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Bioc221 module 1 > Molecular anatomy of genes and genomes > Flashcards

Molecular anatomy of genes and genomes Flashcards

1
Q

How do we know life has only evolved once?

A

Because the genetic code is universal

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2
Q

What is the key difference between prokaryotic and eukaryotic genomes?

A

Eukaryotic genomes are larger because they are multicellular organisms

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3
Q

Draw a eukaryotic gene

A

ADD

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4
Q

What does a cell function depend on?

A

What genes are expressed

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5
Q

What is the purpose of the control region?

A

Determines if a gene is on or off in a particular tissue and its level of expression

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6
Q

What are transcription factors?

A

Proteins that bind to the promoter sequence and control the rate of transcription

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7
Q

What is a promoter?

A

The DNA sequence at which transcription factors bind and recruit RNA polymerace

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8
Q

What do promoters determine?

A

If and how much a gene is transcribed

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9
Q

What is splicing?

A

pre-mRNA -> mRNA

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10
Q

What carries out splicing?

A

A protein complex called the spliceosome

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11
Q

What is alternative splicing?

A

One gene can be spliced in different ways meaning that multiple proteins can be made

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12
Q

What is the role of the 5’ cap?

A

Allows ribosomes to recognise the start of the transcript

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13
Q

What is the role of the PolyA tail?

A

Stabilises transcript

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14
Q

Draw a mRNA strand

A

ADD

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15
Q

What % of our genome codes for proteins?

A

1.2%

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16
Q

What is 48% of our genome?

A

Repetitive DNA elements

17
Q

What are the two types of repetitive DNA?

A

Highly repetitive sequences and transposons

18
Q

What are highly repetitive sequences?

A

Short regions of highly repetitive DNA which arise by replication slippage

19
Q

How can highly repetitive sequences be used for DNA fingerprinting?

A

The difference in how many of the repeats is present in the region varies greatly between individuals

20
Q

Highly repetitive sequences make up ? of the genome

A

3%

21
Q

Where do we see repetitive DNA in the cell?

A

The centromere typically consists of large arrays of repetitive DNA. Repeat sequences are added by telomerase to protect the ends of chromosomes.

22
Q

What are transposons responsible for?

A

The presence of many copies of sequences derived form transposons are responsible for much of the variation in genome sizes

23
Q

Transposons make up ? of the genome

A

45%

24
Q

? of the genome is transcribed and most of this ? encode proteins. This is called ?

A

60%
doesn’t
non-coding RNA

25
Q

What is the role of non-coding RNA?

A

Still fairly unknown however it has a regulatory role as it has the ability to feedback to the DNA and turn genes on and off

26
Q

Why do we have chromosomes?

A

Cells have a lot of DNA that has to be fitted into a very small volume but the cell needs access to it and chromosomes allow this

27
Q

What are chromosomes?

A

DNA + associated proteins

28
Q

What do chromosomes do?

A
  • compacts DNA
  • protects DNA
  • Ensures replicated DNA its properly segregated
  • Provides an organisation to DNA
29
Q

DNA + histone proteins = ?

A

Nucleosome

30
Q

How is a nucleosome formed?

A

DNA is wrapped around positively charged histone proteins forming a nucleosome.

31
Q

What happens after a nucleosome is formed?

A

Histone H1 induces tighter DNA wrapping around the nucleosome compacting the DNA. This is then further compacted into a 30nm chromatin fiber

32
Q

What happens after a chromatin finer is formed?

A

Loops of DNA are attached to a protein scaffold which forms the metaphase chromosome

33
Q

What does the scaffold contain?

A

topoisomerase || and specific proteins eg condensin

34
Q

What is the DNA paradox?

A

Two opposite functions must occur simultaneously. DNA must be in stable compact structures that protects it from damage while the cell needs access to the information in the DNA

35
Q

How are histone tails modified?

A

They are chemically modified by enzymes

36
Q

How is the DNA paradox solved?

A

Modification of the histone tails allows switching between euchromatin and heterochromatin

37
Q

Euchromatin

A

DNA coding genes that are actively transcribed are more loosely packaged and are found associated with RNA plymerases

38
Q

Heterochromatin

A

DNA coding inactive genes are found associated with structural proteins and are more tightly packaged

Bioc221 module 1 (1 decks)

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