Pleasneed assistance with these
1.If an organism is homozygous dominant, homozygous recessive or heterozygous for a
particular trait, in terms of the alleles, what does that mean?
2.How many different types of gametes could a person with the genotype AABbCc produce?
3.Suppose male fruit flies with the HHNN genotype mate with female flies with the hhnn
genotype. H= hairy leg, h= hairless legs; N= normal wings, n=shriveled wings. About what
percentage of offspring flies will have hairy legs and normal wings?
4.DNA exists as a double helical structure, if you know the DNA sequence of one of the strands,
you can easily determine the sequence of the complementary strand. Explain how this is
possible.
5.After sequencing a molecule of DNA, you discover that 20% of the bases are cytosine
(C).What percentage of the bases would you expect to be guanine (G)?What percentage of the
bases would you expect to be thymine (T)?
6.One of the most important functions of DNA is new protein production/synthesis. Explain the
role of (a) transcription and (b) translation in the production/synthesis of proteins.
Solution
1. Characters are usually governed by two alleles (copies) of a gene that reside on a pair of
chromosome. For example, in the pea plant, the plant height (character) may have be governed
by tall (T) or short (t) alleles. A pea plant will have two copies of the allele for plant height; all
combinations are possible, i.e. TT, tt and Tt. The T allele is dominant over the t allele, i.e.
individuals bearing one copy of T allele and one copy of t allele will be tall, not short. Therefore,
the genotypes TT, tt and Tt are also called homozygous dominant, homozygous recessive or
heterozygous, respectively.
2. Individuals with NN or nn genotype produce only 1 (i.e. N or n, respectively) type of gametes.
An individual with Nn genotype produces 2 (i.e. N and n) type of gametes.
Therefore, individual AABbCc will produce 1×2×2 = 4 types of gametes.
3. The HHNN males will produce only one type i.e. HN gametes. Similarly, hhnn females will
also produce only one type i.e. hn gametes. Thus, all progeny (100%) will be HhNn genotype,
i.e. hairy with normal wings.
4. The \'complementary\' strand indeed bears a complementary sequence and hence the name. A
always pairs with T, and G always pairs with C. Thus, if the sequence of bases on one strand is
known, the sequence of the complementary sequence can be determined by equating the
complementary base.
5. 20% bases are C. C always pairs with G. Thus, G must also be 20%. G+C = 20+20 = 40%.
The remaining 100-40 = 60% must be A+T. Again A always pairs with T, and hence, A and T
are equal. Thus, T must be 60/2 = 30%.
6. DNA bears the genetic code. This genetic code is first transcripted into RNA. Three types of
RNA i.e. mRNA (m=messenger), tRNA (t=transfer) and rRNA (r=ribosomal) form the basic
machinery for synthesis of proteins. The process of transcription is, therefore, responsible for
generating the basic machinery on whi.
Pleasneed assistance with these1.If an organism is homozygous domi.pdf
1. Pleasneed assistance with these
1.If an organism is homozygous dominant, homozygous recessive or heterozygous for a
particular trait, in terms of the alleles, what does that mean?
2.How many different types of gametes could a person with the genotype AABbCc produce?
3.Suppose male fruit flies with the HHNN genotype mate with female flies with the hhnn
genotype. H= hairy leg, h= hairless legs; N= normal wings, n=shriveled wings. About what
percentage of offspring flies will have hairy legs and normal wings?
4.DNA exists as a double helical structure, if you know the DNA sequence of one of the strands,
you can easily determine the sequence of the complementary strand. Explain how this is
possible.
5.After sequencing a molecule of DNA, you discover that 20% of the bases are cytosine
(C).What percentage of the bases would you expect to be guanine (G)?What percentage of the
bases would you expect to be thymine (T)?
6.One of the most important functions of DNA is new protein production/synthesis. Explain the
role of (a) transcription and (b) translation in the production/synthesis of proteins.
Solution
1. Characters are usually governed by two alleles (copies) of a gene that reside on a pair of
chromosome. For example, in the pea plant, the plant height (character) may have be governed
by tall (T) or short (t) alleles. A pea plant will have two copies of the allele for plant height; all
combinations are possible, i.e. TT, tt and Tt. The T allele is dominant over the t allele, i.e.
individuals bearing one copy of T allele and one copy of t allele will be tall, not short. Therefore,
the genotypes TT, tt and Tt are also called homozygous dominant, homozygous recessive or
heterozygous, respectively.
2. Individuals with NN or nn genotype produce only 1 (i.e. N or n, respectively) type of gametes.
An individual with Nn genotype produces 2 (i.e. N and n) type of gametes.
Therefore, individual AABbCc will produce 1×2×2 = 4 types of gametes.
3. The HHNN males will produce only one type i.e. HN gametes. Similarly, hhnn females will
also produce only one type i.e. hn gametes. Thus, all progeny (100%) will be HhNn genotype,
i.e. hairy with normal wings.
4. The 'complementary' strand indeed bears a complementary sequence and hence the name. A
always pairs with T, and G always pairs with C. Thus, if the sequence of bases on one strand is
known, the sequence of the complementary sequence can be determined by equating the
complementary base.
2. 5. 20% bases are C. C always pairs with G. Thus, G must also be 20%. G+C = 20+20 = 40%.
The remaining 100-40 = 60% must be A+T. Again A always pairs with T, and hence, A and T
are equal. Thus, T must be 60/2 = 30%.
6. DNA bears the genetic code. This genetic code is first transcripted into RNA. Three types of
RNA i.e. mRNA (m=messenger), tRNA (t=transfer) and rRNA (r=ribosomal) form the basic
machinery for synthesis of proteins. The process of transcription is, therefore, responsible for
generating the basic machinery on which proteins can be synthesized. In the process of
translation, the tRNA and rRNA (along with many other factors) use the information in the
mRNA to produce a specific protein. The process of translation is, therefore, the process that
reads out the genetic code essentially provided by the DNA through mRNA.
