Chapter 18: Genetics and Heredity

Use a Punnett Square to figure out what percentage of pea plants would have purple flowers in the following cross: A purple flowered pea plant (PP) crossed with a white flowered pea plant (pp).

100% would have purple flowers.

Based on the following Punnett square, what percentage of fruit flies would you expect to have a red body and round wings? B (black body), b (red body), F (flat wings), f (round wings)

6%

Alleles A and B are linked on chromosome 1 (such that you have A-B and a-b). Alleles C and D are linked on chromosome 2 (you have C-D and c-d). If a crossover event does not occur between either set of genes, which gamete genotype could NOT be produced by an individual heterozygous at each locus?

A-B; C-d

Alleles A, B, C and D are linked on one chromosome, and alleles a, b, c and d are linked on the homolog. During meiosis, a crossover event occurs between genes A and B. Which of the following is an example of a chromatid that could be found in one of the resulting gametes?

A-b-c-d

Based on Mendel's pea plants, if P is an allele that codes for purple flowers and p is an allele that codes for white flowers, what can you say about a plant that has the alleles Pp?

ALL ARE CORRECT: The flower is purple. The plant carries the allele for white flowers. The plant may have white flowered offspring.

Which phenotype(s) do the red blood cells from a person with AB blood type exhibit?

Both the 'A' and 'B' phenotype in each red blood cell.

The following results were observed from a mating between two black and white speckled cats: 5 black cats, 12 black and white speckled cats, and 4 white cats. Which term describes the relationship between the alleles of the coat color gene?

Codominance

Which of these terms accurately describes Alzheimer's disease?

Complex disease

What type of organism has two copies of every gene?

Diploid

The trait which is expressed in a heterozygous state is known as

Dominant

Gregor Mendel is famous for his involvement in _____.

Genetics

Which of the following statements is/are true? I. A human with an X chromosome and a Y chromosome is male. II. A human with only one type of sex chromosome (an X chromosome) is female. III. All children of a color blind woman and a man who is not color blind will carry a color blind allele.

I, II, and III I. A human with an X chromosome and a Y chromosome is male. II. A human with only one type of sex chromosome (an X chromosome) is female. III. All children of a color blind woman and a man who is not color blind will carry a color blind allele.

Which of the following statements is true? I. The one thousandth base pair on chromosome one of an organism is an example of a locus. II. Changing the DNA in a gene by one base pair could create a new allele. III. Cells in a diploid organism possess two copies of each homolog (except gametes).

I, II, and III I. The one thousandth base pair on chromosome one of an organism is an example of a locus. II. Changing the DNA in a gene by one base pair could create a new allele. III. Cells in a diploid organism possess two copies of each homolog (except gametes).

Evaluate each of the following sets of data separately. Which of them provide evidence that the trait is polygenic? I. The genotype at loci A, B and C each produces a protein that influences the length of an organism by an average of 0.6, 0.4 and 0.3 cm, respectively. II. Three different alleles of gene D affect the length of an organism by an average of 0.6, 0.4 and 0.3 cm, respectively. III. Loci E, F and G each modulates an independent pathway, which plays a role in determining the length of an organism.

I. The genotype at loci A, B and C each produces a protein that influences the length of an organism by an average of 0.6, 0.4 and 0.3 cm, respectively. & III. Loci E, F and G each modulates an independent pathway, which plays a role in determining the length of an organism.

Which of the following statement(s) accurately describes an advantage provided by model organisms? I. The laboratory environment can be controlled. II. True-breeding strains can be generated. III. Specific combinations of alleles can be engineered.

I. The laboratory environment can be controlled. II. True-breeding strains can be generated. III. Specific combinations of alleles can be engineered.

Hemophilia is an X-linked recessive trait. Consider a cross between a woman who is a carrier and a man who suffers from hemophilia. Which of the following statements is/are true? I. All sons of these parents will be a hemophiliac. II. Sons who suffer from hemophilia received the hemophilia allele from their mother. III. Half of the daughters of this cross are predicted to be hemophiliacs.

II. Sons who suffer from hemophilia received the hemophilia allele from their mother. & III. Half of the daughters of this cross are predicted to be hemophiliacs.

Genes A and B are located on the same chromosome arm in the following orientation: centromere, gene A, gene B, telomere. Which of the following recombinant chromatids could be produced by a crossover event between B genes in a heterozygote in which the dominant alleles are linked on one homolog and the recessive ones are linked on the other homolog? I. A B II. a B III. A b IV. a b

II. a B & III. A

All of the following statements are correct EXCEPT:

INCORRECT: Creating new combinations of alleles decreases the genetic diversity of the population. CORRECT: Creating new combinations of alleles makes new combinations of phenotypes. Whether or not the linkage between alleles is altered is determined by the location of crossover events during meiosis. If two alleles of different genes are linked, they are inherited together.

