Genetics: MCAT questions test 1

person of type-B blood has children with a person of type-AB blood, what blood types could their children have?

-A -B -AB

The X-linked recessive trait of color-blindness is present in 5% of males. If a mother who is a carrier and father who is unaffected plan to have 2 children, what is the probability the children will both be male and color-blind?

6.25

Oogenesis, the process that creates female gametes, is halted at prophase I until puberty. Which of the following describes the DNA content of a female's gametes during her childhood? -chromosomes and chromatids?

-46 chromosomes -92 chromatids

Which of the following processes occur in meiosis but don occur in mitosis? I. Spindle formation II. Separation of homologous chromosomes III. Separation of sister chromatids IV. Recombination

-II. Separation of homologous chromosomes -IV. Recombination

If Wilson's Disease is a Mendelian disease with autosomal recessive inheritance, what are the chances that a child of two carriers will be affected?

1/4

In labrador retrievers, the allele for black coat color (B) is dominant to the allele for brown coat color (b). However, if a lab has two copies of the recessive allele for a pigment-depositing gene (e), it can only have yellow coat color. In a cross of two doubly heterozygous black labs (BbEe x BbEe), what fraction of the next generation would one expect to be yellow?

1/4

In a cross of AaBb x AaBb, what fraction of the offspring can be expected to express *one of the two dominant alleles, but not both*?

3/8

9. Suppose the brown allele for eye color (B) is completely dominant over the blue allele for eye color (b). If two brown-eyed parents produce a child that is blue-eyed, what is the probability that at least one out of the next two children they produce will also have blue eyes?

44% -At least rule (P(A or B) = P(A) + P(B) - P(A and B))

Based on the pedigree chart describing the inheritance of an autosomal-dominant disease, what is the probability that person A will birth an affected child if she mates with a wild-type male.

50%

If two heterozygous plants are crossed, what is the probability their offspring will also be heterozygous?

50%

autosomal dominant= ___% chance transmitting the trait to offspring

50%

During metaphase, the chromosomes of the cell are......

Aligned at the mid-plane of the cell

In pea plants, the allele for tall stalks (T) is dominant over the allele for short stalks (t). Suppose a cross between a tall pea plant and a short pea plant produces 43 tall offspring and 47 short offspring. If one of the tall offspring is crossed with one of the short offspring, what ratio of genotypes would be most likely in their offspring?

B) 1 Tt : 1 tt

A cross between two pea plants with genotypes PpLl and PpLl results in an F1 generation that is 25% PPLL, 50% PpLl, and 25% ppll. -Which reason most likely explains why other possible genotypes are not present?

C) The loci of the genes are close together.

Cross pollination of yellow corn and white corn results in ears of corn that have an approximately even mix of yellow and white kernels. -Which term best describes the relationship between the two alleles?

Codominance

If two genes experience independent assortment, which assumption is most likely true? A) The expression of one gene does not affect the expression of the other. B) They are located in close proximity on the same chromosome. C) Crossing over between the genes does not occur. D) The genes are located on different chromosomes or are far apart on the same chromosome

D) The genes are located on different chromosomes or are far apart on the same chromosome

Retinoblastoma protein, RB, is an important cell cycle checkpoint protein that prevents the transition from ___ to ___ phase.

G1 to S

A man with type A -blood and a woman with type AB+ blood have a child. Which blood type is impossible for that child to have?

O-

Which of the following mutation scenarios is least likely to lead to the formation of a neoplasm?

a. No RB mutation and SDK that cannot bind to cyclin

8. Which of the following statements are the true about the significance of meiosis? I. Enhances genetic variation II. Maintains ploidy in sexually reproducing organisms III. Allows for the potential repair of damaged DNA

all the above -Enhances genetic variation -Maintains ploidy in sexually reproducing organisms -Allows for the potential repair of damaged DNA

9. A mouse has a mutation in which its sister chromatids are unable to separate during cell division. -What phase of mitosis should researchers target, in order to alleviate the condition using drug therapy?

anaphase

cystic fibrous is which type of dz?

autosomal recessive

Which of the following is "not" a reason cancer is hard to treat? a. Increased mutation rate b. Increased contact inhibition c. Increased growth rate d. Increased metastasis

b. Increased contact inhibition

Which of the following is not a characteristic of meiosis? a. It produces four haploid daughter cells b. It functions to grow and repair the human body c. It is preceded by the G2 phase d. It produces egg and sperm cells with no homologous chromosomes

b. It functions to grow and repair the human body

Which of the following occurs in mitosis, but does not occur in meiosis? a. Nuclear envelope breakdown b. None of these answers c. Separation f homologous chromosomes d. Separation of sister chromatids

b. None of these answers

A child is determined to have partial trisomy 21, with three copies of some segments of DNA from chromosome 21, and partial monosomy 4, with only one copy. Which of the following mutations could have occurred in one of the parental gametes during development to explain both findings? a. Deletion b. Insertion c. Translocation

c. Translocation

The presence of the ___ releases RB protein from the genes that it binds

cyclin/CDK complex

. Which statement best describes chromosomal movement during mitosis? a. Centrioles on chromatids bind kinetochores to rays sent by the asters b. Each centrosome binds an individual chromatid to ensure equal division. c. Microtubules bind tublin poolymers on centromeres to initiate homologues chromosomes separation. d. Centrioles send out asters, which bind to kinetochores to pull chromatids apart.

d. Centrioles send out asters, which bind to kinetochores to pull chromatids apart.

10. How does meiosis incorporate genetic variation into the creation of haploid cells?

d. The exchange of DNA sequences during prophase I (crossing over)

In a heterozygous offspring the _____ allele is expressed and the recessive allele is suppressed

dominant

During prophase, what must likely happen to the concentration gradient? a. The concentration gradient strengthens because the cell requires more proteins to diffuse into the nucleus during mitosis d. There is no change in the concentration gradient during prophase e. The concentration gradient breaks down because the nuclear membrane breaks down

e. The concentration gradient breaks down because the nuclear membrane breaks down

centrioles can be found in only ____ cells

eukaryotic

A young girl is diagnosed with a x-linked disorder, which parent has to have the dz?

father -(mother is the carrier for the dz)

testcross to determine unknown genotypes involves crossing with?

homo recessive

Suppose a white-furred rabbit breeds with a black-furred rabbit and all of their offspring have a phenotype of gray fur. -What does the gene for fur color in rabbits appear to be an example of?

incomplete dominance

The ---------- is the site of attachment of spindle fibers to sister chromatids during mitosis.

kinetochore

A karyotype can be used to check for certain chromosomal mutations. In what cell cycle phase can cells be karyotyped?

metaphase

Two of the sperm have one extra chromosome and the other two have one missing chromosome. At what step did the problem most likely occur, and what was it?

metaphase 1 -nondisjunction

During which phase does the nuclear envelope begin to disappear?

prometaphase

When does genetic crossover occur during meiosis?

prophase 1

the idea that for any particular trait, the pair of alleles of each parent separate and only one allele from each parent passes to an offspring is Mendel's principle of:

segregation

Meiosis is a form of ---------- reproduction and mitosis is a form of -------- reproduction.

sexual, asexual

X-linked dominant. -An affected man and unaffected woman have a son. What is the likelihood that the son will be affected?

sons cannot be affected