Exam 1 Review (Bio 375- Genetics)

Question 1

Prokaryotic cell

Answer 1

no nucleus; no paired chromosomes (haploid); typically single circular chromosome consisting of a single origin of replication; single chromosome is replicated with each copy moving to opposite sides of the cell; no histone proteins complexed to DNA

Question 2

Eukaryotic Cell

Answer 2

nucleus present; paired chromosomes common (diploid); typically multiple linear chromosomes consisting of centromeres, telomeres, and multiple origins of replication; chromosomes are replicated but require mitosis or meiosis to ensure that chromosome migrates to the proper location; histone proteins are complexed to DNA

Question 3

three predominant stages of interphase of cells active in the cell cycle

Answer 3

G1 -> S Phase -> G2

Question 4

G1 (Gap 1)

Answer 4

cell grows and synthesizes proteins necessary for cell division; once the cell passes the G1/S checkpoint then the cell is committed to divide

Question 5

S phase

Answer 5

DNA replication takes place

Question 6

G2 (Gap 2)

Answer 6

additional biochemical reactions take place that prepare the cell for mitosis; once the cell passes the major G2/M checkpoint it enters into mitosis

Question 7

G0

Answer 7

nondividing stage; found in cells prior to G1/S checkpoint; cells may exit active cell cycle to enter this nondivision stage

Question 8

checkpoints

Answer 8

function to ensure that all cellular components (such as important proteins and chromosomes) are present and functioning before the cell moves to the next stage of the cell cycle; if components are missing or not functioning, then these will prevent the cell from moving to the next stage; these prevent defective cells from replicating and malfunctioning

Question 9

checkpoints of cell cycle

Answer 9

G1/S checkpoint (occurring during G1 prior to S phase); G2/M checkpoint (occurring during G2 prior to mitosis); and spindle-assembly checkpoint (occurring during mitosis)

Question 10

meiosis processes responsible for genetic variation

Answer 10

crossing over, random distribution

Question 11

point during meiosis at which crossing over takes place

Answer 11

begins during the zygotene stage of prophase I and is completed near the end of prophase I

Question 12

point during meiosis at which random distribution of chromosomes to daughter cells takes place

Answer 12

anaphase I of meiosis

Question 13

spermatogenesis

Answer 13

primordial diploid germ cells divide mitotically to produce diploid spermatogonia that can either divide repeatedly by mitosis or enter meiosis. spermatogonium that entered prophase I of meiosis is called a primary spermatocyte and is diploid. upon completion of meiosis I, two haploid cell called secondary spermatocytes are produced. upon completing meiosis II, the secondary spermatocytes produce a total of four haploid spermatids. the spermatids then mature to yield sperm.

Question 14

oogenesis

Answer 14

primordial diploid cells divide mitotically to produce diploid oogonia that can divide repeatedly by mitosis or enter meiosis. oognonium that entered prophase I of meiosis is called a primary oocyte and is diploid. upon completion of meiosis I, the cell divides but unequally. one of the newly produced haploid cells receives most of the cytoplasm and is called the secondary oocyte. the other haploid cell receives only a small portion of the cytoplasm and is called the first polar body. ultimately, the secondary oocyte will complete meiosis II and produce two haploid cells. one cell, the ovum, will receive most of the cytoplasm from the secondary oocyte. the smaller haploid cell is called the second polar body. typically, the polar bodies disintegrate and only the ovum is capable of being fertilized

Question 15

acrocentric chromosome

Answer 15

a chromosome with the centromere located very close to one end

Question 16

metacentric chromosome

Answer 16

Chromosome in which the two chromosome arms are approximately the same length

Question 17

submetacentric chromosome

Answer 17

A chromosome in which the centromere establishes a long arm and a short arm– in which the centromere is halfway between the top and the middle of the chromosome

Question 18

telocentric chromosome

Answer 18

Chromosome in which the centromere is at or very near one end.

Question 19

chromosome alignment in metaphase of mitosis

Answer 19

lined up with centromeres on the metaphase plate

Question 20

(mitosis) G2

Answer 20

4n number of DNA and 2n number of chromosomes - DNA molecules were replicated in S phase

Question 21

(meiosis) metaphase I

Answer 21

4n number of DNA and 2n number of chromosomes - neither homologous chromosomes nor sister chromatids have separated

Question 22

(mitosis) prophase

Answer 22

4n number of DNA and 2n number of chromosomes

Question 23

(meiosis) anaphase I

Answer 23

4n number of DNA and 2n number of chromosomes - homologous chromosomes separate and begin moving to opposite ends of cell, but sister chromatids do not separate

Question 24

(meiosis) anaphase II

Answer 24

2n number of DNA and 2n number of chromosomes - sister chromatids separate, resulting in temporary doubling of chromosome number in haploid daughter cell

Question 25

(meiosis) Prophase II

Answer 25

2n number of DNA and n number of chromosomes - daughter cells are haploid

Question 26

(mitosis) after cytokinesis (during telophase)

Answer 26

2n number of DNA and number of chromosomes - daughter cells enter G1 after mitosis

