Unit 4 Flashcards
(85 cards)
1
Q
What are the two nucleic acids of the cell?
A
- deoxyribonucleic acid (DNA)
- ribonucleic acid (DNA)
2
Q
What are the main functions of DNA and RNA?
A
to serve as the instructions for making proteins within the cell
3
Q
What did Hershey & Chase show in 1952?
A
that hereditary material was DNA and not protein
4
Q
How was Hershey & Chase’s experiment performed?
A
using bacteriophages marked with radioactive DNA and proteins to show that viruses inject DNA into host cells
5
Q
Bacteriophages
A
viruses that infect bacteria
6
Q
What was the result of the Hershey and Chase experiment?
A
only the radioactive phosphorus in DNA was
transported INTO bacteria by bacteriophages
7
Q
What is the monomer of a nucleic acid?
A
a nucleotide
8
Q
What are the 3 things a nucleotide consists of?
A
- Sugar
- Phosphate
- Nitrogenous Base
9
Q
How many nitrogen bases are there for DNA and RNA?
A
4
10
Q
What are the nitrogen bases for DNA?
A
- Adenine
- Guanine
- Thymine
- Cytosine
11
Q
What are the nitrogen bases for RNA?
A
- Adenine
- Guanine
- Uracil
- Cytosine
12
Q
What are the polymers of of nucleic acids?
A
- polynucleotides
13
Q
What do condensation reactions do concerning nucleotides?
A
covalently bond nucleotides
14
Q
What do hydrolysis reactions do concerning polynucleotides?
A
break them apart (hydrolyze)
15
Q
Phosphodiester Bonds
A
covalent bonds that link nucleotides
16
Q
How is a phosphodiester bond formed?
A
the sugar of one nucleotide attaches to the phosphate group of another
17
Q
What are the three ways that RNA is different from DNA?
A
- RNA is a single stranded
- RNA has a ribose sugar, not a deoxyribose
- RNA has Uracil instead of Thymine
18
Q
How are the two strands of DNA being held together?
A
by hydrogen bonds between base pairs
19
Q
In a DNA strand, is the sugar-phosphate backbone on the inside or outside?
A
outside
20
Q
In a DNA strand, are the nitrogen-containing bases on the inside or outside?
A
inside
21
Q
Complementary Base Pairing
A
occurs between nitrogen-containing bases in double stranded DNA
22
Q
Which nitrogen bases go together in DNA?
A
- Adenine hydrogen bonds with Thymine
- Guanine hydrogen bonds with Cytosine
23
Q
What does complementary base pairing ensure?
A
that DNA molecules produced by replication have identical genetic information
24
Q
Antiparallel
A
complementary DNA strands run in opposite directions
25
What is the name for the directions DNA can go?
- 5' to 3' on one side
- 3' to 5' on the other side
26
Double Helix
two strands in the surface of a cylinder that coil around its center axis
27
What two things can hydrogen bonds do?
- hold adjacent sections of the helix together
- hold complementary base pairs together
28
Who worked out the three dimensional structure of DNA?
Watson and Crick
29
What was Watson and Crick's work based on?
the work of Rosalind Franklin & Maurice Wilkins
30
What did Franklin and Wilkins use to study DNA?
X-ray diffraction
31
Who used model building for the structure of DNA?
Watson and Crick
32
genetic code
sequence of nitrogen bases in DNA
33
gene
sequence of DNA that programs an amino acid sequence
34
genome
all an organism's genetic information/DNA
35
genome size
total length of DNA (# nucleotide pairs or base pairs) in an organism (genes plus non-genes)
36
chromatin
complex of DNA and protein found in eukaryotic cells (made of packed nucleosomes)
37
nucleosome
segment of DNA wrapped around 8 histone protein cores stabilized by a linker
38
chromosome
most condensed form of DNA made of packaged chromatin (highest level of DNA packing)
39
When are chromosomes visible?
when the nucleus is dividing
40
What is the process of forming chromosomes?
- DNA is wrapped around a group of 8 histones and stabilized by a linker, forming a nucleosome
- Nucleosomes are packed together to form chromatin
- Chromatin is coiled eventually forming chromosomes
41
Cairns Technique
uses autoradiography to measure the length of a DNA molecule
42
Autoradiography
technique used to visualize molecules that have been radioactively labeled
43
How many chromosomes do human body cells have?
46
44
Body Cells
are all cells except
sperm and egg cells
45
How many matched pairs come out of 46 chromosomes?
