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Biology > Molecular Basis of Inheritance > Flashcards

Molecular Basis of Inheritance Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Human DNA

A

3.3 x 10^9 bp of nucleotides in the DNA of haploid chromosomes

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2
Q

Nucleotides

A

N-glycosidic linkage- Nitrogenous base is attached to OH of 1’C of deoxyribose or ribose sugar

Phosophoester linkage- Phosphate group attached to OH of 5’C of deoxyribose or ribose sugar

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3
Q

Polynucleotide

A

Two nucleotides are joined by 3’-5’ phosphodiester linkage. OH of 3’C of pentose sugar of one nucleotide is attached to the phosphate group of 5’C of another nucleotide

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4
Q

5’ end of polynucleotides

A

Free Phosphate group at 5’C of the pentose sugar

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5
Q

3’ end of polynucleotides

A

Free OH group at 3’C of the pentose sugar

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6
Q

Friedrich Miescher

A

Identified DNA in 1869

Named it ‘Nuclein’

Present in the nucleus and acidic

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7
Q

Maurice Wilkins and Rosalind Franklin

A

Obtained DNA images from X-ray crystallography

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8
Q

James Watson and Francis Crick

A

Proposed the double-helix model of DNA in 1953

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9
Q

Erwin Chargaff

A

Elucidated that the DNA contains equal amounts of adenine and thymine and in the same way guanine and cytosine

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10
Q

DNA double helix

A

Antiparallel strands, coiled in a right-handed fashion

Backbone- sugar-phosphate

Bases are bonded by hydrogen bonds and projected inside

Adenine bonds to thymine by two hydrogen bonds

Guanine bonds to cytosine by three hydrogen bonds

Pitch- 3.4 nm and 10 bp in each turn

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11
Q

Central Dogma

A

Proposed by Francis Crick in 1958

The flow of genetic information from DNA → RNA → Protein

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12
Q

Nucleoid

A

Found in prokaryotes

The region where DNA is concentrated within a cell associated with positively charged proteins

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13
Q

Histones

A

Positively charged basic proteins, rich in lysine and arginine

Eight molecules of histones associated with DNA to form a nucleosome

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14
Q

Nucleosome

A

DNA associated with histones octamer

200 bp of DNA in each nucleosome

Appear as beads on chromatin threads

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15
Q

Euchromatin

A

Loosely packed and lightly stained part of chromatin

Shows active transcription

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16
Q

Heterochromatin

A

Densely packed and darkly stained part of chromatin

Inactive for transcription

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17
Q

Transforming principle

A

Frederick Griffith in 1928

He concluded that there was some transforming principle in the heat-killed S-strain, which transformed R strain Streptococcus pneumoniae to virulent

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18
Q

Avery, MacLeod and McCarty

A

Demonstrated that the DNA caused the bacterial transformation

They showed that proteases and RNAases did not affect transformation, whereas DNAase inhibit transformation

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19
Q

Alfred Hershey and Martha Chase

A

Unequivocal proof of DNA as genetic material in 1952

They worked on bacteriophages

Radioactive 35S labelled- protein capsule

Radioactive 32P labelled- DNA

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20
Q

RNA as a genetic material

A

Present in many viruses, known as a retrovirus

E.g. TMV, QB bacteriophage, etc.

ds RNA- reovirus, etc.

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21
Q

Semiconservative DNA replication

A

Proposed by Watson and Crick

Experimentally proved by Matthew Meselson and Franklin Stahl in 1958 using 15N isotope in the growing medium for E.coli

Taylor and colleagues worked on Vicia faba using radioactive thymidine

22
Q

DNA-dependent DNA polymerase

A

Main enzyme for replication

Polymerisation in 5’→3’ direction

23
Q

DNA ligase

A

Join the DNA strand, which is synthesised discontinuously during replication

24
Q

DNA helicase

A

Unwind DNA at the origin of replication forming replication fork

25
Q

Transcription

A

Synthesis of RNA from DNA

Template strand- 3’→5’ DNA

Coding strand- 5’→3’ DNA, has the same sequence as newly synthesised RNA strand

26
Q

DNA-dependent RNA polymerase

A

Catalyses transcription

Polymerisation in 5’→3’ direction

27
Q

Transcription unit

A

Reference point with respect to the coding strand (5’→3’, DNA)

