Genetics

Principle of independent assortment

(Mendel's second law) genes located on different chromosomes will sort independently

The concept of dominance

(Mendel's third law) when two different alleles are present in a genotype, only the trait encoded by one of them―the "dominant" allele―is observed in the phenotype.

If an F1 plant, which is the progeny of RR and rr plants, is backcrossed to the parent with round seeds, what proportion of the progeny will have wrinkled seeds? (Use a Punnett square.)

(use punnet square and choose) a. ¾ b. ½ c. ¼ d. 0

If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype? a. 100% b. 0% c. 33% d. 25%

0%

Poly-X females

1/1000 female births

XXY Males

1/1000 male births

1. Freckles are caused by a dominant allele. A man has freckles but one of his parents does not have freckles. The man has fathered a child with a woman that does not have freckles. What is the probability that their child has freckles? a. 1/4 b. 1/3 c. 1/2 d. 2/3 e. 3/4

1/2

1. A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. What is the probability of a gamete from this individual that has the following genotype: alleles A and b, chromosome Z? a. 1/2 b. 1/4 c. 1/6 d. 1/8 e. 1/16

1/8

If the probability of being blood-type A is 1/8 and the probability of blood-type O is ½, what is the probability of being either blood-type A or O? a. 5/8 b. ½ c. 1/8 d. 1/16

5/8

1. In Mendel's peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure-breeding green plant. All of the offspring are yellow. If one of these yellow offspring is crossed with a green plant, what will be the expected proportion of plants with green seeds in the next generation? a. 0% b. 25% c. 50% d. 75% e. 100%

50%

1. Which of the following statements is true? a. The genotype is the physical appearance of a trait. b. Alleles, genes, and loci are different names for the same thing. c. The phenotype of a dominant allele is never seen in the F1 progeny of a monohybrid cross. d. A testcross can be used to determine whether an individual is homozygous or heterozygous. e. All of these statements are true.

A testcross can be used to determine whether an individual is homozygous or heterozygous.

How many Barr bodies are present in an individual with Klinefelter syndrome (XXYY)?

A.0 B.1 C.2 D.3 E.4

Red-green color blindness is an X-linked recessive trait in humans. Polydactyly (extra fingers and toes) is an autosomal dominant trait. Martha has normal fingers and toes and normal color vision. Her mother is normal in all respects, but her father is color blind and polydactylous. Bill is color blind and polydactylous. His mother has normal color vision and normal fingers and toes. If Bill and Martha marry, what proportions of children with specific phenotypes would they be expected to produce? (The answers only include the proportions of some of the possible phenotypes; other phenotypes are also expected to occur but are not included.)

A.1/4 color-blind girls with normal fingers, 1/4 boys with normal vision and polydactyly B.1/8 color-blind girls with polydactyly, 1/8 boys with normal vision and normal fingers C.1/3 girls with normal vision and normal fingers, 1/3 boys with normal vision and polydactyly, and 1/3 boys with normal vision and normal fingers D.1/6 girls with normal vision and polydactyly, 1/6 boys with normal vision and polydactyly E.1/8 color-blind girls with normal fingers, 1/4 boys with normal vision and polydactyly

In cats, curled ears result from an allele (Cu) that is dominant over an allele (cu) for normal ears. Black color results from an independently assorting allele (G) that is dominant over an allele for gray (g). A gray cat homozygous for curled ears is mated with a homozygous black cat with normal ears. All the F1 cats are black and have curled ears. An F1 cat mates with a stray cat that is gray and possesses normal ears. What phenotypes and proportions of progeny are expected from this cross? A.All black cats with curled ears 9/16 black cats, curled ears; 3/16 black cats, normal ears; 3/16 gray cats, curled ears; and 1/16 gray cats, normal ears B.1/4 black cats, curled ears; 1/4 black cats, normal ears; 1/4 gray cats, curled ears and 1/4 gray cats, normal ears C.9/16 gray cats, normal ears; 3/16 gray cats, curled ears; 3/16 black cats, normal ears; and 1/16 black cats, curled ears D.All gray cats; normal ears

A.All black cats with curled ears 9/16 black cats, curled ears; 3/16 black cats, normal ears; 3/16 gray cats, curled ears; and 1/16 gray cats, normal ears B.1/4 black cats, curled ears; 1/4 black cats, normal ears; 1/4 gray cats, curled ears and 1/4 gray cats, normal ears C.9/16 gray cats, normal ears; 3/16 gray cats, curled ears; 3/16 black cats, normal ears; and 1/16 black cats, curled ears D.All gray cats; normal ears

If an XX individual has a defective androgen receptor what external characteristics would the person exhibit?

A.Female characteristics B.Male characteristics

If an XY individual has a defective androgen receptor what external characteristics would the person exhibit?

A.Female characteristics B.Male characteristics

How does the heterogametic sex differ from the homogametic sex?