23 (one from each parent)
46
How many pairs of sex chromosomes do humans have?
1
47
autosomes
not directly involved in determining biological sex
48
sex chromosomes
determine biological sex
49
What makes X chromosomes different from Y chromosomes?
X chromosomes are larger and carry more genes
50
What types of sex chromosomes are in a female?
pair of X chromosomes
51
What types of sex chromosomes are in a male?
1 X chromosome and 1 Y chromosome
52
Homologous Chromosomes (2 things to know)
- are nearly identical in length
- include one maternal and one paternal chromosome
53
What is on homologous chromosomes that also makes them homologous?
they carry genes for the same characteristics at the same locations
54
Locus
site where a gene is located on a chromosome
55
Allele
alternative forms of the same gene
56
Karyogram
chart showing the chromosomes of an organism in homologous pairs of decreasing length
57
Karyotype
number and type of chromosomes
58
What are 4 characteristics of the chromosomes of a prokaryote?
- one chromosome
- circular chromosome
- naked (no associated proteins
- plasmids are present
59
What are 4 characteristics of the chromosomes of a eukaryote?
- two or more chromosomes
- linear DNA molecules
- associated with histone proteins
- no plasmids
60
Plasmids (3 things that you need to know)
- carry genes that are useful but not essential
- can be exchanged between prokaryotes
- absent in eukaryotes
61
What must happen before a cell divides?
DNA must be copied
62
Replication
process by which DNA is copied
63
Semiconservative
DNA strands separate and each strand is used as a template to assemble complementary nucleotides
64
What is the result of using complementary base pairing in DNA replication?
two new molecules have the same sequence as the original molecule
65
What is replication like in eukaryotes?
bidirectional and initiated at several locations
66
What is step 1 of DNA replication on the leading and lagging strand?
Helicase separates the double-stranded DNA by breaking the hydrogen bonds between base pairs at the origin of replication creating two replication forks
67
What is step 2 of DNA replication on the leading and lagging strand?
Gyrase relaxes supercoils in DNA to reduces the strain created by the unwinding of DNA by helicase
68
What is step 3 of DNA replication on the leading and lagging strand?
SSB (single-stranded binding) proteins bind to the DNA strands after they have been separated and prevents them from re-annealing
69
What is step 4 of DNA replication on the leading and lagging strand? What is different for the lagging strand?
- DNA Primase follows helicase and synthesizes short RNA primers of 10-12 complementary nucleotides
- (for lagging strand the primer is made closer to the fork)
70
What is step 5 of DNA replication on the leading strand?
DNA Polymerase III adds complementary nucleotides (A-T, C-G) in 5’ to 3’ direction beginning at the RNA primer
71
What is step 5 of DNA replication on the lagging strand?
DNA polymerase III attaches to an RNA primer and adds complementary nucleotides (A-T, C-G) in a 5’ to 3’ direction (away from fork)
72
In what direction does DNA replication occur?
5’ to 3’ direction
73
On the leading strand, which direction is the 5' to 3' replication occurring?
towards the fork
74
On the lagging strand, which direction is the 5' to 3' replication occurring?
away from the fork
75
Continuous Replication
nucleotides are added towards the replication fork on the leading strand
without stopping
76
Discontinuous Replication
nucleotides are added away from the replication fork on the lagging strand
in pieces
77
Okazaki Fragments
sections of copied DNA between RNA primers on the lagging strand of the replication fork, only present on the lagging strand
78
What is step 6 of DNA replication on the lagging strand?
DNA polymerase I moves along the replication fork removing RNA primers and replaces them with complementary DNA nucleotides
79
What is step 7 of DNA replication on the lagging strand?
DNA ligase attaches the Okazaki fragments into a continuous strand of DNA
80
What is another purpose of DNA Polymerase III?
To proofread the possible errors made in replication
81
What is the end replication problem?
DNA shortens with each replication and no DNA can replace the terminal 5’ RNA primer because there is no 3’ end to extend
82
Telomeres
Repetitive DNA sequences at the ends of linear chromosomes that protect coding DNA and shorten with replication
83
Where does replication occur in eukaryotic cells?
the nucleus
84
Where does replication occur in prokaryotic cells?
the cytoplasm
85
What did Meselson's and Stahl's experiment do?
using radioactive nitrogen supported Watson & Crick’s hypothesis that DNA replication is semi-conservative
