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IB HL Biology I > Unit 4 > Flashcards

Unit 4 Flashcards

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1
Q

What are the two nucleic acids of the cell?

A
  • deoxyribonucleic acid (DNA)
  • ribonucleic acid (DNA)
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2
Q

What are the main functions of DNA and RNA?

A

to serve as the instructions for making proteins within the cell

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3
Q

What did Hershey & Chase show in 1952?

A

that hereditary material was DNA and not protein

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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

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5
Q

Bacteriophages

A

viruses that infect bacteria

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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

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7
Q

What is the monomer of a nucleic acid?

A

a nucleotide

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8
Q

What are the 3 things a nucleotide consists of?

A
  • Sugar
  • Phosphate
  • Nitrogenous Base
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9
Q

How many nitrogen bases are there for DNA and RNA?

A

4

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10
Q

What are the nitrogen bases for DNA?

A
  • Adenine
  • Guanine
  • Thymine
  • Cytosine
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11
Q

What are the nitrogen bases for RNA?

A
  • Adenine
  • Guanine
  • Uracil
  • Cytosine
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12
Q

What are the polymers of of nucleic acids?

A
  • polynucleotides
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13
Q

What do condensation reactions do concerning nucleotides?

A

covalently bond nucleotides

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14
Q

What do hydrolysis reactions do concerning polynucleotides?

A

break them apart (hydrolyze)

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15
Q

Phosphodiester Bonds

A

covalent bonds that link nucleotides

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16
Q

How is a phosphodiester bond formed?

A

the sugar of one nucleotide attaches to the phosphate group of another

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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
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18
Q

How are the two strands of DNA being held together?

A

by hydrogen bonds between base pairs

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19
Q

In a DNA strand, is the sugar-phosphate backbone on the inside or outside?

A

outside

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20
Q

In a DNA strand, are the nitrogen-containing bases on the inside or outside?

A

inside

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21
Q

Complementary Base Pairing

A

occurs between nitrogen-containing bases in double stranded DNA

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22
Q

Which nitrogen bases go together in DNA?

A
  • Adenine hydrogen bonds with Thymine
  • Guanine hydrogen bonds with Cytosine
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23
Q

What does complementary base pairing ensure?

A

that DNA molecules produced by replication have identical genetic information

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24
Q

Antiparallel

A

complementary DNA strands run in opposite directions

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25
Q

What is the name for the directions DNA can go?

A
  • 5’ to 3’ on one side
  • 3’ to 5’ on the other side
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26
Q

Double Helix

A

two strands in the surface of a cylinder that coil around its center axis

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27
Q

What two things can hydrogen bonds do?

A
  • hold adjacent sections of the helix together
  • hold complementary base pairs together
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28
Q

Who worked out the three dimensional structure of DNA?

A

Watson and Crick

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29
Q

What was Watson and Crick’s work based on?

A

the work of Rosalind Franklin & Maurice Wilkins

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30
Q

What did Franklin and Wilkins use to study DNA?

A

X-ray diffraction

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31
Q

Who used model building for the structure of DNA?

A

Watson and Crick

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32
Q

genetic code

A

sequence of nitrogen bases in DNA

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33
Q

gene

A

sequence of DNA that programs an amino acid sequence

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34
Q

genome

A

all an organism’s genetic information/DNA

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35
Q

genome size

A

total length of DNA (# nucleotide pairs or base pairs) in an organism (genes plus non-genes)

36
Q

chromatin

A

complex of DNA and protein found in eukaryotic cells (made of packed nucleosomes)

37
Q

nucleosome

A

segment of DNA wrapped around 8 histone protein cores stabilized by a linker

38
Q

chromosome

A

most condensed form of DNA made of packaged chromatin (highest level of DNA packing)

39
Q

When are chromosomes visible?

A

when the nucleus is dividing

40
Q

What is the process of forming chromosomes?

A
  • 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
Q

Cairns Technique

A

uses autoradiography to measure the length of a DNA molecule

42
Q

Autoradiography

A

technique used to visualize molecules that have been radioactively labeled

43
Q

How many chromosomes do human body cells have?

A

46

44
Q

Body Cells

A

are all cells except
sperm and egg cells

45
Q

How many matched pairs come out of 46 chromosomes?

A

23 (one from each parent)

46
Q

How many pairs of sex chromosomes do humans have?

A

1

47
Q

autosomes

A

not directly involved in determining biological sex

48
Q

sex chromosomes

A

determine biological sex

49
Q

What makes X chromosomes different from Y chromosomes?

