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3.5.1. Inheritance of a character (problems solved)

Inheritance of a character solved problems. (Page 1)

We will start by doing genetic problems based on Mendel's first and second laws. I recommend that you do it on paper and then check the result by clicking on "Showing feedback ".

Although the resolution process is the same, we have grouped exercises related to:

As the collection increases, in addition to the problems of genetic inheritance of a character on this page (1) and those of the pages that we have just named (albinism, Rh blood group and eye color), other pages have been made:

Nomenclature for genetic problems

In problems where the trait is determined by two alleles of a gene (monohybridism, dominance / recessiveness), we will use the same letter, since it is the same gene. For example, A and a. We will preferably use the initial of the dominant character, except if it is confusing when writing it by hand (such as O yo, for example). Thus, we will use A as dominant and as recessive, and the possible genotypes are AA, Aa and aa.
Problem solving by gametic board:

Male gametes
A a
Female gametes A AA Aa
a Aa aa

Genetics problem 1

In a certain species of plants the blue color of the flower (A) dominates over the white color (a) .

How will the descendants of the crossing of plants with homozygous  blue flowers with plants with white flowers, also homozygous, be like?

Genetics problem 2

A white-haired guinea pig, whose parents are black, is crossed with another with black hair, whose parents are black-haired one of them and the other white. What will the genotypes of the interbreeding guinea pigs and their offspring be like?

Genetics problem 3

A curly-haired dog and a curly-haired female dog had a straight-haired puppy and a curly-haired one. What will the genotype of the couple and the puppies be like?  Curly hair (R) dominates over straight hair (R).

How would you know if the curly-haired puppy is purebred for that character by a single cross?

Genetics problem 4

A type of inherited deaf-mutism is caused by the existence of a recessive gene (s).  If a man and a woman with normal hearing, whose mothers are both deaf, have a child, what are the chances that he is deaf-mute?

Genetics Problem Simulator

With this simulator you can ask yourself the problem of genetics by choosing the parents and checking the genotypes and phenotypes of the offspring. In these frogs, the green color is dominant over the gray. Choose if the frogs are AA, Aa or aa, think about how the descendants can be, and analyze the result in this frog creation simulator.

Here's another simulator to practice with Mendel's 1st and 2nd law problems, but without frogs this time.

Simulator: Practice posing your own problems on Mendel's First Two Laws.

Simulator: Crossing frogs. Try to find a partner with a frog to obtain the descent that they offer you. It is not as easy as it looks. Highly recommended to do it, and fun.

Genetics problem 5

Some types of myopia depend on the existence of a dominant gene (A), while the gene for normal sight is recessive (a).

What genotypes and phenotypes will the children of a man with normal vision and a myopic heterozygous woman have?

Genetics problem 6

Whether humans can "make the carrycot with their tongue" or "roll their tongue in a U" depends on a dominant gene (L), while the gene that determines not being able to fold it is recessive (l). Ramón can roll it up, but María, his wife, can't. José, Ramón's father, can't roll it up either.
What is the probability that the children of Ramón and María can roll their tongues in a U?


Genetics problem 7

In humans, spike hair (or widow's peak) depends on a dominant gene (W), while the gene that determines straight hair is recessive (w).

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What will be the children of a man with spike hair, homozygous , and a woman with straight hair, homozygous?

Genetics problem 8

Mar has curly hair and Pedro, her partner, has straight hair. They are expecting a child and are wondering how he will have hair. Mar says that he will have it straight because his father (the maternal grandfather of the future child) had straight hair. Pedro, on the other hand, thinks that it will be curly because his parents (the child's paternal grandparents) had curly hair.

Knowing that it is an autosomal (not sexual) character, help Mar and Pedro and explain what the family genotypes are like and how their future child will have hair.


Genetics problem 9

When Mendel crossed a purple-flowered pea plant with another one with white flowers, obtained an F1 formed entirely by plants with purple flowers. When crossing the F1 individuals, he obtained an F2 formed by plants with purple flowers and white flowers in the ratio 3: 1. 
It represents the crosses described and symbolizes the two alternatives of the gene that controls the color of the flowers.

Genetics problem 10

In a breed of rabbit, short hair (A) is dominant over long hair (a). The following crosses were made, obtaining the following results:



a. short x long

1/2 short and 1/2 long

b. short x short

All short

c. short x long

All short

d. long x long

All long

Explain the genotypes used in each cross.


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