Genetics & Meiosis Review

In pea plants, the tall allele is dominant to the short allele. What key would demonstrate this?

• Tall = T
  Short = S

• Tall = T
  Short = t

• Tall = t
  Short = T

• Tall = TT
  Short = tt

Answer explanation

The correct key is 'Tall = T
Short = t' because 'T' represents the dominant tall allele, while 't' represents the recessive short allele. This notation clearly indicates the dominance relationship between the alleles.

In a Punnett square, a lower case letter stands for a ____________ allele.

• dominant

• recessive

• homozygous

• heterozygous

Answer explanation

In a Punnett square, a lower case letter represents a recessive allele. Recessive alleles are masked by dominant alleles, which are represented by uppercase letters.

What is the genotypic ratio of the offspring?

• 3:1

• 1:3

• 1:2:1

• 2:2

Answer explanation

The genotypic ratio of 1:2:1 indicates that in a monohybrid cross, one offspring will be homozygous dominant, two will be heterozygous, and one will be homozygous recessive, making this the correct answer.

If green is dominant over purple, then what is the genotype for this individual?

• Purple

• Green

• GG

• gg

Answer explanation

Since green is dominant over purple, a purple phenotype indicates a homozygous recessive genotype. Therefore, the individual must have the genotype gg, which corresponds to the purple color.

This is an example of

• Complete dominance

• Mendelian Genetics

• Codominance

• Incomplete Dominance

Answer explanation

Codominance occurs when both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows both traits simultaneously. This is distinct from complete dominance, where one allele masks the other.

Some flowers are controlled by codominance. Red flowers (RR), blue flowers (BB) and Speckled flowers (RB).

Cross a red flower with a speckled flower. What is the phenotypic ratio?

• 2 red, 2 speckled

• 2 red, 2 blue

• 2 blue, 2 speckled

Answer explanation

Crossing a red flower (RR) with a speckled flower (RB) results in 2 red (RR) and 2 speckled (RB) offspring. Thus, the phenotypic ratio is 2 red to 2 speckled.

Why do we need meiosis?

• To double the number of chromosomes going into sex cells

• To halve the number of chromosomes going into sex cells

• To triple the number of chromosomes going into sex cells

• To not change the number of chromosomes going into sex cells

Answer explanation

Meiosis is essential because it halves the number of chromosomes in sex cells (gametes). This reduction ensures that when fertilization occurs, the resulting zygote has the correct diploid number of chromosomes.

Human eggs and sperm are _____, and each has ____ chromosomes.

• diploid, 23

• diploid, 46

• haploid, 23

• haploid, 46

Answer explanation

Human eggs and sperm are haploid, meaning they contain half the number of chromosomes. Each has 23 chromosomes, which is crucial for sexual reproduction, allowing the combination of genetic material from both parents.

How many daughter cells are produced from meiosis ?

• 10

• 6

• 4

• 2

Answer explanation

Meiosis produces four daughter cells through two rounds of division (meiosis I and II), each with half the chromosome number of the original cell. Therefore, the correct answer is 4.

If you cross a black guinea pig with a white guinea pig and the offspring are gray, what type of dominant trait would that be.

• incomplete dominance

• codominance

• codependant

• cooperative

Answer explanation

The gray offspring result from a black and white guinea pig cross indicates incomplete dominance, where neither trait is fully dominant, leading to a blending of traits in the phenotype.