Exam 1: Ch. 3 Gene Expression Flashcards
1
Q
Gene expression
A
how DNA controls production of proteins
2
Q
Genes
A
are lengths of DNA that code for polypeptides via synthesis of RNA
3
Q
mRNA carries
A
information for how to make a protein
Is transported out of nucleus to ribosomes where proteins are made
4
Q
Gene expression takes place in 2 stages
A
transcription
translation
5
Q
Transcription
A
occurs when DNA sequence in a gene is turned into a mRNA sequence; occurs in nucleus
6
Q
translation
A
occurs when mRNA sequence is used to make a protein; occurs in cytoplasm
7
Q
Each nucleus contains
A
contains 1 or more dark areas called nucleoli
8
Q
nucleoli
A
contain genes actively making rRNA
9
Q
genome
A
refers to all genes in an individual or in a species;
- humans have ~35,000 (99.9% species identity)
10
Q
Proteome
A
refers to all proteins produced by a genome
>100,000 proteins made by ~35,000 genes
11
Q
chromatin
A
DNA & its associated proteins (=histones);
- threadlike material that makes up chromosomes
12
Q
histones
A
positively charged & form spools around which negatively charged DNA strands wrap
13
Q
nucleosome
A
each histone spool & its DNA
14
Q
euchromatin
A
is the part of chromosomes active in transcription
; light in color
15
Q
heterochromatin
A
is highly condensed region where genes are permanently inactivated
; darker in color forming blotchy colored spots in nucleus
16
Q
condensed chromatin
A
where nucleosomes are compacted
17
Q
acetylation of chromatin
A
produces a more open structure
18
Q
transcription factors attach to chromatin
A
activate genes (producing RNA)
19
Q
deacetylation causes
A
compaction of chromatin, silencing genetic transcription
20
Q
One gene codes for
A
one polypeptide chain
21
Q
each gene is several thousand
A
nucleotide pairs long
22
Q
neucletide
A
5 carbon sugar + 1 nitrogenous base + 1 phosphate group
23
Q
DNA in human cell has
A
3 billion base pairs = > 3 million proteins
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
25
synthesis = Transcription
transcription
26
For transcription to occur
RNA polymerase binds to a "start" sequence on DNA & unzips strands
27
Nearby are promoter regions which
which regulate levels of transcription
28
Transcription factors
regulatory molecules that must bind to promoter region of a gene to initiate transcription
29
RNA synthesis:
| Only 1 strand of DNA serves as a
template for RNA synthesis and contains the gene & is transcribed into RNA
30
RNA base pairs
G pairs with C; A pairs with U; a T in DNA codes for A when copied to RNA
31
RNA polymerase detaches when
hits a "stop" sequence
32
Transcription produces
3 types of RNA:
- mRNA
- tRNA
- rRNA
33
pre-mRNA
(precursor messenger RNA); altered in nucleus to form mRNA
34
mRNA
= (messenger RNA) = contains the code for synthesis of a protein
35
tRNA
(transfer RNA) - decodes the info contained in mRNA
36
rRNA
(ribosomal RNA) forms part of ribosomes
37
Pre-mRNA is much larger than
mRNA and must be processed before leaving the nucleus
38
Pre-mRNA contains
non-coding regions within the gene called introns, which are spliced out of the sequence
39
how many introns can a single gene have
50 introns
40
coding regions are called
exons
41
in nucleus, introns are
, introns are removed & ends of exons spliced together to produce final mRNA
42
protein synthesis
Translation occurs 1 amino acid at-a-time according to sequence of base triplets in mRNA
43
codon
triplets in mRNA
44
in cytoplasm, mRNA
mRNA attaches to several ribosomes forming “string-of-pearls” structure called a polysome where translation occurs
45
At ribosomes 3 mRNA bases are read as
a triplet
46
each triplet is a
codon
47
codon
(3-nitrogenous bases that make a word)
48
codon/triplet specifies
an amino acid
49
ribosomes translate codons into
an amino acid sequence that becomes a polypeptide chain
50
codons are read at the
ribosome with the help of tRNA, which reads codons as anticodons
51
Translation of codons is achieved by
tRNA and enzymes
52
tRNA contains
3 loops, one of which contains an anticodon
53
anticodon is complementary to
complementary to a specific mRNA codon
54
tRNA carries
he amino acid specified by its anticodon to the growing chain of aa’s
55
Protein synthesis:
| from the ribosomes
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
functions of ER:
| Proteins used in the cell are made on
polyribosomes that are free
57
Functions of ER:
| Proteins to be secreted are made at
ribosomes of rough ER
58
Functions of ER:
| amino acids in leader sequence (~ 1st 30 aa’s) of newly-made proteins are
hydrophobic and attracted to ER membrane causing new protein to enter cisternae of ER
59
functions of ER:
| what happens after new protein enter cisgternae of ER
leader sequence removed and the protein is modified
60
Functions of Golgie:
| secretory proteins leave ER in vesicles and
go to Golgi
| packaging and shipping
61
In the Golgi complex:
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
DNA Replication:
| when cells divide
DNA replicates itself & identical copies go to 2 daughter cells
63
helicases
break hydrogen bonds of double helices to produce 2 free strands of DNA
64
DNA polymerase
binds to each strand & makes new complementary copy of old strand using A-T, C-G pairing rules
65
each new copy of complementary base pair is composed of 1 new strand & 1 old strand (called
semiconservative replication
66
in DNA Replication Original DNA sequence is
preserved
67
Most cells of body are in
interphase
68
interphase
the non-dividing stage of life cycle
69
interphase is subdivided into:
G1
S
G2
70
G1
cell performs normal physiological roles
71
S
DNA is replicated in preparation for division
72
G2
chromatin condenses prior to division
73
cyclins
group of proteins that promote different phases of cell cycle
74
Overactivity of genes that code for some cyclins is associated with
cancer
75
oncogenes
genes whose mutations are associated with cancer
| Mutated forms of normal genes
76
Tumor suppresor genes
inhibit cancer development
77
tumor suppresor genes example
gene p53 inhibits cyclin activity
78
Mutations in p53 are associated with
50% of cancers
79
cell death occurs in 2 ways
necrosis
| apoptosis
80
necrosis
occurs when pathological changes kill a cell and thus tissue
81
apoptosis
programmed cell death occurs as a normal physiological response controlled by proteins; tissue repair (immunity) and remodeling (stomach and skin)
82
Mitosis (M phase)
phase of life cycle when cell divides
83
Chromosomes are duplicated during
interphase condensed
84
interphase condensed consists of
2 duplicate identical connected chromosome strands called chromatids, which are connected by a centromere
85
4 stages of mitosis
prophase, metaphase, anaphase, telophase
86
in prophase
chromosomes become visible distinct structures
87
prophase
- 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
in metaphase
chromosomes line up single file along equator; pulled by protein spindle fibers
89
in anaphase
centromeres split; spindle fibers pull each chromatid to opposite poles
90
during telophase
the cytoplasm is divided (= cytokinesis), producing 2 daughter cells
91
All animal cells have a
centrosome located near nucleus in interphase
92
centrosome
microtubule organizing center; microtubules form spindle fibers
93
centrosome is duplicated in
in G1 if cell is going to divide replicates move to opposite poles by metaphase
94
Microtubules grow from
centrosomes to form spindle fibers which attach to centromeres of chromosomes
95
Spindle fibers pull
chromosomes to opposite poles during anaphase
96
telomeres
non-coding regions of DNA at ends of chromosomes
97
Each time a cell divides, a length of telomere is lost
| Because
DNA polymerase can’t copy the very end of DNA strand; each repilcation loses 50 – 100 base pairs
98
When telomere is used up
cell becomes senescent
Believed to represent a molecular clock for aging
That ticks down with each division
99
Germinal (eggs/sperm) & cancer cells can
can divide indefinitely & do not age
100
telomeres:
| Germinal and cancer cells have
enzyme telomerase which replaces nucleotides lost from telomere during divisions
101
Organisms grow by
increasing the number of cells and size of cells:
102
hypertrophy
growth due to an increase in the size of cells
103
what can only grow by hypertrophy
Skeletal and cardiac muscle
104
atrophy
decrease in cell size, opposite of hypertrophy
105
hyperplasia
growth due to an increase in the number of cells
106
hyperplasia results from
mitotic divisions
107
hyperplasia is responsible for
for most growth
108
gametes
oocytes and sperm cells
109
gametes each carry
23 chromosomes, which are structurally identical to each other
Note: This does not mean that the nucleotide sequence if identical
110
When fertilization occurs, the 23 chromosomes from the egg will
pair with the 23 chromosomes carried by sperm and 23 pairs will be formed
111
each pair of chromosomes is called
homologous chromosomes
112
homologous chromosomes example
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
meiosis
process of making gametes (ova & sperm) containing ½ genetic material
114
meiosis occurs in
gonads (ovaries and testes)
115
meiosis is
proceeded by interphase
116
meiosis only makes
eggs and sperm
117
meiosis =
reduction division
| Like mitosis except goes to two rounds of pMats
118
meiosis has 2 divisional sequences
DNA is replicated once & divided twice
119
In 1st division homologous chromosomes pair along equator of cell rather is
1 member of homolog pair is pulled to each pole
| This gives each daughter cell 23 different chromosomes, consisting of 2 chromatids
120
In 2nd division each daughter divides, chromosomes split into 2 chromatids
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