Promoter- present at 5’ end of a structural gene, RNA polymerase binds here

Terminator- at 3’ end of the coding strand

28
Q

Cistron

A

A segment of DNA coding for polypeptide

Monocistronic- eukaryotes

Polycistronic- prokaryotes

29
Q

Exons

A

Coding sequence of DNA expressed in mature and processed RNA

30
Q

Introns

A

Interrupted sequence which are spliced in mature RNA

31
Q

Translation

A

Formation of polypeptide from RNA

mRNA- template for protein synthesis

tRNA- adapter molecule, brings amino acids and reads codon on mRNA

rRNA- structural and catalytic role

32
Q

Eukaryotic transcription

A

RNA polymerase I – 28S, 18S, 5.8S rRNA

RNA polymerase II – hnRNA (mRNA precursor)

RNA polymerase III – tRNA, 5S rRNA, snRNA

33
Q

hnRNA processing

A

Splicing – removal of introns and joining together of exons

Capping – addition of methyl guanosine triphosphate at 5’ end

Tailing – addition of adenylate residues (200-300) at 3’ end

34
Q

Marshall Nirenberg

A

Deciphered first the 64 triplet codons for 20 amino acids present in protein

35
Q

Start codon

A

AUG

Codes for Methionine

36
Q

Stop codons

A

UAA, UAG, UGA

They do not code for any amino acids

37
Q

tRNA

A

Structure- 2° structure like clover leaf, 3° like inverted L

Anticodon loop- complementary mRNA codon for specific codon

Acceptor arm- binds to amino acid

DHU loop, TψC loop and variable loop

Function- Adapter molecule, brings amino acid for translation and reads codon

38
Q

Translation

A

Occurs in cytoplasm

The first step is charging of tRNA, aminoacylation or binding of tRNA to amino acid

Peptide bond formation takes place between the amino acid of growing chain and newly brought amino acid in two sites present in the large subunit of ribosomes

39
Q

Ribozyme

A

Catalytic RNA

28S rRNA in bacteria

40
Q

Untranslated regions (UTR)

A

Regions on mRNA, which are not translated

Present on both 5’ and 3’ ends

Required for efficient translation

41
Q

Francois Jacob and Jacque Monod

A

First elucidated transcriptionally regulated system in lac operon

42
Q

Operon

A

Present in prokaryotes

Contains multiple genes, which are regulated by a promoter and an operator

E.g. lac operon, val operon, his, ara, trp, operon, etc.

43
Q

lac operon

A

i gene- repressor (negative regulation)

Structural genes-

z – beta-galactosidase (β-gal)

y – permease

a – transacetylase

Inducer – lactose or allolactose

44
Q

Human genome project (HGP)

A

Started in 1990, Completed in 2003

3 x 109 base pairs (haploid)

20,000-25,000 genes

Largest gene- Dystrophin gene of the X chromosome (2.4 million bp)

Smallest gene- SRF/TDY gene of the Y chromosome (14 bp)

45
Q

SNPs

A

Single nucleotide polymorphism

Single base differences exist at

1.4 million places in the human genome

46
Q

Sequence annotation

A

Assigning different regions of genome according to function

47
Q

Expressed Sequence Tags (ESTs)

A

Identifying all the genes, which are expressed as RNAs

48
Q

DNA Fingerprinting

A

Developed by Sir Alec Jeffreys

Involves identifying of repeated DNA sequences

Satellite DNA forms smaller peaks and shows a high degree of polymorphism

49
Q

VNTR

A

Variable number of tandem repeats

Mini-satellite

Number and position differs from person to person

Flanked by restriction sites

50
Q

Southern blotting

A

Transfer of electrophoresis separated DNA to nitrocellulose or nylon membrane and detection by probe hybridisation

Used to detect DNA sample in blood or tissue

Biology (2 decks)

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