Fourth Quarterly Test Reviewer in Biology

During which phase of meiosis does crossing over occur?

• Metaphase I

• Anaphase I

• Prophase I

• Telophase I

Answer explanation

Crossing over occurs during Prophase I of meiosis, where homologous chromosomes exchange genetic material, increasing genetic diversity. This process does not happen in Metaphase I, Anaphase I, or Telophase I.

How many pairs of chromosomes are found in a typical human cell?

• 20

• 21

• 22

• 23

Answer explanation

A typical human cell contains 23 pairs of chromosomes, which include 22 pairs of autosomes and 1 pair of sex chromosomes. This makes 23 pairs in total, confirming that the correct answer is 23.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

What blood type is not possible for a child if the mother has IAi and the father has IBi?

• IAIA

• IAi

• IBi

• ii

Answer explanation

The mother (IAi) can pass IA or i, and the father (IBi) can pass IB or i. Therefore, the possible blood types for their child are IAi, IBi, or ii. However, IAIB is not possible since it requires both parents to contribute IA and IB.

Tags

NGSS.HS-LS3-1

What is the significance of tetrads in meiosis?

• They reduce chromosome number

• They allow crossing over

• They separate sister chromatids

• They create identical cells

Answer explanation

Tetrads, formed during prophase I of meiosis, consist of homologous chromosomes paired together. This configuration allows for crossing over, where genetic material is exchanged, increasing genetic diversity in gametes.

Which of the following describes a heterozygous individual?

• Same alleles (TT or tt)

• Different alleles (Tt)

• Only dominant alleles

• Only recessive alleles

Answer explanation

A heterozygous individual has two different alleles for a trait, represented as Tt. The other options describe homozygous individuals (same alleles) or only dominant/recessive alleles, which do not define heterozygosity.

What is the significance of a carrier in genetics?

• They express a dominant trait

• They express a recessive trait

• They carry a recessive trait but do not express it

• They carry a dominant trait but do not express it

Answer explanation

In genetics, a carrier is an individual who has one copy of a recessive allele but does not express the associated trait. This means they can pass the recessive trait to their offspring without showing it themselves.

Which of the following is true about Turner syndrome?

• It is a result of trisomy

• It is a result of monosomy

• It involves extra chromosomes

• It involves missing chromosomes

Answer explanation

Turner syndrome is caused by the absence of one X chromosome, leading to monosomy (45 chromosomes instead of the usual 46). This makes 'It is a result of monosomy' the correct choice, as it involves missing chromosomes.

Which of the following is NOT a characteristic of meiosis?

• Increases genetic variation

• Reduces chromosome number

• Produces identical cells

• Separates homologous chromosomes

Answer explanation

Meiosis produces genetically diverse cells through processes like crossing over and independent assortment. It reduces chromosome number and separates homologous chromosomes, but it does not produce identical cells.

What is the genotypic ratio for the monohybrid cross shown in the Punnett Square?

• 1 Ss : 1 ss

• 2 Ss : 2 ss

• 3 Ss : 1 ss

• 1 SS : 3 ss

Answer explanation

In the monohybrid cross, the Punnett Square shows a 1:1 ratio of genotypes. The correct choice, 1 Ss : 1 ss, indicates one dominant (Ss) and one recessive (ss) genotype, confirming the expected outcome of this cross.

What is the phenotypic ratio for the monohybrid cross in the Punnett Square?

• 1 short fur : 1 long fur

• 2 short fur : 2 long fur

• 3 short fur : 1 long fur

• 1 long fur : 3 short fur

Answer explanation

In a monohybrid cross, the phenotypic ratio of offspring from two heterozygous parents typically results in 1 short fur : 1 long fur. This indicates that half of the offspring will exhibit short fur and half will exhibit long fur.

Tags

NGSS.HS-LS3-3