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bio 137 > chapter four: DNA replication and the cell cycle & chromosomes and heredity > Flashcards

chapter four: DNA replication and the cell cycle & chromosomes and heredity Flashcards

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Biology 101 flashcards
1
Q

What is DNA replication accomplished through?

A

the law of complementary base pairings

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2
Q

What is the first step of the replication process?

A

the double helix unwinds from the histones

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3
Q

What is the function of DNA helicase?

A

an enzyme that “unzips” DNA by opening up one short segment of the helix at a time, exposing its nitrogenous bases

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4
Q

What is the replication fork?

A

the point where DNA is opened up

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5
Q

What is DNA polymerase?

A

an enzyme that moves along each strand of the DNA reading the exposed bases and “matches” complementary base pairs

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6
Q

How are the two separated DNA strands copied?

A

copied by separate polymerase molecules going in opposite directions

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7
Q

What does the polymerase that is moving toward the replication fork make?

A

makes a long, continuous, new strand of DNA to complement the old one

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8
Q

What does the polymerase that moves away from the replication fork copy?

A

copies only a short segment of DNA at a time

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9
Q

What is DNA ligase?

A

an enzyme that joins together the new segments of DNA

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10
Q

What is semiconservative replication?

A

each daughter DNA consists of one new helix and one old helix conserved from the parental DNA

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11
Q

What is the DNA damage response?

A

corrects replication errors

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12
Q

What is one way DNA polymerase prevents damage to cells?

A

double checks the new base pair and replaces an incorrect unstable pair with a more stable, correct pair

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13
Q

What are mutations?

A

changes in DNA structure

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14
Q

What can mutations result from?

A

replication errors
environmental factors (radiation, chemicals, and viruses)

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15
Q

What is one reason mutations may not have an adverse effect?

A

a new base sequence may sometimes code for the same amino acid as the old one

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16
Q

What are the four main phases of the cell cycle?

A

G1
S
G2
M

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17
Q

What phase of the cell cycle is between cell division and DNA replication?

A

G1

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18
Q

What occurs during the G1 phase?

A

a cell synthesizes proteins, grows, and carries out its predestined tasks for the body
accumulates the materials needed to replicate

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19
Q

What occurs during the S phase?

A

a cell makes a duplicate copy of its centrioles and DNA

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20
Q

At what point in the cell cycle does the cell carry out semi conservation replication?

A

S phase

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21
Q

What phase of the cell cycle occurs between DNA replication and cell division?

A

G2

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22
Q

What occurs during the G2 phase? (4)

A

a cell grows more
makes more organelles
finishes replicating its centrioles
synthesizes enzymes that control cell division

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23
Q

In which phase of the cell cycle does the cell check the accuracy of DNA replication and repair any errors?

A

G2

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24
Q

What is the M/mitotic phase?

A

a cell replicates its nucleus and then pinches in two to form two new, identical daughter cells

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25
Q

What is interphase?

A

the part of the cell cycle between one mitotic phase and the next; includes G1, S, and G2

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26
Q

What is G0 phase?

A

“rest” phase where cells stop dividing

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27
Q

What is mitosis?

A

a form of cell division in which a cell divides once and produces two genetically identical daughter cells

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28
Q

What are the four phases of mitosis?

A

prophase
metaphase
anaphase
telophase
(PMAT)

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29
Q

What happens during prophase?

A
  • chromosomes condense
  • nuclear envelope breaks down to release chromosomes into the cytosol
  • centrioles begin to form spindle fibers and migrate to opposite poles of the cell
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30
Q

What happens during metaphase?

A
  • chromosomes align along the midline of cell
  • spindle fibers attach to kinetochores
  • fibers of aster attach to plasma membrane
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31
Q

What happens during anaphase?

A
  • centromeres divide in two
  • spindle fibers pull sister chromatids to opposite poles of cell
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32
Q

After anaphase, what does each pole now have?

A

an identical set of genes

33
Q

What happens during telophase?

A
  • chromosomes gather at each pole of cell and decondense
  • nuclear envelope appears at each pole
  • nucleoli appear in each nucleus
  • mitotic spindle disappears
33
Q

What happens during telophase?

A
  • chromosomes gather at each pole of cell and decondense
  • nuclear envelope appears at each pole
  • nucleoli appear in each nucleus
  • mitotic spindle disappears
34
Q

What is cytokinesis?

