Frequency and Location of Genes

• chiyakotiten
In summary, the F1 generation of children from the man with the blonde hair and blue eyes and the Asian woman who had no hint of blonde hair or blue eyes had a very low frequency of under-represented combinations of hair and eye color.
chiyakotiten
Hello. I'm currently studying for Biology and I'm looking over the quizzes we took in class to see what I need work on. So far, I have trouble on frequency and location of genes. Here's one of the questions I missed on the quiz (my answers are in bold):

A man with the recessive traits of blonde hair and blue eyes marries an Asian woman whose family has no hint of either blonde hair or blue eyes.

a) Provide genotypes for each, then give the gametes for each parent.
Man:
Genotype - aabb
Gametes - ab

Woman:
Genotype - AABB
Gametes - AB

Where A=dark hair; a=blonde hair; B=brown eyes; b=blue eyes

b) All their (F1) children have dark hair and brown eyes. Give their gametes, assuming that hair color and eye assort independently.
AB, Ab, aB, ab

c) One of these F1 children marries an Icelandic person with blonde hair and blue eyes. They are prolific, producing 40 children! Of these, 18 have dark hair and brown eyes; 2 have dark hair and blue eyes; 17 are blue-eyed blondes; and 3 are brown-eyed blondes. What are the under-represented gametes of the F1 generation (i.e., the gametes of the F1 child-not the Icelander-that contribute to the enumerated children)? Why is their frequency so low?
I only received points for answering Ab and aB as the under-represented gametes. Apparently, my reasoning was "inconsistent." I found the frequency of the under-represented to be 12.5%, which I'm not sure has to do with anything.

d) Give all the information you can now infer about the location of the hair color gene and the eye color gene with reference to one another (hint: consider distance).
I did not answer this one because I wasn't sure what it was asking for and I ran out of time.

I have moved this to the Homework help forum.

Hello!
If you haven't already solved it, hopefully I can be of some help...!

chiyakotiten said:
c) One of these F1 children marries an Icelandic person with blonde hair and blue eyes. They are prolific, producing 40 children! Of these, 18 have dark hair and brown eyes; 2 have dark hair and blue eyes; 17 are blue-eyed blondes; and 3 are brown-eyed blondes. What are the under-represented gametes of the F1 generation (i.e., the gametes of the F1 child-not the Icelander-that contribute to the enumerated children)? Why is their frequency so low?

I only received points for answering Ab and aB as the under-represented gametes. Apparently, my reasoning was "inconsistent." I found the frequency of the under-represented to be 12.5%, which I'm not sure has to do with anything.

You would probably need to mention what the number should be if the two genes assorted independently. There would be four different combinations, each with a probability of 0.25. Of 40 children, 10 should have AbBb, 10 Aabb, etc. Then mention what the actual number of children with each are and perhaps note the ratio? For example, the AaBb should be alleles for 10 children, but it makes up 18: $$\frac{18}{10} = 1.8$$, its nearly double what it ‘should’ be.

chiyakotiten said:
d) Give all the information you can now infer about the location of the hair color gene and the eye color gene with reference to one another (hint: consider distance).
I did not answer this one because I wasn't sure what it was asking for and I ran out of time.

If you look at the two ‘under-represented’ combinations, look at how the F1 generation received the combination of alleles it has for the two genes, and look at the possible combinations for crossing over in meiosis in the F1 generation, you can deduce a possible reason why they are under-represented. If two genes are spaced far apart, there is a higher probability of crossing over occurring between them, than if they were closer together.
I hope this makes sense….!

You were a great help! Thank you so much! :) :) :)

1. What is the frequency of a gene in a population?

The frequency of a gene in a population refers to the proportion of individuals in that population who carry a specific allele (variant) of that gene. It is often expressed as a decimal or percentage, with a higher frequency indicating that more individuals in the population carry that particular gene variant.

2. How is the frequency of a gene determined?

The frequency of a gene can be determined through various methods such as genetic testing, statistical analysis of population data, or through direct observation of physical traits associated with the gene. In some cases, the frequency may also be estimated based on known inheritance patterns and the prevalence of a particular gene in related populations.

3. What factors can influence the frequency of a gene in a population?

The frequency of a gene in a population can be influenced by a variety of factors, including natural selection, genetic drift, gene flow, and mutation. Additionally, environmental factors such as diet, lifestyle, and exposure to certain substances can also impact the frequency of a gene in a population.

4. How does the location of a gene affect its frequency?

The location of a gene, or its position on a chromosome, can play a role in its frequency in a population. Genes located on the sex chromosomes (X and Y) may have different frequencies in males and females due to their different inheritance patterns. Additionally, genes located in regions with high recombination rates may have a higher frequency due to the increased likelihood of genetic variation.

5. Can the frequency of a gene change over time?

Yes, the frequency of a gene in a population can change over time. This is due to various factors such as natural selection, genetic drift, and gene flow. For example, if a gene provides a survival advantage, it may increase in frequency over generations through natural selection. Similarly, random events can cause the frequency of a gene to fluctuate over time through genetic drift. Gene flow, or the movement of individuals between populations, can also impact the frequency of a gene by introducing new alleles or removing existing ones.

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