MDCAT Biology Variation and Genetics Online Test MCQs

MDCAT Biology Variation and Genetics Test

Prepare for your MDCAT Biology exam with this online MCQ test on Variation and Genetics. This quiz includes key concepts such as types of variation, causes of genetic differences, and the role of mutations and meiosis, all aligned with the MDCAT 2025 syllabus.

MDCAT Biology Variation and Genetics Chaper Online Test

MDCAT Biology Variation and Genetics MCQS Online Test

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1. Which of the following statements best explains Mendel’s principle of dominance?

One allele may mask the effect of another

Both alleles are equally expressed

The recessive allele is always expressed

Alleles blend to form an intermediate trait

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2. How many alleles control the ABO blood group system?

3

1

2

4

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3. What causes variation in sexually reproducing organisms?

Mutation only

All of the above

Random fertilization

Independent assortment and crossing over

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4. What is a test cross used for?

Determine age

Determine unknown genotype

Alter DNA

Predict phenotype

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5. Which term refers to the genetic makeup of an organism?

Trait

Phenotype

Allele

Genotype

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6. The red-white eye color in Drosophila is an example of:

Dominant-recessive on Y

Polygenic inheritance

Autosomal inheritance

X-linked inheritance

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7. Which organism is commonly used to study sex linkage?

Mouse

Pea plant

Drosophila melanogaster

Bacteria

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8. If a trait is X-linked and recessive, who is more likely to express it?

Both equally

Females

Males

Neither

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9. What does a Punnett square help predict?

Genotypic and phenotypic outcomes

Evolution rate

Chromosome numbers

Blood pressure levels

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10. Who is known as the father of genetics?

Charles Darwin

Gregor Mendel

James Watson

Louis Pasteur

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11. Which blood type is considered the universal donor?

AB−

O−

O+

AB+

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12. What does gene linkage refer to?

Genes with no effect on phenotype

Genes with multiple alleles

Genes located close together on the same chromosome

Genes found on different chromosomes

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13. Which type of inheritance does not follow Mendel’s law of independent assortment?

Monohybrid cross

Dihybrid cross

Co-dominance

Gene linkage

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14. Which term describes having identical alleles?

Genotypic

Heterozygous

Dominant

Homozygous

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15. In a dihybrid cross, how many different phenotypes can be produced?

2

16

4

3

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16. Which is an example of incomplete dominance?

AB blood group

Hemophilia

Red and white flower making a pink flower

Eye color in humans

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17. What are sex chromosomes also known as?

Autosomes

Allosomes

Gametes

Somatic chromosomes

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18. Crossing over occurs during which phase of meiosis?

Anaphase I

Prophase I

Telophase II

Metaphase I

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19. Which of the following disorders is caused by a recessive gene on the X chromosome?

Sickle cell anemia

Down syndrome

Hemophilia

Huntington’s disease

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20. In Drosophila, red eyes are dominant over white eyes. What is the expected outcome of crossing a red-eyed female (carrier) with a white-eyed male?

All white-eyed offspring

All red-eyed offspring

50% white-eyed females

50% white-eyed males

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21. Which of the following is a statistical tool used to predict inheritance?

Spectrophotometer

Punnett square

Thermometer

Graph paper

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22. What is the law of segregation?

All traits blend in offspring

Alleles for a trait separate during gamete formation

Dominant traits are always expressed

Genes exist only in pairs

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23. Which genotype represents a carrier female for hemophilia?

XHXH

XhXh

XHXh

XHY

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24. In Mendel's experiment, round seeds were dominant over:

Green pods

Tall plants

Yellow seeds

Wrinkled seeds

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25. What is the probability of producing a tall pea plant (Tt × Tt), assuming tall (T) is dominant?

50%

25%

75%

100%

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26. In a dihybrid cross, what phenotypic ratio is expected in the F2 generation?

9:3:3:1

3:1

1:1

2:2

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27. What is the expected phenotypic ratio in a monohybrid cross?

3:1

9:3:3:1

1:2:1

1:1

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28. In humans, sex is determined by:

Autosomes

Environment

X and Y chromosomes

Number of genes

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29. A male with hemophilia inherits the gene from:

His mother

Grandparents

His father

Both parents

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30. What is the genotype of a male in terms of sex chromosomes?

YY

XX

XXY

XY

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31. What is meant by codominance?

Both alleles are fully expressed

Traits blend in offspring

One trait is hidden

One allele is completely dominant

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32. Which term describes the failure of chromosomes to separate properly during meiosis?

Translocation

Inversion

Nondisjunction

Mutation

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33. What tool is used to trace inheritance patterns in families?

Microscope

Pedigree chart

Electrophoresis

PCR

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34. How many chromosomes do human gametes contain?

44

22

46

23

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35. A cross between RR and rr individuals will result in which genotype in F1?

rr

Rr

RR

Rr and rr

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36. Which of the following conditions is caused by multiple alleles?

Blood groups

Hemophilia

Cystic fibrosis

Huntington’s disease

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37. What are alternative forms of a gene called?

Traits

Genotypes

Loci

Alleles

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38. If both parents are heterozygous for a trait, what is the chance their child will be homozygous recessive?

100%

25%

50%

75%

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39. Which of the following is a genetic disorder related to blood clotting?

Color blindness

Sickle cell anemia

Hemophilia

Thalassemia

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40. Which generation did Mendel refer to as F1?

First filial

First parental

Final

Second parental

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41. What does the law of independent assortment state?

Traits are always inherited together

All alleles blend equally

Gene pairs separate independently in gametes

Dominant traits skip generations

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42. How many phenotypes are possible in ABO blood group inheritance?

3

5

4

2

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43. A genotype of “Tt” represents a:

Homozygous dominant

Homozygous recessive

Incomplete dominance

Heterozygous

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44. Who rediscovered Mendel’s work in the early 1900s?

Charles Darwin

Watson and Crick

Thomas Morgan

Hugo de Vries, Carl Correns, Erich von Tschermak

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45. Which of the following represents multiple alleles?

IA, IB, i (blood groups)

XY

Rr

Tt

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46. Which of the following is an example of a sex-linked trait?

Hemophilia

Tongue rolling

Blood type

Eye color

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47. Which term refers to the physical appearance of a trait?

Gene

Phenotype

Genotype

Chromosome

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48. What is the result of crossing over?

Genetic variation

Identical gametes

Clones

No change

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49. What organism did Mendel use in his inheritance experiments?

Fruit flies

Corn

Pea plants

Mice

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50. What does the term "locus" refer to?

Type of mutation

Type of chromosome

Physical location of a gene on a chromosome

Type of allele

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