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POM Exam 1 > L1: Genetic Principles of Medicine: Nucleic Acids, Genes, and Chromosomes > Flashcards

L1: Genetic Principles of Medicine: Nucleic Acids, Genes, and Chromosomes Flashcards

1
Q

genome

A
  • the sum of genetic information for an organism
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2
Q

gene

A
  • a specific sequence of DNA that encodes a specific protein
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3
Q

How much DNA in the human genome codes for proteins?

A
  • low

- only around 1.2%

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4
Q

What is non-coding DNA used for

A
  • needed to control expression of genes
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5
Q

Rank size of chromosome, gene, genome, and nucleotide

A
  • nucleotide < gene < chromosome < genome
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6
Q

chromosome

A
  • a single molecule of genomic DNA
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7
Q

genome of prokaryotes

A
  • small, simple genomes

- circular or linear DNA molecules

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8
Q

genome of eukaryotes

A
  • large genomes
  • lots of extra DNA
  • long, linear DNA molecules
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9
Q

origin of replication in prokaryotes

A
  • single site of origin
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10
Q

origin of replication in eukaryotes

A
  • large genome and multiple sites of origins of replication
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11
Q

What challenges do eukaryotes face due to their large genomes and linear chromosomes?

A
  • because the genome is large, that makes it difficult to replicate
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12
Q

what happens as DNA strands are separated on one side of the fork?

A
  • DNA on the other side becomes supercoiled
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13
Q

role of type I topoisomerase

A
  • nicks one DNA strand to allow relaxation of supercoiling

- then seals the nick

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14
Q

role of type II topoisomerase

A
  • makes double-stranded break in one duplex of DNA
  • unbroken duplex is passed through ends of break
  • break is sealed and enzyme releases DNA
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15
Q

template

A
  • basis for instruction
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16
Q

origins of replication

A
  • defined sites where replication begins
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17
Q

helicase

A
  • unwinds DNA at fork
  • present template for instruction
  • breaks the Watson-Crick base pairs that form double helix
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18
Q

topoisomerases

A
  • resolve knots and supercoils

- deals with increased helical tension in advance of the fork

19
Q

SSB proteins

A
  • stabilize unwound DNA that is now single-stranded
20
Q

RNA primers

A
  • initiate DNA synthesis
21
Q

DNA polymerases

A
  • make new DNA
22
Q

ligase

A
  • resolves Okazaki fragments
23
Q

mismatch repair process

A
  • certain DNA polymerases have exonuclease activity that can correct the mistakes
  • cells are provided with the mismatch repair process when polymerase exonuclease activity fails
  • mismatch repair process recognizes errors then correct those errors in the newly synthesized strand
  • MSH2, MSH3, and MSH6 tasked with this
24
Q

Lynch syndrome

A
  • caused by mutations in the mismatch proteins
  • limit the efficiency of the DNA repair process
  • lead to inherited form of colorectal cancer (HNPCC)
25
Q

role of centromeres

A
  • guide accurate segregation during cell division

- spindle fibers attach and guide the chromosomes

26
Q

role of telomeres

A
  • protect ends of chromosome and guard against erosion from the ends
27
Q

what is a telomere?

A
  • short, repeated sequences found at the end of each chromosome
28
Q

telomere as a buffer

A
  • chromosomes have some sequence that acts as a buffer

- can be lost without losing any protein-coding genes

29
Q

in which cells are the gene that encodes for telomerase present?

A
  • all cells
30
Q

when is the gene that encodes for telomerase expressed?

A
  • in different cancers usually
  • in stem cells
  • NOT in neurons - those are post-differentiated
31
Q

how does packaging of DNA work?

A
  • DNA wrapped around histone octomer to form nucleosome
  • further condensed until we get “beads on a string”
  • packaged further
  • regulated by post-translational modification of histones
32
Q

what happens when DNA is highly condensed?

A
  • it is not possible for transcriptional machinery to reach DNA
33
Q

open DNA

A
  • euchromatin
34
Q

closed DNA

A
  • heterochromatin
35
Q

Eukaryotic nuclear DNA is organized into ________ chromosomes.

A

Linear

36
Q

What ensures fast DNA replication in eukaryotic cells?

A

Multiple origins of replication.

37
Q

Describe how DNA is replicated in Prokaryotes.

A
  1. Local opening of the double helix at a single origin of replication
  2. Formation of a replication bubble flanked by replication fork at each end.
  3. DNA replication occurs in a bidirectional manner
  4. 2 circular DNA molecules result, each containing one parental and one daughter strand.
38
Q

During DNA replication, the _______ strand requires repetitive action of ligase to join DNA fragments.

A

Lagging

39
Q

Caused by mutations in key DNA-repair factors and leads to a familial form of colorectal cancer.

A

Lynch syndrome.

40
Q

Name 2 useful repetitive sequences in DNA.

A

Centromeres and Telomeres.

41
Q

Function of telomerase.

A

Enzyme that adds repetitive sequences to the ends of chromosomes.

42
Q

What is a nucleosome?

A

The basic unit of chromosome structure - contain DNA wrapped around a histone octamer.

43
Q

How are nucleosomes packaged?

A

Nucleosomes are futher packaged on top of each other and folded into a series of loops, which are further condensed to produce the mitotic chromosome.

POM Exam 1 (16 decks)

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