Question 1

Which of the following crosses will yield four phenotypes in a ratio of 9:3:3:1?
A)RRYY * RRYY
B)RRYY * rryy
C)RrYy * RrYy
D)RrYy*rryy
E)rryy * rryy

Accepted Answer

This is a classic dihybrid cross, where two traits are being analyzed. The cross in choice C is the only one that involves two heterozygous parents (RrYy x RrYy), which can produce four different phenotypic outcomes (RY, Ry, rY, and ry) in a 9:3:3:1 ratio. The other crosses either have homozygous parents (A and E) or are not true dihybrid crosses (B).

Question 2

A blue-eyed,left-handed woman marries a brown-eyed,right-handed man who is heterozygous for both of his traits.If blue eyes and left-handedness are recessive,how many different phenotypes are possible in their children?
A)one
B)two
C)three
D)four
E)five

Accepted Answer

Given that blue eyes and left-handedness are recessive traits, and considering the man is heterozygous for both of his dominant traits (brown eyes and right-handedness), their children could exhibit four different phenotypes: 1) brown-eyed, right-handed; 2) brown-eyed, left-handed; 3) blue-eyed, right-handed; 4) blue-eyed, left-handed.

Question 3

The four o'clock flower is an example of incomplete dominance: R = red,r = white,and Rr = pink.If two hybrids are crossed,what are the chances that an offspring will have pink flowers?
A)0%
B)25%
C)50%
D)75%
E)100%

Accepted Answer

When two hybrids are crossed, the possible genotypes for their offspring are RR, Rr, and rr. RR will produce red flowers and rr will produce white flowers, while Rr will produce pink flowers. Since incomplete dominance means that the heterozygous genotype (Rr) produces an intermediate phenotype (pink), half of the offspring with the genotype Rr will have pink flowers. Therefore, the chance of an offspring having pink flowers is 50%.

Question 4

A man with a widow's peak (dominant)and can curl his tongue (dominant)has a child who has a continuous hairline and cannot curl the tongue.What is the genotype of the father?
A)WWTT
B)wwtt
C)WwTt
D)Wwtt
E)WT

Accepted Answer

- Widow's peak is a dominant trait, so the father must have at least one dominant allele for the trait. We denote dominant alleles with a capital letter, so we can represent the father's alleles for this trait as either WW or Ww.
- The ability to curl the tongue is also a dominant trait, so the father must have at least one dominant allele for this trait as well. We can represent this allele as T.
- The child has a continuous hairline (recessive trait) and cannot curl their tongue (recessive trait), so they must have received two recessive alleles for both of these traits. We denote recessive alleles with a lowercase letter, so the child's alleles for these traits are ww and tt.
- We know that the father must have passed on one allele for each trait, so we can set up a Punnett square to see the possible combinations:

|   | W  | w  |
|---|---|---|
| T | WT | wT |
| t | Wt | wt |

- Each of these combinations is equally likely, so we need to consider all of them. The only combination that matches the child's traits is Wwtt, so the father's genotype must be WwTt.

Question 5

In guinea pigs,B = black,b = brown,S = short hair,s = long hair.Two heterozygous individuals reproduce.The expected results are
A)9 black long hair,3 black short hair,3 brown long hair,1 brown short hair.
B)9 black short hair,6 black long hair,3 brown long hair,1 black short hair.
C)9 black short hair,3 black long hair,3 brown short hair,1 brown long hair.
D)9 brown short hair,3 black long hair,3 brown long hair,1 black short hair.
E)1 black short hair,1 black long hair,1 brown short hair,1 brown long hair.

Accepted Answer

The cross between two heterozygous individuals (BbSs x BbSs) follows a 9:3:3:1 phenotypic ratio for a dihybrid cross, resulting in 9 black short hair, 3 black long hair, 3 brown short hair, and 1 brown long hair.

Question 6

In horses,black coat (B)is dominant over brown coat (b),and being a trotter (T)is dominant over being a pacer (t).A black horse who is a pacer is crossed with a brown horse who is a trotter.The offspring is a brown pacer.What is the genotype of the brown trotter parent?
A)BBTT
B)BbTt
C)Bbtt
D)bbTt
E)bbtt

Accepted Answer

The brown trotter parent must carry the recessive allele for coat color (b) to produce a brown offspring and must have at least one dominant allele for trotting (T). Since the offspring is a pacer (tt), the brown trotter parent must also carry a recessive allele for pacing (t), making the genotype bbTt.

Question 7

Cold weather can change the ______ of a Himalayan rabbit.
A)genotype
B)phenotype
C)alleles
D)sex
E)rate of genetic mutations

Accepted Answer

Phenotype refers to an individual's physical and observable characteristics, which can be influenced by environmental factors such as cold weather. Genotype refers to an individual's genetic makeup, which may not necessarily change due to environmental factors. Alleles are variations of genes that can also be inherited and do not necessarily change due to environmental factors. Sex and rate of genetic mutations are also not likely to be affected by cold weather in a Himalayan rabbit.

