Meiosis

Question 1

Identical twins

Answer 1

result of one egg fertilized by one sperm; occurs when the morula splits into two masses that develop independently int he uterus; offspring are genetically identical

Question 2

Genetic variation

Answer 2

the permutations and combinations of genes and alleles possible; refers to different combinations of mother’s and father’s alleles in gametes; increases variation in the offspring and translates into better odds of offspring survival in changing environments

Question 3

Fraternal twins

Answer 3

two siblings born at the same time, resulting form he accidental ovulation of two eggs, which are fertilized by two sperm. Fraternal twins are as different as any two siblings

Question 4

Diploid

Answer 4

the chromosome number of a somatic (body) cell; both chromosomes of each homologous pair are present; two sets of chromosomes are present, one from each parent

Question 5

2n

Answer 5

the symbol referring to a diploid cell

Question 6

Haploid

Answer 6

chromosome number of a gamete (sex cell- egg or sperm0, resulting from meiosis; only one chromosome of each homologous pair is present; one set of chromosomes present

Question 7

n

Answer 7

symbol referring to a haploid cell

Question 8

Ploidy

Answer 8

refers to the chromosome number of a cell or how many sets of chromosomes are present; haploid cells have one set, diploid two, tetraploid four, octoploid eight

Question 9

Meiosis I

Answer 9

the first division of meiosis; preceded by DNA replication interphase; results in one secondary oocyte and first polar body in females and two secondary spermatocytes in males. Because homologous pairs are separated from each other in anaphase, cell products are already considered haploid

Question 10

Meiosis II

Answer 10

the second division of meiosis; no DNA replication in interphase; results in one haploid ootid and second polar body in females and four haploid spermatids in males

Question 11

Synapsis

Answer 11

the entering of the homologous pair and attached sister chromatids in prophase I of meiosis; crossing-over between non-sister chromatic may occur

Question 12

Tetrad

Answer 12

formed in prophase of meiosis I when homologous pairs and their attached sister chromatids find each other and entwine in synapsis; may undergo crossing-over with non-sister chromatids, increasing variation in the gametes that result

Question 13

Independent Assortment

Answer 13

one of Mendel’s Laws of Heredity. Occurs spontaneously when alleles of at least two genes are assorted independently into gametes.

Question 14

Alleles

Answer 14

different versions (base sequences) of a gene or trait that will code for slightly different proteins (e.g. sickle cell hemoglobin versus normal hemoglobin). Increased types of alleles int he gene pool increase variation and diversity and protect the species form extinction

Question 15

Crossing over

Answer 15

an occurrence during meiosis I when homologous pairs and their attached sister-chromatids form tetrads, entwine in synapsis, and may be chopped by enzymes into pieces. When chromosomes are reassembled, the mother’s homologue section may be exchanged with the father’s forming chromosomes with new combinations of the mother’s and father’s alleles. This increases variation in gametes and offspring, improving the species’ chances of survival if the environment changes

Question 16

Totipotent

Answer 16

cells that have not specialized or differentiated (e.g. zygote, morula); all genes in the cell have the potential to be expressed (turned on). Totipotent cells have the ability to form a complete organism

Question 17

Clone

Answer 17

to create an exact replica. A cell is a clone if it is the product of asexual reproduction (mitosis or binary fission) that produces two genetically identical cells. An organism can be a clone if it is genetically identical to another organism (e.g. animals can be cloned by taking a nucleus from one animal and inserting it into an empty egg of another, producing an offspring identical to the one that donated the nucleus). Cloning is used in agriculture and pharmaceutical industries to create uniform, consistent products