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SFN 316 Forensic Molecular Biology > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

Webster’s Definition of DNA

A

An essential of all living matter and a basic material in the chromosomes of the cell nucleus: it contains the genetic code and transmits the hereditary pattern

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2
Q

Purpose of DNA

A
  1. Make copies of itself so cells can divide and carry the same information
  2. Carry instructions on how to make proteins
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3
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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4
Q

Where is DNA found?

A

Almost every cell of the body

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5
Q

DNA’s “Alphabet”

A

DNA is made up of four nucleotides, represented by 4 letters: A, T, G, C

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6
Q

What is the important of the letters in DNA?

A

The order of the letters is what makes everyone different

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7
Q

How similar is human DNA?

A

Over 99% of human DNA is the same from person-to-person

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8
Q

How is nuclear DNA inherited?

A

Half of the nuclear comes from the mother and half comes from the father

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9
Q

True or False: An individual’s DNA profile remains the same throughout life

A

True

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10
Q

True or False: Each person’s DNA is the same in every cell

A

True

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11
Q

What are nucleic acids composed of?

A

Long chains of repeating units called nucleotides

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12
Q

What are the three components of nucleotides?

A
  1. Sugar
  2. Nitrogen-containing heterocyclic base
  3. Phosphoric acid unit
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13
Q

What is the sugar in RNA?

A

Ribose

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14
Q

What is the sugar in DNA?

A

Deoxyribose

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15
Q

What is the difference between ribose and deoxyribose?

A

In ribose, there is an H attached to the 2’ position of the ring
In deoxyribose, it is an OH group

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16
Q

Nitrogenous bases

A

Form a bond with carbon 1 of the pentose ring

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17
Q

Purines

A

Double-ringed bases
Adenine and Guanine

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18
Q

Pyrimidines

A

Single-ring bases
Cytosine, Thymine (DNA only), and Uracil (RNA only)

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19
Q

What is the primary structure of DNA?

A

The sequence of bases in a strand of DNA
(e.g. AATTTGGCTTAA)

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20
Q

What is the secondary structure of DNA?

A

The double helix: each DNA molecule has two polypeptide chains wound around each other like a spiral structure

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21
Q

Ladder Analogy for Secondary Structure of DNA

A

The phosphate-sugar backbone represents the handrails
Pairs of bases linked together by hydrogen bonds represent the steps

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22
Q

What does DNA being anti-parallel mean?

A

The strands of the double helix are organized in opposite orientation, so that the 5’ end of one strand is aligned with 3’ end of the other strand

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23
Q

Chromatin

A

The complex of DNA and proteins in the nucleus of the interphase cell

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24
Q

Can individual chromosomes be distinguished in chromatin?

A

No

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25
Q

Nucleosomes

A

The basic subunit of chromatin

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26
Q

What are nucleosomes composed of?

A

200 base pairs and an octane of histone proteins

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27
Q

Histones

A

Conserved DNA-binding proteins of eukaryotes that form the nucleosome

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28
Q

Genes

A

Segments of DNA molecules that control the production of different proteins in an organism

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29
Q

How do genes vary?

A

Vary in terms of the number and sequence of base pairs they contain

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30
Q

What do genes consist of?

A

Exons and introns

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31
Q

Exons

A

Segment of a gene that is represented in the final mRNA product

32
Q

Introns

A

Non-coding DNA which separates neighboring exons in a gene

33
Q

How are genes also described?

A

As the basic units of heredity

34
Q

Genome

A

All the genetic material in the chromosomes of a particular organism

35
Q

How are exons expressed?

A

As proteins

36
Q

What does the Central Dogma define?

A

The paradigm of molecular biology: genes are perpetuated as sequences of nucleic acid, but function by being expressed in the form of proteins

37
Q

How is genetic information perpetuated?

A

By replication

38
Q

Replication

A

Double stranded DNA is duplicated to give identical copies

39
Q

What happens after DNA is duplicated in replication?

A

One of the copies is transmitted to one daughter cell and one to the other

40
Q

What happens before a cell divides during replication?

