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Cell and Molec > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

A DNA molecule consists of

A

2 complementary chains of nucleotides

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2
Q

The structure of DNA provides

A

A mechanism for heredity

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3
Q

Gene expression

A

First step is transcription

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4
Q

The way chromosomes are packaged

A

Makes a difference

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5
Q

DNA is made of 4 nucleotide building blocks

A

Base (A, G, C, T)

Phosphate

Sugar

Nucleotide

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6
Q

Macromolecules

A

Polymers of subunits

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7
Q

DNA subunits

A

Nucleotides

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8
Q

Building blocks of nucleotide

A

Phosphate + sugar + base

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9
Q

DNA has POLARITY

A

Direction

Exposed hydroxyl at 3’ end

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10
Q

DNA held together by __________ bonds

A

Phosphodiester

These are COVALENT bonds

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11
Q

The nucleotide subunits w/in a DNA strand are held together by

A

Phosphodiester bonds

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12
Q

DNA has a ______ on 5’ end and a ______ on 3’ end

A

Phosphate, hydroxyl

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13
Q

DNA Polymerase

A

Enzyme that catalyzes formation of phosphodiester bond

Makes more DNA

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14
Q

The 2 strands of the DNA double helix are held together by _________ between complementary base pairs

A

Hydrogen bonds

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15
Q

Purines

A

2 rings

A and G

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16
Q

Pyrimidines

A

1 ring

C and T/U

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17
Q

Complementary bases

A

G - C

A - T/U

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18
Q

G and C form _______- bonds while A and T form _______ bonds

A

3, 2

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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)

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20
Q

mRNA is the ONLY type of RNA that _____ translated to a protein

A

IS

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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

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22
Q

ALL DNA must be packed into

A

Chromosomes

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23
Q

number of chromosomes

A

VARIES with organisms

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24
Q

Most genes contain information to make

A

Proteins

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25
Q

Most of the genome encodes for something

A

NOT the case for humans

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26
Q

Organisms closely related have same genome ______ but different _____________

A

SIZES, structures and numbers

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27
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 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

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28
Q

How can all of this information be packed neatly into the cell nucleus?

A

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

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29
Q

human chromosomes can be viewed in a

A

Karyotype

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30
Q

Abnormal chromosomes are associated with some inherited

A

Genetic disorders

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31
Q

Translocation

A

Chunk moved b/w 2 chromosomes

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32
Q

In yeast, genes are

A

Closely packed along chromosomes

33
Q

In many eukaryotes, genes include an excess of interspersed

A

Noncoding DNA

34
Q

B globulin

A

One of the polypeptide chains that makes up hemoglobin

35
Q

Closely related species can have similar genome sizes

A

but VERY different chromosome numbers

36
Q

The duplication and segregation of chromosomes occurs through

A

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
Q

Sequence for Segregation

A

Centromere

38
Q

Centromere is NOT a

A

Protein

39
Q

Sequence for Segregation: Centromere

A

ONE on each cell -> proteins recognize and bind to centromere -> mitotic spindle recognizes those proteins -> sister chromatids separate

40
Q

Mutate centromere =

A

Mitosis will NOT occur properly

41
Q

3 DNA sequence elements are needed to produce a eukaryotic chromosome that can proceed through mitosis

A

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
Q

A typical duplicated mitotic chromosome is highly

A

Compact

Occurs prior to meiosis

Some chromosomes are anchored to something (i.e. nuclear envelope)

43
Q

Interphase chromosomes occupy their own distinct territories

A

Within the nucleus

44
Q

The nucleolus is the most prominent structure in the

A

Interphase nucleus

45
Q

Chromosone

A

Mixture of DNA and protein

46
Q

Nucleosome

A

Basic unit of chromosomes

47
Q

As DNA compacts, “beads on a string” move closer together

A

Nucleosome is the DNA wrapped around the histone

48
Q

10 chromosomes each contribute to a loop containing

A

rRNA genes to the nucleolus

49
Q

DNA in interphase chromosomes is less compact than in

A

Mitotic chromosomes

50
Q

Nucleosomes can be seen in

A

The electron microscope

51
Q

Nucleosomes contain DNA wrapped around a protein core of 8 histone molecule

A

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
Q

When digested, individual nucleosomes released

A

Dissociate using salts

53
Q

The structure of the nucleosome core particle reveals how DNA is tightly wrapped around a disc-shaped

A

Histone octamer

54
Q

The Chromatin in human chromosomes is

A

Folded into loop domains

Loops allow DNA to condense down

55
Q

DNA packing occurs on several levels in

A

Chromosomes

56
Q

Regulation of Chromosome Structure

A

MOST important for gene expression

57
Q

Changes in nucleosome structure allow access to

A

DNA

58
Q

Interphase chromosomes contain both highly condensed and more extneded forms of

A

Chromatin

59
Q

Genes are OFF to begin with because they are associated with

A

Histone

60
Q

RNA polymerase doesn’t have access when genes are associated with

A

Histones

61
Q

Chromatin-remodeling complexes locally reposition the DNA wrapped around

A

Nucleosomes

Remodels chromatin

Utilize energy from ATP hydrolysis, push histone out of the way

ATP dependent

62
Q

The pattern of modification of histone tails can determine how a stretch of chromatin is

A

Handled by the cell

63
Q

Histones are BASIC proteins (+ charge)

DNA is negatively charged

A

Modify tails of histones by adding negative protein, changes to overall negative charge, loosens DNA

64
Q

Heterochromatin

A

COMPACT

65
Q

Euchromatin

A

LOOSE

66
Q

Outcomes of modifications are

A

Highly variable and poorly understood

67
Q

Can change overall charge and loosen up DNA OR

A

Can change overall structure and act as a docking site

68
Q

The pattern of modification of histone tails can determine how a stretch of chromatin is handled by the

A

Cell

69
Q

histone H3 tail modification

A

Trimethyl -> heterochromatin formation, gene silencing

Trimethyl, Ac -> Gene expression

transcription is first step of gene expression

70
Q

The structure of chromatin varies along a single

A

Interphase chromosome

71
Q

Heterochromatin

A

NO gene expression

72
Q

Euchromatin

A

Gene expression

73
Q

Heterochromatin-specific histone modifications allow heterochromatin to form and to

A

Spread

74
Q

When cell starts compacting, it is

A

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
Q

Barrier sequence

A

Tells a cell to “stop” compacting DNA

76
Q

Type of anemia where _____________ is mutated and doesn’t stop formation of heterochromatin

A

barrier sequence

77
Q

One of the two X chromosomes is inactivated in the cells of mammalian females by

A

heterochromatin formation

78
Q

Mammalian females have maternal and paternal X, only ONE is active; either the maternal or paternal X is condensed (inactive); this is called a

A

Mosaic: half has maternal active, half has paternal active

79
Q

Calico cats

A

Couple of color genes on X hromosome = patchy color

RARELY can have male calico cats (XXY mutants)

Cell and Molec (9 decks)

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