Which type of dominance describes a situation in which heterozygotes demonstrate a phenotype which is intermediate between the homozygotes?

Incomplete dominance

A geneticist is studying a genetic condition. They determine that the causative gene for this particular condition is located on human chromosome 2. What can we conclude about the condition? Why?

It is autosomal, because the condition is caused by a gene on one of the numbered chromosomes.

When two genes are located on the same chromosome, they are said to be _____.

Linked

The locus is _____.

Location of a gene on a chromosome

Joe is in urgent need of a blood transfusion. His blood genotype is AA. Mike has an oo genotype, and Mary has a BB genotype. Who would be able to donate blood to Joe, and why?

Mike can donate, because oo doesn't produce an extracellular sugar

Which of the following is NOT an example of a phenotype?

NOT AN EXAMPLE: DNA sequence of the alcohol dehydrogenase gene EXAMPLES: Height of a giraffe Wheat resistance to fungal infection Color of a feather

Which of the following is NOT an example of a homozygous genotype?

NOT AN EXAMPLE: Rr EXAMPLE: tt ww GG

Which of the following statements could NOT be used to describe a multifactorial trait?

NOT BE USED: Gene homozygosity and heterozygosity determine the trait. USED: Two independent genetic pathways affect the trait. A continuous range of traits is possible. The phenotypic consequences of genes affecting the trait are additive. An environmental factor affects the trait

Consider the following experiment: A scientist determines that the number of dorsal spines of her experimental fish is determined by a single locus. She mates a fish with 1 dorsal spine with a fish of the same species with 2 dorsal spines. The mating produces ten fish, which all have 1 dorsal spine. Which of the following statements could NOT be true?

NOT TRUE: The progeny fish are homozygous for the '1-spine' allele. TRUE: The '2-spine' parent fish has a homozygous genotype at the dorsal spine locus. The progeny fish may be capable of producing progeny with only 1 spine. The '1-spine' parent fish has a homozygous genotype at the dorsal spine locus. '2 dorsal spines' is a recessive phenotype.

When collecting samples to study the genetics of a complex disease, which of the following factors would you NOT want to be equally represented in both the affected and unaffected groups?

NOT WANT: Family history WANT: Age Smoking Gender

What is Mendel's Second Law?

Non-linked genes do not affect the outcome of other genes.

Let's say P is an allele that codes for purple flowers and p is an allele that codes for white flowers. A plant has alleles Pp. According to the Law of Segregation, what alleles would each gamete have?

One gamete would have P and one would have p.

An allele is _____.

One version of genetic variation at a particular locus.

Skin cancer is a multifactorial trait. Which of the following is plausible?

PLAUSIBLE: Skin cancer is difficult to predict in a susceptible family. NOT PLAUSIBLE: Skin cancers can be prevented by avoiding excessive sunlight. Skin cancer can be diagnosed by testing for proteins coded by the culprit gene. Skin cancers results from allele variations of a gene on chromosome 9. Skin cancer can be cured by targeting multiple promoters of the skin cancer gene.

Which of the following genetic techniques are used in human genetics?

Pedigree analysis

A _____ is a trait which is determined by two or more genes, but not any environmental factors.

Polygenic trait

Which of the following would make sense to represent left and right hand nature (left is recessive and right is dominant) and eye color (brown is dominant and green is recessive) in a Punnet Square.

R for right hand, r for left hand; B for brown eyes b for green eyes

The trait which is not expressed in a heterozygous state is known as

Recessive

A scientist is studying an animal and determines that a gene is located on autosome two. It controls antler production in the male animals. Note that females do not produce antlers. This is an example of a:

Sex-limited trait

In humans, _____ is determined by the presence or absence of the _____ chromosome.

Sex; Y

Which of the following statements about multifactorial traits is TRUE?

TRUE: They are usually determined by a combination of multiple genetic and non-genetic factors. FALSE: Multifactorial traits only refer to traits that do not cause disease. Red/green color blindness is a multifactorial trait. They are determined by multiple non-genetic factors and are not influenced by genotype.

Autosomes are:

The chromosomes in the genome which are not sex chromosomes.

Incomplete dominance governs the pigment gene of a flower. A mating between heterozygotes yields the following phenotypic ratio: 15 red flowers, 32 pink flowers and 14 white flowers. Which statement describes the situation?

The flower pigment gene is defined by a red and a white allele.

If you determined that the percentage of fruit flies that have a red body and round wings is actually 25% what does this tell you based on the following Punnett square? B (black body), b (red body), F (flat wings), f (round wings)

The red body and round wings genes are probably linked.

Some people have blue eyes and some people have brown eyes. Which answer best explains why this is the case?

They have different alleles.

How was Mendel's second law discovered?

Through an experiment observing the shape and color of peas.

When an organism is diploid, that means it has _____.

Two versions of each chromosome.