A

The double helix strand starts to unwind

41
Q

What does each unwinding DNA strand serve to do?

A

They serve as a template for the formation of a new complementary strand

42
Q

What the nucleotides attracted to?

A

Exposed bases and they become hydrogen-bonded to them

43
Q

What is complementary base pairing?

A

A and T are complementary and only bind to each other
C and G are complementary and only bind to each other

44
Q

Codon

A

A sequence of three nucleotides in mRNA

45
Q

Steps of Transcription

A
  1. RNA polymerase binds to specific sequence of DNA known as the promoter
  2. The enzyme unwinds a small segment of the double helix, which exposes the bases of the two single strands
  3. As the polymerase moves along the DNA, complementary ribonucleotides are added to the chain
  4. Generates a single-stranded RNA identical in sequence with one of the stands of the duplex DNA
46
Q

What does transcription generate?

A

A single-stranded RNA identical in sequence with one of the stands of the duplex DNA

47
Q

What do codons code for?

A

An amino acid

48
Q

Where does translation occur?

49
Q

Anticodon

A

A nucleotide triplet at the end of the tRNA

50
Q

What is an anticodon complementary to?

A

An mRNA codon

51
Q

Translation

A

A specific amino acid is bound to the opposite end of tRNA
Converts the nucleotide sequence of the mRNA into the sequence of amino acids comprising a protein

52
Q

Hybridization

A

The binding or reassociation of complementary strands of nucleic acid or oligonucleotides

53
Q

Oligonucleotides

A

Short RNA or DNA molecules, single stranded, typically synthesized in a laboratory

54
Q

Locus

A

Chromosomal positon or location of gene or sequence of DNA; plural is loci

55
Q

DNA Marker Nomenclature

A

D16S539
D: DNA
16: Chromosome 16
S: Single copy sequence
539: 539th locus described on chromosome 16

56
Q

Homologous chromosomes

A
  1. Same size
  2. Contain the same genetic structure
57
Q

Alleles

A

An alternative of a gene or section of DNA at a locus

58
Q

What are the two primary forms of DNA variation?

A
  1. Sequence polymorphism
  2. Length polymorphism
59
Q

Sequence polymorphism

A

One or more nucleotides vary within a particular DNA sequence or length of DNA

60
Q

Length polymorphism

A

Sequence of DNA doesn’t vary, but the number of times that the sequence is repeated varies

61
Q

Power of discrimination

A

Ability of a forensic DNA technique to discern the difference between individuals

62
Q

Genetics

A

Study of patterns of inheritance of specific traits between parents and offspring

63
Q

What does much a genetics involve in modern day?

A

Populations

64
Q

Populations

A

Groups of individuals residing in a given area at a given time

65
Q

How are populations often classified?

A

By grouping together those sharing a common ancestry

66
Q

Population genetics

A

Study of genetic diversity in populations and how it changes through time

67
Q

What are the laws of Mendelian Genetics?

A
  1. Law of segregation
  2. Law of Independent assortment
68
Q

Law of Segregation

A

Chromosome pairs separate during meiosis so that the sex cells (gametes) become haploid and possess only a single copy of a chromosome
An individual can receive only one allele of a particular gene from one parent

69
Q

Law of Independent Assortment

A

Different segregating gene pairs behave independently due to recombination where genetic material is shuffled between generations

70
Q

Recombination

A

The process of exchanging DNA between homologous chromosomes that can occur during meiosis through crossing over

71
Q

What does recombination generate?

A

New combinations of allies or genes, and a shuffling of genetic material

72
Q

Linkage

A

Proximity of two or more markers on a chromosome

73
Q

What does it mean when genetic markers are closer together?

A

The lower the probability that they will separate and the greater the probability that they will be inherited together

74
Q

Linkage equilibrium

A

The condition among alleles at different loci such that any allelic combination in a gamete occurs as the product of the frequencies of each allele at its own locus

75
Q

Linkage disequilibrium

A

The condition among alleles at different loci such that any allelic combination in a gamete do not occur according to the product rule of probability

SFN 316 Forensic Molecular Biology (4 decks)

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