'Heritability of genes' questions
Post Reply
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
15-03-2013, 02:32 AM (This post was last modified: 15-03-2013 03:46 AM by PoolBoyG.)
Question 'Heritability of genes' questions
Lets use eye colour. To my understanding...

There are several genes that determine eye colour. Parents with different eye colour provide their genes. The genes for their eye colour don't mix, but one is chosen over the other. Something about about certain genes being more dominate.

Q1: What makes one gene from a parent more "dominant" than a similar gene from the other parent?
Q2: If the parents have more kids, the eye colours will be different. So what's going on there in relation to "dominant" genes? Why aren't the same genes "dominating"?

note: shame that the closest thing to a biology class that I ever had was geography.
Find all posts by this user
Like Post Quote this message in a reply
15-03-2013, 02:56 AM
RE: 'Heritability of genes' questions
(15-03-2013 02:32 AM)poolboyg88 Wrote:  Lets use eye colour. To my understanding...

There are several genes that determine eye colour. Parents with different eye colour provide their genes. The genes for their eye colour don't mix, but one is chosen over the other. Something about about certain genes being more dominate.

Q1: What makes one gene from a parent more "dominant" than a similar gene from the other parent?
Q2: If the parents have more kids, the eye colours will be different. So what's going on there in relation to "dominate" genes? Why aren't the same genes "dominating"?

note: shame that the closest thing to a biology class that I ever had was geography.

Having fathered many children I think I can answer your question.

Q1: God decided what gene Would be more dominate.
Q2: If parents have children differing eye color, it means each parent carries a recessive gene.

Vosur, Anjele, Hanoff.....have you learned nothing in my absence?
Find all posts by this user
Like Post Quote this message in a reply
15-03-2013, 08:18 AM
RE: 'Heritability of genes' questions
(15-03-2013 02:56 AM)Heywood Jahblome Wrote:  
(15-03-2013 02:32 AM)poolboyg88 Wrote:  Lets use eye colour. To my understanding...

There are several genes that determine eye colour. Parents with different eye colour provide their genes. The genes for their eye colour don't mix, but one is chosen over the other. Something about about certain genes being more dominate.

Q1: What makes one gene from a parent more "dominant" than a similar gene from the other parent?
Q2: If the parents have more kids, the eye colours will be different. So what's going on there in relation to "dominate" genes? Why aren't the same genes "dominating"?

note: shame that the closest thing to a biology class that I ever had was geography.

Having fathered many children I think I can answer your question.

Q1: God decided what gene Would be more dominate.
Q2: If parents have children differing eye color, it means each parent carries a recessive gene.

For an actual answer, start here.

Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.
[Image: flagstiny%206.gif]
Visit this user's website Find all posts by this user
Like Post Quote this message in a reply
[+] 1 user Likes Chas's post
15-03-2013, 08:28 AM
RE: 'Heritability of genes' questions
Hey, Pool.

PLOIDY

Humans are diploids, meaning we have two copies of our chromosome sets, one from our father, one from our mother.

Our parents too have two copies. They, at random, each give us one of their copies.

GENES

Each chromosome set contains genes. If you line up the chromosomes, the genes are in the same position. The chromosomes are HOMOLOGOUS.

ALLELES

An allele is the variant of a given gene, like say blue eyes.

Alleles are at the same position on the homologous chromosome, they're just variants.

ALLELE PAIRS

Diploid chromosomes are always in pairs. So alleles are always in pairs.

Homozygous allele pairs are identical.

Heterozygous allele pairs are different.

DOMINANT/RECESSIVE

Some alleles are dominant and some alleles are recessive. The combination of dominant and recessive alleles is what determines if the allele pair is homozygous or heterozygous.

Which allele is used is based on dominance relationship.

DOMINANCE RELATIONSHIP

There are three kinds of dominance relationship

-Simple dominance
-Partial dominance
-Co-dominance

SIMPLE DOMINANCE

There are three possible allele pair combinations

-Dominant/Dominant (Homo)
-Dominant/Recessive (Hetero)
-Recessive/Recessive (Homo)

Dominant genes are usually expressed over recessive ones. So the dominant gene is expressed 2 out of 3 times.

For example, say there's two alleles: brown eyes and blue eyes. Say the brown eye allele is dominant and the blue is recessive.

Brown/Brown = Brown eyes
Brown/Blue = Brown eyes
Blue/Blue = Blue eyes

PARTIAL DOMINANCE

The exception to the rule is that sometimes, in heterozygous allele pairs, BOTH the dominant and recessive genes are expressed, creating an intermediate trait.

So say the allele pair is for red flowers (dominant) and white flowers (recessive). When both alleles are expressed, perhaps the expressed trait is a pink flower.

CO-DOMINANCE

Co-dominance can occur when a phenotype (the allele expressed within the context of its environment) is controlled by three or more allele types.

Blood type is a perfect example.

A and B are both dominant, while O is recessive.

So the blood types are:

AA = A - Simple dominance
BB = B - Simple dominance
AO = A - Simple dominance
BO = B - Simple dominance
OO = O - Simple dominance
AB = AB - Co-dominant

Now you know why type O blood is the most rare.

Co dominant traits are NOT the same as partial dominance. They do NOT create intermediate traits.

Co-dominant traits don't mix, they are both present. So in the case of our red and white flowers, the co-dominant flower would be BOTH red and white.

Q1: WHAT MAKES A DOMINANT GENE DOMINANT AND A RECESSIVE ONE RECESSIVE?

I have no fucking idea.

All I know is that alleles are dominant "because they're dominant".