Question 27

(meiosis) after cytokinesis (during telophase II)

Answer 27

n number of DNA and number of chromosomes

Question 28

determining diploid number

Answer 28

determine number of centromeres present within a cell that contains homologous pairs of chromosomes, recalling that each chromosome possesses a single centromere

Question 29

location/presence of a centromere

Answer 29

determined by attachment of spindle fibers to chromosome

Question 30

anaphase of meiosis I

Answer 30

separation of homologous pairs of chromosomes

Question 31

anaphase of mitosis

Answer 31

cell contains diploid chromosome number for species, but sister chromatids have separated to result in a doubling of chromosome number within cell

Question 32

anaphase II of meiosis

Answer 32

sister chromatids are being separated, but there are no homologous chromosomes present within the cell

Question 33

independent assortment

Answer 33

occurs during anaphase I of meiosis

Question 34

separation of chromatids

Answer 34

occurs during anaphase of mitosis and anaphase II of meiosis

Question 35

crossing over

Answer 35

occurs during prophase I of meiosis

Question 36

bivalent pairs line up on metaphase plate

Answer 36

occurs during metaphase I of meiosis

Question 37

spermatogonium

Answer 37

2n number of DNA and number of chromosomes (assuming that it is in G1 prior to S phase)

Question 38

first polar body

Answer 38

2n number of DNA and n number of chromosomes (it is a product of meiosis I so it will be haploid, but sister chromatids have not separated so each chromosome consists of two sister chromatids)

Question 39

primary oocyte

Answer 39

4n number of DNA and 2n number of chromosomes (it is stopped in prophase I of meiosis, so homologues have not yet separated and each chromosome consists of two sister chromatids)

Question 40

secondary spermatocyte

Answer 40

2n number of DNA and n number of chromosomes (it is the product of meiosis I and has yet to enter meiosis II, so it will be haploid because the homologous pairs were separated in meiosis I but each chromosome is still composed of two sister chromatids)

Question 41

principle of segregation (mendel’s first law)

Answer 41

states that an organism possesses two alleles for any one particular trait and that these alleles separate during the formation of gametes; ie one allele goes into each gamete; explains that homologous chromosomes segregate during anaphase I of meiosis

Question 42

concept of dominance

Answer 42

when two different alleles are present in a genotype, only the dominant allele is expressed in the phenotype

Question 43

incomplete dominance

Answer 43

when different alleles are expressed in a heterozygous individual, the resulting phenotype is intermediate to the phenotypes of the two homozygotes

Question 44

principle of independent assortment

Answer 44

genes for different characteristics and at different loci segregate independently of one another; an extension of the principle of segregation

Question 45

principle of segregation vs principle of independent assortment

Answer 45

principle of segregation indicates that the two alleles at a locus separate; principle of independent assortment indicates that the separation of alleles at one locus is independent of the separation of other pairs at other loci

Question 46

principle of independent assortment relation to meiosis

Answer 46

in anaphase I of meiosis, each pair of homologous chromosomes separates independently of all other pairs of homologous chromosomes. assortment of homologues explains how genes located on different pairs of chromosomes will separate independently of one another

Question 47

testcross

Answer 47

cross between an organism with an unknown genotype and an organism with a recessive phenotype

Question 48

binomial equation

Answer 48

(n!/s!t!)p^sq^t

Question 49

chi square test

Answer 49

sum of (observed-expected)^2/expected

Question 50

XX-XO system of sex determination

Answer 50

females have two copies of sex-determining chromosome, whereas males have only one copy. males must be considered heterogametic because they produce two different types of gametes with respect to the sex chromosome: either containing an X or not containing an X

Question 51

XX-XY system vs ZZ-ZW system of sex determination

Answer 51

in XX-XY system, males are heterogametic and produce gametes with either an X chromosome or a Y chromosome; in ZZ-ZW system, females are heterogametic and produce gametes with either a Z or a W chromosome

Question 52

pseudoautosomal region

Answer 52

region of similarity between X and Y chromosomes that is responsible for pairing the X and Y chromosomes during meiotic prophase I

Question 53

inheritance of genes in pseudoautosomal region vs inheritance of other Y-linked characteristics

Answer 53

genes in this region are present in two copies in males and females and thus are inherited like autosomal genes; whereas other Y-linked genes are passed on only from father to son

Question 54

tortoiseshell cats

Answer 54

have two different alleles of an X-linked gene: X+ (non-orange / black) and X° (orange)… patchy distribution results from X-inactivation during early embryo development. each cell of early embryo randomly inactivates one of the two X chromosomes, and the inactivation is maintained in all of the daughter cells. so each patch of black fur arises from a single embryonic cell that inactivated X° and each patch of orange fur arises from an embryonic cell that inactivated X+

Question 55

Barr body

Answer 55

darkly staining bodies in nuclei of female mammalian cells; Mary Lyon hypothesized that they are inactivated (condensed) X chromosomes. by inactivating all X chromosomes beyond one, female cells achieve dosage compensation for X-linked genes