A.The heterogametic sex is male; the homogametic sex is female. B.Gametes of the heterogametic sex have different sex chromosomes; gametes of homogametic sex have the same sex chromosome. C.Gametes of the heterogametic sex all contain a Y chromosome. D.Gametes of the homogametic sex all contain an X chromosome.

Characteristic or character

An attribute or feature possessed by an organism

Heterozygote

An individual organism possessing two different alleles at a locus

Homozygote

An individual organism possessing two of the same alleles at a locus

Gene

An inherited factor (encoded in the DNA) that helps determine a characteristic

Principle of segregation: (Mendel's first law)

Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete. **The big letter overshadows the recessive allele

Allele

One of two or more alternative forms of a gene

Genotype

Set of alleles possessed by an individual organism

Locus

Specific place on a chromosome occupied by an allele

Phenotype or trait

The appearance or manifestation of a characteristic

1. In Labrador retrievers, black coat color is dominant to brown. Suppose that a black Lab is mated with a brown one and the offspring are 4 black puppies and 1 brown. What can you conclude about the genotype of the black parent? a. The genotype must be BB. b. The genotype must be bb. c. The genotype must be Bb. d. The genotype could be either BB or Bb. e. The genotype cannot be determined from these data.

The genotype must be Bb.

Does the inheritance of one trait (seed color) effect the inheritance of a second trait (seed shape)?

The inheritance of one trait (seed color) does not effect the inheritance of a second trait (seed shape)

In mammals sex determination occurs through the presence of sex chromosomes called __ and __. Females are __ and males are __.

X and Y XX and XY

Turner syndrome

XO; 1/3000 female births

Klinefelter syndrome

XXY, or XXXY, or XXXXY, or XXYY; 1/1000 male births

Which of the following chromosome constitutions would never lead to a viable human baby being born? a. XXX b. XYY c. XO (O = the absence of a second chromosome) d. YY e. XXY

YY

The following two genotypes are crossed Aa Bb Cc dd Ee x Aa bb Cc Dd Ee. What is the probability of having a Aa bb Cc dd ee progeny? a. 1/16 b. 1/32 c. 1/64 d. 1/128 e. 1/256

a. 1/16 b. 1/32 c. 1/64 d. 1/128 e. 1/256

Which of the following human genotypes is associated with Klinefelter syndrome? a. XXY b. XXXY c. XXXXY d. All of the above e. None of the above

all of above

Genes come in different versions called a. alleles. b. loci. c. genotypes. d. chromosomes. e. genomes.

alleles.

In Mendel's pea plants, how did he know that each F1 generation contained two alleles encoding different characteristics?

b. Both parental phenotypes reappeared in the F2 generation.

1. In Mendel's peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure-breeding green plant. All of the offspring are yellow. If one of these yellow offspring is crossed with a green plant, what will be the expected proportion of plants with green seeds in the next generation? a. 0% b. 25% c. 50% d. 75% e. 100%

c. 50%

1. The ability to curl one's tongue into a U-shape is a genetic trait. Curlers always have at least one curler parent but noncurlers can have one or both parents who are curlers. Using C and c to symbolize the alleles that control this trait, what is the genotype of a noncurler? a. CC b. Cc c. cc d. Any of the above could be correct.

c. cc

1. The ability to curl one's tongue into a U-shape is a genetic trait. Curlers always have at least one curler parent but noncurlers can have one or both parents who are curlers. Using C and c to symbolize the alleles that control this trait, what is the genotype of a noncurler? a. CC b. Cc c. cc d. Any of the above could be correct.

cc

1. Which of the following statements is true? a. The genotype is the physical appearance of a trait. b. Alleles, genes, and loci are different names for the same thing. c. The phenotype of a dominant allele is never seen in the F1 progeny of a monohybrid cross. d. A testcross can be used to determine whether an individual is homozygous or heterozygous. e. All of these statements are true.

d. A testcross can be used to determine whether an individual is homozygous or heterozygous.

bees/flies sex determined by

haploid vs diploid

homologous

having the same relation, relative position, or structure, in particular.

An XXY chromosome constitution produces ________ development in humans and _________ development in fruit flies. a. female; female b. male; male c. female; male d. male; female e. male, intersex

male, female

Sex-determining region Y (SRY) gene is used for what?

necessary to begin male development

birds/snakes/butterflies sex is determined by

presence of W in ZW

insect sex is determined by

ratio of chromosomes

In humans, the X or Y chromosome of the father determines the ___ of the child

sex

Probability

the likelihood of the occurrence of a particular event Used in genetics to predict the outcome of a genetic cross

1. In which of the following organisms is gender/sex determined by the temperature during embryonic development? a. Humans b. Mice c. Fruit flies d. Many snakes and birds e. Many turtles and alligators

turtles/alligators