Question 8

In pea plants,the gene for round seed (R)is dominant,and wrinkled seeds (r)are recessive.The endosperm of the pea is also either starchy,a dominant gene (S),or waxy (s).What CANNOT be said of a cross between two parents that are heterozygous for both traits?
A)It is possible to secure offspring that are homozygous for both dominant genes.
B)It is possible to secure offspring that are homozygous for both recessive genes.
C)It is possible to secure offspring that are homozygous for one dominant gene,such as round seed,and homozygous recessive for the other recessive waxy gene.
D)It is possible to secure offspring that are heterozygous for both genes.
E)It is impossible to secure offspring that are homozygous for both dominant genes.

Accepted Answer

If both parents are heterozygous, then each parent has one dominant and one recessive allele for both traits. This means that there is a possibility of producing offspring with a range of genotypes, including homozygous dominant, heterozygous, and homozygous recessive for each trait. However, it is not possible to produce offspring that are homozygous for both dominant genes (RRSS) because each parent only has one dominant allele for each trait.

Question 9

Two parents with widow's peak and short fingers have a child with a continuous hairline and long fingers.What are the genotypes of the two parents? (W = widow's peak; S = short fingers)
A)WWSS * wwss
B)wwss * WWSS
C)WWss * WWss
D)WwSs * WwSs
E)WwSs * wwss

Accepted Answer

Based on the traits and their inheritance patterns, widow's peak is dominant and short fingers are recessive. Therefore, the parents with widow's peak and short fingers must be heterozygous for widow's peak (Ww) and homozygous recessive for short fingers (ss). The child with continuous hairline and long fingers must have inherited the dominant allele for both traits (WW and LL). Therefore, the genotypes of the parents are WwSs and the best choice is D, which matches this genotype combination for the parents.

Question 10

Which of the following is an example of the blending of phenotypes?
A)codominance
B)sex-linked inheritance
C)polygenic inheritance
D)simple Mendelian inheritance
E)incomplete dominance

Accepted Answer

In incomplete dominance, the phenotype of the offspring is a blend of the phenotypes of the two parental traits. For example, if a red flower (RR) is crossed with a white flower (WW), the offspring (RW) will have pink flowers, which is a blending of the red and white phenotypes.

Question 11

Humans can have any of several eye colors,This is because we possess a variety of
A)particulates.
B)genotypes.
C)loci.
D)alleles.
E)homologous.

Accepted Answer

Eye color is determined by different alleles at specific loci on chromosomes. Therefore, the correct choice is D) alleles.

Question 12

In guinea pigs,B = black,b = brown,S = short hair,s = long hair.A heterozygous black,short-haired animal reproduces with a brown,long-haired animal.What is the expected phenotypic ratio of the offspring?
A)1 black short hair,1 black long hair,1 brown short hair,1 brown long hair
B)3 black short hair,1 brown long hair,3 black long hair,1 brown short hair
C)9 black short hair,3 black long hair,3 brown long hair,1 brown short hair
D)9 black short hair,3 black long hair,3 brown short hair,1 brown long hair
E)9 black short hair,6 black long hair,3 brown long hair,1 brown short hair

Accepted Answer

The heterozygous black, short-haired animal has the genotype BbSs, and the brown, long-haired animal has the genotype bbss. The possible offspring genotypes are BbSs, Bbss, bbSs, and bbss, leading to a phenotypic ratio of 1 black short hair, 1 black long hair, 1 brown short hair, and 1 brown long hair.

Question 13

In which kind of cross could you expect to find ratios of 1:1:1:1 among the offspring?
A)monohybrid cross
B)dihybrid cross
C)one-trait test cross
D)two-trait test cross
E)no cross will yield offspring in 1:1:1:1 ratios

Accepted Answer

A two-trait test cross involves a heterozygous individual for two traits crossed with a homozygous recessive individual, resulting in a 1:1:1:1 phenotypic ratio among the offspring.

Question 14

Traits that are controlled by several sets or pairs of alleles,such as skin color and height in humans,are the result of what form of inheritance?
A)polygenic
B)incomplete dominance
C)multiple allele systems
D)simple Mendelian inheritance
E)codominance

Accepted Answer

Polygenic inheritance refers to traits that are controlled by multiple genes, each with its own set of alleles. This results in a range of phenotypes being possible, with characteristics like skin color and height being determined by the combined effects of many different genes.

Question 15

The inheritance of blood types in humans can be explained by
A)simple Mendelian genetics (one gene pair).
B)linked genes.
C)simple dominance.
D)multiple alleles.
E)polygenic inheritance.

Accepted Answer

The answer of The inheritance of blood types in humans...

