BIOLOGY 1107 MASTERING BIOLOGY 11 HW

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the genotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

0 homozygous black (BB): 1 heterozygote (black) (Bb): 1 homozygous orange (bb) The heterozygous black-eyed MendAlien has the genotype Bb. The orange-eyed MendAlien has the genotype bb. The result of this cross is two Bb offspring and two bb offspring. this 2:2 ratio reduces to 1:1

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

1 black: 1 Orange The heterozygous black-eyed MendAlien has the genotype Bb. The orange-eyed MendAlien has the genotype bb. The result of this cross is two Bb offspring and two bb offspring. This means that two of the offspring have black eyes and two of the offspring have orange eyes. This 2:2 ratio then reduces to 1:1.

Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?

25 The offspring would be in a 3:1 ratio of normally pigmented mice to albino mice.

What number and types of chromosomes are found in a somatic cell in an animal with a diploid number of 48?

48 chromosomes (24 from each parent, including one sex chromosome from each) >>>>>>>>>>>>>>>>>>>> If you had trouble with this question, review the following material: All somatic cells in animals have two sets of chromosomes, one haploid set (n) from each parent, and each set includes one sex chromosome. For an animal with a diploid number of 48 (2n = 48), the number of chromosomes in the somatic cells is 48 and the number of chromosomes in each haploid set is 24 (n = 24). Humans have a diploid number of 46 (2n = 46), and the number of chromosomes in each set is 23 (n = 23), including one sex chromosome.

Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?

A combination of polygenic inheritance and environmental factors. >>>>>>>> Many genes (polygenic inheritance) control height in humans, giving an overall normal distribution. Environmental factors such as nutrition smooth out the curve.

Which of these is a testcross?

A? * aa A testcross is used to determine whether an individual expressing the dominant phenotype is homozygous dominant or heterozygous.

What is the difference between heterozygous and homozygous individuals?

All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ. Since homozygotes carry two identical copies of a gene, all of the gametes will carry the same version. Heterozygotes have two different versions, so there will be two different types of gametes

What is an allele?

An alternative version of a gene A diploid organism carries two alleles for each autosomal gene. The two alleles are found at comparable locations (loci) on homologous chromosomes. The alleles may be identical or slightly different, but they affect the same genetic character.

The result of the following cross indicates that genotypically the offspring _____.

Are all Rr This cross indicates that the wild type head top allele is dominant to the flat head top allele, so all offspring are indeed Rr.

A botanist has acquired a group of sweet pea plants. All of the plants have yellow pea pods (the recessive trait), except for one, which has green pea pods (the dominant trait). Pea pod color is a trait caused by a single gene. In this tutorial, you will determine how the botanist can identify the genotype of the green pea pod, and how this relates to Mendel's laws and meiosis. How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?

Cross the green-pod plant with a yellow-pod plant. A cross between a plant of unknown genotype and one that is known to be homozygous recessive is called a test cross because the recessive homozygote tests whether there are any recessive alleles in the unknown. Because the recessive homozygote will contribute an allele for the recessive characteristic to each offspring, the second allele (from the unknown genotype) will determine the offspring's phenotype.

True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.

False A dominant phenotype is indeed expressed if the individual is homozygous dominant for that trait, but the dominant phenotype is also expressed if the individual is heterozygous for the trait. In fact, heterozygous expression is the definition of dominant.

Select the correct explanation for the fact that a carrier of a recessive genetic disorder does not have the disorder.

In a recessive disorder, only a single functioning allele is necessary to determine a normal phenotype.

Which of the following is true about a plant with the genotype AABbcc?

It is homozygous at two loci. An organism having a pair of identical alleles at a given locus is said to be homozygous for that locus. Here, the plant is homozygous at loci A and C.

In 1981, a stray black cat with unusual rounded, curled-back ears was adopted by a family in California. Thousands of descendants of the cat have since been born, and cat fanciers have developed the curl cat into a show breed. Suppose you owned the first curl cat and wanted to develop a true-breeding variety. How would you determine whether the curl allele is dominant or recessive?

Matings of the original mutant cat with true-breeding noncurl cats will produce both curl and noncurl F1F1 offspring if the curl allele is dominant, but only noncurl offspring if the curl allele is recessive. >>>>>>>>>>>>> You would obtain some true-breeding offspring homozygous for the curl allele from matings between the F1 cats resulting from the original curl××noncurl crosses whether the dominant or recessive >>>>>>>>>>>>>>>>>> .You know that cats are true-breeding when curl ×× curl matings produce only curl offspring.