A

X chromosomes are larger and carry more genes

50
Q

What types of sex chromosomes are in a female?

A

pair of X chromosomes

51
Q

What types of sex chromosomes are in a male?

A

1 X chromosome and 1 Y chromosome

52
Q

Homologous Chromosomes (2 things to know)

A
  • are nearly identical in length
  • include one maternal and one paternal chromosome
53
Q

What is on homologous chromosomes that also makes them homologous?

A

they carry genes for the same characteristics at the same locations

54
Q

Locus

A

site where a gene is located on a chromosome

55
Q

Allele

A

alternative forms of the same gene

56
Q

Karyogram

A

chart showing the chromosomes of an organism in homologous pairs of decreasing length

57
Q

Karyotype

A

number and type of chromosomes

58
Q

What are 4 characteristics of the chromosomes of a prokaryote?

A
  • one chromosome
  • circular chromosome
  • naked (no associated proteins
  • plasmids are present
59
Q

What are 4 characteristics of the chromosomes of a eukaryote?

A
  • two or more chromosomes
  • linear DNA molecules
  • associated with histone proteins
  • no plasmids
60
Q

Plasmids (3 things that you need to know)

A
  • carry genes that are useful but not essential
  • can be exchanged between prokaryotes
  • absent in eukaryotes
61
Q

What must happen before a cell divides?

A

DNA must be copied

62
Q

Replication

A

process by which DNA is copied

63
Q

Semiconservative

A

DNA strands separate and each strand is used as a template to assemble complementary nucleotides

64
Q

What is the result of using complementary base pairing in DNA replication?

A

two new molecules have the same sequence as the original molecule

65
Q

What is replication like in eukaryotes?

A

bidirectional and initiated at several locations

66
Q

What is step 1 of DNA replication on the leading and lagging strand?

A

Helicase separates the double-stranded DNA by breaking the hydrogen bonds between base pairs at the origin of replication creating two replication forks

67
Q

What is step 2 of DNA replication on the leading and lagging strand?

A

Gyrase relaxes supercoils in DNA to reduces the strain created by the unwinding of DNA by helicase

68
Q

What is step 3 of DNA replication on the leading and lagging strand?

A

SSB (single-stranded binding) proteins bind to the DNA strands after they have been separated and prevents them from re-annealing

69
Q

What is step 4 of DNA replication on the leading and lagging strand? What is different for the lagging strand?

A
  • 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
Q

What is step 5 of DNA replication on the leading strand?

A

DNA Polymerase III adds complementary nucleotides (A-T, C-G) in 5’ to 3’ direction beginning at the RNA primer

71
Q

What is step 5 of DNA replication on the lagging strand?

A

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
Q

In what direction does DNA replication occur?

A

5’ to 3’ direction

73
Q

On the leading strand, which direction is the 5’ to 3’ replication occurring?

A

towards the fork

74
Q

On the lagging strand, which direction is the 5’ to 3’ replication occurring?

A

away from the fork

75
Q

Continuous Replication

A

nucleotides are added towards the replication fork on the leading strand
without stopping

76
Q

Discontinuous Replication

A

nucleotides are added away from the replication fork on the lagging strand
in pieces

77
Q

Okazaki Fragments

A

sections of copied DNA between RNA primers on the lagging strand of the replication fork, only present on the lagging strand

78
Q

What is step 6 of DNA replication on the lagging strand?

A

DNA polymerase I moves along the replication fork removing RNA primers and replaces them with complementary DNA nucleotides

79
Q

What is step 7 of DNA replication on the lagging strand?

A

DNA ligase attaches the Okazaki fragments into a continuous strand of DNA

80
Q

What is another purpose of DNA Polymerase III?

A

To proofread the possible errors made in replication

81
Q

What is the end replication problem?

A

DNA shortens with each replication and no DNA can replace the terminal 5’ RNA primer because there is no 3’ end to extend

82
Q

Telomeres

A

Repetitive DNA sequences at the ends of linear chromosomes that protect coding DNA and shorten with replication

83
Q

Where does replication occur in eukaryotic cells?

A

the nucleus

84
Q

Where does replication occur in prokaryotic cells?

A

the cytoplasm

85
Q

What did Meselson’s and Stahl’s experiment do?

A

using radioactive nitrogen supported Watson & Crick’s hypothesis that DNA replication is semi-conservative

IB HL Biology I (10 decks)

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