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Block 0 > DNA and the Organization of the Genome > Flashcards

DNA and the Organization of the Genome Flashcards

1
Q

DNA Structure

A
  • Double Helix
  • Made of nucleotides with sugar-phosphate backbone
  • Two strands held together via hydrogen bonds
  • Each strand has a 5’ and 3’ end
  • Each strand runs in opposite direction (Anti-Parallel)
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2
Q

DNA Replication

A
  1. ) Enzyme Helicase unzips the DNA strands forming a replication fork
  2. ) Enzyme Primase makes piece of RNA called a Primer on the template which marks the starting point of the new strand of DNA
  3. ) Enzyme DNA Polymerase binds to the primer and makes the NEW strand of DNA from 5’ to 3’
  4. ) Enzyme Exonuclease removes the primers and DNA Polymerase fills the gaps with DNA
  5. ) Enzyme DNA Ligase seals up the fragments of DNA in both strands to form continuous double strand
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3
Q

Leading strand

A
  • New strand of DNA during DNA replication

- Made continuously from 5’ to 3’

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4
Q

Lagging strand

A
  • New strand of DNA during DNA replication
  • NOT made continuously as it runs in the opposite direction of the leading strand
  • Still made in the 5’ to 3’ direction
  • Made in small chunks called Okazaki Fragments, each of which is started with an RNA primer
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5
Q

Exonuclease

A
  • Enzyme that removes the RNA primers from both the leading and lagging strand after the new strand of DNA is completed
  • Another DNA Polymerase then fills in the gaps with DNA
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6
Q

DNA Ligase

A

Enzyme that seals up the fragments of DNA in both strands to form continuous double strand

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7
Q

Semi-Conservative DNA Replication

A

Each new DNA molecule has one old (conserved) strand and one new strand

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8
Q

Number of chromosomes in human somatic (non-germline) cells

A
  • 46 Chromosomes

- Arranged in 23 pairs: 22 pairs of autosomes (non-sex chromosomes) and 1 pair of sex cells

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9
Q

Autosome

A

Any chromosome that is not a sex chromosome

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10
Q

Sex cells

Male and Female

A

Male: XY
Female: XX

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11
Q

Chromatin

A

The complex of DNA and proteins of which chromosomes are composed

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12
Q

Nucleosome

A
  • Primary structural unit of chromatin, consisting of DNA wrapped twice around a core of 8 histone molecules
  • Histones have (+) charge
  • Phosphate groups on DNA have (-) charge
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13
Q

Histones

A

Proteins associated with DNA in chromatin. Two copies each of histones H2A, H2B, H3, and H4 make an octamer that is the core of a nucleosome

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14
Q

When is chromatin condensed into compact chromosomes?

A
  • During cell division the chromatin is condensed into compact chromosomes that can easily be separated into two daughter cells
  • When not in cell division the chromatin is in its decondensed state in the nucleus to allow access to the DNA for gene expression
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15
Q

Gene

A
  • Functional hereditary unit of the genome

- Sequence of chromosomal DNA that is required for the production of a functional product

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16
Q

Protein-coding gene

A

Segment of DNA containing the code for the amino acid sequence of a polypeptide chain and the regulatory sequences necessary for its expression

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17
Q

What is the product of noncoding genes?

A

RNA products

18
Q

What direction does transcription occur along DNA?

A

5’ to 3’

19
Q
  • What direction of DNA is considered upstream?

- What direction is downstream?

A
  • The 5’ end is upstream
  • The 3’ end is downstream
  • This is because transcription is read from 5’ to 3’ along the DNA
20
Q

Promotor sequences

A
  • At the 5’ end of each gene
  • Includes sequences responsible for the proper initiation of transcription
  • Common sequence that determines the start site in many genes is the TATA box
  • Promoter sequences are binding sites for the proteins called transcription factors
21
Q

Exons

A
  • Segments of genes that ultimately determine the amino acid sequence of the protein
  • Kept in the mature mRNA during splicing
22
Q

Introns

A
  • Intervening sequences present in the genomic DNA but removed from the mRNA during splicing
  • Not represented in the final protein product
23
Q

Cis Regulatory Elements

A

Sequences on the same molecule of DNA as the gene they regulate

24
Q

Trans Regulatory Elements

A

Sequences that regulate genes distant from the gene from which they were transcribed

25
Q

Enhancer

A
  • Regulatory element

- DNA sequence that acts in cis to increase transcription of a gene

26
Q

Locus Control Region (LCR)

A

A DNA domain, situation outside a cluster of structural genes, responsible for appropriate expression of the genes within the cluster

27
Q

Silencer

A

A DNA sequence that acts in cis to decrease transcription of a nearby gene

28
Q

Transcription Factor

A
  • Large class of proteins
  • Regulates transcription by forming complexes that bind to regulatory regions of genes to either promote or inhibit transcription
29
Q

Nucleotide general structure

A
  • Phosphate Group
  • 5-Carbon Sugar
  • Nitrogenous Base
30
Q

4 Nucleotide Bases in DNA

A
  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)
31
Q

Purines

A
  • Adenine (A)
  • Guanine (G)
  • Made of 2 rings
32
Q

Pyrimidines

A
  • Cytosine (C)
  • Uracil (U) - (RNA only)
  • Thymine (T)
  • Made of 1 ring
33
Q

Nucleotide Complementary Base Pairing

A

(A) binds to (T) via 2 Hydrogen Bonds

(C) Binds with (G) via 3 Hydrogen Bonds

34
Q

Interphase Subphases

A
  • G1 Phase:
  • S Phase: DNA Replication
  • G2 Phase:
35
Q

DNA Replication 3 Main Steps

A
  1. ) Initiation
  2. ) Elongation
  3. ) Termination
36
Q

Initiation Main Steps

A
  1. ) Group of protein form the pre-replication complex
  2. ) Looks for specific nucleotide sequences (Origins of Replication) along the DNA strand (lots of A and T bases)
  3. ) DNA Helicase can easily separate strands here (A = T only has 2 hydrogen bonds)
  4. ) Creates replication fork
37
Q

Single Stranded DNA Binding Proteins

A

Stabilize the unstable single DNA stands during DNA replication

38
Q

DNA Topoisomerase

A
  • DNA that is double stranded becomes more tight when nearby DNA is unzipped into single strands
  • DNA Topoisomerase loosens up this tight DNA coil
39
Q

Elongation Main Steps

A
  1. ) RNA Primase randomly synthesizes small lengths of RNA called RNA Primers
  2. ) RNA Primers bind to complementary strands of DNA
  3. ) DNA Polymerase attaches to this segment of DNA + RNA Primer
  4. ) DNA Polymerase adds complementary nucleotides to the signle stranded DNA (Moves 3’ to 5’ and synthesizes 5’ to 3’)
40
Q

What is the structural difference between DNA and RNA?

A
  • DNA uses Thymine (T) and RNA uses Uracil (U)

- DNA uses Deoxyribose sugars and RNA uses Ribose sugars

41
Q

Termination mains steps

A
  1. ) Telomere (repeating sequences of TTAGGG) at the end of the chromosome signals DNA Polymerase to hop off the strand
  2. ) The two new (semi-conserved) DNA strands separate, finalizing DNA replication

Block 0 (10 decks)

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