Answer+key+activities+from+unit+3+Mendelian+Genetics

=__Unit 3 Mendelian Genetics:__= =__Page 61 lethal genes. Q 14__= =Absence of legs in bulls and cows is caused by a recessive lethal gene.= =P: Pp X Pp= =F1__=
 * || =**P**=

= = || =p= ||
 * =P= || =PP= || =Pp= ||
 * =p= || =Pp= || =pp= ||

Genotypes 1/3 PP 2/3 Pp Phenotypes 100% with legs _._._._._._:- Q.16 Results of quantitative inheritance:

reptile´s leg length

mammal´s height

Page 63 Q. 18

Two linked genes that are in the same pair of chromosomes tend to be transmitted together, but can be

separately if genetic recombination takes place during prohase I of Meiosis.

Q 19.

The chromosome theory of inheritance is able to explain the cases that did not follow Mendel´s third law because the genes can be independent ( in which case they follow Mendel´s third law ) or

linked (they do not follow the law if recombination does not take place).

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Q.31

A woman carries in one of her X chromosome a lethal recessive gene(l), the other X chromosome has a normal dominant one(L).

If this woman has offspring with a normal man, What will the ratio of their sex be?


 * P || **XXl** || **X** || XY ||
 * || =X= || =Y= ||
 * =X= || =XX= || =XY= ||
 * =**Xl**= || =XX= || =**Xl**Y= ||

2/3 WOMEN

1/3 MEN

Q. 32

Alopecia is determined by gender and is dominant in males and recessive in females A alopecia N no alopecia Identify the genotype of a __man with alopecia whose father was not bald__

his __wife who is not bald but her mother was__

their future children?

Not bald NN (Grand-father)

Bald **NA** (Father)X **NA** Mother is not bald, but her mother was bald(AA)


 * || =N= || =A= ||
 * =N= || =NN= || =NA= ||
 * =A= || =NA= || =AA= ||

Males that have AA and AN genotypes will be bald, but only the females with the genotypes AA will be bald.

As a result, 3/4 of male offspring will be bald (AA and NA) and just 1/4 of female offspring will be bald.(AA)

Page 72

Q. 35 Cells involved in the transmission of characteristics from parents to offspring? Gametes Q.36.Pure-bred individuals for a particular characteristic are those that have the same alleles in their homologous chromosomes. They are also known as homozygotes.

Hybrid individuals for a particular characteristic are those that have different alleles in ther homologous chromosomes. They are also known as heterozygotes.. Q. 37 Genotype of the guinea pig shown in the image: nn. The genotypes of both parents could have been black ( Nn). Q38 In pea plants, purple flowers are dominant over white and tall stems are dominant over short stems.

We can deduce the genotype of a tall pea plant with purple flowers carrying out a backcrossing (cruzamiento prueba) with a recessive homozygote for both characteristics. If the offspring have a recessive phenotype for any of the characteristics, this means that the plant was heterozygous for that characteristic. Q. 39 Correct answer: All yellow Q. 41.Curly hair is dominant and smooth hair is recessive. Black fur is dominant over white. a) RRNN X rrnn F1 will be RrNn b)Final result of the Punnet Square: 9/16 curly, black hair 3/16 curly, white hair 3/16 smooth, black hair 1/16 smooth, white hair Q. 47 An animal that has sex determination through the system XX/XY has 25 chromosomes in one cell. Is it a somatic cell or a gamete? It is a gamete ( a sex cell) because 25 is an odd number and the diploid number is always even. Q. 49 In your notebook, draw a range of possibles gametes in an individual that has the following chromosomes:

If genetic recombination does not occur, the gametes will be: AbD, Abd, aBD, aBd If recombination occurs, there will be more possible combinations: AbD, Abd, aBD, aBd, ABD, abD, ABd y abd Q. 50 Correct answer: c. 50% Q. 55. Correct answer: b. recessive