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IMS- Strand 1 > The human genome > Flashcards

The human genome Flashcards

1
Q

What is the genome?

A

All the genetic information of an organism

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2
Q

How many nucleotides making up coding genes in humans?

A

3.2 billion make up 20,000

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3
Q

What is a genome divided up into?

A

2 sex chromosomes
44 (22 pairs) of autosomes
37 genes on circular mitochondrial chromosomes

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4
Q

Why do mitochondria have their own separate set of genes?

A

13 out of 37 provide instructions for making enzymes

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5
Q

What is a nucleotide made of?

A

Nitrogenous base
Phosphate group
5 carbon sugar (deoxyribose)

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6
Q

What chemical bonds hold DNA together?

A

Covalent phosphodiester bonds between 5’ of one sugar and 3’ of another
Hydrogen bonds between base pairs

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7
Q

How is DNA packaged into the nucleus?

A

1-DNA (negatively charged) bound to histone proteins (positively charged) to make nucleosomes
2-Coil nucleosomes to form 30nm thick
3-Chromatin fibres assembled on a protein scaffold to form a chromosome

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8
Q

What is coding DNA?

A

codes for proteins

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9
Q

7 examples of non coding DNA

A

Genes for other RNAs
Promoter regions
Introns
Tandem repeats
Telomeres
Pseudogenes
Viral DNA
Junk DNA

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10
Q

What are Pseudogenes?

A

DNA sequence that resembles a gene but has been mutated into an inactive form over the course of evolution

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11
Q

What are tandem repeats?

A

repeated short DNA sequences, occur due to polymerase “slippage”

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12
Q

What is the role of coding RNA?

A

Messenger mRNA (DNA-mRNA and mRNA- proteins)
Viral genomes (RNA how some viruses store genetic material)

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13
Q

What is the role of structural RNA?

A

Ribosomal rRNA (makes up ribosomes)
Transfer tRNA (carries amino acids to ribosome in translation)

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14
Q

What is the role of regulatory RNA?

A

microRNA (involved in post- transcriptional regulation of gene expression)
Xist (switches off one copy of the X chromosome in XX cells creating a Barr body)

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15
Q

What is the Sense/coding strand?

A

the stand (when read in the right direction) contains the specific code to make a protein, matches mRNA

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16
Q

What is the Antisense/ template strand?

A

the stand with the opposite sequence to the sense strand

17
Q

Steps in DNA replication (leading strand)

A
  • Unzip the double helix (DNA helicase)
  • Attach a primer (primase enzyme)
  • Add complementary nucleotides (DNA polymerase III adds nucleotides)
18
Q

What prevents over coiling?

A

Topoisomerase

19
Q

What direction are nucleotides added in?

A

5’ to 3’ direction and starts at primer

20
Q

Steps in DNA replication (lagging strand)

A

-Unzip
- Add primer (DNA polymerase only works in one direction so primer adds close to helicase)
- DNA polymerase III add nucleotides in 5’3’ direction
- Helicase unzips more and process repeats
- Once replication is complete= lagging strand is a mess

21
Q

What happens after DNA replication of the lagging strand?

A
  • Made up of OKAZAKI FRAGMENTS
  • Mix of RNA and DNA
  • Primers from RNA are turned into to DNA using DNA polymerase I
  • Gaps are stitched together by DNA ligase
22
Q

What is PCR?

A
  • Amplifies a DNA sample in a lab to allow us to perform genetic testing
23
Q

What ingredients are added to PCR tube?

A
  • The DNA sample from your patient
  • Nucleotides
  • Buffer solution
  • Primers
  • DNA Taq polymerase (heat stable DNA polymerase 1)
24
Q

Steps in PCR

A
  • Denaturation (94-95)
  • Annealing (50-60)
  • Extension/ Elongation (72)
    Repeat approx 30 times, num of repeats depends on amount of DNA needed
25
Q

Denaturation (95)

A

Heating to 95 seperates the two strands of double stranded DNA

26
Q

Annealing (55-65)

A

Primers bind to single stranded DNA

27
Q

Extension (72)

A

Taq DNA polymerase activity is optimum at 72 and new DNA is therefore synthesised during this phase

28
Q

What is a Barr body?

A

An inactivated X chromsome in a female somatic cell

29
Q

What is the function of the enzyme DNA telomerase?

A

To prevent the ends of chromosomes from degradation

30
Q

What is semi conservative replication?

A

After replication each strand is made of half of the original strand

IMS- Strand 1 (4 decks)

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