Cell Division: Variations, regulation, Cancer

Question 1

how many chromosomes do humans have

Answer 1

46, 23 pairs

Question 2

how many chromosomes does each parent contribute at fertilization

Answer 2

23 (haploid)

Question 3

what happens in prophase

Answer 3

the chromosomes condense and become visible

Question 4

what happens in pro metaphase

Answer 4

the spines attach to the centromere

Question 5

what happens in metaphase

Answer 5

the chromosomes line up in the middle of the cell

Question 6

what happens in anaphase

Answer 6

the centromeres split and the chromosomes move to opposite poles

Question 7

what happens in telophase

Answer 7

nuclear envelope re-forms and chromosomes decondense

Question 8

how does a contractile ring work

Answer 8

in animals, a contractile ring of actin pinches cell in two

in plants, a new cell wall is synthesized

Question 9

what is meiotic cell division

Answer 9

reduces the number of chromosomes by Hal to produce haploid gametes or sports that have one copy of each chromosome

Question 10

describe the two meiotic cell divisions

Answer 10

meiosis consists of two successive cell divisions. First is reductional (chromosomal number is halved), second is equational (chromosomal number stays the same)

Question 11

describe meiosis 1

Answer 11

homologous chromosomes pair and exchange genetic material. centromeres do not split and sister chromatids do not separate.

Question 12

describe meiosis 2

Answer 12

similar to mitosis: chromosomes align on the metaphase plate, centromeres split, sister chromatids separate

Question 13

the similarity between meiosis 2 and mitosis suggests that

Answer 13

meiosis is evolved from mitosis

Question 14

what does male meiotic cell division result in

Answer 14

four functional sperm cells

Question 15

what does female meiotic cell division result in

Answer 15

one functional egg, three polar bodies

Question 16

what are cyclins

Answer 16

proteins that increase and decrease during cell cycle.
they form complexes withcyclin-dependant kinases (CDK), activating the CDKs to phosphorylate to get proteins involved in cell division

Question 17

what is p13

Answer 17

protein that prevent cell division in the presence of dna damage

Question 18

what is cancer

Answer 18

uncontrolled cell division that results from mutations in genes that control cell division

Question 19

what are tumor suppressors

Answer 19

encode proteins that block cell division

Question 20

how do cancers form

Answer 20

cancers usually result from several mutations in prooncogenes and tutor suppressor genes that have accumulated over time within the same cell

Question 21

explain segregation of the X and Y chromosomes during meiosis

Answer 21

segregation of the X and Y chromosomes during meiosis results in half the sperm receiving an X chromosome and half receiving a Y

Question 22

describe the X-linked gene inheritance pattern

Answer 22

X-inked genes show a crossers inheritance pattern, in which affected individuals are almost always male. Affected males have unaffected sons, and a female with an affected father can have affected sons

Question 23

genes that are close together in the same chromosome are _____ and do not undergo ______

Answer 23

genes that are close together in the same chromosome are linked and do not undergo independent assortment

Question 24

what are recombinant chromosomes

Answer 24

they result from crossing over between genes on the same chromosome and show non-parental combinations of alleles

Question 25

what are non-recombinant chromosomes

Answer 25

have the same configuration of alleles as one of the parental chromosomes

Question 26

describe the fact that most Y-linked genes are passed from father to son

Answer 26

• Y chromosomes contain a gene called SRY that results in male development
• In y-linked inheritance, only males are affected and all sons of an affected males are affected.
• Females are never affected and do not transmit

Question 27

what are autosomes

Answer 27

chromosomes other than the sec chromosomes

Question 28

segregation f the sex chromosomes predicts a ___ ratio of females to males

Answer 28

1-1

Question 29

describe random fertilization

Answer 29

with random fertilization, had are expected to be XX, hals XY.
the sex of each birth appears to be ransom relative to previous births

Question 30

what is the secondary sex ratio

Answer 30

the secondary sex ratio at birth shows slight excess of males

Question 31

what is wild type

Answer 31

the most common phenotype in a population

Question 32

what is criss-cross inhertitance

Answer 32

an X-chromosome present in a male one generation must be transmitted to a female in the next generation, and in the next generation it can be transmitted back to a male

Question 33

what is nondisjunction

Answer 33

chromosomes that fail to separate in meiosis

Question 34

describe the nondisjunction of the X chromosome

Answer 34

can result in eggs containing either two X chromosomes or no X chromosomes

Question 35

describe nondisjunction in autosomes

Answer 35

results in fetuses that have extra copies or missing copies of entire chromosomes

Question 36

sisters of an infected male have each ____ chance of being a heterozygous carrier

Answer 36

50%

Question 37

what are linked genes

Answer 37

genes that are sufficiently close together in the same chromosome

Question 38

describe linked genes

Answer 38

they tend to be transmitted together in inheritance and do not assort independently of each other

Question 39

when crossing over occurs outside the interval between genes, there is no ____ between the allele of the genes

Answer 39

in this case, there is no recombination between the alleles of the genes

Question 40

crossing over between two genes

Answer 40

this results in two recombinant and two non recombinant chromosomes

Question 41

what is the overall frequency of recombinant chromosomes

Answer 41

this is a measure of the genetic distance between the two genes