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Physiology > Exam 1: Ch. 3 Gene Expression > Flashcards

Exam 1: Ch. 3 Gene Expression Flashcards

1
Q

Gene expression

A

how DNA controls production of proteins

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2
Q

Genes

A

are lengths of DNA that code for polypeptides via synthesis of RNA

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3
Q

mRNA carries

A

information for how to make a protein

Is transported out of nucleus to ribosomes where proteins are made

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4
Q

Gene expression takes place in 2 stages

A

transcription

translation

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5
Q

Transcription

A

occurs when DNA sequence in a gene is turned into a mRNA sequence; occurs in nucleus

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6
Q

translation

A

occurs when mRNA sequence is used to make a protein; occurs in cytoplasm

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7
Q

Each nucleus contains

A

contains 1 or more dark areas called nucleoli

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8
Q

nucleoli

A

contain genes actively making rRNA

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9
Q

genome

A

refers to all genes in an individual or in a species;

- humans have ~35,000 (99.9% species identity)

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10
Q

Proteome

A

refers to all proteins produced by a genome

>100,000 proteins made by ~35,000 genes

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11
Q

chromatin

A

DNA & its associated proteins (=histones);

- threadlike material that makes up chromosomes

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12
Q

histones

A

positively charged & form spools around which negatively charged DNA strands wrap

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13
Q

nucleosome

A

each histone spool & its DNA

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14
Q

euchromatin

A

is the part of chromosomes active in transcription

; light in color

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15
Q

heterochromatin

A

is highly condensed region where genes are permanently inactivated
; darker in color forming blotchy colored spots in nucleus

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16
Q

condensed chromatin

A

where nucleosomes are compacted

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17
Q

acetylation of chromatin

A

produces a more open structure

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18
Q

transcription factors attach to chromatin

A

activate genes (producing RNA)

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19
Q

deacetylation causes

A

compaction of chromatin, silencing genetic transcription

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20
Q

One gene codes for

A

one polypeptide chain

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21
Q

each gene is several thousand

A

nucleotide pairs long

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22
Q

neucletide

A

5 carbon sugar + 1 nitrogenous base + 1 phosphate group

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23
Q

DNA in human cell has

A

3 billion base pairs = > 3 million proteins

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24
Q

DNA in human cell has > 3 billion base pairs = > 3 million proteins but human proteome has up to 150,000 proteins so only a fraction of DNA is actively used to make proteins….WHY?

A

the rest are junk

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25
Q

synthesis = Transcription

A

transcription

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26
Q

For transcription to occur

A

RNA polymerase binds to a “start” sequence on DNA & unzips strands

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27
Q

Nearby are promoter regions which

A

which regulate levels of transcription

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28
Q

Transcription factors

A

regulatory molecules that must bind to promoter region of a gene to initiate transcription

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29
Q

RNA synthesis:

Only 1 strand of DNA serves as a

A

template for RNA synthesis and contains the gene & is transcribed into RNA

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30
Q

RNA base pairs

A

G pairs with C; A pairs with U; a T in DNA codes for A when copied to RNA

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31
Q

RNA polymerase detaches when

A

hits a “stop” sequence

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32
Q

Transcription produces

A

3 types of RNA:

  • mRNA
  • tRNA
  • rRNA
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33
Q

pre-mRNA

A

(precursor messenger RNA); altered in nucleus to form mRNA

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34
Q

mRNA

A

= (messenger RNA) = contains the code for synthesis of a protein

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35
Q

tRNA

A

(transfer RNA) - decodes the info contained in mRNA

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36
Q

rRNA

A

(ribosomal RNA) forms part of ribosomes

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37
Q

Pre-mRNA is much larger than

A

mRNA and must be processed before leaving the nucleus

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38
Q

Pre-mRNA contains

A

non-coding regions within the gene called introns, which are spliced out of the sequence

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39
Q

how many introns can a single gene have

A

50 introns

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40
Q

coding regions are called

A

exons

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41
Q

in nucleus, introns are

A

, introns are removed & ends of exons spliced together to produce final mRNA

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42
Q

protein synthesis

A

Translation occurs 1 amino acid at-a-time according to sequence of base triplets in mRNA