Also, alleles are dominant and recessive, not as absolutes, but in relation to one another. Theoretically, an allele that is recessive to one allele could be dominant to another.

That being said, dominance is standardised. Ie, blue is always recessive to brown (for whatever reason).

But yeah, I have no idea what specific property makes one allele dominant and one recessive.

Q2: MORE KIDS

Every time you have a child, which of your two chromosome sets you give to your offspring is different.

Furthermore, in Prophase I of Meiosis, CROSSOVER occurs. Part of the mother's chromosome is transferred to the father's chromosome and vice versa. The result is RECOMBINATION.

Every time you have a child, RECOMBINATION is different.

Because of this, the ALLELE PAIRS are different.

So one child might have brown eyes (brown/brown) the second might have brown (brown/blue) but the third might have blue (blue/blue).

FURTHER DOWN THE LINE

You always have two copies of chromosomes.

A recessive gene can be inherited over several genereations and never be expressed. Then one day, it finds another recessive and poof, there it is.

That's why children sometimes have traits that neither parent has. Ie, both parents have dark hair and their kid is born a ginger.

GENETIC DISEASES

This is problematic for some genetic diseases.

For example, many people have an allele that in its dominant form gives them a natural immunity to the malaria parasite. So as long as the dominant version is expressed, they're good. But in it's recessive form, it causes sickle cell anemia. So parents can carry the recessive gene for generations and have no problems. But if two parents that are carriers of the recessive gene procreate and their offspring winds up with a double recessive allele pair, poof, they have sickle cell anemia.

FURTHER INFORMATION

Check out these two videos from the Khan Academy.








WE OUT!

Hope that was helpful.

Peace and Love and Empathy,

Matt
Find all posts by this user
Like Post Quote this message in a reply
[+] 4 users Like Ghost's post
15-03-2013, 10:40 AM
RE: 'Heritability of genes' questions
(15-03-2013 02:32 AM)poolboyg88 Wrote:  Lets use eye colour. To my understanding...

There are several genes that determine eye colour. Parents with different eye colour provide their genes. The genes for their eye colour don't mix, but one is chosen over the other. Something about about certain genes being more dominate.

Q1: What makes one gene from a parent more "dominant" than a similar gene from the other parent?
Q2: If the parents have more kids, the eye colours will be different. So what's going on there in relation to "dominant" genes? Why aren't the same genes "dominating"?

note: shame that the closest thing to a biology class that I ever had was geography.
What makes one gene dominant over another similar gene? Here are a few possibilities. The dominant gene is able to encode a protein that is able to silence the recessive gene OR the dominant gene is able to encode for a protein that is able to interact with the protein coded by the recessive gene.

Why aren't the same genes dominating? Let's say two parents who have blue eyes produce a child with brown eyes. Let's assume one one type of gene encodes for eye colour. Let's assume the blue eye gene (B) is dominant, while the brown eye gene (b) is recessive.

Now, during a process called meiosis, gametes are produced. Each gamete (sex cell) only takes half of the original chromosome set. So let's say if I have 46 chromosomes in my body cells, my gametes will only have 23 chromosomes. You will get different sets of chromosomes through this process.

Let's say if I have a sperm that contains gene B (blue eyes) while an egg that contains gene b (brown eyes). Gene B is dominant to gene b, and thus will override the effects of the brown eye gene. The child will thus have blue eyes.

If I have two parents who have both Bb, which means they have one blue eye gene and one brown eye gene, both parents will have blue eyes. However, both of them are able to produce kids with brown eyes. This occurs when the sperm and the egg both carry a copy of the brown eye gene. As the blue eye gene is not present, the brown eye gene will be able to codes for proteins to create brown eyes without being interfered by the blue eye gene.

That's the basics. I just realised Ghost covered a lot. You may find his post and videos especially helpful. All the best Smile

Welcome to science. You're gonna like it here - Phil Plait

Have you ever tried taking a comfort blanket away from a small child? - DLJ
Find all posts by this user
Like Post Quote this message in a reply
24-03-2013, 07:47 AM
RE: 'Heritability of genes' questions
Thank you to the comprehensive replies. I'll have to take a couple passes to comprehend everything.

What got me thinking was whether adaptive traits, although present in genes, could never be inherited. The thinking was something along the lines of "Elephants have allele for longer hair, but what if they were recessive, and so would never be adopted, which would prevent the evolution of "Mammoth" like species."
Find all posts by this user
Like Post Quote this message in a reply
24-03-2013, 10:42 AM
RE: 'Heritability of genes' questions
Hey, Pool.

One must be careful. Selection does not happen at the level of the genome. Alleles do not get selected for or against. Selection occurs at the level of the phenotype. That is to say, when the allele is expressed within it's proper environment, then and only then can it be selected for/against. The consequence of that selection is a rise or fall in allele frequency.

A recessive gene for long hair WOULD be expressed whenever the offspring had a double recessive homozygous allele pair.

If mammoth hair was recessive, then yes, only offspring with the double recessive gene would have the hair. BUT, the difference between having short bristles and having long shag, from the standpoint of surviving a particular environment, is, excuse the pun, mammoth. If the bald elephants (bald being different than hairless) all freeze to death before they can procreate, then the baldness allele would slowly be eliminated from the gene pool. If wooly mammoths all died from heat exhaustion when trying to outrun predators (or got caught by those same predators) then that allele would eventually disappear.

Peace and Love and Empathy,

Matt
Find all posts by this user
Like Post Quote this message in a reply
[+] 1 user Likes Ghost's post
Post Reply
Forum Jump: