Lecture 3 Flashcards
1
Q
A DNA molecule consists of
A
2 complementary chains of nucleotides
2
Q
The structure of DNA provides
A
A mechanism for heredity
3
Q
Gene expression
A
First step is transcription
4
Q
The way chromosomes are packaged
A
Makes a difference
5
Q
DNA is made of 4 nucleotide building blocks
A
Base (A, G, C, T)
Phosphate
Sugar
Nucleotide
6
Q
Macromolecules
A
Polymers of subunits
7
Q
DNA subunits
A
Nucleotides
8
Q
Building blocks of nucleotide
A
Phosphate + sugar + base
9
Q
DNA has POLARITY
A
Direction
Exposed hydroxyl at 3’ end
10
Q
DNA held together by __________ bonds
A
Phosphodiester
These are COVALENT bonds
11
Q
The nucleotide subunits w/in a DNA strand are held together by
A
Phosphodiester bonds
12
Q
DNA has a ______ on 5’ end and a ______ on 3’ end
A
Phosphate, hydroxyl
13
Q
DNA Polymerase
A
Enzyme that catalyzes formation of phosphodiester bond
Makes more DNA
14
Q
The 2 strands of the DNA double helix are held together by _________ between complementary base pairs
A
Hydrogen bonds
15
Q
Purines
A
2 rings
A and G
16
Q
Pyrimidines
A
1 ring
C and T/U
17
Q
Complementary bases
A
G - C
A - T/U
18
Q
G and C form _______- bonds while A and T form _______ bonds
A
3, 2
19
Q
Most RNAs are translated into proteins
RNAs that are NOT translated to proteins:
A
tRNA (brings amino acid to polypeptide chain)
rRNA
sRNA and siRNAs (stop protein from being made)
20
Q
mRNA is the ONLY type of RNA that _____ translated to a protein
A
IS
21
Q
How can the information for specifying an organism be carried in chemical form and how can the information be accurately copied?
A
Information is encoded in the order (or sequence) of the nucleotides along each DNA strand
-Each base can be considered a letter that is used to spell out biological messages
22
Q
ALL DNA must be packed into
A
Chromosomes
23
Q
number of chromosomes
A
VARIES with organisms
24
Q
Most genes contain information to make
A
Proteins
25
Most of the genome encodes for something
NOT the case for humans
26
Organisms closely related have same genome ______ but different _____________
SIZES, structures and numbers
27
how can the information for specifying an organism be carried in chemical form and how can the information be accurately copied?
Information is encoded in the order (or seuqence) of the nucleotides along each DNA strand
-Each base can be considered a letter that is used to spell out biological messages
The amount of information in an organisms' DNA is staggering
In eukaryotes, most of the chromosomes are packed together = most of the genome is coding
28
How can all of this information be packed neatly into the cell nucleus?
Eukaryotic DNA is packaged into multiple chromosomes
Chromosomes organize and carry genetic information
Specialized DNA sequences are required for DNA replication and chromosome segregation
Interphase chromosomes are not randomly distributed w/in the nucleus
DNA in chromosomes is ALWAYS highly condensed
Nucleosomes are the basic units of eukaryotic chromosome structure
Chromosome packing occurs on multiple levels
29
human chromosomes can be viewed in a
Karyotype
30
Abnormal chromosomes are associated with some inherited
Genetic disorders
31
Translocation
Chunk moved b/w 2 chromosomes
32
In yeast, genes are
Closely packed along chromosomes
33
In many eukaryotes, genes include an excess of interspersed
Noncoding DNA
34
B globulin
One of the polypeptide chains that makes up hemoglobin
35
Closely related species can have similar genome sizes
but VERY different chromosome numbers
36
The duplication and segregation of chromosomes occurs through
An ordered cell cycle in proliferating cells
1) Interphase:
- Nuclear envelope surrounds nucleus, interphase chromosome undergoes gene expression and chromosome duplication
- Replicated chromosomes
2) M Phase:
- Mitosis begins
- Mitotic spindle and mitotic chromosome initiate cell division
3) Interphase (repeat)
37
Sequence for Segregation
Centromere
38
Centromere is NOT a
Protein
39
Sequence for Segregation: Centromere
ONE on each cell -> proteins recognize and bind to centromere -> mitotic spindle recognizes those proteins -> sister chromatids separate
40
Mutate centromere =
Mitosis will NOT occur properly
41
3 DNA sequence elements are needed to produce a eukaryotic chromosome that can proceed through mitosis
1) Centromere: Sequence of segregation
2) Replication origin: Where replication begins
- Most bacteria have ONE
- Eukaryotes have MANY
- Archaea have MORe than 1
3) Telomere: ONLY organisms with linear structures have this (bacteria and Archaea do NOT have or need telomeres); Need to be on ends to solve problems in replication; Cap the chromosomes
42
A typical duplicated mitotic chromosome is highly
Compact
Occurs prior to meiosis
Some chromosomes are anchored to something (i.e. nuclear envelope)
43
Interphase chromosomes occupy their own distinct territories
Within the nucleus
44
The nucleolus is the most prominent structure in the
Interphase nucleus
45
Chromosone
Mixture of DNA and protein
46
Nucleosome
Basic unit of chromosomes
47
As DNA compacts, "beads on a string" move closer together
Nucleosome is the DNA wrapped around the histone
48
10 chromosomes each contribute to a loop containing
rRNA genes to the nucleolus
49
DNA in interphase chromosomes is less compact than in
Mitotic chromosomes
50
Nucleosomes can be seen in
The electron microscope
51
Nucleosomes contain DNA wrapped around a protein core of 8 histone molecule
Loosen DNA by:
1) Adding - group to histone to reduce net + charge of histone, makes more - overall due to DNA => looser DNA
2) Change conformation of histone
52
When digested, individual nucleosomes released
Dissociate using salts
53
The structure of the nucleosome core particle reveals how DNA is tightly wrapped around a disc-shaped
Histone octamer
54
The Chromatin in human chromosomes is
Folded into loop domains
Loops allow DNA to condense down
55
DNA packing occurs on several levels in
Chromosomes
56
Regulation of Chromosome Structure
MOST important for gene expression
57
Changes in nucleosome structure allow access to
DNA
58
Interphase chromosomes contain both highly condensed and more extneded forms of
Chromatin
59
Genes are OFF to begin with because they are associated with
Histone
60
RNA polymerase doesn't have access when genes are associated with
Histones
61
Chromatin-remodeling complexes locally reposition the DNA wrapped around
Nucleosomes
Remodels chromatin
Utilize energy from ATP hydrolysis, push histone out of the way
ATP dependent
62
The pattern of modification of histone tails can determine how a stretch of chromatin is
Handled by the cell
63
Histones are BASIC proteins (+ charge)
DNA is negatively charged
Modify tails of histones by adding negative protein, changes to overall negative charge, loosens DNA
64
Heterochromatin
COMPACT
65
Euchromatin
LOOSE
66
Outcomes of modifications are
Highly variable and poorly understood
67
Can change overall charge and loosen up DNA OR
Can change overall structure and act as a docking site
68
The pattern of modification of histone tails can determine how a stretch of chromatin is handled by the
Cell
69
histone H3 tail modification
Trimethyl -> heterochromatin formation, gene silencing
Trimethyl, Ac -> Gene expression
transcription is first step of gene expression
70
The structure of chromatin varies along a single
Interphase chromosome
71
Heterochromatin
NO gene expression
72
Euchromatin
Gene expression
73
Heterochromatin-specific histone modifications allow heterochromatin to form and to
Spread
74
When cell starts compacting, it is
Contagious => heterochromatin formation spreads
Change overall charge to induce loosening OR create binding site
Start modifying OTHER heterochromatin tails
DO this until it hits a barrier sequence
Functions:
- Loosening
- Creating sites that proteins can attach to and other cells will recognize
75
Barrier sequence
Tells a cell to "stop" compacting DNA
76
Type of anemia where _____________ is mutated and doesn't stop formation of heterochromatin
barrier sequence
77
One of the two X chromosomes is inactivated in the cells of mammalian females by
heterochromatin formation
78
Mammalian females have maternal and paternal X, only ONE is active; either the maternal or paternal X is condensed (inactive); this is called a
Mosaic: half has maternal active, half has paternal active
79
Calico cats
Couple of color genes on X hromosome = patchy color
RARELY can have male calico cats (XXY mutants)