Question 16

What are the chances that two individuals with wavy hair (an incomplete trait)will have a curly-haired child? Curly hair and straight hair exhibit incomplete dominance.
A)none
B)25%
C)50%
D)75%
E)100%

Accepted Answer

Wavy hair is a result of incomplete dominance, where one allele for curly hair and one allele for straight hair are present. When two wavy-haired individuals (CS) reproduce, there is a 25% chance of having a child with curly hair (CC).

Question 17

Which of the following crosses will yield four phenotypes in the 1:1:1:1 ratio?
A)RRYY * RRYY
B)RRYY * rryy
C)RrYy * RrYy
D)RrYy * rryy
E)rryy *rryy

Accepted Answer

A dihybrid test cross (RrYy x rryy) results in a 1:1:1:1 phenotypic ratio.

Question 18

A cross is made between two parents with genotypes AaBB and aabb.If there are 32 offspring,how many of them would be expected to exhibit both dominant characteristics?
A)32
B)24
C)16
D)8
E)0

Accepted Answer

The dominant characteristics are represented by the alleles A and B. 
The possible gametes for parent 1 (AaBB) are AB and aB.
The possible gametes for parent 2 (aabb) are ab.

The Punnett square for the cross would be:

| A  | a
--|---|--
B | AB | aB
b | Ab | ab

The offspring genotypes and phenotypes would be:

- 25% AaBB (dominant for A and B)
- 25% Aabb (dominant for A)
- 25% aaBB (dominant for B)
- 25% aabb (no dominant characteristics)

Thus, the number of offspring with both dominant characteristics (A and B) would be 25% of 32, which is 8. Therefore, the answer is C.

Question 19

When two or more sets of alleles affect the same trait in an additive fashion,it is termed
A)a single-trait cross.
B)a double-trait cross.
C)codominant.
D)incomplete dominance.
E)polygenic inheritance.

Accepted Answer

Polygenic inheritance occurs when multiple sets of alleles affect the same trait in an additive fashion. This means that each allele contributes a small amount to the phenotype, and the overall phenotype is determined by the sum of these contributions. This process can result in a wide range of phenotypic variation, as seen in traits such as height, skin color, and intelligence.

Question 20

In which kind of cross would you expect to find a ratio of 9:3:3:1 among the F₂ offspring? A)monohybrid cross B)dihybrid cross C)test cross D)homozygous recessive * homozygous dominant E)homozygous dominant *heterozygous

Accepted Answer

The ratio of 9:3:3:1 is the classic ratio seen in a dihybrid cross where two traits are being analyzed.

Quiz 23: Patterns of Gene Inheritance

Which of the following crosses will yield four phenotypes in a ratio of 9:3:3:1?

A blue-eyed,left-handed woman marries a brown-eyed,right-handed man who is heterozygous for both of his traits.If blue eyes and left-handedness are recessive,how many different phenotypes are possible in their children?

The four o'clock flower is an example of incomplete dominance: R = red,r = white,and Rr = pink.If two hybrids are crossed,what are the chances that an offspring will have pink flowers?

A man with a widow's peak (dominant) and can curl his tongue (dominant) has a child who has a continuous hairline and cannot curl the tongue.What is the genotype of the father?

In guinea pigs,B = black,b = brown,S = short hair,s = long hair.Two heterozygous individuals reproduce.The expected results are

In horses,black coat (B) is dominant over brown coat (b) ,and being a trotter (T) is dominant over being a pacer (t) .A black horse who is a pacer is crossed with a brown horse who is a trotter.The offspring is a brown pacer.What is the genotype of the brown trotter parent?

Cold weather can change the ______ of a Himalayan rabbit.

In pea plants,the gene for round seed (R) is dominant,and wrinkled seeds (r) are recessive.The endosperm of the pea is also either starchy,a dominant gene (S) ,or waxy (s) .What CANNOT be said of a cross between two parents that are heterozygous for both traits?

Two parents with widow's peak and short fingers have a child with a continuous hairline and long fingers.What are the genotypes of the two parents? (W = widow's peak; S = short fingers)

Which of the following is an example of the blending of phenotypes?

Humans can have any of several eye colors,This is because we possess a variety of

In guinea pigs,B = black,b = brown,S = short hair,s = long hair.A heterozygous black,short-haired animal reproduces with a brown,long-haired animal.What is the expected phenotypic ratio of the offspring?

In which kind of cross could you expect to find ratios of 1:1:1:1 among the offspring?

Traits that are controlled by several sets or pairs of alleles,such as skin color and height in humans,are the result of what form of inheritance?

The inheritance of blood types in humans can be explained by

What are the chances that two individuals with wavy hair (an incomplete trait) will have a curly-haired child? Curly hair and straight hair exhibit incomplete dominance.

Which of the following crosses will yield four phenotypes in the 1:1:1:1 ratio?

A cross is made between two parents with genotypes AaBB and aabb.If there are 32 offspring,how many of them would be expected to exhibit both dominant characteristics?

When two or more sets of alleles affect the same trait in an additive fashion,it is termed

In which kind of cross would you expect to find a ratio of 9:3:3:1 among the F₂ offspring?