During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur? State your answer as meiosis I or meiosis II followed by a comma and the name of the phase (for example, if your answer is meiosis II and metaphase, enter meiosis II, metaphase).

Meiosis I, anaphase

That each gamete contains a single allele of the eye color gene is an illustration of _____.

Mendel's law of segregation only Mendel's law of segregation is based on gametes getting only one copy of each allele of each gene.

If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?

None Alleles of the same gene must separate during gamete formation; thus, the two B alleles would be distributed to different gametes.

In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?

P>>>> F1 >>>> F2 Mendel started with true-breeding P generation plants and in a typical experiment generated two subsequent generations, called F1 and F2.

Quantitative characters vary in a population along a continuum. How do such characters differ from the characters investigated by Mendel in his experiments on peas?

Quantitative characters are due to polygenic inheritance, the additive effects of two or more genes on a single phenotypic character. A single gene affected all but one of the pea characters studied by Mendel.

The result of the following cross indicates that the genotype of the female parent is _____.

RR Because wild type head top is dominant to flat head top and because all of the F1 generation are wild type head top, the genotype of the female parent must be homozygous dominant.

The result of the following cross indicates the orange eyes are _____ black eyes.

Recessive to The result of this cross indicates that both parents are heterozygous for eye color.

You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?

Red shows incomplete dominance over white.

Look at the Punnett square, which shows the predicted offspring of the F2 generation from a cross between a plant with yellow-round seeds (YYRR) and a plant with green-wrinkled seeds (yyrr). Select the correct statement about wrinkled yellow seeds in the F2 generation.

The chance that an individual taken at random from the F2 generation produces wrinkled seeds is 25% and the chance that the same individual produces yellow seeds is 75%.

Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct?

These homologous chromosomes represent a maternal and a paternal chromosome.

When a dominant allele coexists with a recessive allele in a heterozygote individual, how do they interact with each other?

They do not interact at all. >>>>>>>>>>>>>>>>> An allele is called dominant because it appears in the phenotype of a heterozygote, not because it subdues a recessive allele. Read about dominance.

True or false? The same phenotype can be produced by more than one genotype

True Since there exist dominant and recessive versions of many genes, a phenotype that is based upon the dominant version will be expressed in both homozygous (AA) and heterozygous (Aa) genotypes.

Normal hemoglobin is a tetramer, consisting of two molecules of β-globin and two molecules of α-globin; normal hemoglobin molecules do not associate with each other. In sickle-cell disease, the change in a single amino acid results in mutant hemoglobin tetramers, which associate with each other and assemble into large fibers. Based on this information alone, what can we conclude about the changes in the structure of sickle cell hemoglobin as compared to normal hemoglobin?

altered primary and quaternary structure If you had trouble with this question, review the following material: The primary structure of a protein is its sequence of amino acids, secondary structure is the result of hydrogen bonds between the repeating constituents of the polypeptide backbone, tertiary structure is the three-dimensional shape stabilized by interactions between side chains, and quaternary structure results when two or more polypeptides associate with each other. Normal hemoglobin tetramers do not associate with each other. The single amino acid change that causes sickle-cell disease alters the primary and quaternary structure of the protein, and as a result, the abnormal hemoglobin tetramers aggregate into chains. Not enough information is given to determine whether secondary and tertiary interactions are affected.

When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.

gametes, progeny The Punnett square is representing all of the possible combinations of the gametes from each parent, with the progeny represented in the interior of each box.

Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel's findings does her test cross illustrate?

law of segregation The law of segregation states that the two alleles for a gene separate during gamete formation, and end up in different gametes. In the case of the heterozygous green-pod plant (Gg), one gamete will receive the dominant allele (G), and the other gamete will receive the recessive allele (g). The law of segregation accounts for the prediction that 50% of the offspring of the test cross will have green pods and 50% will have yellow pods.

The result of the following cross indicates that the genotype of the male parent is _____.

rr Because wild type head top is dominant to flat head top, the only genotype that produces the flat head top phenotype is homozygous recessive.

A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?

ttpp The smallest phenotypic group consists of the homozygous recessive plants, which in this case are short and white flowered.