are not identical to the parent ones, due to crossing over etc

Sexual reproduction- you take some of your fathers genes, some from your mother. You are going to be different from your parents.

Its a simple explanation, but I hope it helps

 

[Tommy_Lamp]

timmy managed to condense my 7 line answer into 2

welldone

 

[malkin86]

Diagrams always help...

http://genetics.gsk.com/chromosomes.htm#celldivision

 

[t-i-m-m-y]

a textbook helps too