A

the division of the cytoplasm into two cells

35
Q

What are the 5 times cells divide?

A
  1. they have a large enough cytoplasm
  2. replicated their DNA
  3. receive an adequate supply of nutrients
  4. stimulated by growth factors
  5. neighboring cells divide
36
Q

What are growth factors?

A

a chemical messenger that stimulates mitosis

37
Q

What is contact inhibition?

A

the cessation of cell division in response to contact with other cells

38
Q

Can Cdks work without cyclins?

A

no, without cyclins, Cdks lie dormant and do not function

39
Q

How do checkpoints control the cell cycle?

A

checkpoints determine whether a cell can move on to the next phase of the cycle

40
Q

What is the start or G1 checkpoint?

A

the checkpoint that either allows the cell to proceed toward the S phase or into the G0 phase

41
Q

What is the G2/M checkpoint?

A

the checkpoint that determines whether the cell is able to proceed to mitosis

42
Q

What is heredity?

A

the transmission of genetic characteristics from parent to offspring

43
Q

What are the agents of heredity?

A

genes

44
Q

Where are genes carried?

A

chromosomes

45
Q

What is a karyotype?

A

a chart that lays the 46 chromosomes out in order by size

46
Q

What are homologous chromosomes?

A

the two members of each pair of chromosomes

47
Q

How many pairs do chromosomes occur as?

A

23

48
Q

Which chromosomes are the sex chromosomes?

A

X and Y

49
Q

What are autosomes?

A

any chromosome except the sex chromosomes

50
Q

What is a diploid cell?

A

a cell with 23 pairs of chromosomes; 46 in total

51
Q

What is a haploid cell?

A

a cell with 23 unpaired chromosomes

52
Q

What cells are haploid cells?

A

sperm and egg

53
Q

What are germ cells?

A

a gamete (sperm or egg)

54
Q

What are somatic cells?

A

all other cells besides sperm and egg cells of the body

55
Q

What is the site on a chromosome where a given gene is located?

A

locus

56
Q

What are alleles?

A

the alternative forms that one gene can take; one of two or more versions of DNA sequence (a single base or a segment of bases) at a given gene location

57
Q

What is a dominant allele?

A

the genetic allele that is phenotypically expressed in the presence of any other allele

58
Q

What is a recessive allele?

A

the genetic allele that is not phenotypically expressed in the presence of a dominant allele

59
Q

What are individuals with two identical alleles said to be for that trait?

A

homozygous

60
Q

What are individuals with different alleles for a gene said to be?

A

heterozygous

61
Q

What is a genotype?

A

the paired alleles that an individual possesses for a particular trait

62
Q

What is a phenotype?

A

the observable trait resulting from the genotype

63
Q

What is an expressed allele?

A

an allele is expressed if it shows in the phenotype of an individual

64
Q

What is a carrier?

A

a person who is heterozygous for a recessive allele and does not exhibit the associated phenotype, but may transmit this allele to his or her children

65
Q

What are multiple alleles?

A

genes that exist in more than two allelic forms
(ex. there are 3 alleles for blood type)

66
Q

What is a gene pool?

A

the combination of all the genes present in a population or species

67
Q

What are codominant alleles?

A

alleles that are equally dominant

68
Q

What is incomplete dominance?

A

when two different alleles are present, the phenotype is an intermediate between the traits that each allele would produce alone

69
Q

What is polygenic inheritance?

A

genes at two or more loci, or on different chromosomes, contribute to a single phenotypic trait

70
Q

What are two examples of polygenetic inheritance?

A

eye and skin color

71
Q

What is pleiotropy?

A

one gene produces multiple phenotypic effects

72
Q

What are sex-linked traits?

A

traits carried on the X or Y chromosomes so they tend to be inherited by one sex more than the other

73
Q

If an allele is dominant and is not expressed, what is this called?

A

incomplete penetrance

74
Q

What does all gene expression depend on?

A

nutrition

75
Q

What are epigenetic effects?

A

reversibly activating or silencing genes without changes in base sequence

76
Q

What is DNA methylation?

A

adding methyl groups to DNA bases which silence genes

77
Q

What is epigenetic inheritance?

A

the ability to pass on changes in gene expression to the next generation without changes in the structure of the genes themselves

78
Q

What habits and experiences may affect gene expression in our children?

A

diet
smoking
use of drugs
pollution
stress
epidemics
famines

bio 137 (9 decks)

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