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43
Q

codon

A

triplets in mRNA

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44
Q

in cytoplasm, mRNA

A

mRNA attaches to several ribosomes forming “string-of-pearls” structure called a polysome where translation occurs

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45
Q

At ribosomes 3 mRNA bases are read as

A

a triplet

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46
Q

each triplet is a

A

codon

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47
Q

codon

A

(3-nitrogenous bases that make a word)

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48
Q

codon/triplet specifies

A

an amino acid

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49
Q

ribosomes translate codons into

A

an amino acid sequence that becomes a polypeptide chain

50
Q

codons are read at the

A

ribosome with the help of tRNA, which reads codons as anticodons

51
Q

Translation of codons is achieved by

A

tRNA and enzymes

52
Q

tRNA contains

A

3 loops, one of which contains an anticodon

53
Q

anticodon is complementary to

A

complementary to a specific mRNA codon

54
Q

tRNA carries

A

he amino acid specified by its anticodon to the growing chain of aa’s

55
Q

Protein synthesis:

from the ribosomes

A

At a ribosome, anticodons of tRNA bind to mRNA codons

Amino acids on adjacent tRNAs are brought together & linked enzymatically by peptide bonds

As the polypeptide chain grows, it twists into a helix (secondary structure) and folds and bends and on itself further (tertiary structure)

Polypeptide continues to form and at end detaches from ribosome

Further modifications occur in the RER and Golgi

56
Q

functions of ER:

Proteins used in the cell are made on

A

polyribosomes that are free

57
Q

Functions of ER:

Proteins to be secreted are made at

A

ribosomes of rough ER

58
Q

Functions of ER:

amino acids in leader sequence (~ 1st 30 aa’s) of newly-made proteins are

A

hydrophobic and attracted to ER membrane causing new protein to enter cisternae of ER

59
Q

functions of ER:

what happens after new protein enter cisgternae of ER

A

leader sequence removed and the protein is modified

60
Q

Functions of Golgie:

secretory proteins leave ER in vesicles and

A

go to Golgi

packaging and shipping

61
Q

In the Golgi complex:

A
  1. Carbohydrates are added to make glycoproteins
  2. Proteins are separated according to function and destination
  3. Vesicles leave Golgi for lysosomes or exocytosis
62
Q

DNA Replication:

when cells divide

A

DNA replicates itself & identical copies go to 2 daughter cells

63
Q

helicases

A

break hydrogen bonds of double helices to produce 2 free strands of DNA

64
Q

DNA polymerase

A

binds to each strand & makes new complementary copy of old strand using A-T, C-G pairing rules

65
Q

each new copy of complementary base pair is composed of 1 new strand & 1 old strand (called

A

semiconservative replication

66
Q

in DNA Replication Original DNA sequence is

A

preserved

67
Q

Most cells of body are in

A

interphase

68
Q

interphase

A

the non-dividing stage of life cycle

69
Q

interphase is subdivided into:

A

G1
S
G2

70
Q

G1

A

cell performs normal physiological roles

71
Q

S

A

DNA is replicated in preparation for division

72
Q

G2

A

chromatin condenses prior to division

73
Q

cyclins

A

group of proteins that promote different phases of cell cycle

74
Q

Overactivity of genes that code for some cyclins is associated with

A

cancer

75
Q

oncogenes

A

genes whose mutations are associated with cancer

Mutated forms of normal genes

76
Q

Tumor suppresor genes

A

inhibit cancer development

77
Q

tumor suppresor genes example

A

gene p53 inhibits cyclin activity

78
Q

Mutations in p53 are associated with

A

50% of cancers

79
Q

cell death occurs in 2 ways

A

necrosis

apoptosis

80
Q

necrosis

A

occurs when pathological changes kill a cell and thus tissue

81
Q

apoptosis

A

programmed cell death occurs as a normal physiological response controlled by proteins; tissue repair (immunity) and remodeling (stomach and skin)

82
Q

Mitosis (M phase)

