Biology

Question 1

What is the total number of chromosomes in humans?

Answer 1

46 chromosomes in 23 pairs

Question 2

What are the two types of chromosomes in humans?

Answer 2

• 22 autosomal chromosomes
• 1 pair of sex chromosomes (XX for female, XY for male)

Question 3

Define ‘genes’.

Answer 3

A segment of DNA that codes for a particular trait; found at a specific location on a chromosome.

Question 4

What is a locus?

Answer 4

The location of a gene on a chromosome.

Question 5

What are alleles?

Answer 5

Different versions/forms of a gene (ex. green or blue or brown for eye colour).

Question 6

What is a trait?

Answer 6

A characteristic of an organism (ex. hair colour or sound of your voice).

Question 7

What is chromatin?

Answer 7

Mass of long thin fibres made of DNA with hundreds or thousands of genes on it, wrapped around protein.

Question 8

Define ‘chromosome’.

Answer 8

A more condensed version of chromatin.

Question 9

What are sister chromatids?

Answer 9

Two identical copies formed by the replication of a single chromosome, joined together by a common centromere.

Question 10

What are the phases of the cell cycle?

Answer 10

• G1 phase: growth and metabolic activity
• S phase: DNA replication
• G2 phase: growth, prepares for cell division

Question 11

What is mitosis?

Answer 11

The process by which a eukaryotic cell divides the genetic material in its nucleus into two new identical nuclei.

Question 12

How many stages are there in mitosis?

Answer 12

4 stages plus cytokinesis (PMAT-C).

Question 13

What happens during cytokinesis?

Answer 13

Division of the cytoplasm and organelles, forming a cleavage furrow in animal cells and a cell plate in plant cells.

Question 14

List the functions of cell division and mitosis.

Answer 14

• Growth of the organism
• Repair of tissues and organs
• Maintenance (to replace old or dead cells)
• Asexual reproduction

Question 15

What occurs during prophase of mitosis?

Answer 15

• Chromatin condenses to form visible chromosomes
• Nuclear membrane breaks down
• Duplicated centrioles migrate to opposite poles
• Spindle fibres begin to form

Question 16

What happens during metaphase of mitosis?

Answer 16

• Spindle fibres attach to chromosomes’ centromere
• Chromosomes align along the equatorial plate.
• Sister chromatids face opposite poles.

Question 17

Define ‘meiosis’.

Answer 17

A process that produces gametes with half the number of chromosomes (haploid) and introduces genetic variation.

Question 18

What is the difference between diploid and haploid?

Answer 18

• Diploid (2n): has homologous pairs (ex. human 2n = 46)
• Haploid (n): has only one set of chromosomes (ex. human n = 23)

Question 19

What is the result of asexual reproduction?

Answer 19

Offspring that are genetically identical to a single parent.

Question 20

What is the significance of independent assortment during meiosis?

Answer 20

Increases genetic variation as maternal and paternal chromosomes arrange themselves randomly.

Question 21

What is gametogenesis?

Answer 21

The process in which cells undergo meiosis to form gametes.

Question 22

What is spermatogenesis?

Answer 22

Meiosis that occurs in the testes and produces sperm, starting from a diploid cell called a spermatogonium.

Question 23

What is oogenesis?

Answer 23

Meiosis that occurs in the ovaries and produces ova (eggs), starting from a diploid cell called an oogonium.

Question 24

Define euploidy.

Answer 24

The condition of having the correct number of chromosomes (human = 46).

Question 25

Define aneuploidy.

Answer 25

Condition of having an incorrect number of chromosomes.

Question 26

What is nondisjunction?

Answer 26

The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division.

Question 27

What is a karyotype?

Answer 27

A picture of a person’s particular set of chromosomes, arranged and numbered in order of length.

Question 28

What is trisomy 21?

Answer 28

Down’s Syndrome, an autosomal condition caused by an extra chromosome.

Question 29

Who is Gregor Mendel?

Answer 29

The scientist who figured out inheritance patterns through experiments with pea plants.

Question 30

What are Mendel's conclusions about traits?

Answer 30

* There are alternative forms of traits (alleles) * Alleles can be dominant and recessive * Organisms receive one allele from each parent

Question 31

Define genotype.

Answer 31

An organism’s genetic information.

Question 32

Define phenotype.

Answer 32

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Question 33

What is the law of segregation?

Answer 33

During the formation of gametes, the two alleles for a trait separate, so that each gamete carries only one allele.

Question 34

What is incomplete dominance?

Answer 34

A genetic situation in which one allele does not completely dominate another allele.

Question 35

What is codominance?

Answer 35

A genetic situation where both alleles are expressed in the phenotype.

Question 36

What is a dihybrid cross?

Answer 36

A cross between two organisms that are heterozygous for two traits.

Question 37

What is Mendel’s second law?

Answer 37

Every gene separates independently of one another.