A

phase of life cycle when cell divides

83
Q

Chromosomes are duplicated during

A

interphase condensed

84
Q

interphase condensed consists of

A

2 duplicate identical connected chromosome strands called chromatids, which are connected by a centromere

85
Q

4 stages of mitosis

A

prophase, metaphase, anaphase, telophase

86
Q

in prophase

A

chromosomes become visible distinct structures

87
Q

prophase

A
  • chromosomes are seen to consist of 2 chromatids joined by a centromere
  • the centrioles move apart toward opposite poles of the cell
  • spindle fibers are produced and extend from each centrosome
  • the nuclear membrane starts to disappear
  • the nucleolus is no longer visible
88
Q

in metaphase

A

chromosomes line up single file along equator; pulled by protein spindle fibers

89
Q

in anaphase

A

centromeres split; spindle fibers pull each chromatid to opposite poles

90
Q

during telophase

A

the cytoplasm is divided (= cytokinesis), producing 2 daughter cells

91
Q

All animal cells have a

A

centrosome located near nucleus in interphase

92
Q

centrosome

A

microtubule organizing center; microtubules form spindle fibers

93
Q

centrosome is duplicated in

A

in G1 if cell is going to divide replicates move to opposite poles by metaphase

94
Q

Microtubules grow from

A

centrosomes to form spindle fibers which attach to centromeres of chromosomes

95
Q

Spindle fibers pull

A

chromosomes to opposite poles during anaphase

96
Q

telomeres

A

non-coding regions of DNA at ends of chromosomes

97
Q

Each time a cell divides, a length of telomere is lost

Because

A

DNA polymerase can’t copy the very end of DNA strand; each repilcation loses 50 – 100 base pairs

98
Q

When telomere is used up

A

cell becomes senescent
Believed to represent a molecular clock for aging
That ticks down with each division

99
Q

Germinal (eggs/sperm) & cancer cells can

A

can divide indefinitely & do not age

100
Q

telomeres:

Germinal and cancer cells have

A

enzyme telomerase which replaces nucleotides lost from telomere during divisions

101
Q

Organisms grow by

A

increasing the number of cells and size of cells:

102
Q

hypertrophy

A

growth due to an increase in the size of cells

103
Q

what can only grow by hypertrophy

A

Skeletal and cardiac muscle

104
Q

atrophy

A

decrease in cell size, opposite of hypertrophy

105
Q

hyperplasia

A

growth due to an increase in the number of cells

106
Q

hyperplasia results from

A

mitotic divisions

107
Q

hyperplasia is responsible for

A

for most growth

108
Q

gametes

A

oocytes and sperm cells

109
Q

gametes each carry

A

23 chromosomes, which are structurally identical to each other
Note: This does not mean that the nucleotide sequence if identical

110
Q

When fertilization occurs, the 23 chromosomes from the egg will

A

pair with the 23 chromosomes carried by sperm and 23 pairs will be formed

111
Q

each pair of chromosomes is called

A

homologous chromosomes

112
Q

homologous chromosomes example

A

The 23rd chromosome from sperm pairs with the 23rd chromosome from the egg forming homologous chromosomes and this pair will determine the genetic sex of the new organism

113
Q

meiosis

A

process of making gametes (ova & sperm) containing ½ genetic material

114
Q

meiosis occurs in

A

gonads (ovaries and testes)

115
Q

meiosis is

A

proceeded by interphase

116
Q

meiosis only makes

A

eggs and sperm

117
Q

meiosis =

A

reduction division

 Like mitosis except goes to two rounds of pMats

118
Q

meiosis has 2 divisional sequences

A

DNA is replicated once & divided twice

119
Q

In 1st division homologous chromosomes pair along equator of cell rather is

A

1 member of homolog pair is pulled to each pole

This gives each daughter cell 23 different chromosomes, consisting of 2 chromatids

120
Q

In 2nd division each daughter divides, chromosomes split into 2 chromatids

A

1 goes to each new daughter cell
Each daughter contains 23 chromosomes rather than 46 like parent cell
Which is why meiosis is called reduction division

Physiology (27 decks)

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